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https://issues.apache.org/jira/browse/KAFKA-6249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16261575#comment-16261575
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Matthias J. Sax commented on KAFKA-6249:
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Thanks for giving feedback :) It seems that this is a duplicate of KAFKA-6144 ?
What I am wondering though is: why does it take so long to recover? If
StandbyTasks are configured, those should read the changelog topic and be
almost up-to-date with the active Task. Thus, rebalance and restore should be
super short as the StandbyTask only needs to read the remaining tail of the
changelog. Can you elaborate here? Would be useful to learn how this behaves
"in the wild" -- do StandbyTasks lag behind and cannot keep up maintaining the
hot standby stores?
> Interactive query downtime when node goes down even with standby replicas
> -------------------------------------------------------------------------
>
> Key: KAFKA-6249
> URL: https://issues.apache.org/jira/browse/KAFKA-6249
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 1.0.0
> Reporter: Charles Crain
>
> In a multi-node Kafka Streams application that uses interactive queries, the
> queryable store will become unavailable (throw InvalidStateStoreException)
> for up to several minutes when a node goes down. This happens regardless of
> how many nodes are in the application as well as how many standby replicas
> are configured.
> My expectation is that if a standby replica is present, that the interactive
> query would fail over to the live replica immediately causing negligible
> downtime for interactive queries. Instead, what appears to happen is that
> the queryable store is down for however long it takes for the nodes to
> completely rebalance (this takes a few minutes for a couple GB of total data
> in the queryable store's backing topic).
> I am filing this as a bug, realizing that it may in fact be a feature
> request. However, until there is a way we can use interactive queries with
> minimal (~zero) downtime on node failure, we are having to entertain other
> strategies for serving queries (e.g. manually materializing the topic to an
> external resilient store such as Cassandra) in order to meet our SLAs.
> If there is a way to minimize the downtime of interactive queries on node
> failure that I am missing, I would like to know what it is.
> Our team is super-enthusiastic about Kafka Streams and we're keen to use it
> for just about everything! This is out only major roadblock.
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