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retry.go
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retry.go
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/**
* 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 realis
import (
"io"
"math/rand"
"net/url"
"time"
"github.com/apache/thrift/lib/go/thrift"
"github.com/paypal/gorealis/gen-go/apache/aurora"
"github.com/paypal/gorealis/response"
"github.com/pkg/errors"
)
// Backoff determines how the retry mechanism should react after each failure and how many failures it should
// tolerate.
type Backoff struct {
Duration time.Duration // the base duration
Factor float64 // Duration is multiplied by a factor each iteration
Jitter float64 // The amount of jitter applied each iteration
Steps int // Exit with error after this many steps
}
// Jitter returns a time.Duration between duration and duration + maxFactor *
// duration.
//
// This allows clients to avoid converging on periodic behavior. If maxFactor
// is 0.0, a suggested default value will be chosen.
func Jitter(duration time.Duration, maxFactor float64) time.Duration {
if maxFactor <= 0.0 {
maxFactor = 1.0
}
wait := duration + time.Duration(rand.Float64()*maxFactor*float64(duration))
return wait
}
// ConditionFunc returns true if the condition is satisfied, or an error
// if the loop should be aborted.
type ConditionFunc func() (done bool, err error)
// ExponentialBackoff is a modified version of the Kubernetes exponential-backoff code.
// It repeats a condition check with exponential backoff and checks the condition up to
// Steps times, increasing the wait by multiplying the previous duration by Factor.
//
// If Jitter is greater than zero, a random amount of each duration is added
// (between duration and duration*(1+jitter)).
//
// If the condition never returns true, ErrWaitTimeout is returned. Errors
// do not cause the function to return.
func ExponentialBackoff(backoff Backoff, logger logger, condition ConditionFunc) error {
var err error
var ok bool
var curStep int
duration := backoff.Duration
for curStep = 0; curStep < backoff.Steps; curStep++ {
// Only sleep if it's not the first iteration.
if curStep != 0 {
adjusted := duration
if backoff.Jitter > 0.0 {
adjusted = Jitter(duration, backoff.Jitter)
}
logger.Printf(
"A retryable error occurred during function call, backing off for %v before retrying\n", adjusted)
time.Sleep(adjusted)
duration = time.Duration(float64(duration) * backoff.Factor)
}
// Execute function passed in.
ok, err = condition()
// If the function executed says it succeeded, stop retrying
if ok {
return nil
}
if err != nil {
// If the error is temporary, continue retrying.
if !IsTemporary(err) {
return err
}
// Print out the temporary error we experienced.
logger.Println(err)
}
}
if curStep > 1 {
logger.Printf("retried this function call %d time(s)", curStep)
}
// Provide more information to the user wherever possible
if err != nil {
return newRetryError(errors.Wrap(err, "ran out of retries"), curStep)
}
return newRetryError(errors.New("ran out of retries"), curStep)
}
type auroraThriftCall func() (resp *aurora.Response, err error)
// Duplicates the functionality of ExponentialBackoff but is specifically targeted towards ThriftCalls.
func (r *realisClient) thriftCallWithRetries(
returnOnTimeout bool,
thriftCall auroraThriftCall) (*aurora.Response, error) {
var resp *aurora.Response
var clientErr error
var curStep int
timeouts := 0
backoff := r.config.backoff
duration := backoff.Duration
for curStep = 0; curStep < backoff.Steps; curStep++ {
// If this isn't our first try, backoff before the next try.
if curStep != 0 {
adjusted := duration
if backoff.Jitter > 0.0 {
adjusted = Jitter(duration, backoff.Jitter)
}
r.logger.Printf(
"A retryable error occurred during thrift call, backing off for %v before retry %v",
adjusted,
curStep)
time.Sleep(adjusted)
duration = time.Duration(float64(duration) * backoff.Factor)
}
// Only allow one go-routine make use or modify the thrift client connection.
