158 lines
4.8 KiB
Go
158 lines
4.8 KiB
Go
// Copyright 2016, Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package gax
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import (
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"math/rand"
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"time"
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"google.golang.org/grpc"
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"google.golang.org/grpc/codes"
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"google.golang.org/grpc/status"
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)
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// CallOption is an option used by Invoke to control behaviors of RPC calls.
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// CallOption works by modifying relevant fields of CallSettings.
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type CallOption interface {
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// Resolve applies the option by modifying cs.
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Resolve(cs *CallSettings)
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}
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// Retryer is used by Invoke to determine retry behavior.
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type Retryer interface {
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// Retry reports whether a request should be retriedand how long to pause before retrying
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// if the previous attempt returned with err. Invoke never calls Retry with nil error.
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Retry(err error) (pause time.Duration, shouldRetry bool)
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}
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type retryerOption func() Retryer
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func (o retryerOption) Resolve(s *CallSettings) {
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s.Retry = o
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}
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// WithRetry sets CallSettings.Retry to fn.
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func WithRetry(fn func() Retryer) CallOption {
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return retryerOption(fn)
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}
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// OnCodes returns a Retryer that retries if and only if
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// the previous attempt returns a GRPC error whose error code is stored in cc.
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// Pause times between retries are specified by bo.
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//
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// bo is only used for its parameters; each Retryer has its own copy.
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func OnCodes(cc []codes.Code, bo Backoff) Retryer {
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return &boRetryer{
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backoff: bo,
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codes: append([]codes.Code(nil), cc...),
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}
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}
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type boRetryer struct {
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backoff Backoff
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codes []codes.Code
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}
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func (r *boRetryer) Retry(err error) (time.Duration, bool) {
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st, ok := status.FromError(err)
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if !ok {
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return 0, false
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}
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c := st.Code()
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for _, rc := range r.codes {
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if c == rc {
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return r.backoff.Pause(), true
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}
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}
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return 0, false
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}
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// Backoff implements exponential backoff.
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// The wait time between retries is a random value between 0 and the "retry envelope".
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// The envelope starts at Initial and increases by the factor of Multiplier every retry,
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// but is capped at Max.
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type Backoff struct {
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// Initial is the initial value of the retry envelope, defaults to 1 second.
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Initial time.Duration
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// Max is the maximum value of the retry envelope, defaults to 30 seconds.
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Max time.Duration
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// Multiplier is the factor by which the retry envelope increases.
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// It should be greater than 1 and defaults to 2.
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Multiplier float64
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// cur is the current retry envelope
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cur time.Duration
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}
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func (bo *Backoff) Pause() time.Duration {
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if bo.Initial == 0 {
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bo.Initial = time.Second
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}
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if bo.cur == 0 {
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bo.cur = bo.Initial
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}
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if bo.Max == 0 {
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bo.Max = 30 * time.Second
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}
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if bo.Multiplier < 1 {
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bo.Multiplier = 2
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}
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// Select a duration between zero and the current max. It might seem counterintuitive to
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// have so much jitter, but https://www.awsarchitectureblog.com/2015/03/backoff.html
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// argues that that is the best strategy.
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d := time.Duration(rand.Int63n(int64(bo.cur)))
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bo.cur = time.Duration(float64(bo.cur) * bo.Multiplier)
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if bo.cur > bo.Max {
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bo.cur = bo.Max
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}
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return d
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}
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type grpcOpt []grpc.CallOption
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func (o grpcOpt) Resolve(s *CallSettings) {
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s.GRPC = o
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}
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func WithGRPCOptions(opt ...grpc.CallOption) CallOption {
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return grpcOpt(append([]grpc.CallOption(nil), opt...))
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}
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type CallSettings struct {
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// Retry returns a Retryer to be used to control retry logic of a method call.
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// If Retry is nil or the returned Retryer is nil, the call will not be retried.
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Retry func() Retryer
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// CallOptions to be forwarded to GRPC.
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GRPC []grpc.CallOption
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}
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