cubefs

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/*
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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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	grpcbackoff "google.golang.org/grpc/backoff"
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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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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*(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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