I need assistance with OPC UA Server reconnection issues.

[AppleCitron]

Hello,

I am currently communicating with an OPC Server using the Milo Client, and occasionally, the connection fails when the Server restarts.
If you need any additional information, please let me know.

I have a few questions regarding this issue:

1. Can the reconnection request interval be set longer when the connection is lost in KeepAlive?
2. Why does the reconnection request interval act so quickly when the connection is lost in KeepAlive?

Situation: Normal connection with OPC Server, OPC Server restarts.

Log of successful reconnection:

10:05:37.762 [P-shared-thread-pool-31] DEBUG [P] [547] S(Active)                x E(KeepAlive)             = S'(Active)               - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:37.769 [P-shared-thread-pool-30] DEBUG [P] [547] S(Active)                x E(KeepAliveFailure)      = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:37.770 [P-shared-thread-pool-30] DEBUG [P] [547] S(CreatingWait)          x E(GetSession)            = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:37.770 [P-shared-thread-pool-26] DEBUG [P] [547] S(CreatingWait)          x E(ConnectionLost)        = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:37.770 [P-shared-thread-pool-26] DEBUG [P] [547] S(CreatingWait)          x E(GetSession)            = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:37.771 [P-shared-thread-pool-26] DEBUG [P] [547] S(CreatingWait)          x E(GetSession)            = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:38.769 [P-shared-thread-pool-26] DEBUG [P] [547] S(CreatingWait)          x E(CreatingWaitExpired)   = S'(Creating)             - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:38.778 [P-shared-thread-pool-26] DEBUG [P] [547] S(Creating)              x E(CreateSessionFailure)  = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:40.778 [P-shared-thread-pool-30] DEBUG [P] [547] S(CreatingWait)          x E(CreatingWaitExpired)   = S'(Creating)             - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:40.961 [P-shared-thread-pool-31] DEBUG [P] [547] S(Creating)              x E(CreateSessionSuccess)  = S'(Activating)           - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:40.984 [P-shared-thread-pool-31] DEBUG [P] [547] S(Activating)            x E(ActivateSessionSuccess) = S'(Transferring)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:41.008 [P-shared-thread-pool-26] DEBUG [P] [547] S(Transferring)          x E(TransferSubscriptionsSuccess) = S'(Initializing)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:41.164 [P-shared-thread-pool-26] DEBUG [P] [547] S(Initializing)          x E(InitializeSuccess)     = S'(Active)               - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:42.165 [P-shared-thread-pool-26] DEBUG [P] [547] S(Active)                x E(KeepAlive)             = S'(Active)               - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
10:05:43.165 [P-shared-thread-pool-30] DEBUG [P] [547] S(Active)                x E(KeepAlive)             = S'(Active)               - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]

Log of failed reconnection:

14:06:54.640 [P-shared-thread-pool-4] DEBUG [P] [2] S(Active)                x E(KeepAlive)             = S'(Active)               - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:55.641 [P-shared-thread-pool-0] DEBUG [P] [2] S(Active)                x E(KeepAlive)             = S'(Active)               - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:56.641 [P-shared-thread-pool-4] DEBUG [P] [2] S(Active)                x E(KeepAlive)             = S'(Active)               - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:57.170 [P-shared-thread-pool-6] DEBUG [P] [2] S(Active)                x E(ServiceFault)          = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:57.171 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait)          x E(GetSession)            = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:57.172 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait)          x E(ServiceFault)          = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:57.172 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait)          x E(GetSession)            = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:57.172 [P-shared-thread-pool-0] DEBUG [P] [2] S(CreatingWait)          x E(ServiceFault)          = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:57.214 [P-shared-thread-pool-0] DEBUG [P] [2] S(CreatingWait)          x E(GetSession)            = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:57.214 [P-shared-thread-pool-0] DEBUG [P] [2] S(CreatingWait)          x E(ServiceFault)          = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:58.013 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait)          x E(ConnectionLost)        = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:58.171 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait)          x E(CreatingWaitExpired)   = S'(Creating)             - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:06:59.027 [P-shared-thread-pool-6] DEBUG [P] [2] S(Creating)              x E(CreateSessionFailure)  = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:07:01.028 [P-shared-thread-pool-0] DEBUG [P] [2] S(CreatingWait)          x E(CreatingWaitExpired)   = S'(Creating)             - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:07:05.031 [P-shared-thread-pool-0] DEBUG [P] [2] S(Creating)              x E(CreateSessionFailure)  = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]

14:07:01.028 [P-shared-thread-pool-0] DEBUG [P] [2] S(CreatingWait)          x E(CreatingWaitExpired)   = S'(Creating)             - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
14:07:05.031 [P-shared-thread-pool-0] DEBUG [P] [2] S(Creating)              x E(CreateSessionFailure)  = S'(CreatingWait)         - com.digitalpetri.strictmachine.StrictMachine$PollAndEvaluate.run[200]
The above log repeats, indicating repeated reconnection failures.

[kevinherron]

I'm not entirely sure what you are asking here.

The delay between reconnect attempts backs off exponentially until 16s, i.e. 1s, 2s, 4s, 8s, 16s, 16s, 16s... This isn't currently configurable in any way.

[AppleCitron]

14:06:57.170 [P-shared-thread-pool-6] DEBUG [P] [2] S(Active) x E(ServiceFault) = S'(CreatingWait) -
14:06:57.171 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait) x E(GetSession) = S'(CreatingWait) -
14:06:57.172 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait) x E(ServiceFault) = S'(CreatingWait) -
14:06:57.172 [P-shared-thread-pool-6] DEBUG [P] [2] S(CreatingWait) x E(GetSession) = S'(CreatingWait) -
14:06:57.172 [P-shared-thread-pool-0] DEBUG [P] [2] S(CreatingWait) x E(ServiceFault) = S'(CreatingWait) -

It appears that getSession requests are being made at intervals of 0.001 units after a ServerFault or ConnectionLost. This is happening too quickly.

[kevinherron]

GetSession events happen when your user code requests a Session. They are internal transition in the state machine here - they are not causing immediate action against the Server. There is no issue with this.