...
As part of this KIP we will also add some metrics on the consumer side related to rebalancing. These include:
- total rebalance latency (latency from start to completion of rebalance)
- rebalance-time-avg
- rebalance-time-max
- listener callback latency
- partitions-revoked-time-avg
- partitions-revoked-time-max
- partitions-assigned-time-avg
- partitions-assigned-time-max
- partitions-lost-time-avg
- partitions-lost-time-max
- rebalance rate (# rebalances per day)
- rebalance-rate
...
From the user's perspective, the upgrade path of leveraging new protocols is just the same as switching to a new assignor. For example, assuming the current version of Kafka consumer is 2.2 and "range" assignor is specified in the config. The upgrade path would be:
...
The key point behind this two rolling bounce is that, we want to avoid the situation where leader is on old byte-code and only recognize "eager", but due to compatibility would still be able to deserialize the new protocol data from newer versioned members, and hence just go ahead and do the assignment while new versioned members did not revoke their partitions before joining the group. Note the difference with KIP-415 here: since on consumer we do not have the luxury to leverage on list of built-in assignors since it is user-customizable and hence would be black box to the consumer coordinator, we'd need two rolling bounces instead of one rolling bounce to complete the upgrade, whereas Connect only need one rolling bounce.
...