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minio/cmd/lock-rpc-server.go

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/*
* Minio Cloud Storage, (C) 2016, 2017 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cmd
import (
"fmt"
"math/rand"
"net/rpc"
"path"
"sync"
"time"
router "github.com/gorilla/mux"
"github.com/minio/dsync"
)
const (
// Lock rpc server endpoint.
lockServicePath = "/lock"
// Lock rpc service name.
lockServiceName = "Dsync"
// Lock maintenance interval.
lockMaintenanceInterval = 1 * time.Minute // 1 minute.
// Lock validity check interval.
lockValidityCheckInterval = 2 * time.Minute // 2 minutes.
)
// lockRequesterInfo stores various info from the client for each lock that is requested.
type lockRequesterInfo struct {
writer bool // Bool whether write or read lock.
node string // Network address of client claiming lock.
serviceEndpoint string // RPC path of client claiming lock.
uid string // UID to uniquely identify request of client.
timestamp time.Time // Timestamp set at the time of initialization.
timeLastCheck time.Time // Timestamp for last check of validity of lock.
}
// isWriteLock returns whether the lock is a write or read lock.
func isWriteLock(lri []lockRequesterInfo) bool {
return len(lri) == 1 && lri[0].writer
}
// lockServer is type for RPC handlers
type lockServer struct {
AuthRPCServer
ll localLocker
}
// Start lock maintenance from all lock servers.
func startLockMaintenance(lockServers []*lockServer) {
for _, locker := range lockServers {
// Start loop for stale lock maintenance
go func(lk *lockServer) {
// Initialize a new ticker with a minute between each ticks.
ticker := time.NewTicker(lockMaintenanceInterval)
// Start with random sleep time, so as to avoid "synchronous checks" between servers
time.Sleep(time.Duration(rand.Float64() * float64(lockMaintenanceInterval)))
for {
// Verifies every minute for locks held more than 2minutes.
select {
case <-ticker.C:
lk.lockMaintenance(lockValidityCheckInterval)
case <-globalServiceDoneCh:
// Stop the timer.
ticker.Stop()
}
}
}(locker)
}
}
// Register distributed NS lock handlers.
func registerDistNSLockRouter(mux *router.Router, endpoints EndpointList) error {
// Start lock maintenance from all lock servers.
startLockMaintenance(globalLockServers)
// Register initialized lock servers to their respective rpc endpoints.
return registerStorageLockers(mux, globalLockServers)
}
// registerStorageLockers - register locker rpc handlers for net/rpc library clients
func registerStorageLockers(mux *router.Router, lockServers []*lockServer) error {
for _, lockServer := range lockServers {
lockRPCServer := rpc.NewServer()
if err := lockRPCServer.RegisterName(lockServiceName, lockServer); err != nil {
return traceError(err)
}
lockRouter := mux.PathPrefix(minioReservedBucketPath).Subrouter()
lockRouter.Path(path.Join(lockServicePath, lockServer.ll.serviceEndpoint)).Handler(lockRPCServer)
}
return nil
}
// localLocker implements Dsync.NetLocker
type localLocker struct {
mutex sync.Mutex
serviceEndpoint string
serverAddr string
lockMap map[string][]lockRequesterInfo
}
func (l *localLocker) ServerAddr() string {
return l.serverAddr
}
func (l *localLocker) ServiceEndpoint() string {
return l.serviceEndpoint
}
func (l *localLocker) Lock(args dsync.LockArgs) (reply bool, err error) {
l.mutex.Lock()
defer l.mutex.Unlock()
_, isLockTaken := l.lockMap[args.Resource]
if !isLockTaken { // No locks held on the given name, so claim write lock
l.lockMap[args.Resource] = []lockRequesterInfo{
{
writer: true,
node: args.ServerAddr,
serviceEndpoint: args.ServiceEndpoint,
uid: args.UID,
timestamp: UTCNow(),
timeLastCheck: UTCNow(),
},
}
}
// return reply=true if lock was granted.
