Mongo connection leak with morphia

Question

I have a Servlet with static Mongo = new Mongo() and Morphia morphia = new Morphia() objects. Each time GET is invoked, I do the following:

doGet(...){
...
datastore = morphia.createDatastore(mongo, dbName);
...
}

I don't close datastore, because there is no close method. Each time i invoke the servlet, number of used connections in mongo grow:

{ "current" : 113, "available" : 706, "totalCreated" : NumberLong(122) }
> db.serverStatus().connections { "current" : 115, "available" : 704, "totalCreated" : NumberLong(124) }
> db.serverStatus().connections { "current" : 116, "available" : 703, "totalCreated" : NumberLong(125) }
> db.serverStatus().connections { "current" : 121, "available" : 698, "totalCreated" : NumberLong(130) }
> db.serverStatus().connections { "current" : 122, "available" : 697, "totalCreated" : NumberLong(131) }
> db.serverStatus().connections { "current" : 128, "available" : 691, "totalCreated" : NumberLong(137) }

what is the right way to close connections with mongo and morphia and where the connection is really leaking? Thanks.

Answer 1

You can create a singleton Datastore object

public enum MongoDBHelper { // the best way to implement singletons, due to the author of Effective Java  
INSTANCE;

private DB db;
private Datastore datastore;

private final String SERVER_URL = "...";
private final int SERVER_PORT = ...;
private final String USERNAME= "...";
private final String PASSWORD = "...";
private final String DATABASE_NAME = "...";

private MongoDBHelper() {

    try {

        MongoClient mongoClient = new MongoClient(SERVER_URL, SERVER_PORT);

        this.db = mongoClient.getDB(DATABASE_NAME);
        this.db.authenticate(USERNAME,PASSWORD.toCharArray());

        Morphia morphia = new Morphia();

        this.datastore = morphia.createDatastore(mongoClient, DATABASE_NAME);

        morphia.mapPackage("package");
    } catch (UnknownHostException e) {
        e.printStackTrace();
    }

}

public DB getDB() {
    return this.db;
}

public Datastore getDatastore() {
    return this.datastore;
}
}

and now you can reuse the same Datastore object in your application

 Datastore datastore = MongoDBHelper.INSTANCE.getDatastore()