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From Andy Lester <a...@petdance.com>
Subject Solr makes long requests about once a minute
Date Wed, 08 Aug 2012 15:30:58 GMT
I'm having a problem with Solr under Tomcat unexpectedly taking a long time to respond to queries.
 As part of some stress testing, I wrote a bot that just does random word searches on my Solr
install, and my responses typically come back in 10-50 ms.  The queries are just 1-3 random
words from /usr/share/dict/words, and I cap off the results at 2500 hits.  

The queries run just fine and I typically get responses up to 50ms for large result sets.
 Here's an example of my log:

TIME     HITS   MS SEARCH WORDS
12:33:20    1    5 hoovey Aruru kwachas
12:33:20    8    5 blinis twyver
12:33:20 2500   34 prework burlily sunshine
12:33:20 1928   30 rendu Solly
12:33:20           unnethe
12:33:20           gadwell afterpeak
12:33:20  792   14 steen
12:33:20    4    7 blanchi repaving
12:33:20   32    6 torbanite Storz ungag
12:33:20    7    5 chemostat
12:33:20   15    6 Guauaenok Adao lakist
12:33:20    6    6 bechance viny
12:33:20   20    6 chagigah
12:33:22  532 2404 bonne
12:33:22  143    9 nonman Norrie
12:33:22   24    6 repealers
12:33:22           Pfosi laniard locutory
12:33:22   51    6 sexipolar wordsmith enshield
12:33:22           loggiest Aryanise koels
12:33:22           fogyish unforcing
12:33:22    4    5 Millvale chokies
12:33:22    5    6 Melfa ripal Olva
12:33:22   15    6 apio Heraea latimeria
12:33:22    4    5 nonnitric parleying

See that one line where it 2404ms to return?  I get those about once a minute, but not at
a regular interval.  I ran this for two hours and got 122 spikes in 120 minutes.  I ran it
overnight and came in to work to find that there were 1283 spikes in 1260 minutes.  So that
one-a-minute is a pattern.

As I write this, I'm in IRC with Chris Hostetter and he says:

--snip--
Probably need to tweak your garbage collector settings to something that doesn't involve "stop
the world" ... the specifics of the changes largely depend on what JVM you are using, what
options you already have set, etc.  markrmiller wrote a good blog about this a little while
back: http://searchhub.org/dev/2011/03/27/garbage-collection-bootcamp-1-0/  There's also some
notes here in the LucidWorks Solr Ref Guide: http://lucidworks.lucidimagination.com/display/solr/JVM+Settings
--snip--

GC certainly sounds like a reasonable suspect.  Any other suggestions?  Any hints on Solr-specific
GC tuning?  I'm currently scouring Google.

Thanks,
xoa

--
Andy Lester => andy@petdance.com => www.petdance.com => AIM:petdance


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