From de6d2c524430287c699aaa898c1325da6afea539 Mon Sep 17 00:00:00 2001
From: Niall Sheridan <nsheridan@gmail.com>
Date: Wed, 20 Jun 2018 22:39:07 +0100
Subject: Update dependencies

---
 .../prometheus/client_golang/prometheus/counter.go | 132 +++++--
 .../prometheus/client_golang/prometheus/desc.go    |   3 +-
 .../prometheus/client_golang/prometheus/doc.go     |  15 +-
 .../prometheus/client_golang/prometheus/gauge.go   | 147 ++++++-
 .../client_golang/prometheus/go_collector.go       |  10 +-
 .../client_golang/prometheus/histogram.go          |  94 +++--
 .../prometheus/client_golang/prometheus/http.go    |  24 +-
 .../prometheus/client_golang/prometheus/metric.go  |  34 +-
 .../client_golang/prometheus/observer.go           |   2 +
 .../client_golang/prometheus/process_collector.go  |  15 +-
 .../client_golang/prometheus/promhttp/delegator.go |   6 +-
 .../prometheus/promhttp/delegator_1_8.go           |   2 +-
 .../client_golang/prometheus/promhttp/http.go      | 131 ++++++-
 .../prometheus/promhttp/instrument_client.go       |  29 +-
 .../prometheus/promhttp/instrument_client_1_8.go   |   4 +-
 .../prometheus/promhttp/instrument_server.go       | 155 ++++----
 .../client_golang/prometheus/registry.go           | 351 +++++++++--------
 .../prometheus/client_golang/prometheus/summary.go |  96 +++--
 .../prometheus/client_golang/prometheus/value.go   |  80 +---
 .../prometheus/client_golang/prometheus/vec.go     | 427 +++++++++++++--------
 20 files changed, 1088 insertions(+), 669 deletions(-)

(limited to 'vendor/github.com/prometheus/client_golang/prometheus')

diff --git a/vendor/github.com/prometheus/client_golang/prometheus/counter.go b/vendor/github.com/prometheus/client_golang/prometheus/counter.go
index 273db5f..765e455 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/counter.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/counter.go
@@ -15,6 +15,10 @@ package prometheus
 
 import (
 	"errors"
+	"math"
+	"sync/atomic"
+
+	dto "github.com/prometheus/client_model/go"
 )
 
 // Counter is a Metric that represents a single numerical value that only ever
@@ -42,6 +46,14 @@ type Counter interface {
 type CounterOpts Opts
 
 // NewCounter creates a new Counter based on the provided CounterOpts.
+//
+// The returned implementation tracks the counter value in two separate
+// variables, a float64 and a uint64. The latter is used to track calls of the
+// Inc method and calls of the Add method with a value that can be represented
+// as a uint64. This allows atomic increments of the counter with optimal
+// performance. (It is common to have an Inc call in very hot execution paths.)
+// Both internal tracking values are added up in the Write method. This has to
+// be taken into account when it comes to precision and overflow behavior.
 func NewCounter(opts CounterOpts) Counter {
 	desc := NewDesc(
 		BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
@@ -49,20 +61,58 @@ func NewCounter(opts CounterOpts) Counter {
 		nil,
 		opts.ConstLabels,
 	)
-	result := &counter{value: value{desc: desc, valType: CounterValue, labelPairs: desc.constLabelPairs}}
+	result := &counter{desc: desc, labelPairs: desc.constLabelPairs}
 	result.init(result) // Init self-collection.
 	return result
 }
 
 type counter struct {
-	value
+	// valBits contains the bits of the represented float64 value, while
+	// valInt stores values that are exact integers. Both have to go first
+	// in the struct to guarantee alignment for atomic operations.
+	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	valBits uint64
+	valInt  uint64
+
+	selfCollector
+	desc *Desc
+
+	labelPairs []*dto.LabelPair
+}
+
+func (c *counter) Desc() *Desc {
+	return c.desc
 }
 
 func (c *counter) Add(v float64) {
 	if v < 0 {
 		panic(errors.New("counter cannot decrease in value"))
 	}
-	c.value.Add(v)
+	ival := uint64(v)
+	if float64(ival) == v {
+		atomic.AddUint64(&c.valInt, ival)
+		return
+	}
+
+	for {
+		oldBits := atomic.LoadUint64(&c.valBits)
+		newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
+		if atomic.CompareAndSwapUint64(&c.valBits, oldBits, newBits) {
+			return
+		}
+	}
+}
+
+func (c *counter) Inc() {
+	atomic.AddUint64(&c.valInt, 1)
+}
+
+func (c *counter) Write(out *dto.Metric) error {
+	fval := math.Float64frombits(atomic.LoadUint64(&c.valBits))
+	ival := atomic.LoadUint64(&c.valInt)
+	val := fval + float64(ival)
+
+	return populateMetric(CounterValue, val, c.labelPairs, out)
 }
 
 // CounterVec is a Collector that bundles a set of Counters that all share the
@@ -85,11 +135,10 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 	)
 	return &CounterVec{
 		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
-			result := &counter{value: value{
-				desc:       desc,
-				valType:    CounterValue,
-				labelPairs: makeLabelPairs(desc, lvs),
-			}}
+			if len(lvs) != len(desc.variableLabels) {
+				panic(errInconsistentCardinality)
+			}
+			result := &counter{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
 			result.init(result) // Init self-collection.
 			return result
 		}),
@@ -111,7 +160,7 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 // Counter with the same label values is created later.
 //
 // An error is returned if the number of label values is not the same as the
-// number of VariableLabels in Desc.
+// number of VariableLabels in Desc (minus any curried labels).
 //
 // Note that for more than one label value, this method is prone to mistakes
 // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
@@ -119,8 +168,8 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 // latter has a much more readable (albeit more verbose) syntax, but it comes
 // with a performance overhead (for creating and processing the Labels map).
 // See also the GaugeVec example.
-func (m *CounterVec) GetMetricWithLabelValues(lvs ...string) (Counter, error) {
-	metric, err := m.metricVec.getMetricWithLabelValues(lvs...)
+func (v *CounterVec) GetMetricWithLabelValues(lvs ...string) (Counter, error) {
+	metric, err := v.metricVec.getMetricWithLabelValues(lvs...)
 	if metric != nil {
 		return metric.(Counter), err
 	}
@@ -134,13 +183,13 @@ func (m *CounterVec) GetMetricWithLabelValues(lvs ...string) (Counter, error) {
 // the same as for GetMetricWithLabelValues.
 //
 // An error is returned if the number and names of the Labels are inconsistent
-// with those of the VariableLabels in Desc.
+// with those of the VariableLabels in Desc (minus any curried labels).
 //
 // This method is used for the same purpose as
 // GetMetricWithLabelValues(...string). See there for pros and cons of the two
 // methods.
-func (m *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
-	metric, err := m.metricVec.getMetricWith(labels)
+func (v *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
+	metric, err := v.metricVec.getMetricWith(labels)
 	if metric != nil {
 		return metric.(Counter), err
 	}
@@ -148,18 +197,57 @@ func (m *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
 }
 
 // WithLabelValues works as GetMetricWithLabelValues, but panics where
-// GetMetricWithLabelValues would have returned an error. By not returning an
-// error, WithLabelValues allows shortcuts like
+// GetMetricWithLabelValues would have returned an error. Not returning an
+// error allows shortcuts like
 //     myVec.WithLabelValues("404", "GET").Add(42)
-func (m *CounterVec) WithLabelValues(lvs ...string) Counter {
-	return m.metricVec.withLabelValues(lvs...).(Counter)
+func (v *CounterVec) WithLabelValues(lvs ...string) Counter {
+	c, err := v.GetMetricWithLabelValues(lvs...)
+	if err != nil {
+		panic(err)
+	}
+	return c
 }
 
 // With works as GetMetricWith, but panics where GetMetricWithLabels would have
-// returned an error. By not returning an error, With allows shortcuts like
-//     myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)
-func (m *CounterVec) With(labels Labels) Counter {
-	return m.metricVec.with(labels).(Counter)
+// returned an error. Not returning an error allows shortcuts like
+//     myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Add(42)
+func (v *CounterVec) With(labels Labels) Counter {
+	c, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return c
+}
+
+// CurryWith returns a vector curried with the provided labels, i.e. the
+// returned vector has those labels pre-set for all labeled operations performed
+// on it. The cardinality of the curried vector is reduced accordingly. The
+// order of the remaining labels stays the same (just with the curried labels
+// taken out of the sequence – which is relevant for the
+// (GetMetric)WithLabelValues methods). It is possible to curry a curried
+// vector, but only with labels not yet used for currying before.
+//
+// The metrics contained in the CounterVec are shared between the curried and
+// uncurried vectors. They are just accessed differently. Curried and uncurried
+// vectors behave identically in terms of collection. Only one must be
+// registered with a given registry (usually the uncurried version). The Reset
+// method deletes all metrics, even if called on a curried vector.
+func (v *CounterVec) CurryWith(labels Labels) (*CounterVec, error) {
+	vec, err := v.curryWith(labels)
+	if vec != nil {
+		return &CounterVec{vec}, err
+	}
+	return nil, err
+}
+
+// MustCurryWith works as CurryWith but panics where CurryWith would have
+// returned an error.
+func (v *CounterVec) MustCurryWith(labels Labels) *CounterVec {
+	vec, err := v.CurryWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return vec
 }
 
 // CounterFunc is a Counter whose value is determined at collect time by calling a
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/desc.go b/vendor/github.com/prometheus/client_golang/prometheus/desc.go
index 920abc9..4a755b0 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/desc.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/desc.go
@@ -73,8 +73,7 @@ type Desc struct {
 // and therefore not part of the Desc. (They are managed within the Metric.)
 //
 // For constLabels, the label values are constant. Therefore, they are fully
-// specified in the Desc. See the Opts documentation for the implications of
-// constant labels.
+// specified in the Desc. See the Collector example for a usage pattern.
 func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc {
 	d := &Desc{
 		fqName:         fqName,
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/doc.go b/vendor/github.com/prometheus/client_golang/prometheus/doc.go
index 36ef155..83c3657 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/doc.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/doc.go
@@ -11,10 +11,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package prometheus provides metrics primitives to instrument code for
-// monitoring. It also offers a registry for metrics. Sub-packages allow to
-// expose the registered metrics via HTTP (package promhttp) or push them to a
-// Pushgateway (package push).
+// Package prometheus is the core instrumentation package. It provides metrics
+// primitives to instrument code for monitoring. It also offers a registry for
+// metrics. Sub-packages allow to expose the registered metrics via HTTP
+// (package promhttp) or push them to a Pushgateway (package push). There is
+// also a sub-package promauto, which provides metrics constructors with
+// automatic registration.
 //
 // All exported functions and methods are safe to be used concurrently unless
 // specified otherwise.
@@ -72,7 +74,10 @@
 // The number of exported identifiers in this package might appear a bit
 // overwhelming. However, in addition to the basic plumbing shown in the example
 // above, you only need to understand the different metric types and their
-// vector versions for basic usage.
+// vector versions for basic usage. Furthermore, if you are not concerned with
+// fine-grained control of when and how to register metrics with the registry,
+// have a look at the promauto package, which will effectively allow you to
+// ignore registration altogether in simple cases.
 //
 // Above, you have already touched the Counter and the Gauge. There are two more
 // advanced metric types: the Summary and Histogram. A more thorough description
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/gauge.go b/vendor/github.com/prometheus/client_golang/prometheus/gauge.go
index 13064da..17c72d7 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/gauge.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/gauge.go
@@ -13,6 +13,14 @@
 
 package prometheus
 
+import (
+	"math"
+	"sync/atomic"
+	"time"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
 // Gauge is a Metric that represents a single numerical value that can
 // arbitrarily go up and down.
 //
@@ -48,13 +56,74 @@ type Gauge interface {
 type GaugeOpts Opts
 
