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From Harald Kirsch <Harald.Kir...@raytion.com>
Subject Re: Solr irregularly having QTime > 50000ms, stracing solr cures the problem
Date Wed, 09 Jul 2014 07:50:14 GMT
Good point. I will see if I can get the necessary access rights on this 
machine to run tcpdump.

Thanks for the suggestion,
Harald.

On 09.07.2014 00:32, Steve McKay wrote:
> Sure sounds like a socket bug, doesn't it? I turn to tcpdump when Solr starts behaving
strangely in a socket-related way. Knowing exactly what's happening at the transport level
is worth a month of guessing and poking.
>
> On Jul 8, 2014, at 3:53 AM, Harald Kirsch <Harald.Kirsch@raytion.com> wrote:
>
>> Hi all,
>>
>> This is what happens when I run a regular wget query to log the current number of
documents indexed:
>>
>> 2014-07-08:07:23:28 QTime=20 numFound="5720168"
>> 2014-07-08:07:24:28 QTime=12 numFound="5721126"
>> 2014-07-08:07:25:28 QTime=19 numFound="5721126"
>> 2014-07-08:07:27:18 QTime=50071 numFound="5721126"
>> 2014-07-08:07:29:08 QTime=50058 numFound="5724494"
>> 2014-07-08:07:30:58 QTime=50033 numFound="5730710"
>> 2014-07-08:07:31:58 QTime=13 numFound="5730710"
>> 2014-07-08:07:33:48 QTime=50065 numFound="5734069"
>> 2014-07-08:07:34:48 QTime=16 numFound="5737742"
>> 2014-07-08:07:36:38 QTime=50037 numFound="5737742"
>> 2014-07-08:07:37:38 QTime=12 numFound="5738190"
>> 2014-07-08:07:38:38 QTime=23 numFound="5741208"
>> 2014-07-08:07:40:29 QTime=50034 numFound="5742067"
>> 2014-07-08:07:41:29 QTime=12 numFound="5742067"
>> 2014-07-08:07:42:29 QTime=17 numFound="5742067"
>> 2014-07-08:07:43:29 QTime=20 numFound="5745497"
>> 2014-07-08:07:44:29 QTime=13 numFound="5745981"
>> 2014-07-08:07:45:29 QTime=23 numFound="5746420"
>>
>> As you can see, the QTime is just over 50 seconds at irregular intervals.
>>
>> This happens independent of whether I am indexing documents with around 20 dps or
not. First I thought about a dependence on the auto-commit of 5 minutes, but the the 50 seconds
hits are too irregular.
>>
>> Furthermore, and this is *really strange*: when hooking strace on the solr process,
the 50 seconds QTimes disappear completely and consistently --- a real Heisenbug.
>>
>> Nevertheless, strace shows that there is a socket timeout of 50 seconds defined in
calls like this:
>>
>> [pid  1253] 09:09:37.857413 poll([{fd=96, events=POLLIN|POLLERR}], 1, 50000) = 1
([{fd=96, revents=POLLIN}]) <0.000040>
>>
>> where the fd=96 is the result of
>>
>> [pid 25446] 09:09:37.855235 accept(122, {sa_family=AF_INET, sin_port=htons(57236),
sin_addr=inet_addr("ip address of local host")}, [16]) = 96 <0.000054>
>>
>> where again fd=122 is the TCP port on which solr was started.
>>
>> My hunch is that this is communication between the cores of solr.
>>
>> I tried to search the internet for such a strange connection between socket timeouts
and strace, but could not find anything (the stackoverflow entry from yesterday is my own
:-(
>>
>>
>> This smells a bit like a race condition/deadlock kind of thing which is broken up
by timing differences introduced by stracing the process.
>>
>> Any hints appreciated.
>>
>> For completeness, here is my setup:
>> - solr-4.8.1,
>> - cloud version running
>> - 10 shards on 10 cores in one instance
>> - hosted on SUSE Linux Enterprise Server 11 (x86_64), VERSION 11, PATCHLEVEL 2
>> - hosted on a vmware, 4 CPU cores, 16 GB RAM
>> - single digit million docs indexed, exact number does not matter
>> - zero query load
>>
>>
>> Harald.
>
>

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