151 lines
3.6 KiB
Go
151 lines
3.6 KiB
Go
/*
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Copyright 2015 github.com/ucirello
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package dynamolock
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import (
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"errors"
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"sync"
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"time"
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"github.com/aws/aws-sdk-go/service/dynamodb"
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)
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// Lock item properly speaking.
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type Lock struct {
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semaphore sync.Mutex
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client *Client
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partitionKey string
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data []byte
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ownerName string
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deleteLockOnRelease bool
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isReleased bool
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sessionMonitor *sessionMonitor
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lookupTime time.Time
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recordVersionNumber string
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leaseDuration time.Duration
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additionalAttributes map[string]*dynamodb.AttributeValue
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}
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// Data returns the content of the lock, if any is available.
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func (l *Lock) Data() []byte {
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if l == nil {
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return nil
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}
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return l.data
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}
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// Close releases the lock.
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func (l *Lock) Close() error {
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if l != nil && l.client != nil {
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if l.IsExpired() {
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return ErrLockAlreadyReleased
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}
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_, err := l.client.ReleaseLock(l)
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return err
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}
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return ErrCannotReleaseNullLock
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}
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func (l *Lock) uniqueIdentifier() string {
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return l.partitionKey
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}
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// IsExpired returns if the lock is expired, released, or neither.
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func (l *Lock) IsExpired() bool {
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if l == nil {
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return true
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}
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l.semaphore.Lock()
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defer l.semaphore.Unlock()
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return l.isExpired()
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}
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func (l *Lock) isExpired() bool {
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if l == nil {
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return true
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}
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if l.isReleased {
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return true
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}
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return time.Since(l.lookupTime) > l.leaseDuration
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}
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func (l *Lock) updateRVN(rvn string, lastUpdate time.Time, leaseDuration time.Duration) {
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l.recordVersionNumber = rvn
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l.lookupTime = lastUpdate
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l.leaseDuration = leaseDuration
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}
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// OwnerName returns the lock's owner.
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func (l *Lock) OwnerName() string {
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if l == nil {
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return ""
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}
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return l.ownerName
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}
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// AdditionalAttributes returns the lock's additional data stored during
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// acquisition.
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func (l *Lock) AdditionalAttributes() map[string]*dynamodb.AttributeValue {
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addAttr := make(map[string]*dynamodb.AttributeValue)
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if l != nil {
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for k, v := range l.additionalAttributes {
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addAttr[k] = v
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}
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}
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return addAttr
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}
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// IsAlmostExpired returns whether or not the lock is entering the "danger
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// zone" time period.
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//
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// It returns if the lock has been released or the lock's lease has entered the
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// "danger zone". It returns false if the lock has not been released and the
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// lock has not yet entered the "danger zone"
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func (l *Lock) IsAlmostExpired() (bool, error) {
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t, err := l.timeUntilDangerZoneEntered()
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if err != nil {
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return false, err
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}
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return t <= 0, nil
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}
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// Errors related to session manager life-cycle.
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var (
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ErrSessionMonitorNotSet = errors.New("session monitor is not set")
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ErrLockAlreadyReleased = errors.New("lock is already released")
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ErrCannotReleaseNullLock = errors.New("cannot release null lock item")
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ErrOwnerMismatched = errors.New("lock owner mismatched")
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)
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func (l *Lock) timeUntilDangerZoneEntered() (time.Duration, error) {
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if l == nil {
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return 0, ErrLockAlreadyReleased
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}
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if l.sessionMonitor == nil {
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return 0, ErrSessionMonitorNotSet
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}
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if l.IsExpired() {
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return 0, ErrLockAlreadyReleased
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}
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return l.sessionMonitor.timeUntilLeaseEntersDangerZone(l.lookupTime), nil
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}
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