Are there any significant (or not so significant) changes? I have browsed the release notes and searched JIRA, but the latest news seems to be in 7.3 (where the old Leader-In-Recovery logic was replaced).
We are currently running Solr 7.4 in production. In the past year, we’ve seen two cases where, during a rolling restart, one of the collections inexplicably ends up without a leader. We have ways to mitigate – shutdown all instances then start up just one to have it be leader for everything, and we just learned about the FORCELEADER API. However, when this condition has struck, reads from that collection do not work, so there’s customer impact.
We are planning an upgrade to Solr8. The timing of that could be influenced by whether this upgrade could improve things in this particular area.