Avoid data-transfer in distributed locking (#8004)

cmd/lock-rest-server-common.go

@@ -21,7 +21,7 @@ import (
 	"time"
 )
 
-const lockRESTVersion = "v1"
+const lockRESTVersion = "v2"
 const lockRESTPath = minioReservedBucketPath + "/lock/" + lockRESTVersion
 
 var lockServicePath = path.Join(minioReservedBucketPath, lockServiceSubPath)
@@ -33,6 +33,18 @@ const (
 	lockRESTMethodRUnlock     = "runlock"
 	lockRESTMethodForceUnlock = "forceunlock"
 	lockRESTMethodExpired     = "expired"
+
+	// Unique ID of lock/unlock request.
+	lockRESTUID = "uid"
+	// Source contains the line number, function and file name of the code
+	// on the client node that requested the lock.
+	lockRESTSource = "source"
+	// Resource contains a entity to be locked/unlocked.
+	lockRESTResource = "resource"
+	// ServerAddr contains the address of the server who requested lock/unlock of the above resource.
+	lockRESTServerAddr = "serverAddr"
+	// ServiceEndpoint contains the network path of above server to do lock/unlock.
+	lockRESTServerEndpoint = "serverEndpoint"
 )
 
 // nameLockRequesterInfoPair is a helper type for lock maintenance
@@ -41,10 +53,6 @@ type nameLockRequesterInfoPair struct {
 	lri  lockRequesterInfo
 }
 
-type lockResponse struct {
-	Success bool
-}
-
 // 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)