 // NewGauge creates a new Gauge based on the provided GaugeOpts.
+//
+// The returned implementation is optimized for a fast Set method. If you have a
+// choice for managing the value of a Gauge via Set vs. Inc/Dec/Add/Sub, pick
+// the former. For example, the Inc method of the returned Gauge is slower than
+// the Inc method of a Counter returned by NewCounter. This matches the typical
+// scenarios for Gauges and Counters, where the former tends to be Set-heavy and
+// the latter Inc-heavy.
 func NewGauge(opts GaugeOpts) Gauge {
-	return newValue(NewDesc(
+	desc := NewDesc(
 		BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
 		opts.Help,
 		nil,
 		opts.ConstLabels,
-	), GaugeValue, 0)
+	)
+	result := &gauge{desc: desc, labelPairs: desc.constLabelPairs}
+	result.init(result) // Init self-collection.
+	return result
+}
+
+type gauge struct {
+	// valBits contains the bits of the represented float64 value. It has
+	// to go first in the struct to guarantee alignment for atomic
+	// operations.  http://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	valBits uint64
+
+	selfCollector
+
+	desc       *Desc
+	labelPairs []*dto.LabelPair
+}
+
+func (g *gauge) Desc() *Desc {
+	return g.desc
+}
+
+func (g *gauge) Set(val float64) {
+	atomic.StoreUint64(&g.valBits, math.Float64bits(val))
+}
+
+func (g *gauge) SetToCurrentTime() {
+	g.Set(float64(time.Now().UnixNano()) / 1e9)
+}
+
+func (g *gauge) Inc() {
+	g.Add(1)
+}
+
+func (g *gauge) Dec() {
+	g.Add(-1)
+}
+
+func (g *gauge) Add(val float64) {
+	for {
+		oldBits := atomic.LoadUint64(&g.valBits)
+		newBits := math.Float64bits(math.Float64frombits(oldBits) + val)
+		if atomic.CompareAndSwapUint64(&g.valBits, oldBits, newBits) {
+			return
+		}
+	}
+}
+
+func (g *gauge) Sub(val float64) {
+	g.Add(val * -1)
+}
+
+func (g *gauge) Write(out *dto.Metric) error {
+	val := math.Float64frombits(atomic.LoadUint64(&g.valBits))
+	return populateMetric(GaugeValue, val, g.labelPairs, out)
 }
 
 // GaugeVec is a Collector that bundles a set of Gauges that all share the same
@@ -77,7 +146,12 @@ func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
 	)
 	return &GaugeVec{
 		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
-			return newValue(desc, GaugeValue, 0, lvs...)
+			if len(lvs) != len(desc.variableLabels) {
+				panic(errInconsistentCardinality)
+			}
+			result := &gauge{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
+			result.init(result) // Init self-collection.
+			return result
 		}),
 	}
 }
@@ -98,15 +172,15 @@ func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
 // example.
 //
 // An error is returned if the number of label values is not the same as the
-// number of VariableLabels in Desc.
+// number of VariableLabels in Desc (minus any curried labels).
 //
 // Note that for more than one label value, this method is prone to mistakes
 // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
 // an alternative to avoid that type of mistake. For higher label numbers, the
 // latter has a much more readable (albeit more verbose) syntax, but it comes
 // with a performance overhead (for creating and processing the Labels map).
-func (m *GaugeVec) GetMetricWithLabelValues(lvs ...string) (Gauge, error) {
-	metric, err := m.metricVec.getMetricWithLabelValues(lvs...)
+func (v *GaugeVec) GetMetricWithLabelValues(lvs ...string) (Gauge, error) {
+	metric, err := v.metricVec.getMetricWithLabelValues(lvs...)
 	if metric != nil {
 		return metric.(Gauge), err
 	}
@@ -120,13 +194,13 @@ func (m *GaugeVec) GetMetricWithLabelValues(lvs ...string) (Gauge, error) {
 // the same as for GetMetricWithLabelValues.
 //
 // An error is returned if the number and names of the Labels are inconsistent
-// with those of the VariableLabels in Desc.
+// with those of the VariableLabels in Desc (minus any curried labels).
 //
 // This method is used for the same purpose as
 // GetMetricWithLabelValues(...string). See there for pros and cons of the two
 // methods.
-func (m *GaugeVec) GetMetricWith(labels Labels) (Gauge, error) {
-	metric, err := m.metricVec.getMetricWith(labels)
+func (v *GaugeVec) GetMetricWith(labels Labels) (Gauge, error) {
+	metric, err := v.metricVec.getMetricWith(labels)
 	if metric != nil {
 		return metric.(Gauge), err
 	}
@@ -134,18 +208,57 @@ func (m *GaugeVec) GetMetricWith(labels Labels) (Gauge, error) {
 }
 
 // WithLabelValues works as GetMetricWithLabelValues, but panics where
-// GetMetricWithLabelValues would have returned an error. By not returning an
-// error, WithLabelValues allows shortcuts like
+// GetMetricWithLabelValues would have returned an error. Not returning an
+// error allows shortcuts like
 //     myVec.WithLabelValues("404", "GET").Add(42)
-func (m *GaugeVec) WithLabelValues(lvs ...string) Gauge {
-	return m.metricVec.withLabelValues(lvs...).(Gauge)
+func (v *GaugeVec) WithLabelValues(lvs ...string) Gauge {
+	g, err := v.GetMetricWithLabelValues(lvs...)
+	if err != nil {
+		panic(err)
+	}
+	return g
 }
 
 // With works as GetMetricWith, but panics where GetMetricWithLabels would have
-// returned an error. By not returning an error, With allows shortcuts like
-//     myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)
-func (m *GaugeVec) With(labels Labels) Gauge {
-	return m.metricVec.with(labels).(Gauge)
+// returned an error. Not returning an error allows shortcuts like
+//     myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Add(42)
+func (v *GaugeVec) With(labels Labels) Gauge {
+	g, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return g
+}
+
+// CurryWith returns a vector curried with the provided labels, i.e. the
+// returned vector has those labels pre-set for all labeled operations performed
+// on it. The cardinality of the curried vector is reduced accordingly. The
+// order of the remaining labels stays the same (just with the curried labels
+// taken out of the sequence – which is relevant for the
+// (GetMetric)WithLabelValues methods). It is possible to curry a curried
+// vector, but only with labels not yet used for currying before.
+//
+// The metrics contained in the GaugeVec are shared between the curried and
+// uncurried vectors. They are just accessed differently. Curried and uncurried
+// vectors behave identically in terms of collection. Only one must be
+// registered with a given registry (usually the uncurried version). The Reset
+// method deletes all metrics, even if called on a curried vector.
+func (v *GaugeVec) CurryWith(labels Labels) (*GaugeVec, error) {
+	vec, err := v.curryWith(labels)
+	if vec != nil {
+		return &GaugeVec{vec}, err
+	}
+	return nil, err
+}
+
+// MustCurryWith works as CurryWith but panics where CurryWith would have
+// returned an error.
+func (v *GaugeVec) MustCurryWith(labels Labels) *GaugeVec {
+	vec, err := v.CurryWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return vec
 }
 
 // GaugeFunc is a Gauge whose value is determined at collect time by calling a
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go b/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go
index 096454a..0440bd1 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go
@@ -17,8 +17,12 @@ type goCollector struct {
 	metrics memStatsMetrics
 }
 
-// NewGoCollector returns a collector which exports metrics about the current
-// go process.
+// NewGoCollector returns a collector which exports metrics about the current Go
+// process. This includes memory stats. To collect those, runtime.ReadMemStats
+// is called. This causes a stop-the-world, which is very short with Go1.9+
+// (~25µs). However, with older Go versions, the stop-the-world duration depends
+// on the heap size and can be quite significant (~1.7 ms/GiB as per
+// https://go-review.googlesource.com/c/go/+/34937).
 func NewGoCollector() Collector {
 	return &goCollector{
 		goroutinesDesc: NewDesc(
@@ -265,7 +269,7 @@ func (c *goCollector) Collect(ch chan<- Metric) {
 		quantiles[float64(idx+1)/float64(len(stats.PauseQuantiles)-1)] = pq.Seconds()
 	}
 	quantiles[0.0] = stats.PauseQuantiles[0].Seconds()
-	ch <- MustNewConstSummary(c.gcDesc, uint64(stats.NumGC), float64(stats.PauseTotal.Seconds()), quantiles)
+	ch <- MustNewConstSummary(c.gcDesc, uint64(stats.NumGC), stats.PauseTotal.Seconds(), quantiles)
 
 	ch <- MustNewConstMetric(c.goInfoDesc, GaugeValue, 1)
 
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/histogram.go b/vendor/github.com/prometheus/client_golang/prometheus/histogram.go
index 6cc6e68..331783a 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/histogram.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/histogram.go
@@ -126,23 +126,16 @@ type HistogramOpts struct {
 	// string.
 	Help string
 
-	// ConstLabels are used to attach fixed labels to this
-	// Histogram. Histograms with the same fully-qualified name must have the
-	// same label names in their ConstLabels.
+	// ConstLabels are used to attach fixed labels to this metric. Metrics
+	// with the same fully-qualified name must have the same label names in
+	// their ConstLabels.
 	//
-	// Note that in most cases, labels have a value that varies during the
-	// lifetime of a process. Those labels are usually managed with a
-	// HistogramVec. ConstLabels serve only special purposes. One is for the
-	// special case where the value of a label does not change during the
-	// lifetime of a process, e.g. if the revision of the running binary is
-	// put into a label. Another, more advanced purpose is if more than one
-	// Collector needs to collect Histograms with the same fully-qualified
-	// name. In that case, those Summaries must differ in the values of
-	// their ConstLabels. See the Collector examples.
-	//
-	// If the value of a label never changes (not even between binaries),
-	// that label most likely should not be a label at all (but part of the
-	// metric name).
+	// ConstLabels are only used rarely. In particular, do not use them to
+	// attach the same labels to all your metrics. Those use cases are
+	// better covered by target labels set by the scraping Prometheus
+	// server, or by one specific metric (e.g. a build_info or a
+	// machine_role metric). See also
+	// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels
 	ConstLabels Labels
 
 	// Buckets defines the buckets into which observations are counted. Each
@@ -322,7 +315,7 @@ func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec {
 // example.
 //
 // An error is returned if the number of label values is not the same as the
-// number of VariableLabels in Desc.
+// number of VariableLabels in Desc (minus any curried labels).
 //
 // Note that for more than one label value, this method is prone to mistakes
 // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
@@ -330,8 +323,8 @@ func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec {
 // latter has a much more readable (albeit more verbose) syntax, but it comes
 // with a performance overhead (for creating and processing the Labels map).
 // See also the GaugeVec example.
-func (m *HistogramVec) GetMetricWithLabelValues(lvs ...string) (Observer, error) {
-	metric, err := m.metricVec.getMetricWithLabelValues(lvs...)
+func (v *HistogramVec) GetMetricWithLabelValues(lvs ...string) (Observer, error) {
+	metric, err := v.metricVec.getMetricWithLabelValues(lvs...)
 	if metric != nil {
 		return metric.(Observer), err
 	}
@@ -345,13 +338,13 @@ func (m *HistogramVec) GetMetricWithLabelValues(lvs ...string) (Observer, error)
 // are the same as for GetMetricWithLabelValues.
 //
 // An error is returned if the number and names of the Labels are inconsistent
-// with those of the VariableLabels in Desc.
+// with those of the VariableLabels in Desc (minus any curried labels).
 //
 // This method is used for the same purpose as
 // GetMetricWithLabelValues(...string). See there for pros and cons of the two
 // methods.
-func (m *HistogramVec) GetMetricWith(labels Labels) (Observer, error) {
-	metric, err := m.metricVec.getMetricWith(labels)
+func (v *HistogramVec) GetMetricWith(labels Labels) (Observer, error) {
+	metric, err := v.metricVec.getMetricWith(labels)
 	if metric != nil {
 		return metric.(Observer), err
 	}
@@ -359,18 +352,57 @@ func (m *HistogramVec) GetMetricWith(labels Labels) (Observer, error) {
 }
 
 // WithLabelValues works as GetMetricWithLabelValues, but panics where
-// GetMetricWithLabelValues would have returned an error. By not returning an
-// error, WithLabelValues allows shortcuts like
+// GetMetricWithLabelValues would have returned an error. Not returning an
+// error allows shortcuts like
 //     myVec.WithLabelValues("404", "GET").Observe(42.21)
-func (m *HistogramVec) WithLabelValues(lvs ...string) Observer {
-	return m.metricVec.withLabelValues(lvs...).(Observer)
+func (v *HistogramVec) WithLabelValues(lvs ...string) Observer {
+	h, err := v.GetMetricWithLabelValues(lvs...)
+	if err != nil {
+		panic(err)
+	}
+	return h
 }
 
