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Add experimental locking options (#130)
* Add nested and map lockers * Add constructors * Wire in session manager * Update session logic in locker * Race condition patch * Add options to nested locker * Add cool-off locker * Change to TryLock * Switch to TryLock * Remove unused interface * Refactor map locker * Refactor session manager * Linter * Add options * Linter * Add options * Wire in useTryLock
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,69 @@ | ||
| package lock | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "sync" | ||
| "time" | ||
| ) | ||
|
|
||
| const ( | ||
| coolOffErrFormat = "cooloff expires in %s" | ||
| ) | ||
|
|
||
| // NewCoolOffLocker creates a simple locker that will prevent a lock from | ||
| // being obtained if a previous attempt (successful or not) was made within | ||
| // the specified expiration period. It is intended to be used with other lockers | ||
| // to prevent excessive locking using more expensive resources (e.g. etcd). It is | ||
| // theoretically possible for two callers to obtain the same lock, if the cooloff | ||
| // period expires before the first caller releases the lock; therefore this locker | ||
| // needs to be used with a nested locker to prevent two callers from accessing the | ||
| // same protected resource. | ||
| func NewCoolOffLocker(expiration time.Duration) RuleLocker { | ||
| locker := coolOffLocker{ | ||
| coolOffDuration: expiration, | ||
| locks: make(map[string]time.Time), | ||
| mutex: &sync.Mutex{}, | ||
| } | ||
| return locker | ||
| } | ||
|
|
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| type coolOffLocker struct { | ||
| locks map[string]time.Time | ||
| mutex *sync.Mutex | ||
| coolOffDuration time.Duration | ||
| } | ||
|
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| func (col coolOffLocker) Lock(key string, options ...Option) (RuleLock, error) { | ||
| col.mutex.Lock() | ||
| defer col.mutex.Unlock() | ||
| now := time.Now() | ||
| // Remove any expired keys | ||
| var toDelete []string | ||
| for k, v := range col.locks { | ||
| if now.After(v) { | ||
| toDelete = append(toDelete, k) | ||
| } | ||
| } | ||
| for _, key := range toDelete { | ||
| delete(col.locks, key) | ||
| } | ||
| var err error | ||
| if _, ok := col.locks[key]; ok { | ||
| err = fmt.Errorf(coolOffErrFormat, col.coolOffDuration) | ||
| } | ||
| // Failed attempts to get the lock should also update the cooloff, | ||
| // so always add the key regardless of success or failure. | ||
| col.locks[key] = now.Add(col.coolOffDuration) | ||
|
|
||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return coolOffLock{}, nil | ||
| } | ||
|
|
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| type coolOffLock struct { | ||
| } | ||
|
|
||
| func (coolOffLock) Unlock() error { | ||
| return nil | ||
| } |
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