Takahiro Suzuki | d7bf820 | 2020-12-17 20:21:59 +0900 | [diff] [blame] | 1 | /* |
| 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. |
| 23 | package backoff |
| 24 | |
| 25 | import ( |
| 26 | "time" |
| 27 | |
| 28 | grpcbackoff "google.golang.org/grpc/backoff" |
| 29 | "google.golang.org/grpc/internal/grpcrand" |
| 30 | ) |
| 31 | |
| 32 | // Strategy defines the methodology for backing off after a grpc connection |
| 33 | // failure. |
| 34 | type 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 | |
| 40 | // 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. |
| 43 | var DefaultExponential = Exponential{Config: grpcbackoff.DefaultConfig} |
| 44 | |
| 45 | // Exponential implements exponential backoff algorithm as defined in |
| 46 | // https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md. |
| 47 | type Exponential struct { |
| 48 | // Config contains all options to configure the backoff algorithm. |
| 49 | Config grpcbackoff.Config |
| 50 | } |
| 51 | |
| 52 | // Backoff returns the amount of time to wait before the next retry given the |
| 53 | // number of retries. |
| 54 | func (bc Exponential) Backoff(retries int) time.Duration { |
| 55 | if retries == 0 { |
| 56 | return bc.Config.BaseDelay |
| 57 | } |
| 58 | backoff, max := float64(bc.Config.BaseDelay), float64(bc.Config.MaxDelay) |
| 59 | for backoff < max && retries > 0 { |
| 60 | backoff *= bc.Config.Multiplier |
| 61 | 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. |
| 68 | backoff *= 1 + bc.Config.Jitter*(grpcrand.Float64()*2-1) |
| 69 | if backoff < 0 { |
| 70 | return 0 |
| 71 | } |
| 72 | return time.Duration(backoff) |
| 73 | } |