-// With works as GetMetricWith, but panics where GetMetricWithLabels would have
-// returned an error. By not returning an error, With allows shortcuts like
-//     myVec.With(Labels{"code": "404", "method": "GET"}).Observe(42.21)
-func (m *HistogramVec) With(labels Labels) Observer {
-	return m.metricVec.with(labels).(Observer)
+// With works as GetMetricWith but panics where GetMetricWithLabels would have
+// returned an error. Not returning an error allows shortcuts like
+//     myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Observe(42.21)
+func (v *HistogramVec) With(labels Labels) Observer {
+	h, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return h
+}
+
+// CurryWith returns a vector curried with the provided labels, i.e. the
+// returned vector has those labels pre-set for all labeled operations performed
+// on it. The cardinality of the curried vector is reduced accordingly. The
+// order of the remaining labels stays the same (just with the curried labels
+// taken out of the sequence – which is relevant for the
+// (GetMetric)WithLabelValues methods). It is possible to curry a curried
+// vector, but only with labels not yet used for currying before.
+//
+// The metrics contained in the HistogramVec are shared between the curried and
+// uncurried vectors. They are just accessed differently. Curried and uncurried
+// vectors behave identically in terms of collection. Only one must be
+// registered with a given registry (usually the uncurried version). The Reset
+// method deletes all metrics, even if called on a curried vector.
+func (v *HistogramVec) CurryWith(labels Labels) (ObserverVec, error) {
+	vec, err := v.curryWith(labels)
+	if vec != nil {
+		return &HistogramVec{vec}, err
+	}
+	return nil, err
+}
+
+// MustCurryWith works as CurryWith but panics where CurryWith would have
+// returned an error.
+func (v *HistogramVec) MustCurryWith(labels Labels) ObserverVec {
+	vec, err := v.CurryWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return vec
 }
 
 type constHistogram struct {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/http.go b/vendor/github.com/prometheus/client_golang/prometheus/http.go
index bfee5c6..4d08154 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/http.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/http.go
@@ -61,9 +61,8 @@ func giveBuf(buf *bytes.Buffer) {
 // name).
 //
 // Deprecated: Please note the issues described in the doc comment of
-// InstrumentHandler. You might want to consider using promhttp.Handler instead
-// (which is not instrumented, but can be instrumented with the tooling provided
-// in package promhttp).
+// InstrumentHandler. You might want to consider using
+// promhttp.InstrumentedHandler instead.
 func Handler() http.Handler {
 	return InstrumentHandler("prometheus", UninstrumentedHandler())
 }
@@ -116,7 +115,7 @@ func decorateWriter(request *http.Request, writer io.Writer) (io.Writer, string)
 	header := request.Header.Get(acceptEncodingHeader)
 	parts := strings.Split(header, ",")
 	for _, part := range parts {
-		part := strings.TrimSpace(part)
+		part = strings.TrimSpace(part)
 		if part == "gzip" || strings.HasPrefix(part, "gzip;") {
 			return gzip.NewWriter(writer), "gzip"
 		}
@@ -140,16 +139,6 @@ var now nower = nowFunc(func() time.Time {
 	return time.Now()
 })
 
-func nowSeries(t ...time.Time) nower {
-	return nowFunc(func() time.Time {
-		defer func() {
-			t = t[1:]
-		}()
-
-		return t[0]
-	})
-}
-
 // InstrumentHandler wraps the given HTTP handler for instrumentation. It
 // registers four metric collectors (if not already done) and reports HTTP
 // metrics to the (newly or already) registered collectors: http_requests_total
@@ -353,10 +342,9 @@ func computeApproximateRequestSize(r *http.Request) <-chan int {
 type responseWriterDelegator struct {
 	http.ResponseWriter
 
-	handler, method string
-	status          int
-	written         int64
-	wroteHeader     bool
+	status      int
+	written     int64
+	wroteHeader bool
 }
 
 func (r *responseWriterDelegator) WriteHeader(code int) {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/metric.go b/vendor/github.com/prometheus/client_golang/prometheus/metric.go
index d4063d9..76035bc 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/metric.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/metric.go
@@ -79,20 +79,12 @@ type Opts struct {
 	// with the same fully-qualified name must have the same label names in
 	// their ConstLabels.
 	//
-	// Note that in most cases, labels have a value that varies during the
-	// lifetime of a process. Those labels are usually managed with a metric
-	// vector collector (like CounterVec, GaugeVec, UntypedVec). ConstLabels
-	// serve only special purposes. One is for the special case where the
-	// value of a label does not change during the lifetime of a process,
-	// e.g. if the revision of the running binary is put into a
-	// label. Another, more advanced purpose is if more than one Collector
-	// needs to collect Metrics with the same fully-qualified name. In that
-	// case, those Metrics must differ in the values of their
-	// ConstLabels. See the Collector examples.
-	//
-	// If the value of a label never changes (not even between binaries),
-	// that label most likely should not be a label at all (but part of the
-	// metric name).
+	// ConstLabels are only used rarely. In particular, do not use them to
+	// attach the same labels to all your metrics. Those use cases are
+	// better covered by target labels set by the scraping Prometheus
+	// server, or by one specific metric (e.g. a build_info or a
+	// machine_role metric). See also
+	// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels
 	ConstLabels Labels
 }
 
@@ -135,20 +127,6 @@ func (s LabelPairSorter) Less(i, j int) bool {
 	return s[i].GetName() < s[j].GetName()
 }
 
-type hashSorter []uint64
-
-func (s hashSorter) Len() int {
-	return len(s)
-}
-
-func (s hashSorter) Swap(i, j int) {
-	s[i], s[j] = s[j], s[i]
-}
-
-func (s hashSorter) Less(i, j int) bool {
-	return s[i] < s[j]
-}
-
 type invalidMetric struct {
 	desc *Desc
 	err  error
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/observer.go b/vendor/github.com/prometheus/client_golang/prometheus/observer.go
index b0520e8..5806cd0 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/observer.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/observer.go
@@ -45,6 +45,8 @@ type ObserverVec interface {
 	GetMetricWithLabelValues(lvs ...string) (Observer, error)
 	With(Labels) Observer
 	WithLabelValues(...string) Observer
+	CurryWith(Labels) (ObserverVec, error)
+	MustCurryWith(Labels) ObserverVec
 
 	Collector
 }
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/process_collector.go b/vendor/github.com/prometheus/client_golang/prometheus/process_collector.go
index 94b2553..b80adc6 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/process_collector.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/process_collector.go
@@ -16,7 +16,6 @@ package prometheus
 import "github.com/prometheus/procfs"
 
 type processCollector struct {
-	pid             int
 	collectFn       func(chan<- Metric)
 	pidFn           func() (int, error)
 	cpuTotal        *Desc
@@ -26,8 +25,11 @@ type processCollector struct {
 }
 
 // NewProcessCollector returns a collector which exports the current state of
-// process metrics including cpu, memory and file descriptor usage as well as
-// the process start time for the given process id under the given namespace.
+// process metrics including CPU, memory and file descriptor usage as well as
+// the process start time for the given process ID under the given namespace.
+//
+// Currently, the collector depends on a Linux-style proc filesystem and
+// therefore only exports metrics for Linux.
 func NewProcessCollector(pid int, namespace string) Collector {
 	return NewProcessCollectorPIDFn(
 		func() (int, error) { return pid, nil },
@@ -35,11 +37,8 @@ func NewProcessCollector(pid int, namespace string) Collector {
 	)
 }
 
-// NewProcessCollectorPIDFn returns a collector which exports the current state
-// of process metrics including cpu, memory and file descriptor usage as well
-// as the process start time under the given namespace. The given pidFn is
-// called on each collect and is used to determine the process to export
-// metrics for.
+// NewProcessCollectorPIDFn works like NewProcessCollector but the process ID is
+// determined on each collect anew by calling the given pidFn function.
 func NewProcessCollectorPIDFn(
 	pidFn func() (int, error),
 	namespace string,
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator.go b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator.go
index 5ee095b..9c1c66d 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator.go
@@ -102,10 +102,10 @@ func init() {
 		return d
 	}
 	pickDelegator[closeNotifier] = func(d *responseWriterDelegator) delegator { // 1
-		return closeNotifierDelegator{d}
+		return &closeNotifierDelegator{d}
 	}
 	pickDelegator[flusher] = func(d *responseWriterDelegator) delegator { // 2
-		return flusherDelegator{d}
+		return &flusherDelegator{d}
 	}
 	pickDelegator[flusher+closeNotifier] = func(d *responseWriterDelegator) delegator { // 3
 		return struct {
@@ -115,7 +115,7 @@ func init() {
 		}{d, &flusherDelegator{d}, &closeNotifierDelegator{d}}
 	}
 	pickDelegator[hijacker] = func(d *responseWriterDelegator) delegator { // 4
-		return hijackerDelegator{d}
+		return &hijackerDelegator{d}
 	}
 	pickDelegator[hijacker+closeNotifier] = func(d *responseWriterDelegator) delegator { // 5
 		return struct {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator_1_8.go b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator_1_8.go
index f4d386f..75a905e 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator_1_8.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator_1_8.go
@@ -28,7 +28,7 @@ func (d *pusherDelegator) Push(target string, opts *http.PushOptions) error {
 
 func init() {
 	pickDelegator[pusher] = func(d *responseWriterDelegator) delegator { // 16
-		return pusherDelegator{d}
+		return &pusherDelegator{d}
 	}
 	pickDelegator[pusher+closeNotifier] = func(d *responseWriterDelegator) delegator { // 17
 		return struct {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go
index 2d67f24..0135737 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go
@@ -39,6 +39,7 @@ import (
 	"net/http"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/prometheus/common/expfmt"
 
@@ -67,21 +68,51 @@ func giveBuf(buf *bytes.Buffer) {
 	bufPool.Put(buf)
 }
 
-// Handler returns an HTTP handler for the prometheus.DefaultGatherer. The
-// Handler uses the default HandlerOpts, i.e. report the first error as an HTTP
-// error, no error logging, and compression if requested by the client.
+// Handler returns an http.Handler for the prometheus.DefaultGatherer, using
+// default HandlerOpts, i.e. it reports the first error as an HTTP error, it has
+// no error logging, and it applies compression if requested by the client.
 //
-// If you want to create a Handler for the DefaultGatherer with different
-// HandlerOpts, create it with HandlerFor with prometheus.DefaultGatherer and
-// your desired HandlerOpts.
+// The returned http.Handler is already instrumented using the
+// InstrumentMetricHandler function and the prometheus.DefaultRegisterer. If you
+// create multiple http.Handlers by separate calls of the Handler function, the
+// metrics used for instrumentation will be shared between them, providing
+// global scrape counts.
+//
+// This function is meant to cover the bulk of basic use cases. If you are doing
+// anything that requires more customization (including using a non-default
+// Gatherer, different instrumentation, and non-default HandlerOpts), use the
+// HandlerFor function. See there for details.
 func Handler() http.Handler {
-	return HandlerFor(prometheus.DefaultGatherer, HandlerOpts{})
+	return InstrumentMetricHandler(
+		prometheus.DefaultRegisterer, HandlerFor(prometheus.DefaultGatherer, HandlerOpts{}),
+	)
 }
 
-// HandlerFor returns an http.Handler for the provided Gatherer. The behavior
-// of the Handler is defined by the provided HandlerOpts.
+// HandlerFor returns an uninstrumented http.Handler for the provided
+// Gatherer. The behavior of the Handler is defined by the provided
+// HandlerOpts. Thus, HandlerFor is useful to create http.Handlers for custom
+// Gatherers, with non-default HandlerOpts, and/or with custom (or no)
+// instrumentation. Use the InstrumentMetricHandler function to apply the same
+// kind of instrumentation as it is used by the Handler function.
 func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+	var inFlightSem chan struct{}
+	if opts.MaxRequestsInFlight > 0 {
+		inFlightSem = make(chan struct{}, opts.MaxRequestsInFlight)
+	}
+
+	h := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		if inFlightSem != nil {
+			select {
+			case inFlightSem <- struct{}{}: // All good, carry on.
+				defer func() { <-inFlightSem }()
+			default:
+				http.Error(w, fmt.Sprintf(
+					"Limit of concurrent requests reached (%d), try again later.", opts.MaxRequestsInFlight,
+				), http.StatusServiceUnavailable)
+				return
+			}
+		}
+
 		mfs, err := reg.Gather()
 		if err != nil {
 			if opts.ErrorLog != nil {
@@ -137,9 +168,70 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
 		if encoding != "" {
 			header.Set(contentEncodingHeader, encoding)
 		}
-		w.Write(buf.Bytes())
+		if _, err := w.Write(buf.Bytes()); err != nil && opts.ErrorLog != nil {
+			opts.ErrorLog.Println("error while sending encoded metrics:", err)
+		}
 		// TODO(beorn7): Consider streaming serving of metrics.
 	})
+
+	if opts.Timeout <= 0 {
+		return h
+	}
+	return http.TimeoutHandler(h, opts.Timeout, fmt.Sprintf(
+		"Exceeded configured timeout of %v.\n",
+		opts.Timeout,
+	))
+}
+
+// InstrumentMetricHandler is usually used with an http.Handler returned by the
+// HandlerFor function. It instruments the provided http.Handler with two
+// metrics: A counter vector "promhttp_metric_handler_requests_total" to count
+// scrapes partitioned by HTTP status code, and a gauge
+// "promhttp_metric_handler_requests_in_flight" to track the number of
+// simultaneous scrapes. This function idempotently registers collectors for
+// both metrics with the provided Registerer. It panics if the registration
+// fails. The provided metrics are useful to see how many scrapes hit the
+// monitored target (which could be from different Prometheus servers or other
+// scrapers), and how often they overlap (which would result in more than one
+// scrape in flight at the same time). Note that the scrapes-in-flight gauge
+// will contain the scrape by which it is exposed, while the scrape counter will
+// only get incremented after the scrape is complete (as only then the status
+// code is known). For tracking scrape durations, use the
+// "scrape_duration_seconds" gauge created by the Prometheus server upon each
+// scrape.
+func InstrumentMetricHandler(reg prometheus.Registerer, handler http.Handler) http.Handler {
+	cnt := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "promhttp_metric_handler_requests_total",
+			Help: "Total number of scrapes by HTTP status code.",
+		},
+		[]string{"code"},
+	)
+	// Initialize the most likely HTTP status codes.
+	cnt.WithLabelValues("200")
+	cnt.WithLabelValues("500")
+	cnt.WithLabelValues("503")
+	if err := reg.Register(cnt); err != nil {
+		if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+			cnt = are.ExistingCollector.(*prometheus.CounterVec)
+		} else {
+			panic(err)
+		}
+	}
+
+	gge := prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "promhttp_metric_handler_requests_in_flight",
+		Help: "Current number of scrapes being served.",
+	})
+	if err := reg.Register(gge); err != nil {
+		if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+			gge = are.ExistingCollector.(prometheus.Gauge)
+		} else {
+			panic(err)
+		}
+	}
+
+	return InstrumentHandlerCounter(cnt, InstrumentHandlerInFlight(gge, handler))
 }
 
