SOLR-14942 added the inflightUpdatesCounter logic to reduce leader election time on node shutdown.
From my understanding of the code so far:
- Since the earlier triggering of an election is specific to ZK-aware Solr then one could say that ContentStreamHandlerBase.handleRequestBody doing inflight update registers and deregisters is unnecessary.
- Alternatively if waiting for inflight updates to complete (at that point in the shutdown sequence) is generally beneficial then one could say that the pauseUpdatesAndAwaitInflightRequests logic should be added for the ZK-unware code path in CoreContainer.shutdown also.
Illustrative draft pull request with both options: https://github.com/apache/solr/pull/180