Spring data mongodb not closing mongodb connections

Question

I am using spring-data-mongodb (1.7.0.RELEASE) with spring-webmvc framework for my web application. I am using basic CRUD functions using mongoRepository but i am not closing mongo connections in my code cause i thought that spring-data-mongodb will close it by itself, But it keeps on opening new connections and not closing them. These too many connections ares crashing my application and i have to restart tomcat again and again (twice a day) to overcome this.

Note: Spring Application & mongod is on same server. This is log just after crashing -

    2015-07-17T01:31:20.068-0400 I NETWORK  [conn3645] end connection 127.0.0.1:55302 (2583 connections now open)
    2015-07-17T01:31:20.071-0400 I NETWORK  [conn1713] end connection 127.0.0.1:48174 (2352 connections now open)
    2015-07-17T01:31:20.072-0400 I NETWORK  [conn2250] end connection 127.0.0.1:51017 (2325 connections now open)
    2015-07-17T01:31:20.072-0400 I NETWORK  [conn2149] end connection 127.0.0.1:50670 (2320 connections now open)

This is log after restarting tomcat

2015-07-17T01:31:29.994-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:53599 #3984 (1 connection now open)
2015-07-17T01:31:33.263-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:53740 #3985 (2 connections now open)
2015-07-17T01:31:33.580-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:53750 #3986 (3 connections now open)
2015-07-17T02:10:06.477-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:50086 #3987 (4 connections now open)
2015-07-17T02:10:06.590-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:50090 #3988 (5 connections now open)
2015-07-17T02:10:11.682-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:50242 #3989 (6 connections now open)
2015-07-17T02:10:11.780-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:50244 #3990 (7 connections now open)
2015-07-17T02:10:12.545-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:50255 #3991 (8 connections now open)
2015-07-17T02:10:12.605-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:50258 #3992 (9 connections now open)
2015-07-17T02:10:13.413-0400 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:50299 #3993 (10 connections now open)

it increase whenever i sends request to the app.

And this is the tomcat log just after crash -

Jul 16, 2015 3:59:57 PM org.apache.tomcat.util.net.JIoEndpoint$Acceptor run
SEVERE: Socket accept failed
java.net.SocketException: Too many open files
    at java.net.PlainSocketImpl.socketAccept(Native Method)
    at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:404)
    at java.net.ServerSocket.implAccept(ServerSocket.java:545)
    at java.net.ServerSocket.accept(ServerSocket.java:513)
    at org.apache.tomcat.util.net.DefaultServerSocketFactory.acceptSocket(DefaultServerSocketFactory.java:60)
    at org.apache.tomcat.util.net.JIoEndpoint$Acceptor.run(JIoEndpoint.java:222)
    at java.lang.Thread.null(Unknown Source)

its a development server, it have traffic lesser than 10 call per minute.

Someone please suggest how should i close these connections ?

Answer 1

The MongoClient maintains a connection pool,You open a Db connection once with MongoClient and reuse it across your application because setting up a new TCP connection is EXPENSIVE timewise and memory wise that's why you reuse connections. Also a new connection will cause a new Thread to be created on MongoDB using memory on the Db as well.

• point to be noted that there is a race condition in the connectToMongo method. You need to synchronize access to that method to ensure that at most one instance of MongoClient is ever created.