Status

Current state: Accepted(vote)

Discussion thread: here

JIRA:

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

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.

Proposed Changes

To distinguish different types of error, we need to handle all InvalidStateStoreException 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.

public class StreamsNotStartedException extends InvalidStateStoreException
public class StreamsRebalancingException extends InvalidStateStoreException
public class StateStoreMigratedException extends InvalidStateStoreException
public class StateStoreNotAvailableException extends InvalidStateStoreException
public class UnknownStateStoreException extends InvalidStateStoreException
public class InvalidStateStorePartitionException extends InvalidStateStoreException

StreamsNotStartedException: will be thrown when stream thread state is CREATED, the user can retry until to RUNNING.
StreamsRebalancingException: 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: will be thrown when state store already closed and stream state is RUNNING. The user need to rediscover the store and cannot blindly retry as the store handle is invalid and a new store handle must be retrived.
StateStoreNotAvailableException: will be thrown when state store closed and stream state is PENDING_SHUTDOWN / NOT_RUNNING / ERROR. The user cannot retry when this exception is thrown.
UnknownStateStoreException: will be thrown when passing an unknown state store. The user cannot retry when this exception is thrown.
InvalidStateStorePartitionException: will be thrown when user requested partition is not available on the stream instance.

The following is the public methods that users will call to get state store instance:

KafkaStreams
- @Deprecated store(storeName, queryableStoreType)
- store(storeQureyParams)

All the above methods could be throw exceptions:

StreamsNotStartedException, StreamsRebalancingException, StateStoreMigratedException, StateStoreNotAvailableException, UnknownStateStoreException, InvalidStateStorePartitionException

The following is the public methods that users will call to get store values:

interface ReadOnlyKeyValueStore(class CompositeReadOnlyKeyValueStore)
- get(key)
- range(from, to)
- all()
- approximateNumEntries()
interface ReadOnlySessionStore(class CompositeReadOnlySessionStore)
- fetch(key)
- fetch(from, to)
interface ReadOnlyWindowStore(class CompositeReadOnlyWindowStore)
- fetch(key, time)
- fetch(key, from, to)
- fetch(from, to, fromTime, toTime)
- all()
- fetchAll(from, to)
- @Deprecated fetch(key, timeFrom, timeTo)
- @Deprecated fetch(from, to, timeFrom, timeTo)
- @Deprecated fetchAll(timeFrom, timeTo)
interface KeyValueIterator(class DelegatingPeekingKeyValueIterator)
- next()
- hasNext()
- peekNextKey()

All the above methods could be throw following exceptions:

StreamsRebalancingException, StateStoreMigratedException, StateStoreNotAvailableException, InvalidStateStorePartitionException

Compatibility, Deprecation, and Migration Plan

All new exceptions extend from InvalidStateStoreException, this change will be fully backward compatible.

Rejected Alternatives

None.