Do not ignore Lock()'s return value (#8142)

cmd/lock-rest-client.go

@@ -43,6 +43,20 @@ type lockRESTClient struct {
 	timer      *time.Timer
 }
 
+func toLockError(err error) error {
+	if err == nil {
+		return nil
+	}
+
+	switch err.Error() {
+	case errLockConflict.Error():
+		return errLockConflict
+	case errLockNotExpired.Error():
+		return errLockNotExpired
+	}
+	return err
+}
+
 // ServerAddr - dsync.NetLocker interface compatible method.
 func (client *lockRESTClient) ServerAddr() string {
 	return client.serverURL.Host
@@ -88,7 +102,6 @@ func (client *lockRESTClient) markHostDown() {
 // permanently. The only way to restore the connection is at the xl-sets layer by xlsets.monitorAndConnectEndpoints()
 // after verifying format.json
 func (client *lockRESTClient) call(method string, values url.Values, body io.Reader, length int64) (respBody io.ReadCloser, err error) {
-
 	if !client.isHostUp() {
 		return nil, errors.New("Lock rest server node is down")
 	}
@@ -98,7 +111,6 @@ func (client *lockRESTClient) call(method string, values url.Values, body io.Rea
 	}
 
 	respBody, err = client.restClient.Call(method, values, body, length)
-
 	if err == nil {
 		return respBody, nil
 	}
@@ -107,7 +119,7 @@ func (client *lockRESTClient) call(method string, values url.Values, body io.Rea
 		client.markHostDown()
 	}
 
-	return nil, err
+	return nil, toLockError(err)
 }
 
 // Stringer provides a canonicalized representation of node.
@@ -138,7 +150,14 @@ func (client *lockRESTClient) restCall(call string, args dsync.LockArgs) (reply
 
 	respBody, err := client.call(call, values, nil, -1)
 	defer http.DrainBody(respBody)
-	return err == nil, err
+	switch err {
+	case nil:
+		return true, nil
+	case errLockConflict, errLockNotExpired:
+		return false, nil
+	default:
+		return false, err
+	}
 }
 
 // RLock calls read lock REST API.

cmd/lock-rest-server-common.go

@@ -17,6 +17,7 @@
 package cmd
 
 import (
+	"errors"
 	"path"
 	"time"
 )
@@ -53,6 +54,9 @@ type nameLockRequesterInfoPair struct {
 	lri  lockRequesterInfo
 }
 
+var errLockConflict = errors.New("lock conflict")
+var errLockNotExpired = errors.New("lock not expired")
+
 // Similar to removeEntry but only removes an entry only if the lock entry exists in map.
 func (l *localLocker) removeEntryIfExists(nlrip nameLockRequesterInfoPair) {
 	// Check if entry is still in map (could have been removed altogether by 'concurrent' (R)Unlock of last entry)

cmd/lock-rest-server-common_test.go

@@ -35,7 +35,7 @@ func createLockTestServer(t *testing.T) (string, *lockRESTServer, string) {
 	}
 
 	locker := &lockRESTServer{
-		ll: localLocker{
+		ll: &localLocker{
 			mutex:           sync.Mutex{},
 			serviceEndpoint: "rpc-path",
 			lockMap:         make(map[string][]lockRequesterInfo),

cmd/lock-rest-server.go

@@ -42,7 +42,7 @@ const (
 
 // To abstract a node over network.
 type lockRESTServer struct {
-	ll localLocker
+	ll *localLocker
 }
 
