Re: Why does MongoDB (Version 3.2) creates two connections instead of one?

From: Jason Carey <jason.carey@xxxxxxxxxxx>
To: mongodb-user@xxxxxxxxxxxxxxxx
Date: Thu, 14 Apr 2016 18:11:42 -0400
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Mayank,

You may be seeing the Monitor Thread
<https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring.rst#monitor-thread>.
Drivers are required by the MongoDB Server Discovery and Monitoring
Specification to do a variety of background health checks to monitor the
topology behind a given MongoDB URI.  This catches things like replica set
failover, the addition of new mongos' in sharding, etc.

Most drivers handle this with a background thread, those that don't are
forced to periodically block during processing instead.

-Jason

On Wed, Apr 13, 2016 at 2:40 PM, Mayank Jain <firesofmay@xxxxxxxxx> wrote:

Hi,

I have noticed that after I create a connection, and do say an insert
mongodb creates another connection.

I have seen this behaviour with mongodb python and clojure (which uses
java) library both.

Here's an example of how to reproduce it:

from pymongo import MongoClient


## Run `db.serverStatus().connections`via mongo shell to check the current
number of connections
client = MongoClient()


## Run the `db.serverStatus().connections` command again, it should
increment by 1
client.test_database.posts.insert_one({"author": "Mike"}).inserted_id
## Now if you run `db.serverStatus().connections` command again, it again
increments by 1

##But if you repeat insert (or any other command besides createing a new
connection) it wont create another connection

I am using:
Python        - 3.5.1
Mac OSX       - 10.10.5
Mongo Version - 3.2.4

Is this expected? Has anyone else seen this?

Thanks.

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