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From Maulin Rathod <mrat...@asite.com>
Subject RE: Long GC Pauses
Date Wed, 07 Feb 2018 12:20:03 GMT
Hi Erick,



Thanks for your response. It shows GC pauses in Solr GC logs (refer below solr gc log where
it shows 138.4138211 sec pause).



Seems like some bad query causes high memory allocation.

Further analyzing issue we found that asking for too many rows (e.g. rows=10000000) can cause
full GC problem as mentioned in below link. We had some query which was asking for too many
rows….so for now we have reduced number rows. After changing this we don’t see any large
GC Pause (Max GC pause is 3-4 second). So seems like issue is resolved for now…But still
please let me know if you have any other suggestion which can help us to understand the root
cause…


https://wiki.apache.org/solr/SolrPerformanceProblems#GC_pause_problems
https://sbdevel.wordpress.com/2015/10/05/speeding-up-core-search/





Solr GC Log

==========



2018-01-04T12:13:40.346+0000: 140501.570: [CMS-concurrent-abortable-preclean-start]

{Heap before GC invocations=8909 (full 1001):

par new generation   total 10922688K, used 4187699K [0x0000000080000000, 0x00000003a0000000,
0x00000003a0000000)

  eden space 8738176K,  41% used [0x0000000080000000, 0x000000015fb1f6d8, 0x0000000295560000)

  from space 2184512K,  23% used [0x0000000295560000, 0x00000002b53cd8b8, 0x000000031aab0000)

  to   space 2184512K,   0% used [0x000000031aab0000, 0x000000031aab0000, 0x00000003a0000000)

concurrent mark-sweep generation total 39321600K, used 38082444K [0x00000003a0000000, 0x0000000d00000000,
0x0000000d00000000)

Metaspace       used 46676K, capacity 47372K, committed 50136K, reserved 51200K

2018-01-04T12:13:40.393+0000: 140501.618: [GC (Allocation Failure) 140501.618: [CMS2018-01-04T12:13:40.534+0000:
140501.766: [CMS-concurrent-abortable-preclean: 0.149/0.196 secs] [Times: user=0.41 sys=0.00,
real=0.19 secs]

 (concurrent mode failure): 38082444K->18127660K(39321600K), 138.3709254 secs] 42270144K->18127660K(50244288K),
[Metaspace: 46676K->46676K(51200K)], 138.3746435 secs] [Times: user=12.75 sys=22.89, real=138.38
secs]

Heap after GC invocations=8910 (full 1002):

par new generation   total 10922688K, used 0K [0x0000000080000000, 0x00000003a0000000, 0x00000003a0000000)

  eden space 8738176K,   0% used [0x0000000080000000, 0x0000000080000000, 0x0000000295560000)

  from space 2184512K,   0% used [0x0000000295560000, 0x0000000295560000, 0x000000031aab0000)

  to   space 2184512K,   0% used [0x000000031aab0000, 0x000000031aab0000, 0x00000003a0000000)

concurrent mark-sweep generation total 39321600K, used 18127660K [0x00000003a0000000, 0x0000000d00000000,
0x0000000d00000000)

Metaspace       used 46676K, capacity 47372K, committed 50136K, reserved 51200K

}

2018-01-04T12:15:58.772+0000: 140639.993: Total time for which application threads were stopped:
138.4138211 seconds, Stopping threads took: 0.0369886 seconds







Regards,



Maulin





-----Original Message-----
From: Erick Erickson [mailto:erickerickson@gmail.com]
Sent: 31 January 2018 22:47
To: solr-user <solr-user@lucene.apache.org>
Subject: Re: Long GC Pauses



Just to double check, when you san you're seeing 60-200 sec  GC pauses are you looking at
the GC logs (or using some kind of monitor) or is that the time it takes the query to respond
to the client? Because a single GC pause that long on 40G is unusual no matter what. Another
take on Jason's question is For all the JVMs you're running, how much _total_ heap is allocated?

And how much physical memory is on the box? I generally start with _at least_ half the memory
left to the OS....



These are fairly horrible, what generates such queries?

AND * AND *



Best,

Erick







On Wed, Jan 31, 2018 at 7:28 AM, Jason Gerlowski <gerlowskija@gmail.com<mailto:gerlowskija@gmail.com>>
wrote:

> Hi Maulin,

>

> To clarify, when you said "...allocated 40 GB RAM to each shard."

> above, I'm going to assume you meant "to each node" instead.  If you

> actually did mean "to each shard" above, please correct me and anyone

> who chimes in afterward.

