Poor MongoDB performance with C# driver

[mike.g...@morrisby.com]

I am having a problem with poor query performance on a small mongo database I have set up. I have asked a question on stack-overflow so I won't repeat the nitty gritty here. the question is at (question contains details of document structure, collections size, query execution plan using .explain() etc):  

http://stackoverflow.com/questions/21336012/slow-responses-from-mongodb-with-c-sharp

In a nutshell I have recently been working to set up a Mongo db server to act as an object cache for a website. However after setting everything up I am concerned that the performance is quite slow.

It is a single server, not part of a replica set or sharded. I am running all tests from my local machine to the server which is on a Windows Azure VM.

For example I have a collection of approximately 5,500 documents where each document stores a link to an external site. Performing a basic search that return approx 3000 results takes nearly 3 seconds. I have all the relevant indexes configured and I just can't understand why it would take so long to retrieve a relatively small result set from a very small collection

[Asya Kamsky]

Windows on Azure have problems with performance.  This is not limited to MongoDB.

Asya

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[Asya Kamsky]

The problems we know about have to do with IOPs.

Looking at your details, it seems clear     the time is not spent in MongoDB - the queries are running in single digit milliseconds. What the network between application and DB?

Asya

On Jan 27, 2014 5:38 AM, <mike.g...@morrisby.com> wrote:

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[mike.g...@morrisby.com]

The network is fairly simple (at least until it gets to Microsoft's datacentre). We are a small company and our network is not very large. It goes from my machine through local server/firewall and then straight to the internet. On azure it is connecting to the VM via a load balancer.

[mike.g...@morrisby.com]

After spending the day doing profiling it seems it is network latency that is the main problem. When I pushed a build of the websites to Azure and ran it (so the connection would have been entirely inside Microsoft data centre) we saw an immediate speed up by a factor of 10! Thank you everyone for you help on the issue

[Asya Kamsky]

Mike,

Excellent, thanks for letting us know where the problem was.

This of course highlights the importance of measuring *both* the time
the operations take on the DB (slow ones > 99ms will be logged to
mongod log by default) *and* from the application as the end user
certainly doesn't care if the delay is in the application, the network
or the database, they just care that it's slow! :)

As developers and ops for the application though we care *very* much
where the bottleneck is!

Asya