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316 lines
10 KiB
316 lines
10 KiB
/*
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* Minio Cloud Storage, (C) 2016, 2017 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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"math/rand"
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"net/rpc"
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"path"
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"sync"
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"time"
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router "github.com/gorilla/mux"
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"github.com/minio/dsync"
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)
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const (
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// Lock rpc server endpoint.
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lockServicePath = "/lock"
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// Lock rpc service name.
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lockServiceName = "Dsync"
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// Lock maintenance interval.
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lockMaintenanceInterval = 1 * time.Minute // 1 minute.
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// Lock validity check interval.
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lockValidityCheckInterval = 2 * time.Minute // 2 minutes.
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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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}
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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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// lockServer is type for RPC handlers
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type lockServer struct {
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AuthRPCServer
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serviceEndpoint string
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mutex sync.Mutex
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lockMap map[string][]lockRequesterInfo
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}
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// Start lock maintenance from all lock servers.
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func startLockMaintainence(lockServers []*lockServer) {
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for _, locker := range lockServers {
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// Start loop for stale lock maintenance
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go func(lk *lockServer) {
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// Initialize a new ticker with a minute between each ticks.
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ticker := time.NewTicker(lockMaintenanceInterval)
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// Start with random sleep time, so as to avoid "synchronous checks" between servers
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time.Sleep(time.Duration(rand.Float64() * float64(lockMaintenanceInterval)))
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for {
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// Verifies every minute for locks held more than 2minutes.
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select {
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case <-ticker.C:
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lk.lockMaintenance(lockValidityCheckInterval)
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case <-globalServiceDoneCh:
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// Stop the timer.
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ticker.Stop()
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}
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}
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}(locker)
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}
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}
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// Register distributed NS lock handlers.
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func registerDistNSLockRouter(mux *router.Router, endpoints EndpointList) error {
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// Initialize a new set of lock servers.
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lockServers := newLockServers(endpoints)
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// Start lock maintenance from all lock servers.
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startLockMaintainence(lockServers)
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// Register initialized lock servers to their respective rpc endpoints.
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return registerStorageLockers(mux, lockServers)
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}
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// Create one lock server for every local storage rpc server.
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func newLockServers(endpoints EndpointList) (lockServers []*lockServer) {
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for _, endpoint := range endpoints {
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// Initialize new lock server for each local node.
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if endpoint.IsLocal {
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lockServers = append(lockServers, &lockServer{
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serviceEndpoint: endpoint.Path,
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mutex: sync.Mutex{},
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lockMap: make(map[string][]lockRequesterInfo),
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})
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}
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}
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return lockServers
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}
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// registerStorageLockers - register locker rpc handlers for net/rpc library clients
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func registerStorageLockers(mux *router.Router, lockServers []*lockServer) error {
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for _, lockServer := range lockServers {
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lockRPCServer := rpc.NewServer()
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if err := lockRPCServer.RegisterName(lockServiceName, lockServer); err != nil {
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return traceError(err)
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}
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lockRouter := mux.PathPrefix(minioReservedBucketPath).Subrouter()
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lockRouter.Path(path.Join(lockServicePath, lockServer.serviceEndpoint)).Handler(lockRPCServer)
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}
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return nil
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}
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/// Distributed lock handlers
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// Lock - rpc handler for (single) write lock operation.
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func (l *lockServer) Lock(args *LockArgs, reply *bool) error {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if err := args.IsAuthenticated(); err != nil {
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return err
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}
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_, *reply = l.lockMap[args.LockArgs.Resource]
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if !*reply { // No locks held on the given name, so claim write lock
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l.lockMap[args.LockArgs.Resource] = []lockRequesterInfo{
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{
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writer: true,
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node: args.LockArgs.ServerAddr,
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serviceEndpoint: args.LockArgs.ServiceEndpoint,
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uid: args.LockArgs.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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*reply = !*reply // Negate *reply to return true when lock is granted or false otherwise
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return nil
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}
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// Unlock - rpc handler for (single) write unlock operation.
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func (l *lockServer) Unlock(args *LockArgs, reply *bool) error {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if err := args.IsAuthenticated(); err != nil {
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return err
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}
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var lri []lockRequesterInfo
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if lri, *reply = l.lockMap[args.LockArgs.Resource]; !*reply { // No lock is held on the given name
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return fmt.Errorf("Unlock attempted on an unlocked entity: %s", args.LockArgs.Resource)
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}
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if *reply = isWriteLock(lri); !*reply { // Unless it is a write lock
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return fmt.Errorf("Unlock attempted on a read locked entity: %s (%d read locks active)", args.LockArgs.Resource, len(lri))
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}
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if !l.removeEntry(args.LockArgs.Resource, args.LockArgs.UID, &lri) {
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return fmt.Errorf("Unlock unable to find corresponding lock for uid: %s", args.LockArgs.UID)
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}
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return nil
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}
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// RLock - rpc handler for read lock operation.
