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From Joe Gresock <jgres...@gmail.com>
Subject Re: Uneven shard heap usage
Date Sun, 01 Jun 2014 12:32:49 GMT
These are some good ideas.  The "huge document" idea could add up, since I
think the shard1 index is a little larger (32.5GB on disk instead of
31.9GB), so it is possible there's one or 2 really big ones that are
getting loaded into memory there.

Btw, I did find an article on the Solr document routing (
http://searchhub.org/2013/06/13/solr-cloud-document-routing/), so I don't
think that our ID structure is a problem in itself.  But I will follow up
on the large document idea.

I used this article (
https://support.datastax.com/entries/38367716-Solr-Configuration-Best-Practices-and-Troubleshooting-Tips)
to find the index heap and disk usage:
http://localhost:8983/solr/admin/cores?action=STATUS&memory=true

Though looking at the data index directory on disk basically said the same
thing.

I am pretty sure we're using the smart round-robining client, but I will
double check on Monday.

We have been using CollectD and graphite to monitor our VMs, as well as
jvisualvm, though we haven't tried SPM.

Thanks for all the ideas, guys.


On Sat, May 31, 2014 at 11:54 PM, Otis Gospodnetic <
otis.gospodnetic@gmail.com> wrote:

> Hi Joe,
>
> Are you/how are you sure all 3 shards are roughly the same size?  Can you
> share what you run/see that shows you that?
>
> Are you sure queries are evenly distributed?  Something like SPM
> <http://sematext.com/spm/> should give you insight into that.
>
> How big are your caches?
>
> Otis
> --
> Performance Monitoring * Log Analytics * Search Analytics
> Solr & Elasticsearch Support * http://sematext.com/
>
>
> On Sat, May 31, 2014 at 5:54 PM, Joe Gresock <jgresock@gmail.com> wrote:
>
> > Interesting thought about the routing.  Our document ids are in 3 parts:
> >
> > <10-digit identifier>!<epoch timestamp>!<format>
> >
> > e.g., 5/12345678!130000025603!TEXT
> >
> > Each object has an identifier, and there may be multiple versions of the
> > object, hence the timestamp.  We like to be able to pull back all of the
> > versions of an object at once, hence the routing scheme.
> >
> > The nature of the identifier is that a great many of them begin with a
> > certain number.  I'd be interested to know more about the hashing scheme
> > used for the document routing.  Perhaps the first character gives it more
> > weight as to which shard it lands in?
> >
> > It seems strange that certain of the most highly-searched documents would
> > happen to fall on this shard, but you may be onto something.   We'll
> scrape
> > through some non-distributed queries and see what we can find.
> >
> >
> > On Sat, May 31, 2014 at 1:47 PM, Erick Erickson <erickerickson@gmail.com
> >
> > wrote:
> >
> > > This is very weird.
> > >
> > > Are you sure that all the Java versions are identical? And all the JVM
> > > parameters are the same? Grasping at straws here.
> > >
> > > More grasping at straws: I'm a little suspicious that you are using
> > > routing. You say that the indexes are about the same size, but is it is
> > > possible that your routing is somehow loading the problem shard
> > abnormally?
> > > By that I mean somehow the documents on that shard are different, or
> > have a
> > > drastically higher number of hits than the other shards?
> > >
> > > You can fire queries at shards with &distrib=false and NOT have it go
> to
> > > other shards, perhaps if you can isolate the problem queries that might
> > > shed some light on the problem.
> > >
> > >
> > > Best
> > > Erick@Baffled.com
> > >
> > >
> > > On Sat, May 31, 2014 at 8:33 AM, Joe Gresock <jgresock@gmail.com>
> wrote:
> > >
> > > > It has taken as little as 2 minutes to happen the last time we tried.
> >  It
> > > > basically happens upon high query load (peak user hours during the
> > day).
> > > >  When we reduce functionality by disabling most searches, it
> > stabilizes.
> > > >  So it really is only on high query load.  Our ingest rate is fairly
> > low.
> > > >
> > > > It happens no matter how many nodes in the shard are up.
> > > >
> > > >
> > > > Joe
> > > >
> > > >
> > > > On Sat, May 31, 2014 at 11:04 AM, Jack Krupansky <
> > > jack@basetechnology.com>
> > > > wrote:
> > > >
