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// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package backoff
import (
"context"
"sync"
"time"
)
type (
// Operation to retry
Operation func() error
// IsRetryable handler can be used to exclude certain errors during retry
IsRetryable func(error) bool
// ConcurrentRetrier is used for client-side throttling. It determines whether to
// throttle outgoing traffic in case downstream backend server rejects
// requests due to out-of-quota or server busy errors.
ConcurrentRetrier struct {
sync.Mutex
retrier Retrier // Backoff retrier
failureCount int64 // Number of consecutive failures seen
}
)
// Throttle Sleep if there were failures since the last success call.
func (c *ConcurrentRetrier) Throttle() {
c.throttleInternal()
}
func (c *ConcurrentRetrier) throttleInternal() time.Duration {
next := done
// Check if we have failure count.
c.Lock()
if c.failureCount > 0 {
next = c.retrier.NextBackOff()
}
c.Unlock()
if next != done {
time.Sleep(next)
}
return next
}
// Succeeded marks client request succeeded.
func (c *ConcurrentRetrier) Succeeded() {
defer c.Unlock()
c.Lock()
c.failureCount = 0
c.retrier.Reset()
}
// Failed marks client request failed because backend is busy.
func (c *ConcurrentRetrier) Failed() {
defer c.Unlock()
c.Lock()
c.failureCount++
}
// NewConcurrentRetrier returns an instance of concurrent backoff retrier.
func NewConcurrentRetrier(retryPolicy RetryPolicy) *ConcurrentRetrier {
retrier := NewRetrier(retryPolicy, SystemClock)
return &ConcurrentRetrier{retrier: retrier}
}
// Retry function can be used to wrap any call with retry logic using the passed in policy
func Retry(ctx context.Context, operation Operation, policy RetryPolicy, isRetryable IsRetryable) error {
var err error
var next time.Duration
r := NewRetrier(policy, SystemClock)
Retry_Loop:
for {
// operation completed successfully. No need to retry.
if err = operation(); err == nil {
return nil
}
if next = r.NextBackOff(); next == done {
return err
}
// Check if the error is retryable
if isRetryable != nil && !isRetryable(err) {
return err
}
// check if ctx is done
if ctxDone := ctx.Done(); ctxDone != nil {
timer := time.NewTimer(next)
select {
case <-ctxDone:
return err
case <-timer.C:
continue Retry_Loop
}
}
// ctx is not cancellable
time.Sleep(next)
}
}
// IgnoreErrors can be used as IsRetryable handler for Retry function to exclude certain errors from the retry list
func IgnoreErrors(errorsToExclude []error) func(error) bool {
return func(err error) bool {
for _, errorToExclude := range errorsToExclude {
if err == errorToExclude {
return false
}
}
return true
}
}
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