Force Merge API Status

Elastic Stack Elasticsearch
1

Is there a way to check progress of a force merge? Or a way to see if one is running in the cluster? On an index? on a shard?

I saw that clintongormley@ was directing similar github issues to this: https://github.com/elastic/elasticsearch/issues/15117

Doesn't appear to be any additional information there though if the work for force_merge tasks was competed or not.

2

There's not at this point in time, I believe something is planned though.

3

Ok. Is there a rough estimate of how long it should take? i.e. 100 segments each around 1Gb should take NN seconds to force merge down to 1 segment?

From this guide page I see that heavy merging is not throttled on IO and that it should be done on dedicated "merge" host. What does this mean for replicas? Does merging get done on the primary first and then copied to replicas dropping existing replicas? Or does the merge occur on any host that holds an active copy of the shard (replica or primary) meaning that I need to allocate both primaries AND replicas to "dedicated force merge" hosts?

4

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