Problems with the connection pool?

I am facing some issues since I deployed my app a couple of weeks ago!

I found that Spring Data gets Mongo down after some time of use and printed this message:

"desc": "can't call something : vdbmongo1/10.20.0.211:27017/V1; nested exception is com.mongodb.MongoException$Network: can't call something : vdbmongo1/10.20.0.211:27017/V1"


First we saw there were too many open files, we used debian 7 which has a limit of 4096. We increased that number and doubled to 8192 all open files (If I am right, connections in linux are sockets, same that files, don't they?)

Increasing that value shoots up usage of memory, then we increased memory too, but we do not have so much memory available and the vm shuts down.

Finally we set a cron service to restart each 6 hours while we try to get a solution and it seems to work for now.

My app is deployed in a tomcat 7.0.28 running on Debian 7.

<spring.core.version>3.2.0.RELEASE</spring.core.version>
<spring.data.mongodb.version>1.2.0.RELEASE</spring.data.mongodb.version>
<mongodb.driver.version>2.10.0</mongodb.driver.version>

This is the piece of my xml to create the mongo instance:
<mongo:mongo host="${mongo.host.name}" port="${mongo.host.port}" write-concern="SAFE"/>

I am reading the section 5.3.5. of Spring Data MongoDB - Reference Documentation
( http://static.springsource.org/sprin.../html/#d0e1210 )

But I don't understand all those parameters to tune it

Thanks!