 // HandlerErrorHandling defines how a Handler serving metrics will handle
@@ -183,6 +275,21 @@ type HandlerOpts struct {
 	// If DisableCompression is true, the handler will never compress the
 	// response, even if requested by the client.
 	DisableCompression bool
+	// The number of concurrent HTTP requests is limited to
+	// MaxRequestsInFlight. Additional requests are responded to with 503
+	// Service Unavailable and a suitable message in the body. If
+	// MaxRequestsInFlight is 0 or negative, no limit is applied.
+	MaxRequestsInFlight int
+	// If handling a request takes longer than Timeout, it is responded to
+	// with 503 ServiceUnavailable and a suitable Message. No timeout is
+	// applied if Timeout is 0 or negative. Note that with the current
+	// implementation, reaching the timeout simply ends the HTTP requests as
+	// described above (and even that only if sending of the body hasn't
+	// started yet), while the bulk work of gathering all the metrics keeps
+	// running in the background (with the eventual result to be thrown
+	// away). Until the implementation is improved, it is recommended to
+	// implement a separate timeout in potentially slow Collectors.
+	Timeout time.Duration
 }
 
 // decorateWriter wraps a writer to handle gzip compression if requested.  It
@@ -195,7 +302,7 @@ func decorateWriter(request *http.Request, writer io.Writer, compressionDisabled
 	header := request.Header.Get(acceptEncodingHeader)
 	parts := strings.Split(header, ",")
 	for _, part := range parts {
-		part := strings.TrimSpace(part)
+		part = strings.TrimSpace(part)
 		if part == "gzip" || strings.HasPrefix(part, "gzip;") {
 			return gzip.NewWriter(writer), "gzip"
 		}
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client.go b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client.go
index 65f9425..86fd564 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client.go
@@ -45,12 +45,11 @@ func InstrumentRoundTripperInFlight(gauge prometheus.Gauge, next http.RoundTripp
 
 // InstrumentRoundTripperCounter is a middleware that wraps the provided
 // http.RoundTripper to observe the request result with the provided CounterVec.
-// The CounterVec must have zero, one, or two labels. The only allowed label
-// names are "code" and "method". The function panics if any other instance
-// labels are provided. Partitioning of the CounterVec happens by HTTP status
-// code and/or HTTP method if the respective instance label names are present
-// in the CounterVec. For unpartitioned counting, use a CounterVec with
-// zero labels.
+// The CounterVec must have zero, one, or two non-const non-curried labels. For
+// those, the only allowed label names are "code" and "method". The function
+// panics otherwise. Partitioning of the CounterVec happens by HTTP status code
+// and/or HTTP method if the respective instance label names are present in the
+// CounterVec. For unpartitioned counting, use a CounterVec with zero labels.
 //
 // If the wrapped RoundTripper panics or returns a non-nil error, the Counter
 // is not incremented.
@@ -69,15 +68,15 @@ func InstrumentRoundTripperCounter(counter *prometheus.CounterVec, next http.Rou
 }
 
 // InstrumentRoundTripperDuration is a middleware that wraps the provided
-// http.RoundTripper to observe the request duration with the provided ObserverVec.
-// The ObserverVec must have zero, one, or two labels. The only allowed label
-// names are "code" and "method". The function panics if any other instance
-// labels are provided. The Observe method of the Observer in the ObserverVec
-// is called with the request duration in seconds. Partitioning happens by HTTP
-// status code and/or HTTP method if the respective instance label names are
-// present in the ObserverVec. For unpartitioned observations, use an
-// ObserverVec with zero labels. Note that partitioning of Histograms is
-// expensive and should be used judiciously.
+// http.RoundTripper to observe the request duration with the provided
+// ObserverVec.  The ObserverVec must have zero, one, or two non-const
+// non-curried labels. For those, the only allowed label names are "code" and
+// "method". The function panics otherwise. The Observe method of the Observer
+// in the ObserverVec is called with the request duration in
+// seconds. Partitioning happens by HTTP status code and/or HTTP method if the
+// respective instance label names are present in the ObserverVec. For
+// unpartitioned observations, use an ObserverVec with zero labels. Note that
+// partitioning of Histograms is expensive and should be used judiciously.
 //
 // If the wrapped RoundTripper panics or returns a non-nil error, no values are
 // reported.
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client_1_8.go b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client_1_8.go
index 0bd80c3..a034d1e 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client_1_8.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_client_1_8.go
@@ -81,8 +81,8 @@ func InstrumentRoundTripperTrace(it *InstrumentTrace, next http.RoundTripper) Ro
 				}
 			},
 			DNSDone: func(_ httptrace.DNSDoneInfo) {
-				if it.DNSStart != nil {
-					it.DNSStart(time.Since(start).Seconds())
+				if it.DNSDone != nil {
+					it.DNSDone(time.Since(start).Seconds())
 				}
 			},
 			ConnectStart: func(_, _ string) {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go
index 3d145ad..9db2438 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go
@@ -14,6 +14,7 @@
 package promhttp
 
 import (
+	"errors"
 	"net/http"
 	"strconv"
 	"strings"
@@ -42,10 +43,10 @@ func InstrumentHandlerInFlight(g prometheus.Gauge, next http.Handler) http.Handl
 
 // InstrumentHandlerDuration is a middleware that wraps the provided
 // http.Handler to observe the request duration with the provided ObserverVec.
-// The ObserverVec must have zero, one, or two labels. The only allowed label
-// names are "code" and "method". The function panics if any other instance
-// labels are provided. The Observe method of the Observer in the ObserverVec
-// is called with the request duration in seconds. Partitioning happens by HTTP
+// The ObserverVec must have zero, one, or two non-const non-curried labels. For
+// those, the only allowed label names are "code" and "method". The function
+// panics otherwise. The Observe method of the Observer in the ObserverVec is
+// called with the request duration in seconds. Partitioning happens by HTTP
 // status code and/or HTTP method if the respective instance label names are
 // present in the ObserverVec. For unpartitioned observations, use an
 // ObserverVec with zero labels. Note that partitioning of Histograms is
@@ -77,14 +78,13 @@ func InstrumentHandlerDuration(obs prometheus.ObserverVec, next http.Handler) ht
 	})
 }
 
-// InstrumentHandlerCounter is a middleware that wraps the provided
-// http.Handler to observe the request result with the provided CounterVec.
-// The CounterVec must have zero, one, or two labels. The only allowed label
-// names are "code" and "method". The function panics if any other instance
-// labels are provided. Partitioning of the CounterVec happens by HTTP status
-// code and/or HTTP method if the respective instance label names are present
-// in the CounterVec. For unpartitioned counting, use a CounterVec with
-// zero labels.
+// InstrumentHandlerCounter is a middleware that wraps the provided http.Handler
+// to observe the request result with the provided CounterVec.  The CounterVec
+// must have zero, one, or two non-const non-curried labels. For those, the only
+// allowed label names are "code" and "method". The function panics
+// otherwise. Partitioning of the CounterVec happens by HTTP status code and/or
+// HTTP method if the respective instance label names are present in the
+// CounterVec. For unpartitioned counting, use a CounterVec with zero labels.
 //
 // If the wrapped Handler does not set a status code, a status code of 200 is assumed.
 //
@@ -111,14 +111,13 @@ func InstrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler)
 // InstrumentHandlerTimeToWriteHeader is a middleware that wraps the provided
 // http.Handler to observe with the provided ObserverVec the request duration
 // until the response headers are written. The ObserverVec must have zero, one,
-// or two labels. The only allowed label names are "code" and "method". The
-// function panics if any other instance labels are provided. The Observe
-// method of the Observer in the ObserverVec is called with the request
-// duration in seconds. Partitioning happens by HTTP status code and/or HTTP
-// method if the respective instance label names are present in the
-// ObserverVec. For unpartitioned observations, use an ObserverVec with zero
-// labels. Note that partitioning of Histograms is expensive and should be used
-// judiciously.
+// or two non-const non-curried labels. For those, the only allowed label names
+// are "code" and "method". The function panics otherwise. The Observe method of
+// the Observer in the ObserverVec is called with the request duration in
+// seconds. Partitioning happens by HTTP status code and/or HTTP method if the
+// respective instance label names are present in the ObserverVec. For
+// unpartitioned observations, use an ObserverVec with zero labels. Note that
+// partitioning of Histograms is expensive and should be used judiciously.
 //
 // If the wrapped Handler panics before calling WriteHeader, no value is
 // reported.
@@ -140,15 +139,15 @@ func InstrumentHandlerTimeToWriteHeader(obs prometheus.ObserverVec, next http.Ha
 }
 
 // InstrumentHandlerRequestSize is a middleware that wraps the provided
-// http.Handler to observe the request size with the provided ObserverVec.
-// The ObserverVec must have zero, one, or two labels. The only allowed label
-// names are "code" and "method". The function panics if any other instance
-// labels are provided. The Observe method of the Observer in the ObserverVec
-// is called with the request size in bytes. Partitioning happens by HTTP
-// status code and/or HTTP method if the respective instance label names are
-// present in the ObserverVec. For unpartitioned observations, use an
-// ObserverVec with zero labels. Note that partitioning of Histograms is
-// expensive and should be used judiciously.
+// http.Handler to observe the request size with the provided ObserverVec.  The
+// ObserverVec must have zero, one, or two non-const non-curried labels. For
+// those, the only allowed label names are "code" and "method". The function
+// panics otherwise. The Observe method of the Observer in the ObserverVec is
+// called with the request size in bytes. Partitioning happens by HTTP status
+// code and/or HTTP method if the respective instance label names are present in
+// the ObserverVec. For unpartitioned observations, use an ObserverVec with zero
+// labels. Note that partitioning of Histograms is expensive and should be used
+// judiciously.
 //
 // If the wrapped Handler does not set a status code, a status code of 200 is assumed.
 //
@@ -175,15 +174,15 @@ func InstrumentHandlerRequestSize(obs prometheus.ObserverVec, next http.Handler)
 }
 
 // InstrumentHandlerResponseSize is a middleware that wraps the provided
-// http.Handler to observe the response size with the provided ObserverVec.
-// The ObserverVec must have zero, one, or two labels. The only allowed label
-// names are "code" and "method". The function panics if any other instance
-// labels are provided. The Observe method of the Observer in the ObserverVec
-// is called with the response size in bytes. Partitioning happens by HTTP
-// status code and/or HTTP method if the respective instance label names are
-// present in the ObserverVec. For unpartitioned observations, use an
-// ObserverVec with zero labels. Note that partitioning of Histograms is
-// expensive and should be used judiciously.
+// http.Handler to observe the response size with the provided ObserverVec.  The
+// ObserverVec must have zero, one, or two non-const non-curried labels. For
+// those, the only allowed label names are "code" and "method". The function
+// panics otherwise. The Observe method of the Observer in the ObserverVec is
+// called with the response size in bytes. Partitioning happens by HTTP status
+// code and/or HTTP method if the respective instance label names are present in
+// the ObserverVec. For unpartitioned observations, use an ObserverVec with zero
+// labels. Note that partitioning of Histograms is expensive and should be used
+// judiciously.
 //
 // If the wrapped Handler does not set a status code, a status code of 200 is assumed.
 //
@@ -204,9 +203,12 @@ func checkLabels(c prometheus.Collector) (code bool, method bool) {
 	// once Descriptors can have their dimensionality queried.
 	var (
 		desc *prometheus.Desc
+		m    prometheus.Metric
 		pm   dto.Metric
+		lvs  []string
 	)
 
+	// Get the Desc from the Collector.
 	descc := make(chan *prometheus.Desc, 1)
 	c.Describe(descc)
 
@@ -223,49 +225,54 @@ func checkLabels(c prometheus.Collector) (code bool, method bool) {
 
 	close(descc)
 
