New dsync and added ForceUnlock to lock rpc server (#2956)

* Update dsync and added ForceUnlock function
* Added test cases for ForceUnlock

cmd/lock-rpc-server.go

@@ -252,6 +252,23 @@ func (l *lockServer) RUnlock(args *LockArgs, reply *bool) error {
 	return nil
 }
 
+// ForceUnlock - rpc handler for force unlock operation.
+func (l *lockServer) ForceUnlock(args *LockArgs, reply *bool) error {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+	if err := l.validateLockArgs(args); err != nil {
+		return err
+	}
+	if len(args.UID) != 0 {
+		return fmt.Errorf("ForceUnlock called with non-empty UID: %s", args.UID)
+	}
+	if _, ok := l.lockMap[args.Name]; ok { // Only clear lock when set
+		delete(l.lockMap, args.Name) // Remove the lock (irrespective of write or read lock)
+	}
+	*reply = true
+	return nil
+}
+
 // Expired - rpc handler for expired lock status.
 func (l *lockServer) Expired(args *LockArgs, reply *bool) error {
 	l.mutex.Lock()

cmd/lock-rpc-server_test.go

@@ -326,6 +326,74 @@ func TestLockRpcServerRUnlock(t *testing.T) {
 	}
 }
 
+// Test ForceUnlock functionality
+func TestLockRpcServerForceUnlock(t *testing.T) {
+
+	timestamp := time.Now().UTC()
+	testPath, locker, token := createLockTestServer(t)
+	defer removeAll(testPath)
+
+	laForce := LockArgs{
+		Name:      "name",
+		Token:     token,
+		Timestamp: timestamp,
+		Node:      "node",
+		RPCPath:   "rpc-path",
+		UID:	   "1234-5678",
+	}
+
+	// First test that UID should be empty
+	var result bool
+	err := locker.ForceUnlock(&laForce, &result)
+	if err == nil {
+		t.Errorf("Expected error, got %#v", nil)
+	}
+
+	// Then test force unlock of a lock that does not exist (not returning an error)
+	laForce.UID = ""
+	err = locker.ForceUnlock(&laForce, &result)
+	if err != nil {
+		t.Errorf("Expected no error, got %#v", err)
+	}
+
+	la := LockArgs{
+		Name:      "name",
+		Token:     token,
+		Timestamp: timestamp,
+		Node:      "node",
+		RPCPath:   "rpc-path",
+		UID:       "0123-4567",
+	}
+
+	// Create lock ... (so that we can force unlock)
+	err = locker.Lock(&la, &result)
+	if err != nil {
+		t.Errorf("Expected %#v, got %#v", nil, err)
+	} else if !result {
+		t.Errorf("Expected %#v, got %#v", true, result)
+	}
+
+	// Forcefully unlock the lock (not returning an error)
+	err = locker.ForceUnlock(&laForce, &result)
+	if err != nil {
+		t.Errorf("Expected no error, got %#v", err)
+	}
+
+	// Try to get lock again (should be granted)
+	err = locker.Lock(&la, &result)
+	if err != nil {
+		t.Errorf("Expected %#v, got %#v", nil, err)
+	} else if !result {
+		t.Errorf("Expected %#v, got %#v", true, result)
+	}
+
+	// Finally forcefully unlock the lock once again
+	err = locker.ForceUnlock(&laForce, &result)
+	if err != nil {
+		t.Errorf("Expected no error, got %#v", err)
+	}
+}
+
 // Test Expired functionality
 func TestLockRpcServerExpired(t *testing.T) {
 	timestamp := time.Now().UTC()

vendor/github.com/minio/dsync/drwmutex.go

@@ -124,7 +124,7 @@ func (dm *DRWMutex) lockBlocking(isReadLock bool) {
 
 			// if success, copy array to object
 			if isReadLock {
-				// append new array of bools at the end
+				// append new array of strings at the end
 				dm.readersLocks = append(dm.readersLocks, make([]string, dnodeCount))
 				// and copy stack array into last spot
 				copy(dm.readersLocks[len(dm.readersLocks)-1], locks[:])
@@ -315,12 +315,14 @@ func (dm *DRWMutex) Unlock() {
 			panic("Trying to Unlock() while no Lock() is active")
 		}
 
