Implement war offloading in Enterprise Search controller to allow readOnlyFilesystem

[pebrc]

          Is this something we should make the operator do by default for Enterprise Search?

Originally posted by @thbkrkr in https://github.com/elastic/cloud-on-k8s/issues/7898#issuecomment-2178658537

Implement the documented workaround directly in the operator. Copy war files to emptyDir volumes via initcontainer

Less than half a GB, so it seems reasonable.

tested in 8.14.0 (https://github.com/elastic/cloud-on-k8s/blob/main/config/samples/enterprisesearch/ent_es.yaml) enterprise-search@ent-sample-ent-67fff4c559-zkqmn:~$ du -sh /usr/share/enterprise-search/{tmp,filebeat/data,lib/war} 4.7M /usr/share/enterprise-search/tmp 24K /usr/share/enterprise-search/filebeat/data 428M /usr/share/enterprise-search/lib/war

https://github.com/elastic/cloud-on-k8s/pull/7898#issuecomment-2178920182

[barkbay]

Should we not try to fix the image first? Or make it easier to run it in a read only fs? For example by including the script to copy the files in the image or in the Enterprise Search startup script? @leemthompo do you know if this is something that can be improved on the Enterprise Search side?

The fact that ECK must rely on this level of detail on the Enterprise Search image implementation feels a bit wrong to me tbh.

[pebrc]

That's a very good point @barkbay and we should do that for future versions of Enterprise Search (the workaround might still be relevant for already released ones).

[leemthompo]

@leemthompo do you know if this is something that can be improved on the Enterprise Search side?

Pinging the dev team for input!

[leemthompo]

Because this hasn't come up before and we have a documented workaround the feedback from team is that we won't be prioritizing updating the image right now