1 files changed, 340 insertions, 0 deletions
diff --git a/vendor/google.golang.org/grpc/balancer.go b/vendor/google.golang.org/grpc/balancer.go
new file mode 100644
index 0000000..348bf97
--- /dev/null
+++ b/vendor/google.golang.org/grpc/balancer.go
@@ -0,0 +1,340 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package grpc
+
+import (
+	"fmt"
+	"sync"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/naming"
+	"google.golang.org/grpc/transport"
+)
+
+// Address represents a server the client connects to.
+// This is the EXPERIMENTAL API and may be changed or extended in the future.
+type Address struct {
+	// Addr is the server address on which a connection will be established.
+	Addr string
+	// Metadata is the information associated with Addr, which may be used
+	// to make load balancing decision.
+	Metadata interface{}
+}
+
+// BalancerGetOptions configures a Get call.
+// This is the EXPERIMENTAL API and may be changed or extended in the future.
+type BalancerGetOptions struct {
+	// BlockingWait specifies whether Get should block when there is no
+	// connected address.
+	BlockingWait bool
+}
+
+// Balancer chooses network addresses for RPCs.
+// This is the EXPERIMENTAL API and may be changed or extended in the future.
+type Balancer interface {
+	// Start does the initialization work to bootstrap a Balancer. For example,
+	// this function may start the name resolution and watch the updates. It will
+	// be called when dialing.
+	Start(target string) error
+	// Up informs the Balancer that gRPC has a connection to the server at
+	// addr. It returns down which is called once the connection to addr gets
+	// lost or closed.
+	// TODO: It is not clear how to construct and take advantage the meaningful error
+	// parameter for down. Need realistic demands to guide.
+	Up(addr Address) (down func(error))
+	// Get gets the address of a server for the RPC corresponding to ctx.
+	// i) If it returns a connected address, gRPC internals issues the RPC on the
+	// connection to this address;
+	// ii) If it returns an address on which the connection is under construction
+	// (initiated by Notify(...)) but not connected, gRPC internals
+	//  * fails RPC if the RPC is fail-fast and connection is in the TransientFailure or
+	//  Shutdown state;
+	//  or
+	//  * issues RPC on the connection otherwise.
+	// iii) If it returns an address on which the connection does not exist, gRPC
+	// internals treats it as an error and will fail the corresponding RPC.
+	//
+	// Therefore, the following is the recommended rule when writing a custom Balancer.
+	// If opts.BlockingWait is true, it should return a connected address or
+	// block if there is no connected address. It should respect the timeout or
+	// cancellation of ctx when blocking. If opts.BlockingWait is false (for fail-fast
+	// RPCs), it should return an address it has notified via Notify(...) immediately
+	// instead of blocking.
+	//
+	// The function returns put which is called once the rpc has completed or failed.
+	// put can collect and report RPC stats to a remote load balancer. gRPC internals
+	// will try to call this again if err is non-nil (unless err is ErrClientConnClosing).
+	//
+	// TODO: Add other non-recoverable errors?
+	Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error)
+	// Notify returns a channel that is used by gRPC internals to watch the addresses
+	// gRPC needs to connect. The addresses might be from a name resolver or remote
+	// load balancer. gRPC internals will compare it with the existing connected
+	// addresses. If the address Balancer notified is not in the existing connected
+	// addresses, gRPC starts to connect the address. If an address in the existing
+	// connected addresses is not in the notification list, the corresponding connection
+	// is shutdown gracefully. Otherwise, there are no operations to take. Note that
+	// the Address slice must be the full list of the Addresses which should be connected.
+	// It is NOT delta.
+	Notify() <-chan []Address
+	// Close shuts down the balancer.
+	Close() error
+}
+
+// downErr implements net.Error. It is constructed by gRPC internals and passed to the down
+// call of Balancer.
+type downErr struct {
+	timeout   bool
+	temporary bool
+	desc      string
+}
+
+func (e downErr) Error() string   { return e.desc }
+func (e downErr) Timeout() bool   { return e.timeout }
+func (e downErr) Temporary() bool { return e.temporary }
+
+func downErrorf(timeout, temporary bool, format string, a ...interface{}) downErr {
+	return downErr{
+		timeout:   timeout,
+		temporary: temporary,
+		desc:      fmt.Sprintf(format, a...),
+	}
+}
+
+// RoundRobin returns a Balancer that selects addresses round-robin. It uses r to watch
+// the name resolution updates and updates the addresses available correspondingly.
+func RoundRobin(r naming.Resolver) Balancer {
+	return &roundRobin{r: r}
+}
+
+type roundRobin struct {
+	r         naming.Resolver
+	w         naming.Watcher
+	open      []Address // all the addresses the client should potentially connect
+	mu        sync.Mutex
+	addrCh    chan []Address // the channel to notify gRPC internals the list of addresses the client should connect to.
+	connected []Address      // all the connected addresses
+	next      int            // index of the next address to return for Get()
+	waitCh    chan struct{}  // the channel to block when there is no connected address available
+	done      bool           // The Balancer is closed.
