[
https://issues.apache.org/jira/browse/KAFKA-6555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16361492#comment-16361492
]
Matthias J. Sax commented on KAFKA-6555:
----------------------------------------
[~asurana] Thanks for create this JIRA: how is this different to KAFKA-6144 ?
> Making state store queryable during restoration
> -----------------------------------------------
>
> Key: KAFKA-6555
> URL: https://issues.apache.org/jira/browse/KAFKA-6555
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Ashish Surana
> Priority: Major
>
> State store in Kafka streams are currently only queryable when StreamTask is
> in RUNNING state. The idea is to make it queryable even in the RESTORATION
> (PARTITION_ASSIGNED) state as the time spend on restoration can be huge and
> making the data inaccessible during this time could be downtime not suitable
> for many applications.
> When the active partition goes down then one of the following occurs:
> # One of the standby replica partition gets promoted to active: Replica task
> has to restore the remaining state from the changelog topic before it can
> become RUNNING. The time taken for this depends on how much the replica is
> lagging behind. During this restoration time the state store for that
> partition is currently not queryable giving making the partition down. We can
> make the state store partition queryable for the data already present in the
> state store.
> # When there is no replica or standby task, then active task will be started
> in one of the existing node. That node has to build the entire state from the
> changelog topic which can take lot of time depending on how big is the
> changelog topic, and keeping state store not queryable during this time is
> the downtime for the parition.
> It's very important improvement as it could simply improve the availability
> of microservices developed using kafka streams. Any feedback or comments are
> welcome.
>
>
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