-		// Copy writelocks to stack array
+		// Copy write locks to stack array
 		copy(locks, dm.writeLocks[:])
+		// Clear write locks array
+		dm.writeLocks = make([]string, dnodeCount)
 	}
 
 	isReadLock := false
-	unlock(&locks, dm.Name, isReadLock)
+	unlock(locks, dm.Name, isReadLock)
 }
 
 // RUnlock releases a read lock held on dm.
@@ -344,25 +346,42 @@ func (dm *DRWMutex) RUnlock() {
 	}
 
 	isReadLock := true
-	unlock(&locks, dm.Name, isReadLock)
+	unlock(locks, dm.Name, isReadLock)
 }
 
-func unlock(locks *[]string, name string, isReadLock bool) {
+func unlock(locks []string, name string, isReadLock bool) {
 
 	// We don't need to synchronously wait until we have released all the locks (or the quorum)
 	// (a subsequent lock will retry automatically in case it would fail to get quorum)
 
 	for index, c := range clnts {
 
-		if isLocked((*locks)[index]) {
-			// broadcast lock release to all nodes the granted the lock
-			sendRelease(c, name, (*locks)[index], isReadLock)
-
-			(*locks)[index] = ""
+		if isLocked(locks[index]) {
+			// broadcast lock release to all nodes that granted the lock
+			sendRelease(c, name, locks[index], isReadLock)
 		}
 	}
 }
 
+// ForceUnlock will forcefully clear a write or read lock.
+func (dm *DRWMutex) ForceUnlock() {
+
+	{
+		dm.m.Lock()
+		defer dm.m.Unlock()
+
+		// Clear write locks array
+		dm.writeLocks = make([]string, dnodeCount)
+		// Clear read locks array
+		dm.readersLocks = nil
+	}
+
+	for _, c := range clnts {
+		// broadcast lock release to all nodes that granted the lock
+		sendRelease(c, dm.Name, "", false)
+	}
+}
+
 // sendRelease sends a release message to a node that previously granted a lock
 func sendRelease(c RPC, name, uid string, isReadLock bool) {
 
@@ -383,7 +402,20 @@ func sendRelease(c RPC, name, uid string, isReadLock bool) {
 			// i.e. it is safe to call them from multiple concurrently running goroutines.
 			var unlocked bool
 			args := LockArgs{Name: name, UID: uid} // Just send name & uid (and leave out node and rpcPath; unimportant for unlocks)
-			if isReadLock {
+			if len(uid) == 0 {
+				if err := c.Call("Dsync.ForceUnlock", &args, &unlocked); err == nil {
+					// ForceUnlock delivered, exit out
+					return
+				} else if err != nil {
+					if dsyncLog {
+						log.Println("Unable to call Dsync.ForceUnlock", err)
+					}
+					if nErr, ok := err.(net.Error); ok && nErr.Timeout() {
+						// ForceUnlock possibly failed with server timestamp mismatch, server may have restarted.
+						return
+					}
+				}
+			} else if isReadLock {
 				if err := c.Call("Dsync.RUnlock", &args, &unlocked); err == nil {
 					// RUnlock delivered, exit out
 					return

vendor/vendor.json

@@ -111,10 +111,10 @@
 			"revisionTime": "2015-11-18T20:00:48-08:00"
 		},
 		{
-			"checksumSHA1": "5DKBTLXf5GY5RkVC9DGP2XFMabc=",
+			"checksumSHA1": "UWpLeW+oLfe/MiphMckp1HqKrW0=",
 			"path": "github.com/minio/dsync",
-			"revision": "66c2a42bf14fcaad0322e9f06d9ab85dd6dba9b7",
-			"revisionTime": "2016-10-07T07:30:36Z"
+			"revision": "fcea3bf5533c1b8a5af3cb377d30363782d2532d",
+			"revisionTime": "2016-10-15T15:40:54Z"
 		},
 		{
 			"path": "github.com/minio/go-homedir",