mirror of
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110 lines
3.3 KiB
Go
110 lines
3.3 KiB
Go
/*
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*
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* Copyright 2017 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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// Package backoff implement the backoff strategy for gRPC.
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//
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// This is kept in internal until the gRPC project decides whether or not to
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// allow alternative backoff strategies.
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package backoff
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import (
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"context"
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"errors"
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"math/rand"
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"time"
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grpcbackoff "google.golang.org/grpc/backoff"
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)
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// Strategy defines the methodology for backing off after a grpc connection
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// failure.
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type Strategy interface {
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// Backoff returns the amount of time to wait before the next retry given
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// the number of consecutive failures.
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Backoff(retries int) time.Duration
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}
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// DefaultExponential is an exponential backoff implementation using the
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// default values for all the configurable knobs defined in
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// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
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var DefaultExponential = Exponential{Config: grpcbackoff.DefaultConfig}
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// Exponential implements exponential backoff algorithm as defined in
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// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
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type Exponential struct {
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// Config contains all options to configure the backoff algorithm.
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Config grpcbackoff.Config
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}
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// Backoff returns the amount of time to wait before the next retry given the
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// number of retries.
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func (bc Exponential) Backoff(retries int) time.Duration {
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if retries == 0 {
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return bc.Config.BaseDelay
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}
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backoff, max := float64(bc.Config.BaseDelay), float64(bc.Config.MaxDelay)
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for backoff < max && retries > 0 {
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backoff *= bc.Config.Multiplier
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retries--
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}
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if backoff > max {
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backoff = max
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}
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// Randomize backoff delays so that if a cluster of requests start at
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// the same time, they won't operate in lockstep.
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backoff *= 1 + bc.Config.Jitter*(rand.Float64()*2-1)
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if backoff < 0 {
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return 0
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}
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return time.Duration(backoff)
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}
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// ErrResetBackoff is the error to be returned by the function executed by RunF,
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// to instruct the latter to reset its backoff state.
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var ErrResetBackoff = errors.New("reset backoff state")
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// RunF provides a convenient way to run a function f repeatedly until the
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// context expires or f returns a non-nil error that is not ErrResetBackoff.
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// When f returns ErrResetBackoff, RunF continues to run f, but resets its
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// backoff state before doing so. backoff accepts an integer representing the
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// number of retries, and returns the amount of time to backoff.
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func RunF(ctx context.Context, f func() error, backoff func(int) time.Duration) {
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attempt := 0
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timer := time.NewTimer(0)
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for ctx.Err() == nil {
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select {
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case <-timer.C:
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case <-ctx.Done():
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timer.Stop()
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return
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}
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err := f()
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if errors.Is(err, ErrResetBackoff) {
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timer.Reset(0)
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attempt = 0
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continue
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}
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if err != nil {
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return
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}
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timer.Reset(backoff(attempt))
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attempt++
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}
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}
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