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/*
*
* Copyright 2017 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
// Package backoff implement the backoff strategy for gRPC.
//
// This is kept in internal until the gRPC project decides whether or not to
// allow alternative backoff strategies.
package backoff
import (
"time"
"google.golang.org/grpc/internal/grpcrand"
)
// Strategy defines the methodology for backing off after a grpc connection
// failure.
//
type Strategy interface {
// Backoff returns the amount of time to wait before the next retry given
// the number of consecutive failures.
Backoff(retries int) time.Duration
}
const (
// baseDelay is the amount of time to wait before retrying after the first
// failure.
baseDelay = 1.0 * time.Second
// factor is applied to the backoff after each retry.
factor = 1.6
// jitter provides a range to randomize backoff delays.
jitter = 0.2
)
// Exponential implements exponential backoff algorithm as defined in
// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
type Exponential struct {
// MaxDelay is the upper bound of backoff delay.
MaxDelay time.Duration
}
// Backoff returns the amount of time to wait before the next retry given the
// number of retries.
func (bc Exponential) Backoff(retries int) time.Duration {
if retries == 0 {
return baseDelay
}
backoff, max := float64(baseDelay), float64(bc.MaxDelay)
for backoff < max && retries > 0 {
backoff *= factor
retries--
}
if backoff > max {
backoff = max
}
// Randomize backoff delays so that if a cluster of requests start at
// the same time, they won't operate in lockstep.
backoff *= 1 + jitter*(grpcrand.Float64()*2-1)
if backoff < 0 {
return 0
}
return time.Duration(backoff)
}
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