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.
# Two category exceptions public class RetryableStateStoreException extends InvalidStateStoreException public class FatalStateStoreException extends InvalidStateStoreException # Retryable exceptions public class StreamThreadNotStartedException extends RetryableStateStoreException public class StreamThreadRebalancingException extends RetryableStateStoreException public class StateStoreMigratedException extends RetryableStateStoreException # Fatal exceptions public class StreamThreadNotRunningException extends FatalStateStoreException
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.
The following is the public methods that users will call to get state store instance or get store values:
fetch(key, from, to)
All the above methods could be throw following exceptions: