Yes, in memory stores are backed by a changelog topic as far as I'm aware. I have filed https://issues.apache.org/jira/browse/KAFKA-6214
On Tue, Nov 14, 2017 at 10:53 PM Matthias J. Sax <[email protected]> wrote: > Thanks for reporting. > > Sounds like a bug to me. Please file a Jira. > > Question: even if you use an In-Memory store, it's still backed by a > changelog topic, right? > > > -Matthias > > On 11/14/17 3:07 PM, Matt Farmer wrote: > > Hey everyone, > > > > We ran across a little bit of a landmine in Kafka Streams 0.11.0.1. > > > > We decided to flip num.standby.replicas to 1 so that we had a hot copy of > > our state stores on other hosts to facilitate fast failover. However, one > > of the applications we tried this on currently uses an in memory store. > > When we flipped the setting on, we then started to restart the running > > instances. > > > > When we restarted the first instance of the application, it came up fine. > > > > When we restarted the second instance, both instances crashed with the > > following exception: > > > > 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) > > > > Changing the application to use a persistent store seems to have resolved > > the issue. > > > > A few questions: > > > > 1. This feels like a bug... is this a bug? :D > > 2. If so, is this already filed somewhere? I did some searching on JIRA > but > > didn't turn up much. > > > > Happy to file an issue and (potentially) tinker with a fix if this is > > indeed a bug. > > > > Thanks, > > Matt Farmer > > > >