-	if _, err := prometheus.NewConstMetric(desc, prometheus.UntypedValue, 0); err == nil {
-		return
+	// Create a ConstMetric with the Desc. Since we don't know how many
+	// variable labels there are, try for as long as it needs.
+	for err := errors.New("dummy"); err != nil; lvs = append(lvs, magicString) {
+		m, err = prometheus.NewConstMetric(desc, prometheus.UntypedValue, 0, lvs...)
+	}
+
+	// Write out the metric into a proto message and look at the labels.
+	// If the value is not the magicString, it is a constLabel, which doesn't interest us.
+	// If the label is curried, it doesn't interest us.
+	// In all other cases, only "code" or "method" is allowed.
+	if err := m.Write(&pm); err != nil {
+		panic("error checking metric for labels")
 	}
-	if m, err := prometheus.NewConstMetric(desc, prometheus.UntypedValue, 0, magicString); err == nil {
-		if err := m.Write(&pm); err != nil {
-			panic("error checking metric for labels")
+	for _, label := range pm.Label {
+		name, value := label.GetName(), label.GetValue()
+		if value != magicString || isLabelCurried(c, name) {
+			continue
 		}
-		for _, label := range pm.Label {
-			name, value := label.GetName(), label.GetValue()
-			if value != magicString {
-				continue
-			}
-			switch name {
-			case "code":
-				code = true
-			case "method":
-				method = true
-			default:
-				panic("metric partitioned with non-supported labels")
-			}
-			return
+		switch name {
+		case "code":
+			code = true
+		case "method":
+			method = true
+		default:
+			panic("metric partitioned with non-supported labels")
 		}
-		panic("previously set label not found – this must never happen")
 	}
-	if m, err := prometheus.NewConstMetric(desc, prometheus.UntypedValue, 0, magicString, magicString); err == nil {
-		if err := m.Write(&pm); err != nil {
-			panic("error checking metric for labels")
+	return
+}
+
+func isLabelCurried(c prometheus.Collector, label string) bool {
+	// This is even hackier than the label test above.
+	// We essentially try to curry again and see if it works.
+	// But for that, we need to type-convert to the two
+	// types we use here, ObserverVec or *CounterVec.
+	switch v := c.(type) {
+	case *prometheus.CounterVec:
+		if _, err := v.CurryWith(prometheus.Labels{label: "dummy"}); err == nil {
+			return false
 		}
-		for _, label := range pm.Label {
-			name, value := label.GetName(), label.GetValue()
-			if value != magicString {
-				continue
-			}
-			if name == "code" || name == "method" {
-				continue
-			}
-			panic("metric partitioned with non-supported labels")
+	case prometheus.ObserverVec:
+		if _, err := v.CurryWith(prometheus.Labels{label: "dummy"}); err == nil {
+			return false
 		}
-		code = true
-		method = true
-		return
+	default:
+		panic("unsupported metric vec type")
 	}
-	panic("metric partitioned with non-supported labels")
+	return true
 }
 
 // emptyLabels is a one-time allocation for non-partitioned metrics to avoid
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/registry.go b/vendor/github.com/prometheus/client_golang/prometheus/registry.go
index c84a442..fdb7bad 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/registry.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/registry.go
@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"runtime"
 	"sort"
 	"sync"
 	"unicode/utf8"
@@ -36,13 +37,14 @@ const (
 // DefaultRegisterer and DefaultGatherer are the implementations of the
 // Registerer and Gatherer interface a number of convenience functions in this
 // package act on. Initially, both variables point to the same Registry, which
-// has a process collector (see NewProcessCollector) and a Go collector (see
-// NewGoCollector) already registered. This approach to keep default instances
-// as global state mirrors the approach of other packages in the Go standard
-// library. Note that there are caveats. Change the variables with caution and
-// only if you understand the consequences. Users who want to avoid global state
-// altogether should not use the convenience function and act on custom
-// instances instead.
+// has a process collector (currently on Linux only, see NewProcessCollector)
+// and a Go collector (see NewGoCollector, in particular the note about
+// stop-the-world implication with Go versions older than 1.9) already
+// registered. This approach to keep default instances as global state mirrors
+// the approach of other packages in the Go standard library. Note that there
+// are caveats. Change the variables with caution and only if you understand the
+// consequences. Users who want to avoid global state altogether should not use
+// the convenience functions and act on custom instances instead.
 var (
 	defaultRegistry              = NewRegistry()
 	DefaultRegisterer Registerer = defaultRegistry
@@ -124,15 +126,23 @@ type Registerer interface {
 type Gatherer interface {
 	// Gather calls the Collect method of the registered Collectors and then
 	// gathers the collected metrics into a lexicographically sorted slice
-	// of MetricFamily protobufs. Even if an error occurs, Gather attempts
-	// to gather as many metrics as possible. Hence, if a non-nil error is
-	// returned, the returned MetricFamily slice could be nil (in case of a
-	// fatal error that prevented any meaningful metric collection) or
-	// contain a number of MetricFamily protobufs, some of which might be
-	// incomplete, and some might be missing altogether. The returned error
-	// (which might be a MultiError) explains the details. In scenarios
-	// where complete collection is critical, the returned MetricFamily
-	// protobufs should be disregarded if the returned error is non-nil.
+	// of uniquely named MetricFamily protobufs. Gather ensures that the
+	// returned slice is valid and self-consistent so that it can be used
+	// for valid exposition. As an exception to the strict consistency
+	// requirements described for metric.Desc, Gather will tolerate
+	// different sets of label names for metrics of the same metric family.
+	//
+	// Even if an error occurs, Gather attempts to gather as many metrics as
+	// possible. Hence, if a non-nil error is returned, the returned
+	// MetricFamily slice could be nil (in case of a fatal error that
+	// prevented any meaningful metric collection) or contain a number of
+	// MetricFamily protobufs, some of which might be incomplete, and some
+	// might be missing altogether. The returned error (which might be a
+	// MultiError) explains the details. Note that this is mostly useful for
+	// debugging purposes. If the gathered protobufs are to be used for
+	// exposition in actual monitoring, it is almost always better to not
+	// expose an incomplete result and instead disregard the returned
+	// MetricFamily protobufs in case the returned error is non-nil.
 	Gather() ([]*dto.MetricFamily, error)
 }
 
@@ -202,6 +212,13 @@ func (errs MultiError) Error() string {
 	return buf.String()
 }
 
+// Append appends the provided error if it is not nil.
+func (errs *MultiError) Append(err error) {
+	if err != nil {
+		*errs = append(*errs, err)
+	}
+}
+
 // MaybeUnwrap returns nil if len(errs) is 0. It returns the first and only
 // contained error as error if len(errs is 1). In all other cases, it returns
 // the MultiError directly. This is helpful for returning a MultiError in a way
@@ -361,29 +378,18 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 	var (
 		metricChan        = make(chan Metric, capMetricChan)
 		metricHashes      = map[uint64]struct{}{}
-		dimHashes         = map[string]uint64{}
 		wg                sync.WaitGroup
 		errs              MultiError          // The collected errors to return in the end.
 		registeredDescIDs map[uint64]struct{} // Only used for pedantic checks
 	)
 
 	r.mtx.RLock()
+	goroutineBudget := len(r.collectorsByID)
 	metricFamiliesByName := make(map[string]*dto.MetricFamily, len(r.dimHashesByName))
-
-	// Scatter.
-	// (Collectors could be complex and slow, so we call them all at once.)
-	wg.Add(len(r.collectorsByID))
-	go func() {
-		wg.Wait()
-		close(metricChan)
-	}()
+	collectors := make(chan Collector, len(r.collectorsByID))
 	for _, collector := range r.collectorsByID {
-		go func(collector Collector) {
-			defer wg.Done()
-			collector.Collect(metricChan)
-		}(collector)
+		collectors <- collector
 	}
-
 	// In case pedantic checks are enabled, we have to copy the map before
 	// giving up the RLock.
 	if r.pedanticChecksEnabled {
@@ -392,127 +398,173 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 			registeredDescIDs[id] = struct{}{}
 		}
 	}
-
 	r.mtx.RUnlock()
 
+	wg.Add(goroutineBudget)
+
+	collectWorker := func() {
+		for {
+			select {
+			case collector := <-collectors:
+				collector.Collect(metricChan)
+				wg.Done()
+			default:
+				return
+			}
+		}
+	}
+
+	// Start the first worker now to make sure at least one is running.
+	go collectWorker()
+	goroutineBudget--
+
+	// Close the metricChan once all collectors are collected.
+	go func() {
+		wg.Wait()
+		close(metricChan)
+	}()
+
 	// Drain metricChan in case of premature return.
 	defer func() {
 		for range metricChan {
 		}
 	}()
 
-	// Gather.
-	for metric := range metricChan {
-		// This could be done concurrently, too, but it required locking
-		// of metricFamiliesByName (and of metricHashes if checks are
-		// enabled). Most likely not worth it.
-		desc := metric.Desc()
-		dtoMetric := &dto.Metric{}
-		if err := metric.Write(dtoMetric); err != nil {
-			errs = append(errs, fmt.Errorf(
-				"error collecting metric %v: %s", desc, err,
-			))
-			continue
-		}
-		metricFamily, ok := metricFamiliesByName[desc.fqName]
-		if ok {
-			if metricFamily.GetHelp() != desc.help {
-				errs = append(errs, fmt.Errorf(
-					"collected metric %s %s has help %q but should have %q",
-					desc.fqName, dtoMetric, desc.help, metricFamily.GetHelp(),
-				))
-				continue
+collectLoop:
+	for {
+		select {
+		case metric, ok := <-metricChan:
+			if !ok {
+				// metricChan is closed, we are done.
+				break collectLoop
 			}
-			// TODO(beorn7): Simplify switch once Desc has type.
-			switch metricFamily.GetType() {
-			case dto.MetricType_COUNTER:
-				if dtoMetric.Counter == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Counter",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_GAUGE:
-				if dtoMetric.Gauge == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Gauge",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_SUMMARY:
-				if dtoMetric.Summary == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Summary",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_UNTYPED:
-				if dtoMetric.Untyped == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be Untyped",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_HISTOGRAM:
-				if dtoMetric.Histogram == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Histogram",
-						desc.fqName, dtoMetric,
+			errs.Append(processMetric(
+				metric, metricFamiliesByName,
+				metricHashes,
+				registeredDescIDs,
+			))
+		default:
+			if goroutineBudget <= 0 || len(collectors) == 0 {
+				// All collectors are already being worked on or
+				// we have already as many goroutines started as
+				// there are collectors. Just process metrics
+				// from now on.
+				for metric := range metricChan {
+					errs.Append(processMetric(
+						metric, metricFamiliesByName,
+						metricHashes,
+						registeredDescIDs,
 					))
-					continue
 				}
-			default:
-				panic("encountered MetricFamily with invalid type")
-			}
-		} else {
-			metricFamily = &dto.MetricFamily{}
-			metricFamily.Name = proto.String(desc.fqName)
-			metricFamily.Help = proto.String(desc.help)
-			// TODO(beorn7): Simplify switch once Desc has type.
-			switch {
-			case dtoMetric.Gauge != nil:
-				metricFamily.Type = dto.MetricType_GAUGE.Enum()
-			case dtoMetric.Counter != nil:
-				metricFamily.Type = dto.MetricType_COUNTER.Enum()
-			case dtoMetric.Summary != nil:
-				metricFamily.Type = dto.MetricType_SUMMARY.Enum()
-			case dtoMetric.Untyped != nil:
-				metricFamily.Type = dto.MetricType_UNTYPED.Enum()
-			case dtoMetric.Histogram != nil:
-				metricFamily.Type = dto.MetricType_HISTOGRAM.Enum()
-			default:
-				errs = append(errs, fmt.Errorf(
-					"empty metric collected: %s", dtoMetric,
-				))
-				continue
+				break collectLoop
 			}
-			metricFamiliesByName[desc.fqName] = metricFamily
+			// Start more workers.
+			go collectWorker()
+			goroutineBudget--
+			runtime.Gosched()
 		}
-		if err := checkMetricConsistency(metricFamily, dtoMetric, metricHashes, dimHashes); err != nil {
-			errs = append(errs, err)
-			continue
+	}
+	return normalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
+}
+
+// processMetric is an internal helper method only used by the Gather method.
+func processMetric(
+	metric Metric,
+	metricFamiliesByName map[string]*dto.MetricFamily,
+	metricHashes map[uint64]struct{},
+	registeredDescIDs map[uint64]struct{},
+) error {
+	desc := metric.Desc()
+	dtoMetric := &dto.Metric{}
+	if err := metric.Write(dtoMetric); err != nil {
+		return fmt.Errorf("error collecting metric %v: %s", desc, err)
+	}
+	metricFamily, ok := metricFamiliesByName[desc.fqName]
+	if ok {
+		if metricFamily.GetHelp() != desc.help {
+			return fmt.Errorf(
+				"collected metric %s %s has help %q but should have %q",
+				desc.fqName, dtoMetric, desc.help, metricFamily.GetHelp(),
+			)
 		}
-		if r.pedanticChecksEnabled {
-			// Is the desc registered at all?
-			if _, exist := registeredDescIDs[desc.id]; !exist {
-				errs = append(errs, fmt.Errorf(
-					"collected metric %s %s with unregistered descriptor %s",
-					metricFamily.GetName(), dtoMetric, desc,
-				))
-				continue
+		// TODO(beorn7): Simplify switch once Desc has type.
+		switch metricFamily.GetType() {
+		case dto.MetricType_COUNTER:
+			if dtoMetric.Counter == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Counter",
+					desc.fqName, dtoMetric,
+				)
+			}
+		case dto.MetricType_GAUGE:
+			if dtoMetric.Gauge == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Gauge",
+					desc.fqName, dtoMetric,
+				)
 			}
-			if err := checkDescConsistency(metricFamily, dtoMetric, desc); err != nil {
-				errs = append(errs, err)
-				continue
+		case dto.MetricType_SUMMARY:
+			if dtoMetric.Summary == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Summary",
+					desc.fqName, dtoMetric,
+				)
 			}
+		case dto.MetricType_UNTYPED:
+			if dtoMetric.Untyped == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be Untyped",
+					desc.fqName, dtoMetric,
+				)
+			}
+		case dto.MetricType_HISTOGRAM:
+			if dtoMetric.Histogram == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Histogram",
+					desc.fqName, dtoMetric,
+				)
+			}
+		default:
+			panic("encountered MetricFamily with invalid type")
 		}
-		metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
+	} else {
+		metricFamily = &dto.MetricFamily{}
+		metricFamily.Name = proto.String(desc.fqName)
+		metricFamily.Help = proto.String(desc.help)
+		// TODO(beorn7): Simplify switch once Desc has type.
+		switch {
+		case dtoMetric.Gauge != nil:
+			metricFamily.Type = dto.MetricType_GAUGE.Enum()
+		case dtoMetric.Counter != nil:
+			metricFamily.Type = dto.MetricType_COUNTER.Enum()
+		case dtoMetric.Summary != nil:
+			metricFamily.Type = dto.MetricType_SUMMARY.Enum()
+		case dtoMetric.Untyped != nil:
+			metricFamily.Type = dto.MetricType_UNTYPED.Enum()
+		case dtoMetric.Histogram != nil:
+			metricFamily.Type = dto.MetricType_HISTOGRAM.Enum()
+		default:
+			return fmt.Errorf("empty metric collected: %s", dtoMetric)
+		}
+		metricFamiliesByName[desc.fqName] = metricFamily
 	}
-	return normalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
+	if err := checkMetricConsistency(metricFamily, dtoMetric, metricHashes); err != nil {
+		return err
+	}
+	if registeredDescIDs != nil {
+		// Is the desc registered at all?
+		if _, exist := registeredDescIDs[desc.id]; !exist {
+			return fmt.Errorf(
+				"collected metric %s %s with unregistered descriptor %s",
+				metricFamily.GetName(), dtoMetric, desc,
+			)
+		}
+		if err := checkDescConsistency(metricFamily, dtoMetric, desc); err != nil {
+			return err
+		}
+	}
+	metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
+	return nil
 }
 
