Issue: Bad_ConnectionClosed / Bad_SecureChannelIdInvalid during async recursive browse

[ravi-kothapally]

I'm using Eclipse Milo to recursively browse an OPC UA server using the async Method:
I’m passing a custom executor:

Executors.newFixedThreadPool(10)
//config
configBuilder.setExecutor(executor);

//calling this recursively
client.getAddressSpace().browseNodesAsync(nodeId, browseOptions)

The issue: when the recursion goes deeper, I get errors like:

UaException: Bad_ConnectionClosed
UaServiceFaultException: Bad_SecureChannelIdInvalid

Even reducing the thread pool size to 1–2 doesn't help.
It seems like the new session getting created after the first one(may be this one closed because of load)

How can I keep the session/channel alive and stable during async operations?
Is there a better way to do deep recursive browsing asynchronously?

Any suggestions or best practices would be really helpful. Thanks in advance!

[kevinherron]

You need to write your recursive async browse routine so that it is clever enough not to go infinitely wide with the concurrent requests. Just setting an Executor with a fixed size isn't going to do anything - none of these browses are blocking a thread because they are async!

[kevinherron]

Ah, and my recommendation: don't do a full recursive async browse at all. Most servers you encounter in the real world will fall over when you try this, especially if they're the kind that are embedded on PLCs or otherwise limited hardware.

[ravi-kothapally]

Thanks @kevinherron

I was indeed referencing the https://github.com/eclipse-milo/milo/blob/master/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client/BrowseAsyncExample.java as a starting point

will limit the concurrency and depth for recursion
thank you for suggestion