Rolling Upgrade support https://issues.apache.org/jira/browse/NIFI-13659

[soenkeliebau]

According to https://issues.apache.org/jira/browse/NIFI-13659 we suspect that rolling upgrades should now be possible.

Do some further investigation and if yes, bypass the code in NiFi op that does a full cluster restart for upgrades.

[xeniape]

Outcome of Research

As stated by Mark (apache) in NiFi Slack https://apachenifi.slack.com/archives/C0L9UPWJZ/p1743009153536569?thread_ts=1742975023.688019&cid=C0L9UPWJZ NiFi supports rolling upgrade from 2.x to 2.y. They are not supported in 1.x and are not expected to work there.

Local testing of a rolling upgrade succeeded for the upgrades 1.27.0 -> 1.28.1 and 1.28.1 -> 2.2.0, but was tested only with a simple Flow of two standard Processors. But also as mentioned by Mark such an upgrade might or might not work. There is no guarantee.

[xeniape]

Link to PR: #771