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// 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 gax
import (
"math/rand"
"time"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
)
// CallOption is an option used by Invoke to control behaviors of RPC calls.
// CallOption works by modifying relevant fields of CallSettings.
type CallOption interface {
// Resolve applies the option by modifying cs.
Resolve(cs *CallSettings)
}
// Retryer is used by Invoke to determine retry behavior.
type Retryer interface {
// Retry reports whether a request should be retriedand how long to pause before retrying
// if the previous attempt returned with err. Invoke never calls Retry with nil error.
Retry(err error) (pause time.Duration, shouldRetry bool)
}
type retryerOption func() Retryer
func (o retryerOption) Resolve(s *CallSettings) {
s.Retry = o
}
// WithRetry sets CallSettings.Retry to fn.
func WithRetry(fn func() Retryer) CallOption {
return retryerOption(fn)
}
// OnCodes returns a Retryer that retries if and only if
// the previous attempt returns a GRPC error whose error code is stored in cc.
// Pause times between retries are specified by bo.
//
// bo is only used for its parameters; each Retryer has its own copy.
func OnCodes(cc []codes.Code, bo Backoff) Retryer {
return &boRetryer{
backoff: bo,
codes: append([]codes.Code(nil), cc...),
}
}
type boRetryer struct {
backoff Backoff
codes []codes.Code
}
func (r *boRetryer) Retry(err error) (time.Duration, bool) {
st, ok := status.FromError(err)
if !ok {
return 0, false
}
c := st.Code()
for _, rc := range r.codes {
if c == rc {
return r.backoff.Pause(), true
}
}
return 0, false
}
// Backoff implements exponential backoff.
// The wait time between retries is a random value between 0 and the "retry envelope".
// The envelope starts at Initial and increases by the factor of Multiplier every retry,
// but is capped at Max.
type Backoff struct {
// Initial is the initial value of the retry envelope, defaults to 1 second.
Initial time.Duration
// Max is the maximum value of the retry envelope, defaults to 30 seconds.
Max time.Duration
// Multiplier is the factor by which the retry envelope increases.
// It should be greater than 1 and defaults to 2.
Multiplier float64
// cur is the current retry envelope
cur time.Duration
}
func (bo *Backoff) Pause() time.Duration {
if bo.Initial == 0 {
bo.Initial = time.Second
}
if bo.cur == 0 {
bo.cur = bo.Initial
}
if bo.Max == 0 {
bo.Max = 30 * time.Second
}
if bo.Multiplier < 1 {
bo.Multiplier = 2
}
// Select a duration between zero and the current max. It might seem counterintuitive to
// have so much jitter, but https://www.awsarchitectureblog.com/2015/03/backoff.html
// argues that that is the best strategy.
d := time.Duration(rand.Int63n(int64(bo.cur)))
bo.cur = time.Duration(float64(bo.cur) * bo.Multiplier)
if bo.cur > bo.Max {
bo.cur = bo.Max
}
return d
}
type grpcOpt []grpc.CallOption
func (o grpcOpt) Resolve(s *CallSettings) {
s.GRPC = o
}
func WithGRPCOptions(opt ...grpc.CallOption) CallOption {
return grpcOpt(append([]grpc.CallOption(nil), opt...))
}
type CallSettings struct {
// Retry returns a Retryer to be used to control retry logic of a method call.
// If Retry is nil or the returned Retryer is nil, the call will not be retried.
Retry func() Retryer
// CallOptions to be forwarded to GRPC.
GRPC []grpc.CallOption
}
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