Identify clients that leak fetch sessions in a Kafka cluster

[Martin Schneppenheim <ma...@gmail.com>]

In one of our Kafka clusters we noticed that fetch sessions are being 
evicted and lots of clients print `FETCH_SESSION_ID_NOT_FOUND` log 
messages. We tried to increase max.incremental.fetch.session.cache.slots 
from 1k to 10k in the brokers but the slots were immediately used up 
again and slots were evicted as well. We assume it's caused by one or 
more clients that leak sessions but we have no clue which one it might 
be. Is there a good way to figure it out - ideally something like 
listing the fetch sessions by client.id, sasl username and/or ip 
address? Optionally, can we limit the number of fetch sessions either 
per client.id, IP address or SASL user?

It's alarming that a single client can cause these issues (even though 
they are not critical) for the whole cluster.


Best,

Martin.