 // Gatherers is a slice of Gatherer instances that implements the Gatherer
@@ -538,7 +590,6 @@ func (gs Gatherers) Gather() ([]*dto.MetricFamily, error) {
 	var (
 		metricFamiliesByName = map[string]*dto.MetricFamily{}
 		metricHashes         = map[uint64]struct{}{}
-		dimHashes            = map[string]uint64{}
 		errs                 MultiError // The collected errors to return in the end.
 	)
 
@@ -578,7 +629,7 @@ func (gs Gatherers) Gather() ([]*dto.MetricFamily, error) {
 				metricFamiliesByName[mf.GetName()] = existingMF
 			}
 			for _, m := range mf.Metric {
-				if err := checkMetricConsistency(existingMF, m, metricHashes, dimHashes); err != nil {
+				if err := checkMetricConsistency(existingMF, m, metricHashes); err != nil {
 					errs = append(errs, err)
 					continue
 				}
@@ -655,18 +706,13 @@ func normalizeMetricFamilies(metricFamiliesByName map[string]*dto.MetricFamily)
 }
 
 // checkMetricConsistency checks if the provided Metric is consistent with the
-// provided MetricFamily. It also hashed the Metric labels and the MetricFamily
+// provided MetricFamily. It also hashes the Metric labels and the MetricFamily
 // name. If the resulting hash is already in the provided metricHashes, an error
-// is returned. If not, it is added to metricHashes. The provided dimHashes maps
-// MetricFamily names to their dimHash (hashed sorted label names). If dimHashes
-// doesn't yet contain a hash for the provided MetricFamily, it is
-// added. Otherwise, an error is returned if the existing dimHashes in not equal
-// the calculated dimHash.
+// is returned. If not, it is added to metricHashes.
 func checkMetricConsistency(
 	metricFamily *dto.MetricFamily,
 	dtoMetric *dto.Metric,
 	metricHashes map[uint64]struct{},
-	dimHashes map[string]uint64,
 ) error {
 	// Type consistency with metric family.
 	if metricFamily.GetType() == dto.MetricType_GAUGE && dtoMetric.Gauge == nil ||
@@ -681,24 +727,23 @@ func checkMetricConsistency(
 	}
 
 	for _, labelPair := range dtoMetric.GetLabel() {
-		if !utf8.ValidString(*labelPair.Value) {
-			return fmt.Errorf("collected metric's label %s is not utf8: %#v", *labelPair.Name, *labelPair.Value)
+		if !utf8.ValidString(labelPair.GetValue()) {
+			return fmt.Errorf("collected metric's label %s is not utf8: %#v", labelPair.GetName(), labelPair.GetValue())
 		}
 	}
 
-	// Is the metric unique (i.e. no other metric with the same name and the same label values)?
+	// Is the metric unique (i.e. no other metric with the same name and the same labels)?
 	h := hashNew()
 	h = hashAdd(h, metricFamily.GetName())
 	h = hashAddByte(h, separatorByte)
-	dh := hashNew()
 	// Make sure label pairs are sorted. We depend on it for the consistency
 	// check.
 	sort.Sort(LabelPairSorter(dtoMetric.Label))
 	for _, lp := range dtoMetric.Label {
+		h = hashAdd(h, lp.GetName())
+		h = hashAddByte(h, separatorByte)
 		h = hashAdd(h, lp.GetValue())
 		h = hashAddByte(h, separatorByte)
-		dh = hashAdd(dh, lp.GetName())
-		dh = hashAddByte(dh, separatorByte)
 	}
 	if _, exists := metricHashes[h]; exists {
 		return fmt.Errorf(
@@ -706,16 +751,6 @@ func checkMetricConsistency(
 			metricFamily.GetName(), dtoMetric,
 		)
 	}
-	if dimHash, ok := dimHashes[metricFamily.GetName()]; ok {
-		if dimHash != dh {
-			return fmt.Errorf(
-				"collected metric %s %s has label dimensions inconsistent with previously collected metrics in the same metric family",
-				metricFamily.GetName(), dtoMetric,
-			)
-		}
-	} else {
-		dimHashes[metricFamily.GetName()] = dh
-	}
 	metricHashes[h] = struct{}{}
 	return nil
 }
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/summary.go b/vendor/github.com/prometheus/client_golang/prometheus/summary.go
index 21c031e..f7dc85b 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/summary.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/summary.go
@@ -101,23 +101,16 @@ type SummaryOpts struct {
 	// string.
 	Help string
 
-	// ConstLabels are used to attach fixed labels to this
-	// Summary. Summaries with the same fully-qualified name must have the
-	// same label names in their ConstLabels.
+	// ConstLabels are used to attach fixed labels to this metric. Metrics
+	// with the same fully-qualified name must have the same label names in
+	// their ConstLabels.
 	//
-	// Note that in most cases, labels have a value that varies during the
-	// lifetime of a process. Those labels are usually managed with a
-	// SummaryVec. ConstLabels serve only special purposes. One is for the
-	// special case where the value of a label does not change during the
-	// lifetime of a process, e.g. if the revision of the running binary is
-	// put into a label. Another, more advanced purpose is if more than one
-	// Collector needs to collect Summaries with the same fully-qualified
-	// name. In that case, those Summaries must differ in the values of
-	// their ConstLabels. See the Collector examples.
-	//
-	// If the value of a label never changes (not even between binaries),
-	// that label most likely should not be a label at all (but part of the
-	// metric name).
+	// ConstLabels are only used rarely. In particular, do not use them to
+	// attach the same labels to all your metrics. Those use cases are
+	// better covered by target labels set by the scraping Prometheus
+	// server, or by one specific metric (e.g. a build_info or a
+	// machine_role metric). See also
+	// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels
 	ConstLabels Labels
 
 	// Objectives defines the quantile rank estimates with their respective
@@ -433,13 +426,13 @@ func NewSummaryVec(opts SummaryOpts, labelNames []string) *SummaryVec {
 //
 // Keeping the Summary for later use is possible (and should be considered if
 // performance is critical), but keep in mind that Reset, DeleteLabelValues and
-// Delete can be used to delete the Summary from the SummaryVec. In that case, the
-// Summary will still exist, but it will not be exported anymore, even if a
+// Delete can be used to delete the Summary from the SummaryVec. In that case,
+// the Summary will still exist, but it will not be exported anymore, even if a
 // Summary with the same label values is created later. See also the CounterVec
 // example.
 //
 // An error is returned if the number of label values is not the same as the
-// number of VariableLabels in Desc.
+// number of VariableLabels in Desc (minus any curried labels).
 //
 // Note that for more than one label value, this method is prone to mistakes
 // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
@@ -447,8 +440,8 @@ func NewSummaryVec(opts SummaryOpts, labelNames []string) *SummaryVec {
 // latter has a much more readable (albeit more verbose) syntax, but it comes
 // with a performance overhead (for creating and processing the Labels map).
 // See also the GaugeVec example.
-func (m *SummaryVec) GetMetricWithLabelValues(lvs ...string) (Observer, error) {
-	metric, err := m.metricVec.getMetricWithLabelValues(lvs...)
+func (v *SummaryVec) GetMetricWithLabelValues(lvs ...string) (Observer, error) {
+	metric, err := v.metricVec.getMetricWithLabelValues(lvs...)
 	if metric != nil {
 		return metric.(Observer), err
 	}
@@ -462,13 +455,13 @@ func (m *SummaryVec) GetMetricWithLabelValues(lvs ...string) (Observer, error) {
 // the same as for GetMetricWithLabelValues.
 //
 // An error is returned if the number and names of the Labels are inconsistent
-// with those of the VariableLabels in Desc.
+// with those of the VariableLabels in Desc (minus any curried labels).
 //
 // This method is used for the same purpose as
 // GetMetricWithLabelValues(...string). See there for pros and cons of the two
 // methods.
-func (m *SummaryVec) GetMetricWith(labels Labels) (Observer, error) {
-	metric, err := m.metricVec.getMetricWith(labels)
+func (v *SummaryVec) GetMetricWith(labels Labels) (Observer, error) {
+	metric, err := v.metricVec.getMetricWith(labels)
 	if metric != nil {
 		return metric.(Observer), err
 	}
@@ -476,18 +469,57 @@ func (m *SummaryVec) GetMetricWith(labels Labels) (Observer, error) {
 }
 
 // WithLabelValues works as GetMetricWithLabelValues, but panics where
-// GetMetricWithLabelValues would have returned an error. By not returning an
-// error, WithLabelValues allows shortcuts like
+// GetMetricWithLabelValues would have returned an error. Not returning an
+// error allows shortcuts like
 //     myVec.WithLabelValues("404", "GET").Observe(42.21)
-func (m *SummaryVec) WithLabelValues(lvs ...string) Observer {
-	return m.metricVec.withLabelValues(lvs...).(Observer)
+func (v *SummaryVec) WithLabelValues(lvs ...string) Observer {
+	s, err := v.GetMetricWithLabelValues(lvs...)
+	if err != nil {
+		panic(err)
+	}
+	return s
 }
 
 // With works as GetMetricWith, but panics where GetMetricWithLabels would have
-// returned an error. By not returning an error, With allows shortcuts like
-//     myVec.With(Labels{"code": "404", "method": "GET"}).Observe(42.21)
-func (m *SummaryVec) With(labels Labels) Observer {
-	return m.metricVec.with(labels).(Observer)
+// returned an error. Not returning an error allows shortcuts like
+//     myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Observe(42.21)
+func (v *SummaryVec) With(labels Labels) Observer {
+	s, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return s
+}
+
+// CurryWith returns a vector curried with the provided labels, i.e. the
+// returned vector has those labels pre-set for all labeled operations performed
+// on it. The cardinality of the curried vector is reduced accordingly. The
+// order of the remaining labels stays the same (just with the curried labels
+// taken out of the sequence – which is relevant for the
+// (GetMetric)WithLabelValues methods). It is possible to curry a curried
+// vector, but only with labels not yet used for currying before.
+//
+// The metrics contained in the SummaryVec are shared between the curried and
+// uncurried vectors. They are just accessed differently. Curried and uncurried
+// vectors behave identically in terms of collection. Only one must be
+// registered with a given registry (usually the uncurried version). The Reset
+// method deletes all metrics, even if called on a curried vector.
+func (v *SummaryVec) CurryWith(labels Labels) (ObserverVec, error) {
+	vec, err := v.curryWith(labels)
+	if vec != nil {
+		return &SummaryVec{vec}, err
+	}
+	return nil, err
+}
+
+// MustCurryWith works as CurryWith but panics where CurryWith would have
+// returned an error.
+func (v *SummaryVec) MustCurryWith(labels Labels) ObserverVec {
+	vec, err := v.CurryWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return vec
 }
 
 type constSummary struct {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/value.go b/vendor/github.com/prometheus/client_golang/prometheus/value.go
index 4a9cca6..9fb7eab 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/value.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/value.go
@@ -15,10 +15,7 @@ package prometheus
 
 import (
 	"fmt"
-	"math"
 	"sort"
-	"sync/atomic"
-	"time"
 
 	dto "github.com/prometheus/client_model/go"
 
@@ -36,79 +33,6 @@ const (
 	UntypedValue
 )
 
-// value is a generic metric for simple values. It implements Metric, Collector,
-// Counter, Gauge, and Untyped. Its effective type is determined by
-// ValueType. This is a low-level building block used by the library to back the
-// implementations of Counter, Gauge, and Untyped.
-type value struct {
-	// valBits contains the bits of the represented float64 value. It has
-	// to go first in the struct to guarantee alignment for atomic
-	// operations.  http://golang.org/pkg/sync/atomic/#pkg-note-BUG
-	valBits uint64
-
-	selfCollector
-
-	desc       *Desc
-	valType    ValueType
-	labelPairs []*dto.LabelPair
-}
-
-// newValue returns a newly allocated value with the given Desc, ValueType,
-// sample value and label values. It panics if the number of label
-// values is different from the number of variable labels in Desc.
-func newValue(desc *Desc, valueType ValueType, val float64, labelValues ...string) *value {
-	if len(labelValues) != len(desc.variableLabels) {
-		panic(errInconsistentCardinality)
-	}
-	result := &value{
-		desc:       desc,
-		valType:    valueType,
-		valBits:    math.Float64bits(val),
-		labelPairs: makeLabelPairs(desc, labelValues),
-	}
-	result.init(result)
-	return result
-}
-
-func (v *value) Desc() *Desc {
-	return v.desc
-}
-
-func (v *value) Set(val float64) {
-	atomic.StoreUint64(&v.valBits, math.Float64bits(val))
-}
-
-func (v *value) SetToCurrentTime() {
-	v.Set(float64(time.Now().UnixNano()) / 1e9)
-}
-
-func (v *value) Inc() {
-	v.Add(1)
-}
-
-func (v *value) Dec() {
-	v.Add(-1)
-}
-
-func (v *value) Add(val float64) {
-	for {
-		oldBits := atomic.LoadUint64(&v.valBits)
-		newBits := math.Float64bits(math.Float64frombits(oldBits) + val)
-		if atomic.CompareAndSwapUint64(&v.valBits, oldBits, newBits) {
-			return
-		}
-	}
-}
-
-func (v *value) Sub(val float64) {
-	v.Add(val * -1)
-}
-
-func (v *value) Write(out *dto.Metric) error {
-	val := math.Float64frombits(atomic.LoadUint64(&v.valBits))
-	return populateMetric(v.valType, val, v.labelPairs, out)
-}
-
 // valueFunc is a generic metric for simple values retrieved on collect time
 // from a function. It implements Metric and Collector. Its effective type is
 // determined by ValueType. This is a low-level building block used by the
@@ -228,9 +152,7 @@ func makeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair {
 			Value: proto.String(labelValues[i]),
 		})
 	}
-	for _, lp := range desc.constLabelPairs {
-		labelPairs = append(labelPairs, lp)
-	}
+	labelPairs = append(labelPairs, desc.constLabelPairs...)
 	sort.Sort(LabelPairSorter(labelPairs))
 	return labelPairs
 }
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/vec.go b/vendor/github.com/prometheus/client_golang/prometheus/vec.go
index 65d13fe..14ed9e8 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/vec.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/vec.go
@@ -23,88 +23,31 @@ import (
 // metricVec is a Collector to bundle metrics of the same name that differ in
 // their label values. metricVec is not used directly (and therefore
 // unexported). It is used as a building block for implementations of vectors of
-// a given metric type, like GaugeVec, CounterVec, SummaryVec, HistogramVec, and
-// UntypedVec.
+// a given metric type, like GaugeVec, CounterVec, SummaryVec, and HistogramVec.
+// It also handles label currying. It uses basicMetricVec internally.
 type metricVec struct {
-	mtx      sync.RWMutex // Protects the children.
-	children map[uint64][]metricWithLabelValues
-	desc     *Desc
+	*metricMap
 
-	newMetric   func(labelValues ...string) Metric
-	hashAdd     func(h uint64, s string) uint64 // replace hash function for testing collision handling
+	curry []curriedLabelValue
+
+	// hashAdd and hashAddByte can be replaced for testing collision handling.
+	hashAdd     func(h uint64, s string) uint64
 	hashAddByte func(h uint64, b byte) uint64
 }
 
 // newMetricVec returns an initialized metricVec.
 func newMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *metricVec {
 	return &metricVec{
-		children:    map[uint64][]metricWithLabelValues{},
-		desc:        desc,
-		newMetric:   newMetric,
+		metricMap: &metricMap{
+			metrics:   map[uint64][]metricWithLabelValues{},
+			desc:      desc,
+			newMetric: newMetric,
+		},
 		hashAdd:     hashAdd,
 		hashAddByte: hashAddByte,
 	}
 }
 
-// metricWithLabelValues provides the metric and its label values for
-// disambiguation on hash collision.
-type metricWithLabelValues struct {
-	values []string
-	metric Metric
-}
-
-// Describe implements Collector. The length of the returned slice
-// is always one.
-func (m *metricVec) Describe(ch chan<- *Desc) {
-	ch <- m.desc
-}
-
-// Collect implements Collector.
-func (m *metricVec) Collect(ch chan<- Metric) {
-	m.mtx.RLock()
-	defer m.mtx.RUnlock()
-
-	for _, metrics := range m.children {
-		for _, metric := range metrics {
-			ch <- metric.metric
-		}
-	}
-}
-
-func (m *metricVec) getMetricWithLabelValues(lvs ...string) (Metric, error) {
-	h, err := m.hashLabelValues(lvs)
-	if err != nil {
-		return nil, err
-	}
-
-	return m.getOrCreateMetricWithLabelValues(h, lvs), nil
-}
-
-func (m *metricVec) getMetricWith(labels Labels) (Metric, error) {
-	h, err := m.hashLabels(labels)
-	if err != nil {
-		return nil, err
-	}
-
-	return m.getOrCreateMetricWithLabels(h, labels), nil
-}
-
-func (m *metricVec) withLabelValues(lvs ...string) Metric {
-	metric, err := m.getMetricWithLabelValues(lvs...)
-	if err != nil {
-		panic(err)
-	}
-	return metric
-}
-
-func (m *metricVec) with(labels Labels) Metric {
-	metric, err := m.getMetricWith(labels)
-	if err != nil {
-		panic(err)
-	}
-	return metric
-}
-
 // DeleteLabelValues removes the metric where the variable labels are the same
 // as those passed in as labels (same order as the VariableLabels in Desc). It
 // returns true if a metric was deleted.
@@ -121,14 +64,12 @@ func (m *metricVec) with(labels Labels) Metric {
 // with a performance overhead (for creating and processing the Labels map).
 // See also the CounterVec example.
 func (m *metricVec) DeleteLabelValues(lvs ...string) bool {
-	m.mtx.Lock()
-	defer m.mtx.Unlock()
-
 	h, err := m.hashLabelValues(lvs)
 	if err != nil {
 		return false
 	}
-	return m.deleteByHashWithLabelValues(h, lvs)
+
+	return m.metricMap.deleteByHashWithLabelValues(h, lvs, m.curry)
 }
 
 // Delete deletes the metric where the variable labels are the same as those
@@ -142,35 +83,190 @@ func (m *metricVec) DeleteLabelValues(lvs ...string) bool {
 // This method is used for the same purpose as DeleteLabelValues(...string). See
 // there for pros and cons of the two methods.
 func (m *metricVec) Delete(labels Labels) bool {
-	m.mtx.Lock()
-	defer m.mtx.Unlock()
-
 	h, err := m.hashLabels(labels)
 	if err != nil {
 		return false
 	}
 
-	return m.deleteByHashWithLabels(h, labels)
+	return m.metricMap.deleteByHashWithLabels(h, labels, m.curry)
+}
+
+func (m *metricVec) curryWith(labels Labels) (*metricVec, error) {
+	var (
+		newCurry []curriedLabelValue
+		oldCurry = m.curry
+		iCurry   int
+	)
+	for i, label := range m.desc.variableLabels {
+		val, ok := labels[label]
+		if iCurry < len(oldCurry) && oldCurry[iCurry].index == i {
+			if ok {
+				return nil, fmt.Errorf("label name %q is already curried", label)
+			}
+			newCurry = append(newCurry, oldCurry[iCurry])
+			iCurry++
+		} else {
+			if !ok {
+				continue // Label stays uncurried.
+			}
+			newCurry = append(newCurry, curriedLabelValue{i, val})
+		}
+	}
+	if l := len(oldCurry) + len(labels) - len(newCurry); l > 0 {
+		return nil, fmt.Errorf("%d unknown label(s) found during currying", l)
+	}
+
+	return &metricVec{
+		metricMap:   m.metricMap,
+		curry:       newCurry,
+		hashAdd:     m.hashAdd,
+		hashAddByte: m.hashAddByte,
+	}, nil
+}
+
+func (m *metricVec) getMetricWithLabelValues(lvs ...string) (Metric, error) {
+	h, err := m.hashLabelValues(lvs)
+	if err != nil {
+		return nil, err
+	}
+
+	return m.metricMap.getOrCreateMetricWithLabelValues(h, lvs, m.curry), nil
+}
+
+func (m *metricVec) getMetricWith(labels Labels) (Metric, error) {
+	h, err := m.hashLabels(labels)
+	if err != nil {
+		return nil, err
+	}
+
+	return m.metricMap.getOrCreateMetricWithLabels(h, labels, m.curry), nil
+}
+
+func (m *metricVec) hashLabelValues(vals []string) (uint64, error) {
+	if err := validateLabelValues(vals, len(m.desc.variableLabels)-len(m.curry)); err != nil {
+		return 0, err
+	}
+
+	var (
+		h             = hashNew()
+		curry         = m.curry
+		iVals, iCurry int
+	)
+	for i := 0; i < len(m.desc.variableLabels); i++ {
+		if iCurry < len(curry) && curry[iCurry].index == i {
+			h = m.hashAdd(h, curry[iCurry].value)
+			iCurry++
+		} else {
+			h = m.hashAdd(h, vals[iVals])
+			iVals++
+		}
+		h = m.hashAddByte(h, model.SeparatorByte)
+	}
+	return h, nil
+}
+
+func (m *metricVec) hashLabels(labels Labels) (uint64, error) {
+	if err := validateValuesInLabels(labels, len(m.desc.variableLabels)-len(m.curry)); err != nil {
+		return 0, err
+	}
+
+	var (
+		h      = hashNew()
+		curry  = m.curry
+		iCurry int
+	)
+	for i, label := range m.desc.variableLabels {
+		val, ok := labels[label]
+		if iCurry < len(curry) && curry[iCurry].index == i {
+			if ok {
+				return 0, fmt.Errorf("label name %q is already curried", label)
+			}
+			h = m.hashAdd(h, curry[iCurry].value)
+			iCurry++
+		} else {
+			if !ok {
+				return 0, fmt.Errorf("label name %q missing in label map", label)
+			}
+			h = m.hashAdd(h, val)
+		}
+		h = m.hashAddByte(h, model.SeparatorByte)
+	}
+	return h, nil
+}
+
+// metricWithLabelValues provides the metric and its label values for
+// disambiguation on hash collision.
+type metricWithLabelValues struct {
+	values []string
+	metric Metric
+}
+
+// curriedLabelValue sets the curried value for a label at the given index.
+type curriedLabelValue struct {
+	index int
+	value string
+}
+
+// metricMap is a helper for metricVec and shared between differently curried
+// metricVecs.
+type metricMap struct {
+	mtx       sync.RWMutex // Protects metrics.
+	metrics   map[uint64][]metricWithLabelValues
+	desc      *Desc
+	newMetric func(labelValues ...string) Metric
+}
+
+// Describe implements Collector. It will send exactly one Desc to the provided
+// channel.
+func (m *metricMap) Describe(ch chan<- *Desc) {
+	ch <- m.desc
+}
+
+// Collect implements Collector.
+func (m *metricMap) Collect(ch chan<- Metric) {
+	m.mtx.RLock()
+	defer m.mtx.RUnlock()
+
+	for _, metrics := range m.metrics {
+		for _, metric := range metrics {
+			ch <- metric.metric
+		}
+	}
+}
+
+// Reset deletes all metrics in this vector.
+func (m *metricMap) Reset() {
+	m.mtx.Lock()
+	defer m.mtx.Unlock()
+
+	for h := range m.metrics {
+		delete(m.metrics, h)
+	}
 }
 
