Logstash 6.3.0 has landed, and with it comes some useful improvements to the Persistent Queue, an opt-in feature that enables disk-based spooling and resiliency across abnormal shutdowns.
If you're using the Persistent Queue, you'll want to pay some special attention to the Upgrade Notes: while we make every attempt to make upgrades as hands-off as possible, this upgrade is going to require a little hands-on involvement. We wanted to also start a thread here in the community forums to make sure our users were well-informed.
Unfortunately, PQ serialization issues were found in Logstash 6.2.x (affecting the PQ in all previous releases) that could not be resolved in a fully backward-compatible way, and some queue elements that were spooled to disk using a Logstash 6.2.x or earlier cannot be processed on versions of Logstash that include the fix.
We are recommending that users who have enabled the Persistent Queue drain your queues prior to upgrading.