return !isLockTaken, nil
}
func (l *localLocker) Unlock(args dsync.LockArgs) (reply bool, err error) {
l.mutex.Lock()
defer l.mutex.Unlock()
var lri []lockRequesterInfo
if lri, reply = l.lockMap[args.Resource]; !reply {
// No lock is held on the given name
return reply, fmt.Errorf("Unlock attempted on an unlocked entity: %s", args.Resource)
}
if reply = isWriteLock(lri); !reply {
// Unless it is a write lock
return reply, fmt.Errorf("Unlock attempted on a read locked entity: %s (%d read locks active)", args.Resource, len(lri))
}
if !l.removeEntry(args.Resource, args.UID, &lri) {
return false, fmt.Errorf("Unlock unable to find corresponding lock for uid: %s", args.UID)
}
return true, nil
}
func (l *localLocker) RLock(args dsync.LockArgs) (reply bool, err error) {
l.mutex.Lock()
defer l.mutex.Unlock()
lrInfo := lockRequesterInfo{
writer: false,
node: args.ServerAddr,
serviceEndpoint: args.ServiceEndpoint,
uid: args.UID,
timestamp: UTCNow(),
timeLastCheck: UTCNow(),
}
if lri, ok := l.lockMap[args.Resource]; ok {
if reply = !isWriteLock(lri); reply {
// Unless there is a write lock
l.lockMap[args.Resource] = append(l.lockMap[args.Resource], lrInfo)
}
} else {
// No locks held on the given name, so claim (first) read lock
l.lockMap[args.Resource] = []lockRequesterInfo{lrInfo}
reply = true
}
return reply, nil
}
func (l *localLocker) RUnlock(args dsync.LockArgs) (reply bool, err error) {
l.mutex.Lock()
defer l.mutex.Unlock()
var lri []lockRequesterInfo
if lri, reply = l.lockMap[args.Resource]; !reply {
// No lock is held on the given name
return reply, fmt.Errorf("RUnlock attempted on an unlocked entity: %s", args.Resource)
}
if reply = !isWriteLock(lri); !reply {
// A write-lock is held, cannot release a read lock
return reply, fmt.Errorf("RUnlock attempted on a write locked entity: %s", args.Resource)
}
if !l.removeEntry(args.Resource, args.UID, &lri) {
return false, fmt.Errorf("RUnlock unable to find corresponding read lock for uid: %s", args.UID)
}
return reply, nil
}
func (l *localLocker) ForceUnlock(args dsync.LockArgs) (reply bool, err error) {
l.mutex.Lock()
defer l.mutex.Unlock()
if len(args.UID) != 0 {
return false, fmt.Errorf("ForceUnlock called with non-empty UID: %s", args.UID)
}
if _, ok := l.lockMap[args.Resource]; ok {
// Only clear lock when it is taken
// Remove the lock (irrespective of write or read lock)
delete(l.lockMap, args.Resource)
}
return true, nil
}
/// Distributed lock handlers
// Lock - rpc handler for (single) write lock operation.
func (l *lockServer) Lock(args *LockArgs, reply *bool) (err error) {
if err = args.IsAuthenticated(); err != nil {
return err
}
*reply, err = l.ll.Lock(args.LockArgs)
return err
}
// Unlock - rpc handler for (single) write unlock operation.
func (l *lockServer) Unlock(args *LockArgs, reply *bool) (err error) {
if err = args.IsAuthenticated(); err != nil {
return err
}
*reply, err = l.ll.Unlock(args.LockArgs)
return err
}
// RLock - rpc handler for read lock operation.
func (l *lockServer) RLock(args *LockArgs, reply *bool) (err error) {
if err = args.IsAuthenticated(); err != nil {
return err
}
*reply, err = l.ll.RLock(args.LockArgs)
return err
}
// RUnlock - rpc handler for read unlock operation.
func (l *lockServer) RUnlock(args *LockArgs, reply *bool) (err error) {
if err = args.IsAuthenticated(); err != nil {
return err
}
*reply, err = l.ll.RUnlock(args.LockArgs)
return err
}
// ForceUnlock - rpc handler for force unlock operation.
func (l *lockServer) ForceUnlock(args *LockArgs, reply *bool) (err error) {
if err = args.IsAuthenticated(); err != nil {
return err
}
*reply, err = l.ll.ForceUnlock(args.LockArgs)
return err
}
// Expired - rpc handler for expired lock status.
func (l *lockServer) Expired(args *LockArgs, reply *bool) error {
if err := args.IsAuthenticated(); err != nil {
return err
}
l.ll.mutex.Lock()
defer l.ll.mutex.Unlock()
// Lock found, proceed to verify if belongs to given uid.
if lri, ok := l.ll.lockMap[args.LockArgs.Resource]; ok {
// Check whether uid is still active
for _, entry := range lri {
if entry.uid == args.LockArgs.UID {
*reply = false // When uid found, lock is still active so return not expired.
return nil // When uid found *reply is set to true.
}
}
}
// When we get here lock is no longer active due to either args.LockArgs.Resource
// being absent from map or uid not found for given args.LockArgs.Resource
*reply = true
return nil
}
// nameLockRequesterInfoPair is a helper type for lock maintenance
type nameLockRequesterInfoPair struct {
name string
lri lockRequesterInfo
}
// lockMaintenance loops over locks that have been active for some time and checks back
// with the original server whether it is still alive or not
//
// Following logic inside ignores the errors generated for Dsync.Active operation.
// - server at client down
// - some network error (and server is up normally)
//
// We will ignore the error, and we will retry later to get a resolve on this lock
func (l *lockServer) lockMaintenance(interval time.Duration) {
l.ll.mutex.Lock()
// Get list of long lived locks to check for staleness.
nlripLongLived := getLongLivedLocks(l.ll.lockMap, interval)
l.ll.mutex.Unlock()
serverCred := serverConfig.GetCredential()
// Validate if long lived locks are indeed clean.
for _, nlrip := range nlripLongLived {
// Initialize client based on the long live locks.
c := newLockRPCClient(authConfig{
accessKey: serverCred.AccessKey,
secretKey: serverCred.SecretKey,
serverAddr: nlrip.lri.node,
secureConn: globalIsSSL,
serviceEndpoint: nlrip.lri.serviceEndpoint,
serviceName: lockServiceName,
})
// Call back to original server verify whether the lock is still active (based on name & uid)
expired, _ := c.Expired(dsync.LockArgs{
UID: nlrip.lri.uid,
Resource: nlrip.name,
})
// Close the connection regardless of the call response.
c.rpcClient.Close()
// For successful response, verify if lock is indeed active or stale.
if expired {
// The lock is no longer active at server that originated the lock
// So remove the lock from the map.
l.ll.mutex.Lock()
l.ll.removeEntryIfExists(nlrip) // Purge the stale entry if it exists.
l.ll.mutex.Unlock()
}
}
}