The QueryableStoreProviders class is used to route queries to the correct state store on the owning StreamThread, making it a critical piece of IQ. It gets instantiated when you create a new KafkaStreams, and is passed in a list of StreamThreadStateStoreProviders which it then copies and stores. Because it only stores a copy it only ever contains a provider for the StreamThreads that were created during the app's startup, and unfortunately is never updated during an add/remove/replace thread event.
This means that IQ can’t get a handle on any stores that belong to a thread that wasn’t in the original set. If the app is starting up new threads through the #addStreamThread API or following a REPLACE_THREAD event, none of the data in any of the stores owned by that new thread will be accessible by IQ. If a user is removing threads through #removeStreamThread, or threads die and get replaced, you can fall into an endless loop of InvalidStateStoreException from doing a lookup into stores that have been closed since the thread was removed/died.
If over time all of the original threads are removed or replaced, then IQ won’t work at all.
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