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From Erick Erickson <>
Subject Re: Recommendations for number of open files?
Date Thu, 05 Oct 2017 17:23:13 GMT
Well, Lucene keeps an open file handle for _every_ file in _every_
index directory. So, for instance, let's say a replica has 10
segments. Each segment is 10-15 individual files. So that's 100-150
file handles right there. And indexes can have many segments.

Check to see if "cfs" extensions are in your indexing directory,
that's "compound file system" and if present will reduce the number of
file handles needed.

A second thing you might be able to do is increase the maximum segment
size by setting maxMergedSegmentMB in your solrconfig file for
TieredMergePolicy, something like
<double name="maxMergedSegmentMB">10000</double>
eventually that'll merge segments into fewer, but that'll take a while.

As to your question, we usually recommend to set the file limit to
"unlimited". You do have to monitor it however, at some point there's
a lot of bookkeeping.

one replica trying to open > 8,000 files seems very odd though. Is it
a massive index? The default max segment size is 5G, so you could have
a gazillion small segments in which case you might want to split that
shard up and move the sub-shards to some other machine.


On Thu, Oct 5, 2017 at 10:02 AM, Webster Homer <> wrote:
> We have begun to see errors around too many open files on one of our
> solrcloud nodes. One replica tries to open >8000 files. This replica tries
> to startup and then fails the open files are exceeded upon startup as it
> tries to recover.
> Our solrclouds have 12 distinct collections. I would think that the number
> of open files would depend upon the number of collections as well as
> numbers of files per index etc...
> Our current setting is 8192 open files per process.
> What values are recommended? is there a normal number of open files?
> What would lead to there being lots of open files?
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