A. Sophie Blee-Goldman created KAFKA-13096:
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Summary: QueryableStoreProvider is not updated when threads are
added/removed/replaced rendering IQ impossible
Key: KAFKA-13096
URL: https://issues.apache.org/jira/browse/KAFKA-13096
Project: Kafka
Issue Type: Bug
Components: streams
Affects Versions: 2.8.0
Reporter: A. Sophie Blee-Goldman
Fix For: 3.0.0, 2.8.1
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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