> > > > > When you restart, how long does it take it hit the problem? And how
> > > much
> > > > > query or update activity is happening in that time? Is there any
> > other
> > > > > activity showing up in the log?
> > > > >
> > > > > If you bring up only a single node in that problematic shard, do
> you
> > > > still
> > > > > see the problem?
> > > > >
> > > > > -- Jack Krupansky
> > > > >
> > > > > -----Original Message----- From: Joe Gresock
> > > > > Sent: Saturday, May 31, 2014 9:34 AM
> > > > > To: solr-user@lucene.apache.org
> > > > > Subject: Uneven shard heap usage
> > > > >
> > > > >
> > > > > Hi folks,
> > > > >
> > > > > I'm trying to figure out why one shard of an evenly-distributed
> > 3-shard
> > > > > cluster would suddenly start running out of heap space, after 9+
> > months
> > > > of
> > > > > stable performance.  We're using the "!" delimiter in our ids to
> > > > distribute
> > > > > the documents, and indeed the disk size of our shards are very
> > similar
> > > > > (31-32GB on disk per replica).
> > > > >
> > > > > Our setup is:
> > > > > 9 VMs with 16GB RAM, 8 vcpus (with a 4:1 oversubscription ratio,
so
> > > > > basically 2 physical CPUs), 24GB disk
> > > > > 3 shards, 3 replicas per shard (1 leader, 2 replicas, whatever).
>  We
> > > > > reserve 10g heap for each solr instance.
> > > > > Also 3 zookeeper VMs, which are very stable
> > > > >
> > > > > Since the troubles started, we've been monitoring all 9 with
> > jvisualvm,
> > > > and
> > > > > shards 2 and 3 keep a steady amount of heap space reserved, always
> > > having
> > > > > horizontal lines (with some minor gc).  They're using 4-5GB heap,
> and
> > > > when
> > > > > we force gc using jvisualvm, they drop to 1GB usage.  Shard 1,
> > however,
> > > > > quickly has a steep slope, and eventually has concurrent mode
> > failures
> > > in
> > > > > the gc logs, requiring us to restart the instances when they can
no
> > > > longer
> > > > > do anything but gc.
> > > > >
> > > > > We've tried ruling out physical host problems by moving all 3
> Shard 1
> > > > > replicas to different hosts that are underutilized, however we
> still
> > > get
> > > > > the same problem.  We'll still be working on ruling out
> > infrastructure
> > > > > issues, but I wanted to ask the questions here in case it makes
> > sense:
> > > > >
> > > > > * Does it make sense that all the replicas on one shard of a
> cluster
> > > > would
> > > > > have heap problems, when the other shard replicas do not, assuming
> a
> > > > fairly
> > > > > even data distribution?
> > > > > * One thing we changed recently was to make all of our fields
> stored,
> > > > > instead of only half of them.  This was to support atomic updates.
> >  Can
> > > > > stored fields, even though lazily loaded, cause problems like this?
> > > > >
> > > > > Thanks for any input,
> > > > > Joe
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > I know what it is to be in need, and I know what it is to have
> > plenty.
> > >  I
> > > > > have learned the secret of being content in any and every
> situation,
> > > > > whether well fed or hungry, whether living in plenty or in want.
 I
> > can
> > > > do
> > > > > all this through him who gives me strength.    *-Philippians
> 4:12-13*
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > I know what it is to be in need, and I know what it is to have
> plenty.
> >  I
> > > > have learned the secret of being content in any and every situation,
> > > > whether well fed or hungry, whether living in plenty or in want.  I
> can
> > > do
> > > > all this through him who gives me strength.    *-Philippians 4:12-13*
> > > >
> > >
> >
> >
> >
> > --
> > I know what it is to be in need, and I know what it is to have plenty.  I
> > have learned the secret of being content in any and every situation,
> > whether well fed or hungry, whether living in plenty or in want.  I can
> do
> > all this through him who gives me strength.    *-Philippians 4:12-13*
> >
>



-- 
I know what it is to be in need, and I know what it is to have plenty.  I
have learned the secret of being content in any and every situation,
whether well fed or hungry, whether living in plenty or in want.  I can do
all this through him who gives me strength.    *-Philippians 4:12-13*

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