Failed to connect to backoff(elasticsearch(http://es01:9200)): Connection marked as failed because the onConnect callback failed: resource 'apm-7.5.2-error' exists, but it is not an alias

Elastic Observability APM
2

@mac_71128 welcome to the forum!

This sounds like a known issue which occurs when an alias is deleted: https://github.com/elastic/apm-server/issues/3698#issuecomment-620865066. Perhaps someone deleted apm-* in Elasticsearch? The recovery steps are in the proceeding comment of that issue.

We have some work underway that should prevent this from recurring, but hopefully that issue helps you resolve the problem in the short term.