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Status

Current state:  [One of "Under Discussion", "Accepted", "Rejected"] Accepted(vote)

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
JIRA: KAFKA-5876 [Change the link from KAFKA-1 to your own ticket]

JIRA: 

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

Motivation

Describe the problems you are trying to solve.

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

A public interface is any change to the following:

• Binary log format

• The network protocol and api behavior

• Any class in the public packages under clientsConfiguration, especially client configuration

  • org/apache/kafka/common/serialization

  • org/apache/kafka/common

  • org/apache/kafka/common/errors

  • org/apache/kafka/clients/producer

  • org/apache/kafka/clients/consumer (eventually, once stable)

• Monitoring

• Command line tools and arguments

• Anything else that will likely break existing users in some way when they upgrade

Proposed Changes

...

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)

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()

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Rejected Alternatives

...

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

Rejected Alternatives

None.