+}
+
+func (rr *roundRobin) watchAddrUpdates() error {
+	updates, err := rr.w.Next()
+	if err != nil {
+		grpclog.Println("grpc: the naming watcher stops working due to %v.", err)
+		return err
+	}
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	for _, update := range updates {
+		addr := Address{
+			Addr: update.Addr,
+		}
+		switch update.Op {
+		case naming.Add:
+			var exist bool
+			for _, v := range rr.open {
+				if addr == v {
+					exist = true
+					grpclog.Println("grpc: The name resolver wanted to add an existing address: ", addr)
+					break
+				}
+			}
+			if exist {
+				continue
+			}
+			rr.open = append(rr.open, addr)
+		case naming.Delete:
+			for i, v := range rr.open {
+				if v == addr {
+					copy(rr.open[i:], rr.open[i+1:])
+					rr.open = rr.open[:len(rr.open)-1]
+					break
+				}
+			}
+		default:
+			grpclog.Println("Unknown update.Op ", update.Op)
+		}
+	}
+	// Make a copy of rr.open and write it onto rr.addrCh so that gRPC internals gets notified.
+	open := make([]Address, len(rr.open), len(rr.open))
+	copy(open, rr.open)
+	if rr.done {
+		return ErrClientConnClosing
+	}
+	rr.addrCh <- open
+	return nil
+}
+
+func (rr *roundRobin) Start(target string) error {
+	if rr.r == nil {
+		// If there is no name resolver installed, it is not needed to
+		// do name resolution. In this case, rr.addrCh stays nil.
+		return nil
+	}
+	w, err := rr.r.Resolve(target)
+	if err != nil {
+		return err
+	}
+	rr.w = w
+	rr.addrCh = make(chan []Address)
+	go func() {
+		for {
+			if err := rr.watchAddrUpdates(); err != nil {
+				return
+			}
+		}
+	}()
+	return nil
+}
+
+// Up appends addr to the end of rr.connected and sends notification if there
+// are pending Get() calls.
+func (rr *roundRobin) Up(addr Address) func(error) {
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	for _, a := range rr.connected {
+		if a == addr {
+			return nil
+		}
+	}
+	rr.connected = append(rr.connected, addr)
+	if len(rr.connected) == 1 {
+		// addr is only one available. Notify the Get() callers who are blocking.
+		if rr.waitCh != nil {
+			close(rr.waitCh)
+			rr.waitCh = nil
+		}
+	}
+	return func(err error) {
+		rr.down(addr, err)
+	}
+}
+
+// down removes addr from rr.connected and moves the remaining addrs forward.
+func (rr *roundRobin) down(addr Address, err error) {
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	for i, a := range rr.connected {
+		if a == addr {
+			copy(rr.connected[i:], rr.connected[i+1:])
+			rr.connected = rr.connected[:len(rr.connected)-1]
+			return
+		}
+	}
+}
+
+// Get returns the next addr in the rotation.
+func (rr *roundRobin) Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error) {
+	var ch chan struct{}
+	rr.mu.Lock()
+	if rr.done {
+		rr.mu.Unlock()
+		err = ErrClientConnClosing
+		return
+	}
+	if rr.next >= len(rr.connected) {
+		rr.next = 0
+	}
+	if len(rr.connected) > 0 {
+		addr = rr.connected[rr.next]
+		rr.next++
+		rr.mu.Unlock()
+		return
+	}
+	// There is no address available. Wait on rr.waitCh.
+	// TODO(zhaoq): Handle the case when opts.BlockingWait is false.
+	if rr.waitCh == nil {
+		ch = make(chan struct{})
+		rr.waitCh = ch
+	} else {
+		ch = rr.waitCh
+	}
+	rr.mu.Unlock()
+	for {
+		select {
+		case <-ctx.Done():
+			err = transport.ContextErr(ctx.Err())
+			return
+		case <-ch:
+			rr.mu.Lock()
+			if rr.done {
+				rr.mu.Unlock()
+				err = ErrClientConnClosing
+				return
+			}
+			if len(rr.connected) == 0 {
+				// The newly added addr got removed by Down() again.
+				if rr.waitCh == nil {
+					ch = make(chan struct{})
+					rr.waitCh = ch
+				} else {
+					ch = rr.waitCh
+				}
+				rr.mu.Unlock()
+				continue
+			}
+			if rr.next >= len(rr.connected) {
+				rr.next = 0
+			}
+			addr = rr.connected[rr.next]
+			rr.next++
+			rr.mu.Unlock()
+			return
+		}
+	}
+}
+
+func (rr *roundRobin) Notify() <-chan []Address {
+	return rr.addrCh
+}
+
+func (rr *roundRobin) Close() error {
+	rr.mu.Lock()
+	defer rr.mu.Unlock()
+	rr.done = true
+	if rr.w != nil {
+		rr.w.Close()
+	}
+	if rr.waitCh != nil {
+		close(rr.waitCh)
+		rr.waitCh = nil
+	}
+	if rr.addrCh != nil {
+		close(rr.addrCh)
+	}
+	return nil
+}