 // deleteByHashWithLabelValues removes the metric from the hash bucket h. If
 // there are multiple matches in the bucket, use lvs to select a metric and
 // remove only that metric.
-func (m *metricVec) deleteByHashWithLabelValues(h uint64, lvs []string) bool {
-	metrics, ok := m.children[h]
+func (m *metricMap) deleteByHashWithLabelValues(
+	h uint64, lvs []string, curry []curriedLabelValue,
+) bool {
+	m.mtx.Lock()
+	defer m.mtx.Unlock()
+
+	metrics, ok := m.metrics[h]
 	if !ok {
 		return false
 	}
 
-	i := m.findMetricWithLabelValues(metrics, lvs)
+	i := findMetricWithLabelValues(metrics, lvs, curry)
 	if i >= len(metrics) {
 		return false
 	}
 
 	if len(metrics) > 1 {
-		m.children[h] = append(metrics[:i], metrics[i+1:]...)
+		m.metrics[h] = append(metrics[:i], metrics[i+1:]...)
 	} else {
-		delete(m.children, h)
+		delete(m.metrics, h)
 	}
 	return true
 }
@@ -178,71 +274,38 @@ func (m *metricVec) deleteByHashWithLabelValues(h uint64, lvs []string) bool {
 // deleteByHashWithLabels removes the metric from the hash bucket h. If there
 // are multiple matches in the bucket, use lvs to select a metric and remove
 // only that metric.
-func (m *metricVec) deleteByHashWithLabels(h uint64, labels Labels) bool {
-	metrics, ok := m.children[h]
+func (m *metricMap) deleteByHashWithLabels(
+	h uint64, labels Labels, curry []curriedLabelValue,
+) bool {
+	m.mtx.Lock()
+	defer m.mtx.Unlock()
+
+	metrics, ok := m.metrics[h]
 	if !ok {
 		return false
 	}
-	i := m.findMetricWithLabels(metrics, labels)
+	i := findMetricWithLabels(m.desc, metrics, labels, curry)
 	if i >= len(metrics) {
 		return false
 	}
 
 	if len(metrics) > 1 {
-		m.children[h] = append(metrics[:i], metrics[i+1:]...)
+		m.metrics[h] = append(metrics[:i], metrics[i+1:]...)
 	} else {
-		delete(m.children, h)
+		delete(m.metrics, h)
 	}
 	return true
 }
 
-// Reset deletes all metrics in this vector.
-func (m *metricVec) Reset() {
-	m.mtx.Lock()
-	defer m.mtx.Unlock()
-
-	for h := range m.children {
-		delete(m.children, h)
-	}
-}
-
-func (m *metricVec) hashLabelValues(vals []string) (uint64, error) {
-	if err := validateLabelValues(vals, len(m.desc.variableLabels)); err != nil {
-		return 0, err
-	}
-
-	h := hashNew()
-	for _, val := range vals {
-		h = m.hashAdd(h, val)
-		h = m.hashAddByte(h, model.SeparatorByte)
-	}
-	return h, nil
-}
-
-func (m *metricVec) hashLabels(labels Labels) (uint64, error) {
-	if err := validateValuesInLabels(labels, len(m.desc.variableLabels)); err != nil {
-		return 0, err
-	}
-
-	h := hashNew()
-	for _, label := range m.desc.variableLabels {
-		val, ok := labels[label]
-		if !ok {
-			return 0, fmt.Errorf("label name %q missing in label map", label)
-		}
-		h = m.hashAdd(h, val)
-		h = m.hashAddByte(h, model.SeparatorByte)
-	}
-	return h, nil
-}
-
 // getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
 // or creates it and returns the new one.
 //
 // This function holds the mutex.
-func (m *metricVec) getOrCreateMetricWithLabelValues(hash uint64, lvs []string) Metric {
+func (m *metricMap) getOrCreateMetricWithLabelValues(
+	hash uint64, lvs []string, curry []curriedLabelValue,
+) Metric {
 	m.mtx.RLock()
-	metric, ok := m.getMetricWithHashAndLabelValues(hash, lvs)
+	metric, ok := m.getMetricWithHashAndLabelValues(hash, lvs, curry)
 	m.mtx.RUnlock()
 	if ok {
 		return metric
@@ -250,13 +313,11 @@ func (m *metricVec) getOrCreateMetricWithLabelValues(hash uint64, lvs []string)
 
 	m.mtx.Lock()
 	defer m.mtx.Unlock()
-	metric, ok = m.getMetricWithHashAndLabelValues(hash, lvs)
+	metric, ok = m.getMetricWithHashAndLabelValues(hash, lvs, curry)
 	if !ok {
-		// Copy to avoid allocation in case wo don't go down this code path.
-		copiedLVs := make([]string, len(lvs))
-		copy(copiedLVs, lvs)
-		metric = m.newMetric(copiedLVs...)
-		m.children[hash] = append(m.children[hash], metricWithLabelValues{values: copiedLVs, metric: metric})
+		inlinedLVs := inlineLabelValues(lvs, curry)
+		metric = m.newMetric(inlinedLVs...)
+		m.metrics[hash] = append(m.metrics[hash], metricWithLabelValues{values: inlinedLVs, metric: metric})
 	}
 	return metric
 }
@@ -265,9 +326,11 @@ func (m *metricVec) getOrCreateMetricWithLabelValues(hash uint64, lvs []string)
 // or creates it and returns the new one.
 //
 // This function holds the mutex.
-func (m *metricVec) getOrCreateMetricWithLabels(hash uint64, labels Labels) Metric {
+func (m *metricMap) getOrCreateMetricWithLabels(
+	hash uint64, labels Labels, curry []curriedLabelValue,
+) Metric {
 	m.mtx.RLock()
-	metric, ok := m.getMetricWithHashAndLabels(hash, labels)
+	metric, ok := m.getMetricWithHashAndLabels(hash, labels, curry)
 	m.mtx.RUnlock()
 	if ok {
 		return metric
@@ -275,21 +338,23 @@ func (m *metricVec) getOrCreateMetricWithLabels(hash uint64, labels Labels) Metr
 
 	m.mtx.Lock()
 	defer m.mtx.Unlock()
-	metric, ok = m.getMetricWithHashAndLabels(hash, labels)
+	metric, ok = m.getMetricWithHashAndLabels(hash, labels, curry)
 	if !ok {
-		lvs := m.extractLabelValues(labels)
+		lvs := extractLabelValues(m.desc, labels, curry)
 		metric = m.newMetric(lvs...)
-		m.children[hash] = append(m.children[hash], metricWithLabelValues{values: lvs, metric: metric})
+		m.metrics[hash] = append(m.metrics[hash], metricWithLabelValues{values: lvs, metric: metric})
 	}
 	return metric
 }
 
 // getMetricWithHashAndLabelValues gets a metric while handling possible
 // collisions in the hash space. Must be called while holding the read mutex.
-func (m *metricVec) getMetricWithHashAndLabelValues(h uint64, lvs []string) (Metric, bool) {
-	metrics, ok := m.children[h]
+func (m *metricMap) getMetricWithHashAndLabelValues(
+	h uint64, lvs []string, curry []curriedLabelValue,
+) (Metric, bool) {
+	metrics, ok := m.metrics[h]
 	if ok {
-		if i := m.findMetricWithLabelValues(metrics, lvs); i < len(metrics) {
+		if i := findMetricWithLabelValues(metrics, lvs, curry); i < len(metrics) {
 			return metrics[i].metric, true
 		}
 	}
@@ -298,10 +363,12 @@ func (m *metricVec) getMetricWithHashAndLabelValues(h uint64, lvs []string) (Met
 
 // getMetricWithHashAndLabels gets a metric while handling possible collisions in
 // the hash space. Must be called while holding read mutex.
-func (m *metricVec) getMetricWithHashAndLabels(h uint64, labels Labels) (Metric, bool) {
-	metrics, ok := m.children[h]
+func (m *metricMap) getMetricWithHashAndLabels(
+	h uint64, labels Labels, curry []curriedLabelValue,
+) (Metric, bool) {
+	metrics, ok := m.metrics[h]
 	if ok {
-		if i := m.findMetricWithLabels(metrics, labels); i < len(metrics) {
+		if i := findMetricWithLabels(m.desc, metrics, labels, curry); i < len(metrics) {
 			return metrics[i].metric, true
 		}
 	}
@@ -310,9 +377,11 @@ func (m *metricVec) getMetricWithHashAndLabels(h uint64, labels Labels) (Metric,
 
 // findMetricWithLabelValues returns the index of the matching metric or
 // len(metrics) if not found.
-func (m *metricVec) findMetricWithLabelValues(metrics []metricWithLabelValues, lvs []string) int {
+func findMetricWithLabelValues(
+	metrics []metricWithLabelValues, lvs []string, curry []curriedLabelValue,
+) int {
 	for i, metric := range metrics {
-		if m.matchLabelValues(metric.values, lvs) {
+		if matchLabelValues(metric.values, lvs, curry) {
 			return i
 		}
 	}
@@ -321,32 +390,51 @@ func (m *metricVec) findMetricWithLabelValues(metrics []metricWithLabelValues, l
 
 // findMetricWithLabels returns the index of the matching metric or len(metrics)
 // if not found.
-func (m *metricVec) findMetricWithLabels(metrics []metricWithLabelValues, labels Labels) int {
+func findMetricWithLabels(
+	desc *Desc, metrics []metricWithLabelValues, labels Labels, curry []curriedLabelValue,
+) int {
 	for i, metric := range metrics {
-		if m.matchLabels(metric.values, labels) {
+		if matchLabels(desc, metric.values, labels, curry) {
 			return i
 		}
 	}
 	return len(metrics)
 }
 
-func (m *metricVec) matchLabelValues(values []string, lvs []string) bool {
-	if len(values) != len(lvs) {
+func matchLabelValues(values []string, lvs []string, curry []curriedLabelValue) bool {
+	if len(values) != len(lvs)+len(curry) {
 		return false
 	}
+	var iLVs, iCurry int
 	for i, v := range values {
-		if v != lvs[i] {
+		if iCurry < len(curry) && curry[iCurry].index == i {
+			if v != curry[iCurry].value {
+				return false
+			}
+			iCurry++
+			continue
+		}
+		if v != lvs[iLVs] {
 			return false
 		}
+		iLVs++
 	}
 	return true
 }
 
-func (m *metricVec) matchLabels(values []string, labels Labels) bool {
-	if len(labels) != len(values) {
+func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabelValue) bool {
+	if len(values) != len(labels)+len(curry) {
 		return false
 	}
-	for i, k := range m.desc.variableLabels {
+	iCurry := 0
+	for i, k := range desc.variableLabels {
+		if iCurry < len(curry) && curry[iCurry].index == i {
+			if values[i] != curry[iCurry].value {
+				return false
+			}
+			iCurry++
+			continue
+		}
 		if values[i] != labels[k] {
 			return false
 		}
@@ -354,10 +442,31 @@ func (m *metricVec) matchLabels(values []string, labels Labels) bool {
 	return true
 }
 
-func (m *metricVec) extractLabelValues(labels Labels) []string {
-	labelValues := make([]string, len(labels))
-	for i, k := range m.desc.variableLabels {
+func extractLabelValues(desc *Desc, labels Labels, curry []curriedLabelValue) []string {
+	labelValues := make([]string, len(labels)+len(curry))
+	iCurry := 0
+	for i, k := range desc.variableLabels {
+		if iCurry < len(curry) && curry[iCurry].index == i {
+			labelValues[i] = curry[iCurry].value
+			iCurry++
+			continue
+		}
 		labelValues[i] = labels[k]
 	}
 	return labelValues
 }
+
+func inlineLabelValues(lvs []string, curry []curriedLabelValue) []string {
+	labelValues := make([]string, len(lvs)+len(curry))
+	var iCurry, iLVs int
+	for i := range labelValues {
+		if iCurry < len(curry) && curry[iCurry].index == i {
+			labelValues[i] = curry[iCurry].value
+			iCurry++
+			continue
+		}
+		labelValues[i] = lvs[iLVs]
+		iLVs++
+	}
+	return labelValues
+}
-- 
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