Unable to close connections in MongoDB - Java Driver

Question

I am interacting with many db collections of MongoDB using Java driver. The queries are basically INSERT,DELETE and FETCH documents. Everything is working fine except the connections are open in the logs.

Below is the log file

Fri Dec 27 17:27:28.484 [initandlisten] connection accepted from 127.0.0.1:51018 #125 (41 connections now open)
Fri Dec 27 17:27:29.209 [initandlisten] connection accepted from 127.0.0.1:51020 #126  (42 connections now open)
Fri Dec 27 17:27:30.222 [initandlisten] connection accepted from 127.0.0.1:51021 #127 (43 connections now open)
Fri Dec 27 17:27:30.254 [conn126] end connection 127.0.0.1:51020 (42 connections now open)
Fri Dec 27 17:27:31.492 [conn125] info DFM::findAll(): extent 0:9f000 was empty, skipping ahead. ns:pingpong.SearchResult
Fri Dec 27 17:27:31.516 [conn125] end connection 127.0.0.1:51018 (41 connections now open)
Fri Dec 27 17:27:40.038 [initandlisten] connection accepted from 127.0.0.1:51032 #128 (42 connections now open)
Fri Dec 27 17:27:40.625 [initandlisten] connection accepted from 127.0.0.1:51033 #129 (43 connections now open)
Fri Dec 27 17:27:41.640 [initandlisten] connection accepted from 127.0.0.1:51034 #130 (44 connections now open)
Fri Dec 27 17:27:41.675 [conn129] end connection 127.0.0.1:51033 (43 connections now open)
Fri Dec 27 17:27:43.062 [conn128] end connection 127.0.0.1:51032 (42 connections now open)
Fri Dec 27 17:27:52.595 [initandlisten] connection accepted from 127.0.0.1:51037 #131 (43 connections now open)
Fri Dec 27 17:27:53.275 [initandlisten] connection accepted from 127.0.0.1:51038 #132 (44 connections now open)
Fri Dec 27 17:27:53.601 [conn131] info DFM::findAll(): extent 0:9f000 was empty, skipping ahead. ns:pingpong.SearchResult
Fri Dec 27 17:27:54.330 [initandlisten] connection accepted from 127.0.0.1:51039 #133 (45 connections now open)
Fri Dec 27 17:27:54.375 [conn132] end connection 127.0.0.1:51038 (44 connections now open)
Fri Dec 27 17:27:55.619 [conn131] end connection 127.0.0.1:51037 (43 connections now open)
Fri Dec 27 17:28:07.823 [initandlisten] connection accepted from 127.0.0.1:51042 #134 (44 connections now open)
Fri Dec 27 17:28:08.439 [initandlisten] connection accepted from 127.0.0.1:51043 #135 (45 connections now open)
Fri Dec 27 17:28:09.475 [initandlisten] connection accepted from 127.0.0.1:51044 #136 (46 connections now open)
Fri Dec 27 17:28:09.496 [conn135] info DFM::findAll(): extent 0:24000 was empty, skipping ahead. ns:pingpong.Messages
Fri Dec 27 17:28:09.509 [conn135] end connection 127.0.0.1:51043 (45 connections now open)
Fri Dec 27 17:28:10.838 [conn134] end connection 127.0.0.1:51042 (44 connections now open)
Sat Dec 28 04:10:58.018 [initandlisten] connection accepted from 127.0.0.1:53778 #137 (45 connections now open)
Sat Dec 28 04:11:04.501 [initandlisten] connection accepted from 127.0.0.1:53779 #138 (46 connections now open)
Sat Dec 28 04:11:05.561 [initandlisten] connection accepted from 127.0.0.1:53780 #139 (47 connections now open)
Sat Dec 28 04:11:05.621 [conn138] info DFM::findAll(): extent 0:24000 was empty, skipping ahead. ns:pingpong.Messages
Sat Dec 28 04:11:05.658 [conn138] info DFM::findAll(): extent 0:24000 was empty, skipping ahead. ns:pingpong.Messages
Sat Dec 28 04:11:05.699 [conn138] info DFM::findAll(): extent 0:24000 was empty,  Sat Dec 28 04:11:05.737 [conn138] end connection 127.0.0.1:53779 (46 connections now open)

I am using mongoclient.close() after each of the INSERT,DELETE and FETCH commands. But still the connections are open. Am I missing something. The below is the delete code

MongoClient mongoclient;
String mobileID=getMobileID(messageid);     
DBUtils dbUtils=new DBUtils();
mongoclient=dbUtils.connectToDB("pingpong");
dbUtils.deleteMessage(mobileID,messageid);
mongoclient.close();

Am I missing something. Please let me know.

`MongoClient` is a connection pool, not a single connection. You should be sharing a single instance across your multi-threaded app rather than trying to create and close one for each operation. — JohnnyHK, Dec 27 '13 at 19:22
See http://stackoverflow.com/questions/4057696/java-mongodb-driver-connection-question - where they're talking about "Mongo" you can infer it applies to MongoClient as well. — Trisha, Dec 30 '13 at 13:18

score 0 · Answer 1 · edited May 23 '17 at 12:07

As JohnnyHK mentioned that in the comments, it is not the best approach.

In the case you're building a web application (example: REST structure), and using a container for your app' (example: Tomcat 8) what you should do is declaring a shared MongoClient instance like this: private static MongoClient mongoClient;

Then you have to set up a servletContextListener and implement the basic two methods that are called when the context is initialized and/or stopped.

See below example. I'm using the mongo java driver 3.0.3, tomcat and the servlet-api 3.1.0, which is added as dependency with Maven

Dependency:

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.1.0</version>
</dependency>

Example:

@Path("/rest")
@WebListener
public class RESTInterface implements ServletContextListener{
    private static MongoClient mongoClient;

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent)            {
        System.out.println("initialized");
        try
        {
            ServerAddress serverAddress = new ServerAddress(IP_connectionString,27017); //default port 27017
            mongoClient = new MongoClient(serverAddress,options);
        }
        catch (Exception e)
        {
            ...
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        System.out.println("MongoClient closed");
        mongoClient.close();
    }

    //whatever you want with the mongoClient !
}

Unable to close connections in MongoDB - Java Driver

1 Answers1

Dependency:

Example: