On 11/7/2019 2:33 AM, Nitin Midas wrote:
We have Apache Solr version 6.2.1 installed on server and we are getting
this warning on Apache Solr log from few days which has affected
performance of solr queries and put latency on our App:
SolrCore [user_details] PERFORMANCE WARNING: Overlapping onDeckSearchers=2
This is the wrong mailing list for your question. It belongs on
solr-user, not dev. This mailing list is for discussions around the
development/code of Lucene and Solr.
That message means that you are doing commits, those that open a new
searcher, too frequently. This has resulted in a situation where you
have more than one searcher warming up at the same time. That is the
source of your performance woes.
The solution is to do commits less frequently.
The default configurations that Solr ships with include an autoCommit
section that it set to a maxTime of 15 seconds and has openSearcher set
to false. That default configuration will NOT cause this message to be
logged.
The configuration can also have an autoSoftCommit setting, which *will*
open a new searcher, and thus could cause that message to be logged if
its intervals are too frequent.
Commit operations that are submitted manually or by an indexing program
will normally have openSearcher set to true (which is the default
setting) and could cause the same problem.
Solr ships with autoSoftCommit disabled ... but depending on exactly how
an index is created, it MIGHT automatically have autoSoftCommit enabled
with a 3 second maxTime. I think that three seconds is far too short an
interval for most indexes. It doesn't take much for warming a new
searcher to take more than 3 seconds.
Here's a blog post that provides some useful information:
https://lucidworks.com/post/understanding-transaction-logs-softcommit-and-commit-in-sorlcloud/
Note that this page says a soft commit is less expensive than a hard
commit. This is only *sometimes* true. There are situations that can
make a soft commit just as expensive as a hard commit. And it's also
worthwhile to note that a hard commit with openSearcher=false is NOT
more expensive than a soft commit. Opening a new searcher is the
expensive part, so a hard commit with openSearcher=false is far less
expensive than a soft commit.
Here's the wiki FAQ page on the particular log message you mentioned:
https://cwiki.apache.org/confluence/display/solr/FAQ#FAQ-Whatdoes%22PERFORMANCEWARNING:OverlappingonDeckSearchers=X%22meaninmylogs?
Thanks,
Shawn
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