 func (l *lockRESTServer) writeErrorResponse(w http.ResponseWriter, err error) {
@@ -62,6 +62,7 @@ func (l *lockRESTServer) IsValid(w http.ResponseWriter, r *http.Request) bool {
 func getLockArgs(r *http.Request) dsync.LockArgs {
 	return dsync.LockArgs{
 		UID:             r.URL.Query().Get(lockRESTUID),
+		Source:          r.URL.Query().Get(lockRESTSource),
 		Resource:        r.URL.Query().Get(lockRESTResource),
 		ServerAddr:      r.URL.Query().Get(lockRESTServerAddr),
 		ServiceEndpoint: r.URL.Query().Get(lockRESTServerEndpoint),
@@ -75,7 +76,11 @@ func (l *lockRESTServer) LockHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if _, err := l.ll.Lock(getLockArgs(r)); err != nil {
+	success, err := l.ll.Lock(getLockArgs(r))
+	if err == nil && !success {
+		err = errLockConflict
+	}
+	if err != nil {
 		l.writeErrorResponse(w, err)
 		return
 	}
@@ -88,7 +93,10 @@ func (l *lockRESTServer) UnlockHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if _, err := l.ll.Unlock(getLockArgs(r)); err != nil {
+	_, err := l.ll.Unlock(getLockArgs(r))
+	// Ignore the Unlock() "reply" return value because if err == nil, "reply" is always true
+	// Consequently, if err != nil, reply is always false
+	if err != nil {
 		l.writeErrorResponse(w, err)
 		return
 	}
@@ -101,7 +109,11 @@ func (l *lockRESTServer) RLockHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if _, err := l.ll.RLock(getLockArgs(r)); err != nil {
+	success, err := l.ll.RLock(getLockArgs(r))
+	if err == nil && !success {
+		err = errLockConflict
+	}
+	if err != nil {
 		l.writeErrorResponse(w, err)
 		return
 	}
@@ -114,7 +126,10 @@ func (l *lockRESTServer) RUnlockHandler(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	if _, err := l.ll.RUnlock(getLockArgs(r)); err != nil {
+	// Ignore the RUnlock() "reply" return value because if err == nil, "reply" is always true.
+	// Consequently, if err != nil, reply is always false
+	_, err := l.ll.RUnlock(getLockArgs(r))
+	if err != nil {
 		l.writeErrorResponse(w, err)
 		return
 	}
@@ -127,6 +142,8 @@ func (l *lockRESTServer) ForceUnlockHandler(w http.ResponseWriter, r *http.Reque
 		return
 	}
 
+	// Ignore the ForceUnlock() "reply" return value because if err == nil, "reply" is always true
+	// Consequently, if err != nil, reply is always false
 	if _, err := l.ll.ForceUnlock(getLockArgs(r)); err != nil {
 		l.writeErrorResponse(w, err)
 		return
@@ -142,7 +159,6 @@ func (l *lockRESTServer) ExpiredHandler(w http.ResponseWriter, r *http.Request)
 
 	lockArgs := getLockArgs(r)
 
-	success := true
 	l.ll.mutex.Lock()
 	defer l.ll.mutex.Unlock()
 	// Lock found, proceed to verify if belongs to given uid.
@@ -150,15 +166,11 @@ func (l *lockRESTServer) ExpiredHandler(w http.ResponseWriter, r *http.Request)
 		// Check whether uid is still active
 		for _, entry := range lri {
 			if entry.UID == lockArgs.UID {
-				success = false // When uid found, lock is still active so return not expired.
+				l.writeErrorResponse(w, errLockNotExpired)
-				break
+				return
 			}
 		}
 	}
-	if !success {
-		l.writeErrorResponse(w, errors.New("lock already expired"))
-		return
-	}
 }
 
 // lockMaintenance loops over locks that have been active for some time and checks back
@@ -189,11 +201,15 @@ func (l *lockRESTServer) lockMaintenance(interval time.Duration) {
 		}
 
 		// Call back to original server verify whether the lock is still active (based on name & uid)
-		expired, _ := c.Expired(dsync.LockArgs{
+		expired, err := c.Expired(dsync.LockArgs{
 			UID:      nlrip.lri.UID,
 			Resource: nlrip.name,
 		})
 
+		if err != nil {
+			continue
+		}
+
 		// For successful response, verify if lock was indeed active or stale.
 		if expired {
 			// The lock is no longer active at server that originated

cmd/namespace-lock.go

@@ -67,7 +67,7 @@ func newDsyncNodes(endpoints EndpointList) (clnts []dsync.NetLocker, myNode int)
 			myNode = len(clnts)
 
 			receiver := &lockRESTServer{
-				ll: localLocker{
+				ll: &localLocker{
 					serverAddr:      endpoint.Host,
 					serviceEndpoint: lockServicePath,
 					lockMap:         make(map[string][]lockRequesterInfo),
@@ -75,7 +75,7 @@ func newDsyncNodes(endpoints EndpointList) (clnts []dsync.NetLocker, myNode int)
 			}
 
 			globalLockServer = receiver
-			locker = &(receiver.ll)
+			locker = receiver.ll
 		} else {
 			host, err := xnet.ParseHost(endpoint.Host)
 			logger.FatalIf(err, "Unable to parse Lock RPC Host")