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arin  
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 More options Sep 7 2012, 8:57 pm
From: arin <a...@jeraff.com>
Date: Fri, 7 Sep 2012 17:57:58 -0700 (PDT)
Local: Fri, Sep 7 2012 8:57 pm
Subject: need help understanding write locks
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Hey guys,

From time to time my app will exhibit, what seems to me, high lock times.
Here's an example from my mongodb.log (i'm profiling everything while I
troubleshoot this)

Sat Sep  8 00:38:36 [conn69541] insert jeraff.notification keyUpdates:0
locks(micros) w:121485 121ms
Sat Sep  8 00:40:46 [conn69259] insert jeraff.activityStream keyUpdates:0
locks(micros) w:3100666 3105ms

My notification docs' size is:

jeraffprod:PRIMARY> Object.bsonsize(db.notification.findOne());
232

And my activityStream docs' size is:
jeraffprod:PRIMARY> Object.bsonsize(db.activityStream.findOne());
226

My entire DB's index size is about 1.5GB
The DB's data size: is a hair under 2.8GB
the DB's file size is 14GB
The machine has 8GB RAM.
Mongo has 22.2g mapped & 5.75g resident.

Now - my questions is:
What should I be looking into to find out why seemingly "simple" inserts
are locking for so long?

I'm sure my code's doing something to make mongo unhappy - I just want to
know what procedures to employ to get down to the bottom of these problems.

Thanks


 
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Kenny Gorman  
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 More options Sep 7 2012, 9:13 pm
From: Kenny Gorman <k...@kennygorman.com>
Date: Fri, 7 Sep 2012 18:12:57 -0700
Local: Fri, Sep 7 2012 9:12 pm
Subject: Re: [mongodb-user] need help understanding write locks
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Can you post the code that you are using for the inserts?

Thanks
Kenny

On Sep 7, 2012, at 5:57 PM, arin wrote:


 
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Arin Sarkissian  
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 More options Sep 7 2012, 9:39 pm
From: Arin Sarkissian <a...@toodo.com>
Date: Fri, 7 Sep 2012 18:38:58 -0700
Local: Fri, Sep 7 2012 9:38 pm
Subject: Re: [mongodb-user] need help understanding write locks
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Hi Kenny,  

We're using Java w/ Morphia.
The code for the inserts is super boring…

https://gist.github.com/3671210

using mongo-java-driver v 2.5
morphia version .99

- Arin

Arin Sarkissian
650-759-9272
http://well.io/phatduckk


 
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Jenna deBoisblanc  
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 More options Sep 25 2012, 3:39 pm
From: Jenna deBoisblanc <jenna.deboisbl...@10gen.com>
Date: Tue, 25 Sep 2012 12:39:28 -0700 (PDT)
Local: Tues, Sep 25 2012 3:39 pm
Subject: Re: [mongodb-user] need help understanding write locks
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Hi Arin,

There could be a handful of reasons why inserts are taking a while,
especially since your data appears to exceed RAM.  It would be nice to see
additional metrics- page faults, lock percentage, etc.  Are you servers in
MMS?
https://mms.10gen.com/user/login


 
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David K Storrs  
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 More options Sep 25 2012, 3:45 pm
From: David K Storrs <da...@channelmeter.com>
Date: Tue, 25 Sep 2012 12:45:44 -0700 (PDT)
Local: Tues, Sep 25 2012 3:45 pm
Subject: Re: need help understanding write locks
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Arin,

What version of Mongo are you using?  The <2.0 versions had real
problems with global write locking.  2.0 greatly improved this, and
2.2 (the current stable) goes much farther.  You may see significant
improvement simply upgrading.  http://docs.mongodb.org/manual/release-notes/2.2/#upgrading

Also, how many threads / processes do you have doing the writes?
About how many writes / s do you expect to see, and how many do you
typically see / do you see during a slowdown?

Do you have any externalities that might be impacting you?  (e.g. cron
jobs that run stats over the DB)

Dave

On Sep 7, 6:39 pm, Arin Sarkissian <a...@toodo.com> wrote:


 
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