// Placing this in an anonymous function in order to create a new, short-lived stack allowing unlock
// to be run in case of a panic inside of thriftCall.
func() {
r.lock.Lock()
defer r.lock.Unlock()
resp, clientErr = thriftCall()
r.logger.tracePrintf("Aurora Thrift Call ended resp: %v clientErr: %v", resp, clientErr)
}()
// Check if our thrift call is returning an error. This is a retryable event as we don't know
// if it was caused by network issues.
if clientErr != nil {
// Print out the error to the user
r.logger.Printf("Client Error: %v", clientErr)
// Determine if error is a temporary URL error by going up the stack
e, ok := clientErr.(thrift.TTransportException)
if ok {
r.logger.debugPrint("Encountered a transport exception")
e, ok := e.Err().(*url.Error)
if ok {
// EOF error occurs when the server closes the read buffer of the client. This is common
// when the server is overloaded and should be retried. All other errors that are permanent
// will not be retried.
if e.Err != io.EOF && !e.Temporary() && r.RealisConfig().failOnPermanentErrors {
return nil, errors.Wrap(clientErr, "permanent connection error")
}
// Corner case where thrift payload was received by Aurora but connection timedout before Aurora was
// able to reply. In this case we will return whatever response was received and a TimedOut behaving
// error. Users can take special action on a timeout by using IsTimedout and reacting accordingly.
if e.Timeout() {
timeouts++
r.logger.debugPrintf(
"Client closed connection (timedout) %d times before server responded, "+
"consider increasing connection timeout",
timeouts)
if returnOnTimeout {
return resp, newTimedoutError(errors.New("client connection closed before server answer"))
}
}
}
}
// In the future, reestablish connection should be able to check if it is actually possible
// to make a thrift call to Aurora. For now, a reconnect should always lead to a retry.
// Ignoring error due to the fact that an error should be retried regardless
reestablishErr := r.ReestablishConn()
if reestablishErr != nil {
r.logger.debugPrintf("error re-establishing connection ", reestablishErr)
}
} else {
// If there was no client error, but the response is nil, something went wrong.
// Ideally, we'll never encounter this but we're placing a safeguard here.
if resp == nil {
return nil, errors.New("response from aurora is nil")
}
// Check Response Code from thrift and make a decision to continue retrying or not.
switch responseCode := resp.GetResponseCode(); responseCode {
// If the thrift call succeeded, stop retrying
case aurora.ResponseCode_OK:
return resp, nil
// If the response code is transient, continue retrying
case aurora.ResponseCode_ERROR_TRANSIENT:
r.logger.Println("Aurora replied with Transient error code, retrying")
continue
// Failure scenarios, these indicate a bad payload or a bad config. Stop retrying.
case aurora.ResponseCode_INVALID_REQUEST,
aurora.ResponseCode_ERROR,
aurora.ResponseCode_AUTH_FAILED,
aurora.ResponseCode_JOB_UPDATING_ERROR:
r.logger.Printf("Terminal Response Code %v from Aurora, won't retry\n", resp.GetResponseCode().String())
return resp, errors.New(response.CombineMessage(resp))
// The only case that should fall down to here is a WARNING response code.
// It is currently not used as a response in the scheduler so it is unknown how to handle it.
default:
r.logger.debugPrintf("unhandled response code %v received from Aurora\n", responseCode)
return nil, errors.Errorf("unhandled response code from Aurora %v", responseCode.String())
}
}
}
r.logger.debugPrintf("it took %v retries to complete this operation\n", curStep)
if curStep > 1 {
r.config.logger.Printf("retried this thrift call %d time(s)", curStep)
}
// Provide more information to the user wherever possible.
if clientErr != nil {
return nil, newRetryError(errors.Wrap(clientErr, "ran out of retries, including latest error"), curStep)
}
return nil, newRetryError(errors.New("ran out of retries"), curStep)
}