I'm currently using Axon Framework alongside Axon Server for my event-based microservices application. Recently I've encountered the need to wait for saga to fully complete and return its execution result (success or error) to the client, and I've solved it by creating a subscription query before dispatching a command that triggers the saga that locks then waits for updates that are being dispatched from saga and returns the result to client.
Now, that worked a treat in reporting on saga completion status to client, but now I've stumbled upon another seemingly connected problem. Every time a client queries our system's API, we perform an existence check of the client's account - and we do that by dispatching the corresponding query before we perform any business logic. After I've introduced the subscription query, when the client receives the response about saga completion status they immediately send a query to us for an updated list of certain entities, but the query that checks for account's existence fails with org.axonframework.queryhandling.NoHandlerForQueryException: No handler for query: ... which is returned by Axon Server upon sending despite the fact that there definitely is a handler registered for it and it's just handled exactly the same command during the previous request by client. This started to happen after I've added the inner subscription query mechanism to the equation.
This error disappears if we repeat the exact same query a bit later or put a delay of a couple hundred milliseconds between the calls, but that's certainly not a solution - what if our clients start to send loads of requests simultaneously, what will happen to account checking query? Are we unable to process some type of query when the subscription is not closed? I close the subscription on doFinally of Mono returned from SubscriptionQueryResult, but is there a chance that it doesn't actually get closed in Axon Server when the next query arrives? Or, which I think is closer to the truth, I need to somehow tune the query handling capacity of Axon Server? The documentation is rather concise on this topic, IMHO, especially concerning queries, not events/commands.
