Burrow doesn't work at all even if just 1 Kafka cluster out of several other clusters are not reachable.

Burrow is starting and seem to be working, but in reality it is not providing any consumer metrics of any Kafka cluster. It's because I have about 10 Kafka clusters and 2-3 of them are not working (e.g. for testing purposes).

If I remove those testing clusters from the burrow and all other remaining clusters are working fine - Burrow is also working fine.

Am I missing something or is it intended behavior?

Start by reproducing the configuration with several Kafka clusters, including unreachable testing clusters, and inspect Burrow's cluster startup and consumer-metrics behavior. The issue is resolved when reachable clusters still provide consumer metrics while other configured clusters are unavailable, with the intended behavior established.

Written by the indexing model from the issue text.