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Matteo Scandoloa6a3aee2019-11-26 13:30:14 -07001/*
2 *
3 * Copyright 2017 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19// Package backoff implement the backoff strategy for gRPC.
20//
21// This is kept in internal until the gRPC project decides whether or not to
22// allow alternative backoff strategies.
23package backoff
24
25import (
26 "time"
27
Arjun E K57a7fcb2020-01-30 06:44:45 +000028 grpcbackoff "google.golang.org/grpc/backoff"
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070029 "google.golang.org/grpc/internal/grpcrand"
30)
31
32// Strategy defines the methodology for backing off after a grpc connection
33// failure.
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070034type Strategy interface {
35 // Backoff returns the amount of time to wait before the next retry given
36 // the number of consecutive failures.
37 Backoff(retries int) time.Duration
38}
39
Arjun E K57a7fcb2020-01-30 06:44:45 +000040// DefaultExponential is an exponential backoff implementation using the
41// default values for all the configurable knobs defined in
42// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
43var DefaultExponential = Exponential{Config: grpcbackoff.DefaultConfig}
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070044
45// Exponential implements exponential backoff algorithm as defined in
46// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
47type Exponential struct {
Arjun E K57a7fcb2020-01-30 06:44:45 +000048 // Config contains all options to configure the backoff algorithm.
49 Config grpcbackoff.Config
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070050}
51
52// Backoff returns the amount of time to wait before the next retry given the
53// number of retries.
54func (bc Exponential) Backoff(retries int) time.Duration {
55 if retries == 0 {
Arjun E K57a7fcb2020-01-30 06:44:45 +000056 return bc.Config.BaseDelay
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070057 }
Arjun E K57a7fcb2020-01-30 06:44:45 +000058 backoff, max := float64(bc.Config.BaseDelay), float64(bc.Config.MaxDelay)
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070059 for backoff < max && retries > 0 {
Arjun E K57a7fcb2020-01-30 06:44:45 +000060 backoff *= bc.Config.Multiplier
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070061 retries--
62 }
63 if backoff > max {
64 backoff = max
65 }
66 // Randomize backoff delays so that if a cluster of requests start at
67 // the same time, they won't operate in lockstep.
Arjun E K57a7fcb2020-01-30 06:44:45 +000068 backoff *= 1 + bc.Config.Jitter*(grpcrand.Float64()*2-1)
Matteo Scandoloa6a3aee2019-11-26 13:30:14 -070069 if backoff < 0 {
70 return 0
71 }
72 return time.Duration(backoff)
73}