163 lines
5.1 KiB
Go
163 lines
5.1 KiB
Go
/*
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* Minio Cloud Storage, (C) 2018, 2019 Minio, Inc.
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*
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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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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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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 cmd
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import (
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"fmt"
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"sync"
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"time"
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"github.com/minio/dsync"
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)
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// lockRequesterInfo stores various info from the client for each lock that is requested.
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type lockRequesterInfo struct {
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Writer bool // Bool whether write or read lock.
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Node string // Network address of client claiming lock.
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ServiceEndpoint string // RPC path of client claiming lock.
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UID string // UID to uniquely identify request of client.
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Timestamp time.Time // Timestamp set at the time of initialization.
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TimeLastCheck time.Time // Timestamp for last check of validity of lock.
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Source string // Contains line, function and filename reqesting the lock.
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}
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// isWriteLock returns whether the lock is a write or read lock.
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func isWriteLock(lri []lockRequesterInfo) bool {
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return len(lri) == 1 && lri[0].Writer
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}
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// localLocker implements Dsync.NetLocker
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type localLocker struct {
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mutex sync.Mutex
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serviceEndpoint string
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serverAddr string
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lockMap map[string][]lockRequesterInfo
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}
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func (l *localLocker) ServerAddr() string {
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return l.serverAddr
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}
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func (l *localLocker) ServiceEndpoint() string {
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return l.serviceEndpoint
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}
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func (l *localLocker) Lock(args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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_, isLockTaken := l.lockMap[args.Resource]
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if !isLockTaken { // No locks held on the given name, so claim write lock
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l.lockMap[args.Resource] = []lockRequesterInfo{
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{
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Writer: true,
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Node: args.ServerAddr,
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ServiceEndpoint: args.ServiceEndpoint,
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Source: args.Source,
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UID: args.UID,
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Timestamp: UTCNow(),
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TimeLastCheck: UTCNow(),
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},
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}
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}
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// return reply=true if lock was granted.
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return !isLockTaken, nil
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}
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func (l *localLocker) Unlock(args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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var lri []lockRequesterInfo
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if lri, reply = l.lockMap[args.Resource]; !reply {
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// No lock is held on the given name
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return reply, fmt.Errorf("Unlock attempted on an unlocked entity: %s", args.Resource)
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}
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if reply = isWriteLock(lri); !reply {
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// Unless it is a write lock
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return reply, fmt.Errorf("Unlock attempted on a read locked entity: %s (%d read locks active)", args.Resource, len(lri))
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}
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if !l.removeEntry(args.Resource, args.UID, &lri) {
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return false, fmt.Errorf("Unlock unable to find corresponding lock for uid: %s", args.UID)
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}
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return true, nil
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}
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func (l *localLocker) RLock(args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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lrInfo := lockRequesterInfo{
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Writer: false,
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Node: args.ServerAddr,
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ServiceEndpoint: args.ServiceEndpoint,
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Source: args.Source,
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UID: args.UID,
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Timestamp: UTCNow(),
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TimeLastCheck: UTCNow(),
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}
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if lri, ok := l.lockMap[args.Resource]; ok {
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if reply = !isWriteLock(lri); reply {
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// Unless there is a write lock
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l.lockMap[args.Resource] = append(l.lockMap[args.Resource], lrInfo)
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}
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} else {
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// No locks held on the given name, so claim (first) read lock
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l.lockMap[args.Resource] = []lockRequesterInfo{lrInfo}
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reply = true
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}
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return reply, nil
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}
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func (l *localLocker) RUnlock(args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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var lri []lockRequesterInfo
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if lri, reply = l.lockMap[args.Resource]; !reply {
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// No lock is held on the given name
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return reply, fmt.Errorf("RUnlock attempted on an unlocked entity: %s", args.Resource)
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}
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if reply = !isWriteLock(lri); !reply {
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// A write-lock is held, cannot release a read lock
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return reply, fmt.Errorf("RUnlock attempted on a write locked entity: %s", args.Resource)
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}
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if !l.removeEntry(args.Resource, args.UID, &lri) {
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return false, fmt.Errorf("RUnlock unable to find corresponding read lock for uid: %s", args.UID)
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}
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return reply, nil
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}
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func (l *localLocker) ForceUnlock(args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if len(args.UID) != 0 {
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return false, fmt.Errorf("ForceUnlock called with non-empty UID: %s", args.UID)
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}
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// Only clear lock when it is taken
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// Remove the lock (irrespective of write or read lock)
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delete(l.lockMap, args.Resource)
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return true, nil
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}
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func (l *localLocker) DupLockMap() map[string][]lockRequesterInfo {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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lockCopy := make(map[string][]lockRequesterInfo)
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for k, v := range l.lockMap {
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lockCopy[k] = append(lockCopy[k], v...)
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}
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return lockCopy
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}
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