MongoDB::Connection - A connection to a MongoDB server (DEPRECATED)


version v0.704.1.0


NOTE: MongoDB::Connection is DEPRECATED as of version 0.502.0 of the MongoDB CPAN distribution. It is no longer maintained and will be removed in a future version. Use MongoDB::MongoClient instead.


The MongoDB::Connection class creates a connection to the MongoDB server.

By default, it connects to a single server running on the local machine listening on the default port:

    # connects to localhost:27017
    my $connection = MongoDB::Connection->new;

It can connect to a database server running anywhere, though:

    my $connection = MongoDB::Connection->new(host => '');

See the "host" section for more options for connecting to MongoDB.


Core documentation on connections:



Server or servers to connect to. Defaults to mongodb://localhost:27017.

To connect to more than one database server, use the format:


An arbitrary number of hosts can be specified.

The connect method will return success if it can connect to at least one of the hosts listed. If it cannot connect to any hosts, it will die.

If a port is not specified for a given host, it will default to 27017. For example, to connecting to localhost:27017 and localhost:27018:

    $conn = MongoDB::Connection->new("host" => "mongodb://localhost,localhost:27018");

This will succeed if either localhost:27017 or localhost:27018 are available.

The connect method will also try to determine who is master if more than one server is given. It will try the hosts in order from left to right. As soon as one of the hosts reports that it is master, the connect will return success. If no hosts report themselves as masters, the connect will die, reporting that it could not find a master.

If username and password are given, success is conditional on being able to log into the database as well as connect. By default, the driver will attempt to authenticate with the admin database. If a different database is specified using the db_name property, it will be used instead.


Only supported in MongoDB server version 1.5+.

The default number of mongod slaves to replicate a change to before reporting success for all operations on this collection.

Defaults to 1 (just the current master).

If this is not set, a safe insert will wait for 1 machine (the master) to ack the operation, then return that it was successful. If the master has slaves, the slaves may not yet have a record of the operation when success is reported. Thus, if the master goes down, the slaves will never get this operation.

To prevent this, you can set w to a value greater than 1. If you set w to <N>, it means that safe operations must have succeeded on the master and N-1 slaves before the client is notified that the operation succeeded. If the operation did not succeed or could not be replicated to N-1 slaves within the timeout (see wtimeout below), the safe operation will fail (croak).

Some examples of a safe insert with w set to 3 and wtimeout set to 100:

The master inserts the document, but 100 milliseconds pass before the slaves have a chance to replicate it. The master returns failure and the client croaks.
The master inserts the document and two or more slaves replicate the operation within 100 milliseconds. The safe insert returns success.
The master inserts the document but there is only one slave up. The safe insert times out and croaks.

MongoDB server version 2.0+: "majority" and Data Center Awareness

As of MongoDB 2.0+, the 'w' parameter can be passed strings. This can be done by passing it the string "majority" this will wait till the majority of of the nodes in the replica set have received the data. For more information see:

This can be useful for "Data Center Awareness." In v2.0+, you can "tag" replica members. With "tagging" you can specify a new "getLastErrorMode" where you can create new rules on how your data is replicated. To used you getLastErrorMode, you pass in the name of the mode to the 'w' parameter. For more information see:


The number of milliseconds an operation should wait for w slaves to replicate it.

Defaults to 1000 (1 second).

See w above for more information.


If true, awaits the journal commit before returning. If the server is running without journaling, it returns immediately, and successfully.


Boolean indicating whether or not to reconnect if the connection is interrupted. Defaults to 1.


Boolean indication whether or not to connect automatically on object construction. Defaults to 1.


Connection timeout in milliseconds. Defaults to 20000.


Username for this connection. Optional. If this and the password field are set, the connection will attempt to authenticate on connection/reconnection.


Password for this connection. Optional. If this and the username field are set, the connection will attempt to authenticate on connection/reconnection.


Database to authenticate on for this connection. Optional. If this, the username, and the password fields are set, the connection will attempt to authenticate against this database on connection/reconnection. Defaults to "admin".


