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78 lines
2.2 KiB
78 lines
2.2 KiB
/*
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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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"time"
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"google.golang.org/grpc/internal/grpcrand"
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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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//
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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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const (
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// baseDelay is the amount of time to wait before retrying after the first
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// failure.
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baseDelay = 1.0 * time.Second
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// factor is applied to the backoff after each retry.
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factor = 1.6
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// jitter provides a range to randomize backoff delays.
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jitter = 0.2
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)
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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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// MaxDelay is the upper bound of backoff delay.
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MaxDelay time.Duration
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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 baseDelay
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}
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backoff, max := float64(baseDelay), float64(bc.MaxDelay)
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for backoff < max && retries > 0 {
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backoff *= factor
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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 + jitter*(grpcrand.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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