Engine java threads daemon type?

Of the threads created at startup ... do they run with daemon flag set?
Such that they will restart in case of a thread exception.

And speaking of that, will an exception be caught and logged in elastic
logs, or lower? Does Lucene have neutrality or safety contract for the
exposure runtime exceptions. Yeah that second one may be a dev list
question?

I'm familiar with log4j use, but have seen solr escape stack traces with
production settings. Just wanna be prepared.

thx in advance (tia)
b

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