Remove duration field from lock instrumentation (#4111)

Duration for which a lock was held can be computed from the `Since`
field of `OpsLockState`. It is the difference between current time and
time at which the namespace lock was held. This change avoids
superfluous instrumentation.

cmd/lock-instrument_test.go

@@ -141,7 +141,6 @@ func getSystemLockState() (SystemLockState, error) {
 				LockType:    lockInfo.lType,
 				Status:      lockInfo.status,
 				Since:       lockInfo.since,
-				Duration:    UTCNow().Sub(lockInfo.since),
 			})
 		}
 		lockState.LocksInfoPerObject = append(lockState.LocksInfoPerObject, volLockInfo)

cmd/lockinfo-handlers.go

@@ -62,7 +62,6 @@ type OpsLockState struct {
 	LockType    lockType   `json:"type"`   // Lock type (RLock, WLock)
 	Status      statusType `json:"status"` // Status can be Running/Ready/Blocked.
 	Since       time.Time  `json:"since"`  // Time when the lock was initially held.
-	Duration    time.Duration `json:"duration"` // Duration since the lock was held.
 }
 
 // listLocksInfo - Fetches locks held on bucket, matching prefix held for longer than duration.
@@ -105,7 +104,6 @@ func listLocksInfo(bucket, prefix string, duration time.Duration) []VolumeLockIn
 					LockType:    lockInfo.lType,
 					Status:      lockInfo.status,
 					Since:       lockInfo.since,
-					Duration:    elapsed,
 				})
 			volumeLocks = append(volumeLocks, volLockInfo)
 		}

pkg/madmin/lock-commands.go

@@ -47,7 +47,6 @@ type OpsLockState struct {
 	LockType    lockType   `json:"type"`   // Lock type (RLock, WLock)
 	Status      statusType `json:"status"` // Status can be Running/Ready/Blocked.
 	Since       time.Time  `json:"since"`  // Time when the lock was initially held.
-	Duration    time.Duration `json:"duration"` // Duration since the lock was held.
 }
 
 // VolumeLockInfo - represents summary and individual lock details of all