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Adds a retry capability to lock monitors in the API client.

This commit is contained in:
James Phillips 2015-11-30 17:09:41 -08:00
parent 87ccd1eb34
commit 86e6230de6
1 changed files with 30 additions and 6 deletions
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36
api/lock.go
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@ -2,6 +2,7 @@ package api
import (
"fmt"
"strings"
"sync"
"time"
)
@ -22,9 +23,15 @@ const (
// DefaultLockRetryTime is how long we wait after a failed lock acquisition
// before attempting to do the lock again. This is so that once a lock-delay
// is in affect, we do not hot loop retrying the acquisition.
// is in effect, we do not hot loop retrying the acquisition.
DefaultLockRetryTime = 5 * time.Second
// DefaultMonitorRetryTime is how long we wait after a failed monitor check
// of a lock (500 response code). This allows the monitor to ride out brief
// periods of unavailability, subject to the MonitorRetries setting in the
// lock options which is by default set to 0, disabling this feature.
DefaultMonitorRetryTime = 2 * time.Second
// LockFlagValue is a magic flag we set to indicate a key
// is being used for a lock. It is used to detect a potential
// conflict with a semaphore.
@ -62,11 +69,12 @@ type Lock struct {
// LockOptions is used to parameterize the Lock behavior.
type LockOptions struct {
Key string // Must be set and have write permissions
Value []byte // Optional, value to associate with the lock
Session string // Optional, created if not specified
SessionName string // Optional, defaults to DefaultLockSessionName
SessionTTL string // Optional, defaults to DefaultLockSessionTTL
Key string // Must be set and have write permissions
Value []byte // Optional, value to associate with the lock
Session string // Optional, created if not specified
SessionName string // Optional, defaults to DefaultLockSessionName
SessionTTL string // Optional, defaults to DefaultLockSessionTTL
MonitorRetries int // Optional, defaults to 0 which means no retries
}
// LockKey returns a handle to a lock struct which can be used
@ -327,8 +335,24 @@ func (l *Lock) monitorLock(session string, stopCh chan struct{}) {
kv := l.c.KV()
opts := &QueryOptions{RequireConsistent: true}
WAIT:
retries := l.opts.MonitorRetries
RETRY:
pair, meta, err := kv.Get(l.opts.Key, opts)
if err != nil {
// TODO (slackpad) - Make a real error type here instead of using
// a string check.
const serverError = "Unexpected response code: 500"
// If configured we can try to ride out a brief Consul unavailability
// by doing retries. Note that we have to attempt the retry in a non-
// blocking fashion so that we have a clean place to reset the retry
// counter if service is restored.
if retries > 0 && strings.Contains(err.Error(), serverError) {
time.Sleep(DefaultMonitorRetryTime)
retries--
opts.WaitIndex = 0
goto RETRY
}
return
}
if pair != nil && pair.Session == session {