Hello,
just updated to 5.4 and wanted to share a problem i had with the solution
so i already had 5.x installed after upgrade i also installed x-pack (for the first time) and started to get the below in the logs, which didnt explain much and no logs in elastic
"For path: events", :error=>"LogStash::Instrument::MetricStore::MetricNotFound"}
so after trying some config changes i started to run my configs one by one with --debug then realized that it was an issue with the plugins had to re install them and all is good
dont know why you cant see the plugin errors on the normal logs but though you should know
hope it helps