Elasticsearch version 8.5.2

Machine learning datafeeds cannot be listed if any are not modified since version 6.x

If you have a datafeed that was created in version 5.x or 6.x and has not been updated since 7.0, it is not possible to list datafeeds in 8.4 and 8.5. This means that anomaly detection jobs cannot be managed using Kibana. This issue is fixed in 8.6.0.

If you upgrade to 8.4 or 8.5 with such a datafeed, you need to work around the problem by updating each datafeed’s authorization information using these steps.

Orchestrators which use a settings.json file to configure Elasticsearch may encounter deadlocks during master elections (issue: #92812)

To resolve the deadlock, remove the settings.json file and restart the affected node.

When the ingest attachment processor is used, the interaction of Tika with log4j 2.18.0 and higher (introduced in Elasticsearch 8.4.0) results in excessive logging. This logging is so excessive that it can lead to cluster instability, to the point where the cluster is unusable and nodes must be restarted. (issue: #91964). This issue is fixed in Elasticsearch 8.7.0 (#93878)

To resolve the issue, upgrade to 8.7.0 or higher.