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From Sudhakar Maddineni <maddineni...@gmail.com>
Subject Re: Rogue query killed several replicas with OOM, after recovering - match all docs query problem
Date Mon, 22 Apr 2013 23:18:09 GMT
We had encountered similar issue few days back with 4.0- Beta version.
We have 6 node - 3 shard cluster setup.And, one of our replica
servers[tomcat] was not responding to any requests because it reached the
max no of the threads[200 -default]. To temporarily fix the issue, we had
to restart the server.After restarting, we realized that there were 2
tomcat processes running[old one + new one].So, we manually killed the two
tomcat processes and had a clean start.And, we observed the numDocs of
replica server not matching to the count on leader.
So, this discrepancy is because we manually killed the process which
interrupted the sync process?

Thx,Sudhakar.




On Mon, Apr 22, 2013 at 3:28 PM, Mark Miller <markrmiller@gmail.com> wrote:

> No worries, thanks for the info. Let me know if you gain any more insight!
> I'd love to figure out what happened here and address it. And I'm
> especially interested in knowing if you lost any updates if you are able to
> determine that.
>
> - Mark
>
> On Apr 22, 2013, at 5:02 PM, Timothy Potter <thelabdude@gmail.com> wrote:
>
> > I ended up just nuking the index on the replica with less docs and
> > restarting it - which triggered the snap pull from the leader. So now
> > I'm in sync and have better processes in place to capture the
> > information if it happens again, which given some of the queries my UI
> > team develops, is highly likely ;-)
> >
> > Also, all our input data to Solr lives in Hive so I'm doing some id
> > -to- id comparisons of what is in Solr vs. what is in Hive to find any
> > discrepancies.
> >
> > Again, sorry about the loss of the logs. This is a tough scenario to
> > try to re-create as it was a perfect storm of high indexing throughput
> > and a rogue query.
> >
> > Tim
> >
> > On Mon, Apr 22, 2013 at 2:41 PM, Mark Miller <markrmiller@gmail.com>
> wrote:
> >> What do you know about the # of docs you *should*? Do you have that
> mean when taking the bad replica out of the equation?
> >>
> >> - Mark
> >>
> >> On Apr 22, 2013, at 4:33 PM, Mark Miller <markrmiller@gmail.com> wrote:
> >>
> >>> Bummer on the log loss :(
> >>>
> >>> Good info though. Somehow that replica became active without actually
> syncing? This is heavily tested (though not with OOM's I suppose), so I'm a
> little surprised, but it's hard to speculate how it happened without the
> logs. Specially, the logs from the node that is off would be great - we
> would see what it did when it recovered and why it might think it was in
> sync :(
> >>>
> >>> - Mark
> >>>
> >>> On Apr 22, 2013, at 2:19 PM, Timothy Potter <thelabdude@gmail.com>
> wrote:
> >>>
> >>>> nm - can't read my own output - the leader had more docs than the
> replica ;-)
> >>>>
> >>>> On Mon, Apr 22, 2013 at 11:42 AM, Timothy Potter <
> thelabdude@gmail.com> wrote:
> >>>>> Have a little more info about this ... the numDocs for *:* fluctuates
> >>>>> between two values (difference of 324 docs) depending on which nodes
> I
> >>>>> hit (distrib=true)
> >>>>>
> >>>>> 589,674,416
> >>>>> 589,674,092
> >>>>>
> >>>>> Using distrib=false, I found 1 shard with a mis-match:
> >>>>>
> >>>>> shard15: {
> >>>>> leader = 32,765,254
> >>>>> replica = 32,764,930 diff:324
> >>>>> }
> >>>>>
> >>>>> Interesting that the replica has more docs than the leader.
> >>>>>
> >>>>> Unfortunately, due to some bad log management scripting on my part,
> >>>>> the logs were lost when these instances got re-started, which really
> >>>>> bums me out :-(
> >>>>>
> >>>>> For now, I'm going to assume the replica with more docs is the one
I
> >>>>> want to keep and will replicate the full index over to the other
one.
> >>>>> Sorry about losing the logs :-(
> >>>>>
> >>>>> Tim
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Sat, Apr 20, 2013 at 10:23 AM, Timothy Potter <
> thelabdude@gmail.com> wrote:
> >>>>>> Thanks for responding Mark. I'll collect the information you
asked
> >>>>>> about and open a JIRA once I have a little more understanding
of
> what
> >>>>>> happened. Hopefully I can piece together some story after going
over
> >>>>>> the logs.
> >>>>>>
> >>>>>> As for replica / leader, I suspect some leaders went down but
> >>>>>> fail-over to new leaders seemed to work fine. We lost about
9 nodes
> at
> >>>>>> once and continued to serve queries, which is awesome.
> >>>>>>
> >>>>>> On Sat, Apr 20, 2013 at 10:11 AM, Mark Miller <
> markrmiller@gmail.com> wrote:
> >>>>>>> Yeah, thats no good.
> >>>>>>>
> >>>>>>> You might hit each node with distrib=false to get the doc
counts.
> >>>>>>>
> >>>>>>> Which ones have what you think are the right counts and
which the
> wrong - eg is it all replicas that are off, or leaders as well?
> >>>>>>>
> >>>>>>> You say several replicas - do you mean no leaders went down?
> >>>>>>>
> >>>>>>> You might look closer at the logs for a node that has it's
count
> off.
> >>>>>>>
> >>>>>>> Finally, I guess I'd try and track it in a JIRA issue.
> >>>>>>>
> >>>>>>> - Mark
> >>>>>>>
> >>>>>>> On Apr 19, 2013, at 6:37 PM, Timothy Potter <thelabdude@gmail.com>
> wrote:
> >>>>>>>
> >>>>>>>> We had a rogue query take out several replicas in a
large 4.2.0
> cluster
> >>>>>>>> today, due to OOM's (we use the JVM args to kill the
process on
> OOM).
> >>>>>>>>
> >>>>>>>> After recovering, when I execute the match all docs
query (*:*),
> I get a
> >>>>>>>> different count each time.
> >>>>>>>>
> >>>>>>>> In other words, if I execute q=*:* several times in
a row, then I
> get a
> >>>>>>>> different count back for numDocs.
> >>>>>>>>
> >>>>>>>> This was not the case prior to the failure as that is
one thing
> we monitor
> >>>>>>>> for.
> >>>>>>>>
> >>>>>>>> I think I should be worried ... any ideas on how to
troubleshoot
> this? One
> >>>>>>>> thing to mention is that several of my replicas had
to do full
> recoveries
> >>>>>>>> from the leader when they came back online. Indexing
was
> happening when the
> >>>>>>>> replicas failed.
> >>>>>>>>
> >>>>>>>> Thanks.
> >>>>>>>> Tim
> >>>>>>>
> >>>
> >>
>
>

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