Elasticsearch version 7.15.0

Frozen tier: (Windows only) The frozen data tier relies on multiple caching mechanisms to speed up access to searchable snapshot files. One of these caches uses sparse files to avoid creating large files on disk when it is not strictly required. A bug prevented files from being created with the right options to enable sparse support on Windows, leading Elasticsearch to create potentially large files that can end up consuming all the disk space.

This issue is fixed in Elasticsearch versions 7.15.2 and later. There is no known workaround for earlier versions. Filesystems that enable sparse files by default are not affected. For more details, see #79371.

Aggregations: In Elasticsearch 7.14.0–7.15.0, when a cross-cluster search (CCS) request is proxied, the memory for the aggregations on the proxy node will not be freed. The trigger is cross-cluster search using aggregations where minimize roundtrips is not effective (for example, when minimize roundtrips is explicitly disabled, or implicitly disabled when using scroll, async and point-in-time searches).

This affects Kibana CCS aggregations because Kibana uses async search by default. This issue can also happen in all modes of remote connections configured for cross-cluster search (sniff and proxy). In sniff mode, we only connect to a subset of the remote nodes (by default 3). So if the remote node we want to send a request to is not one of those 3, we must send the request as a proxy request. The workaround is to periodically restart nodes with heap pressure.

We have fixed this issue in Elasticsearch 7.15.1 and later versions. For more details, see #78404.