1// Copyright 2018, OpenCensus Authors 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14 15package ocagent 16 17import ( 18 "math/rand" 19 "time" 20) 21 22var randSrc = rand.New(rand.NewSource(time.Now().UnixNano())) 23 24// retries function fn upto n times, if fn returns an error lest it returns nil early. 25// It applies exponential backoff in units of (1<<n) + jitter microsends. 26func nTriesWithExponentialBackoff(nTries int64, timeBaseUnit time.Duration, fn func() error) (err error) { 27 for i := int64(0); i < nTries; i++ { 28 err = fn() 29 if err == nil { 30 return nil 31 } 32 // Backoff for a time period with a pseudo-random jitter 33 jitter := time.Duration(randSrc.Float64()*100) * time.Microsecond 34 ts := jitter + ((1 << uint64(i)) * timeBaseUnit) 35 <-time.After(ts) 36 } 37 return err 38} 39