This is a minor observation on 7.17:
When ILM tries to forcemerge a new & completely empty index, it takes surprisingly long.
I often reindex like this: I first create and empty index with
index.lifecycle.origination_date set, wait for ILM to reach "complete" and put the index "whereever it is supposed to be", remove write block and then start reindexing. However, recently I started using ILM forcemerges.
ILM used to zip through all the states and reach complete almost immediately, but the "forcemerge" action is different. It spends about 250-300 seconds in step "segment-count". Is it just because it is waiting for segment count 1, but segment count is zero, or there is a deeper problem?