Current state: Under Discussion
Discussion thread: here
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Currently, IQ throws InvalidStateStoreException for any types of error, that means a user cannot handle different types of error.
Because of that, we should throw different exceptions for each type.
To distinguish different types of error, we need to handle all InvalidStateStoreExceptions better during these public methods invoked. The main change is to introduce new exceptions that extend from InvalidStateStoreException. InvalidStateStoreException is not thrown at all anymore, but only new sub-classes.
Various state store exceptions can classify into two category exceptions: RetryableStateStoreException and FatalStateStoreException. The user can use the two exceptions if they only need to distinguish whether it can retry.
- Retryable exceptions
- StreamThreadNotStartedException: will be thrown when streams thread state is CREATED, the user can retry until to RUNNING.
- StreamThreadRebalancingException: will be thrown when stream thread is not running and stream state is REBALANCING, the user just retry and wait until rebalance finished (RUNNING).
- StateStoreMigratedException: A wrapper for StateStoreClosedException / EmptyStateStoreException. Will be thrown when stream thread is RUNNING / REBALANCING. The user needs to rediscover the state store.
- Fatal exceptions
- StreamThreadNotRunningException: will be thrown when stream thread is not running and stream state is PENDING_SHUTDOWN / NOT_RUNNING / ERROR. The user cannot retry when this exception is thrown.
- StateStoreNotAvailableException: A wrapper for StateStoreClosedException / EmptyStateStoreException. Will be thrown when stream thread is PENDING_SHUTDOWN / NOT_RUNNING / ERROR. The user cannot retry when this exception is thrown.
- Internal exceptions
- StateStoreClosedException: will be thrown when state store is not open. This is an internal exception and will be wrapped in StateStoreMigratedException or StateStoreNotAvailableException later.
- EmptyStateStoreException: will be thrown when state store cannot be found in all StateStoreProviders. This is an internal exception and will be wrapped in StateStoreMigratedException or StateStoreNotAvailableException later.
The following is the public methods that users will call to get state store instance or get store values:
- store(storeName, queryableStoreType)
- interface ReadOnlyKeyValueStore(class CompositeReadOnlyKeyValueStore)
- range(from, to)
- interface ReadOnlySessionStore(class CompositeReadOnlySessionStore)
- fetch(from, to)
- interface ReadOnlyWindowStore(class CompositeReadOnlyWindowStore)
- fetch(key, time)
- fetch(key, from, to)
- fetch(from, to, fromTime, toTime)
- fetchAll(from, to)
- @Deprecated fetch(key, timeFrom, timeTo)
- @Deprecated fetch(from, to, timeFrom, timeTo)
- @Deprecated fetchAll(timeFrom, timeTo)
- interface KeyValueIterator(class DelegatingPeekingKeyValueIterator)
All the above methods could be throw following exceptions:
Compatibility, Deprecation, and Migration Plan
- All new exceptions extend from InvalidStateStoreException, this change will be fully backward compatible.