[jira] [Created] (KAFKA-6214) Using standby replicas with an in memory state store causes Streams to crash

["Matt Farmer (JIRA)" <ji...@apache.org>]

Matt Farmer created KAFKA-6214:
----------------------------------

             Summary: Using standby replicas with an in memory state store causes Streams to crash
                 Key: KAFKA-6214
                 URL: https://issues.apache.org/jira/browse/KAFKA-6214
             Project: Kafka
          Issue Type: Bug
          Components: streams
    Affects Versions: 0.11.0.1
            Reporter: Matt Farmer


We decided to start experimenting with Standby Replicas of our State Stores by setting the following configuration setting:

{code}
num.standby.replicas=1
{code}

Most applications did okay with this except for one that used an in memory state store instead of a persistent state store. With the new configuration, the first instance of this application booted fine. When the second instance came up, both instances crashed with the following exception:

{code}
java.lang.IllegalStateException: Consumer is not subscribed to any topics or assigned any partitions
        at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1037)
        at org.apache.kafka.streams.processor.internals.StreamThread.maybeUpdateStandbyTasks(StreamThread.java:752)
        at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:524)
        at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:480)
        at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:457)
{code}

Monit attempted to restart both instances but they would just continue to crash over and over again. The state store in our problematic application is declared like so:

{code}
Stores
    .create("TheStateStore")
    .withStringKeys()
    .withStringValues()
    .inMemory()
    .build()
{code}

Luckily we had a config switch in place that could turn on an alternate, persistent state store. As soon as we flipped to the persistent state store, things started working as we expected.



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