Subscriptions not resuming after server restart , only read requests seen on NodeId i=2259

[ravi-kothapally]

Hi,

I’m using Eclipse Milo SDK version 0.6.15 and have implemented subscription to a few nodes.
Initially, I can see Publish requests reaching the server and data change notifications working fine.

However, after I restart the server, my client reconnects successfully, but I only see Read requests on

NodeId: i=2259

and no further Publish requests or subscription updates.

Could someone help me understand why the subscriptions are not resuming after the reconnect?
Do I need to explicitly recreate the subscriptions and monitored items after the server restarts,
or should Milo handle this automatically?

[kevinherron]

You need to implement onSubscriptionTransferFailed on one of the subscription listeners, e.g.

milo/opc-ua-sdk/sdk-client/src/main/java/org/eclipse/milo/opcua/sdk/client/api/subscriptions/UaSubscription.java

Lines 311 to 320 in bd15067

	/**
	* A new {@link UaSession} was established, and upon attempting to transfer an existing subscription to this
	* new session, a failure occurred.
	* <p>
	* This subscription will be removed from {@link UaSubscriptionManager}'s bookkeeping. It must be re-created.
	*
	* @param subscription the {@link UaSubscription} that could not be transferred.
	* @param statusCode the {@link StatusCode} for the transfer failure.
	*/
	default void onSubscriptionTransferFailed(UaSubscription subscription, StatusCode statusCode) {}

When the client reconnects and fails to transfer the existing subscriptions this callback is invoked and you must create them again. Milo will never create subscriptions or monitored items for you; only attempt to recover them upon reconnecting, either by resuming the previous session (only in 1.0), or if that fails by creating a new session and trying to transfer them (both 0.6.x and 1.0).

In your case it's destined to fail because you restarted the server and all the state is gone, so you'll get the callback.