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https://issues.apache.org/jira/browse/KAFKA-6520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17110746#comment-17110746
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Vince Mu commented on KAFKA-6520:
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[~guozhang] that makes sense. I just want to clarify whether we are adding a
DISCONNECTED state purely to streamThread or whether we need to add it
KafkaStreams client as well? If it's the latter, would it make sense to transit
the client to the DISCONNECTED state when all it's streamThreads are in the
DISCONNECTED state?
> When a Kafka Stream can't communicate with the server, it's Status stays
> RUNNING
> --------------------------------------------------------------------------------
>
> Key: KAFKA-6520
> URL: https://issues.apache.org/jira/browse/KAFKA-6520
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Michael Kohout
> Priority: Major
> Labels: newbie, user-experience
>
> KIP WIP:
> [https://cwiki.apache.org/confluence/display/KAFKA/KIP-457%3A+Add+DISCONNECTED+status+to+Kafka+Streams]
> When you execute the following scenario the application is always in RUNNING
> state
>
> 1)start kafka
> 2)start app, app connects to kafka and starts processing
> 3)kill kafka(stop docker container)
> 4)the application doesn't give any indication that it's no longer
> connected(Stream State is still RUNNING, and the uncaught exception handler
> isn't invoked)
>
>
> It would be useful if the Stream State had a DISCONNECTED status.
>
> See
> [this|https://groups.google.com/forum/#!topic/confluent-platform/nQh2ohgdrIQ]
> for a discussion from the google user forum. This is a link to a related
> issue.
> -------------------------
> Update: there are some discussions on the PR itself which leads me to think
> that a more general solution should be at the ClusterConnectionStates rather
> than at the Streams or even Consumer level. One proposal would be:
> * Add a new metric named `failedConnection` in SelectorMetrics which is
> recorded at `connect()` and `pollSelectionKeys()` functions, upon capture the
> IOException / RuntimeException which indicates the connection disconnected.
> * And then users of Consumer / Streams can monitor on this metric, which
> normally will only have close to zero values as we have transient
> disconnects, if it is spiking it means the brokers are consistently being
> unavailable indicting the state.
> [~Yohan123] WDYT?
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