@Chris_Hegarty Sorry I forgot to post an update in this thread, only shared it in another related thread: OOM since 8.16.1 with openjdk23 - #9 by Evesy
Increasing the amount of memory regions allowed to be used by Elastic appears to have resolved the issue for us.
Assuming our Elasticsearch nodes were right on the limit prior to upgrading from 8.15 to 8.17 it would appear Elastic is now using at least ~30% more memory regions than it was previously.
If this feels like something I should raise as a bug report somewhere please let me know. It's certainly unexpected behaviour for us, we've never breached the previous limit of 260k, but after upgrading (and having to then subsequently increase the limit) we've seen nodes going close to 400k