    # set query timeout to 1 second
    my $conn = MongoDB::Connection->new(query_timeout => 1000);

    # set query timeout to 6 seconds

This will cause all queries (including find_ones and run_commands) to die after this period if the database has not responded.

This value is in milliseconds and defaults to the value of "timeout" in MongoDB::Cursor.

    $MongoDB::Cursor::timeout = 5000;
    # query timeout for $conn will be 5 seconds
    my $conn = MongoDB::Connection->new;

A value of -1 will cause the driver to wait forever for responses and 0 will cause it to die immediately.

This value overrides "timeout" in MongoDB::Cursor.

    $MongoDB::Cursor::timeout = 1000;
    my $conn = MongoDB::Connection->new(query_timeout => 10);
    # timeout for $conn is 10 milliseconds


This is the largest document, in bytes, storable by MongoDB. The driver queries MongoDB on connection to determine this value. It defaults to 4MB.


If this is true, the driver will attempt to find a master given the list of hosts. The master-finding algorithm looks like:

    for host in hosts

        if host is master
             return host

        else if host is a replica set member
            master := replica set's master
            return master

If no master is found, the connection will fail.

If this is not set (or set to the default, 0), the driver will simply use the first host in the host list for all connections. This can be useful for directly connecting to slaves for reads.

If you are connecting to a slave, you should check out the "slave_okay" in MongoDB::Cursor documentation for information on reading from a slave.

You can use the ismaster command to find the members of a replica set:

    my $result = $db->run_command({ismaster => 1});

The primary and secondary hosts are listed in the hosts field, the slaves are in the passives field, and arbiters are in the arbiters field.


This tells the driver that you are connecting to an SSL mongodb instance.

This option will be ignored if the driver was not compiled with the SSL flag. You must also be using a database server that supports SSL.


Sets the type of object which is returned for DateTime fields. The default is DateTime. Other acceptable values are DateTime::Tiny and undef. The latter will give you the raw epoch value rather than an object.




Connects to the mongo server. Called automatically on object construction if auto_connect is true.


    my @dbs = $connection->database_names;

Lists all databases on the mongo server.


    my $database = $connection->get_database('foo');

Returns a MongoDB::Database instance for database with the given $name.


    $master = $connection->get_master

Determines which host of a paired connection is master. Does nothing for a non-paired connection. This need never be invoked by a user, it is called automatically by internal functions. Returns the index of the master connection in the list of connections or -1 if it cannot be determined.

authenticate ($dbname, $username, $password, $is_digest?)

    $connection->authenticate('foo', 'username', 'secret');

Attempts to authenticate for use of the $dbname database with $username and $password. Passwords are expected to be cleartext and will be automatically hashed before sending over the wire, unless $is_digest is true, which will assume you already did the hashing on yourself.

See also the core documentation on authentication:


    my ($insert, $ids) = MongoDB::write_insert('', [{name => "joe", age => 40}]);

Low-level function to send a string directly to the database. Use MongoDB::write_insert, MongoDB::write_update, MongoDB::write_remove, or MongoDB::write_query to create a valid string.


    my $cursor = $conn->recv({ns => ""});

Low-level function to receive a response from the database. Returns a MongoDB::Cursor. At the moment, the only required field for $info is "ns", although "request_id" is likely to be required in the future. The $info hash will be automatically created for you by MongoDB::write_query.



A function that will forces the server to flush all pending writes to the storage layer.

The fsync operation is synchronous by default, to run fsync asynchronously, use the following form:

    $conn->fsync({async => 1});

The primary use of fsync is to lock the database during backup operations. This will flush all data to the data storage layer and block all write operations until you unlock the database. Note: you can still read while the database is locked.

    $conn->fsync({lock => 1});



Unlocks a database server to allow writes and reverses the operation of a $conn->fsync({lock => 1}); operation.


  • David Golden <>

  • Mike Friedman <>

  • Kristina Chodorow <>

  • Florian Ragwitz <>


This software is Copyright (c) 2014 by MongoDB, Inc..

This is free software, licensed under:

  The Apache License, Version 2.0, January 2004