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func (l *lockServer) RLock(args *LockArgs, reply *bool) error {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if err := args.IsAuthenticated(); err != nil {
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return err
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}
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lrInfo := lockRequesterInfo{
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writer: false,
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node: args.LockArgs.ServerAddr,
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serviceEndpoint: args.LockArgs.ServiceEndpoint,
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uid: args.LockArgs.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.LockArgs.Resource]; ok {
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if *reply = !isWriteLock(lri); *reply { // Unless there is a write lock
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l.lockMap[args.LockArgs.Resource] = append(l.lockMap[args.LockArgs.Resource], lrInfo)
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}
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} else { // No locks held on the given name, so claim (first) read lock
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l.lockMap[args.LockArgs.Resource] = []lockRequesterInfo{lrInfo}
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*reply = true
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}
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return nil
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}
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// RUnlock - rpc handler for read unlock operation.
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func (l *lockServer) RUnlock(args *LockArgs, reply *bool) error {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if err := args.IsAuthenticated(); err != nil {
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return err
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}
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var lri []lockRequesterInfo
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if lri, *reply = l.lockMap[args.LockArgs.Resource]; !*reply { // No lock is held on the given name
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return fmt.Errorf("RUnlock attempted on an unlocked entity: %s", args.LockArgs.Resource)
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}
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if *reply = !isWriteLock(lri); !*reply { // A write-lock is held, cannot release a read lock
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return fmt.Errorf("RUnlock attempted on a write locked entity: %s", args.LockArgs.Resource)
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}
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if !l.removeEntry(args.LockArgs.Resource, args.LockArgs.UID, &lri) {
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return fmt.Errorf("RUnlock unable to find corresponding read lock for uid: %s", args.LockArgs.UID)
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}
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return nil
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}
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// ForceUnlock - rpc handler for force unlock operation.
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func (l *lockServer) ForceUnlock(args *LockArgs, reply *bool) error {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if err := args.IsAuthenticated(); err != nil {
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return err
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}
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if len(args.LockArgs.UID) != 0 {
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return fmt.Errorf("ForceUnlock called with non-empty UID: %s", args.LockArgs.UID)
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}
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if _, ok := l.lockMap[args.LockArgs.Resource]; ok { // Only clear lock when set
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delete(l.lockMap, args.LockArgs.Resource) // Remove the lock (irrespective of write or read lock)
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}
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*reply = true
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return nil
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}
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// Expired - rpc handler for expired lock status.
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func (l *lockServer) Expired(args *LockArgs, reply *bool) error {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if err := args.IsAuthenticated(); err != nil {
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return err
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}
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// Lock found, proceed to verify if belongs to given uid.
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if lri, ok := l.lockMap[args.LockArgs.Resource]; ok {
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// Check whether uid is still active
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for _, entry := range lri {
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if entry.uid == args.LockArgs.UID {
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*reply = false // When uid found, lock is still active so return not expired.
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return nil // When uid found *reply is set to true.
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}
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}
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}
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// When we get here lock is no longer active due to either args.LockArgs.Resource
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// being absent from map or uid not found for given args.LockArgs.Resource
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*reply = true
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return nil
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}
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// nameLockRequesterInfoPair is a helper type for lock maintenance
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type nameLockRequesterInfoPair struct {
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name string
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lri lockRequesterInfo
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}
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// lockMaintenance loops over locks that have been active for some time and checks back
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// with the original server whether it is still alive or not
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//
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// Following logic inside ignores the errors generated for Dsync.Active operation.
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// - server at client down
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// - some network error (and server is up normally)
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//
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// We will ignore the error, and we will retry later to get a resolve on this lock
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func (l *lockServer) lockMaintenance(interval time.Duration) {
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l.mutex.Lock()
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// Get list of long lived locks to check for staleness.
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nlripLongLived := getLongLivedLocks(l.lockMap, interval)
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l.mutex.Unlock()
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serverCred := serverConfig.GetCredential()
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// Validate if long lived locks are indeed clean.
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for _, nlrip := range nlripLongLived {
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// Initialize client based on the long live locks.
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c := newLockRPCClient(authConfig{
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accessKey: serverCred.AccessKey,
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secretKey: serverCred.SecretKey,
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serverAddr: nlrip.lri.node,
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secureConn: globalIsSSL,
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serviceEndpoint: nlrip.lri.serviceEndpoint,
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serviceName: lockServiceName,
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})
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// Call back to original server verify whether the lock is still active (based on name & uid)
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expired, _ := c.Expired(dsync.LockArgs{
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UID: nlrip.lri.uid,
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Resource: nlrip.name,
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})
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// Close the connection regardless of the call response.
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c.rpcClient.Close()
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// For successful response, verify if lock is indeed active or stale.
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if expired {
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// The lock is no longer active at server that originated the lock
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// So remove the lock from the map.
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l.mutex.Lock()
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l.removeEntryIfExists(nlrip) // Purge the stale entry if it exists.
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l.mutex.Unlock()
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}
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}
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}
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