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1. Re: JMS Client discovery of Live/Backup server for remote client
How would I determine which of the two servers the Queue in its JNDI?
As far as I can tell, this is the essential question you're asking. Unfortunately I don't understand it. It seems to be missing one or more important words.
That said, let me give you a little overview on JMS and JNDI that might help...
JMS and JNDI are fundamentally independent. They are completely different specs and implemented by completely different projects. The convention outlined by the JMS specification is for clients to leverage JNDI when finding administered objects (e.g. destinations and connection factories), but it's not actually required. JNDI certainly has no knowledge of HornetQ fail-over/back semantics.
Therefore, if the client wishes to use JNDI when connecting to a HornetQ live/backup pair it is up to the client to find the active server. With EAP 6.x I think the simplest way to do this is using multiple URLs in your JNDI look-up.
Does that address your question? If not, please clarify.
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2. Re: JMS Client discovery of Live/Backup server for remote client
True, I missed a word.
How would I determine which of the two servers has the Queue in its JNDI?
Of course, JMS and JNDI are fundamentally independent, I understand that. The point is that that backup HornetQ removes all ConnectionFactories and destinations from the Directory when starts in or returns to backup mode. Using multiple values in the PROVIDER_URL in your InitialContext will fail if the first server in the list is up, but is not the active HornetQ server. You can connect to the directory, but when searching for the JMS objects it will throw an exception because it it not found.
The question therefore is, is there a method using HornetQ to determine which server is live, and has all the required objects in its directory, so the client can connect to the active HornetQ server regardless of which JBoss servers are up?
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3. Re: JMS Client discovery of Live/Backup server for remote client
How would I determine which of the two servers has the Queue in its JNDI?
Try the look-up on one server, if the look-up fails then try the look-up on the other server.
Using multiple values in the PROVIDER_URL in your InitialContext will fail if the first server in the list is up, but is not the active HornetQ server. You can connect to the directory, but when searching for the JMS objects it will throw an exception because it it not found.
If you keep the URLs ordered properly and use fail-back then this should rarely be a problem. However, if you're worried about this possibility then see my answer to your previous question.
The question therefore is, is there a method using HornetQ to determine which server is live, and has all the required objects in its directory, so the client can connect to the active HornetQ server regardless of which JBoss servers are up?
Your question here is two-fold...
Yes, there is a way for a HornetQ client to determine which server is live. It's outlined in the documentation you cited previously (i.e. section 38.2.1.4.1 here). It's worth noting that you can avoid JNDI entirely using org.hornetq.api.jms.HornetQJMSClient. It can create JMS connection factories and destinations.
No, there is no way using HornetQ to determine which server has all the required objects in JNDI. If you want to know what's in JNDI then you should use the JNDI API, not the HornetQ (or JMS) API.