Guozhang Wang created KAFKA-12812:
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Summary: Consider refactoring state store registration path
Key: KAFKA-12812
URL: https://issues.apache.org/jira/browse/KAFKA-12812
Project: Kafka
Issue Type: Bug
Components: streams
Reporter: Guozhang Wang
Today our state store registration call path within the stateManager (both
local and global) is like this:
{code}
for each store: store.init(store, context)
-> context.register(root, callback)
-> stateManager.registerStore(store, callback)
{code}
One can see that, we have an awkward loop from stateManager back to
stateManager, and we require users to not forget calling context.register(root,
callback). We do this only in order to let users pass the customized callback
implementation to the stateManager.
What about a different path like this:
1) We add a new interface in StateStore, like `StateRestoreCallback
getCallback()` that each impl class need to provide.
2) We remove the `context.register(root, callback)` call; and because of that,
we do not need to pass in `root` in the store.init as well.
3) stateManager just call `store.init(context)` (without the first parameter),
and then put the store along with its restore callback into the map, without
the separate `registerStore` function.
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