>

> Firstly, it's really hard to even take guesses about potential causes

> or remediations without more details about your load characteristics

> (average/peak QPS, index size, average document size, etc.).  If no

> one gives any satisfactory advice, please consider uploading

> additional details to help us help you.

>

> Secondly, I don't know anything about the load characteristics you're

> putting on your Solr cluster, but I'm curious whether you've

> experimented with lower RAM settings.  Generally speaking, the more

> RAM you have, the longer your GC pauses are likely to be (even with

> the tuning that various GC settings provide).  If you can get away

> with giving the Solr process less RAM, you should see your GC pauses

> shrink.  Was 40GB chosen after some trial-and-error experimentation, or is it something
you could investigate?

>

> For a bit more overview on this, see this slightly outdated (but still

> useful) wiki page:

> https://wiki.apache.org/solr/SolrPerformanceProblems#RAM

>

> Hope that helps, even if just to disqualify some potential

> causes/solutions to close in on a real fix.

>

> Best,

>

> Jason

>

> On Wed, Jan 31, 2018 at 8:17 AM, Maulin Rathod <mrathod@asite.com<mailto:mrathod@asite.com>>
wrote:

>

>> Hi,

>>

>> We are using solr cloud 6.1. We have around 20 collection on 4 nodes

>> (We have 2 shards and each shard have 2 replicas). We have allocated

>> 40 GB RAM to each shard.

>>

>> Intermittently we found long GC pauses (60 sec to 200 sec) due to

>> which solr stops responding and hence collections goes in recovering

>> mode. It takes minimum 5-10 minutes (sometime it takes more and we

>> have to restart the solr node) for recovering all collections. We are

>> using default GC setting (CMS) as per solr.cmd.

>>

>> We tried different G1 GC to see if it help, but still we see long GC

>> pauses(60 sec to 200 sec) and also found that memory usage is more in

>> in case G1 GC.

>>

>> What could be reason for long GC pauses and how can fix it?

>> Insufficient memory or problem with GC setting or something else? Any

>> suggestion would be greatly appreciated.

>>

>> In our analysis, we also found some inefficient queries (which uses *

>> many times in query) in solr logs. Could it be reason for high memory usage?

>>

>> Slow Query

>> --------------

>>

>> INFO  (qtp1239731077-498778) [c:documents s:shard1 r:core_node1

>> x:documents] o.a.s.c.S.Request [documents]  webapp=/solr path=/select

>> params={df=summary&distrib=false&fl=id&shards.purpose=4&

>> start=0&fsv=true&sort=description+asc,id+desc&fq=&shard.url=

>> s1.asite.com:8983/solr/documents|s1r1.asite.com:

>> 8983/solr/documents&rows=250&version=2&q=((id:(

>> REV78364_24705418+REV78364_24471492+REV78364_24471429+

>> REV78364_24470771+REV78364_24470271+))+OR+summary:((HPC*+

>> AND+*+AND+*+AND+OH1150*+AND+*+AND+*+AND+U0*+AND+*+AND+*+AND+

>> HGS*+AND+*+AND+*+AND+MDL*+AND+*+AND+*+AND+100067*+AND+*+AND+

>> -*+AND+Reinforcement*+AND+*+AND+Mode*)+))++AND++(title:((*

>> HPC\+\-\+OH1150\+\-\+U0\+\-\+HGS\+\-\+MDL\+\-\+100067\+-\+

>> Reinforcement\+Mode*)+))+AND+project_id:(-2+78243+78365+

>> 78364)+AND+is_active:true+AND+((isLatest:(true)+AND+

>> isFolderActive:true+AND+isXref:false+AND+-document_

>> type_id:(3+7)+AND+((is_public:true+OR+distribution_list:

>> 4858120+OR+folderadmin_list:4858120+OR+author_user_id:

>> 4858120)+AND+((defaultAccess:(true)+OR+allowedUsers:(

>> 4858120)+OR+allowedRoles:(6342201+172408+6336860)+OR+

>> combinationUsers:(4858120))+AND+-blockedUsers:(4858120))))

>> +OR+(isLatestRevPrivate:(true)+AND+allowedUsersForPvtRev:(

>> 4858120)+AND+-folderadmin_list:(4858120)))&shards.tolerant=true&NOW=

>> 1516786982952&isShard=true&wt=javabin} hits=0 status=0 QTime=83309

>>

>>

>>

>>

>> Regards,

>>

>> Maulin

>>

>> [CC Award Winners!]

>>

>>
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