• Connecting
  • Replica Sets

  • Replica Sets
  • Replica Sets

    Replica Sets

    To connect to a replica set, specify one or more
    members of the set and use the “replicaSet” option.
    Multiple servers may be delimited by a comma.

    Example #1 ReplicaSet seed list

    // Using multiple servers as the seed list (prefered)
    $m = new MongoClient("mongodb://,");

    // Using one server as the seed list
    $m = new MongoClient("mongodb://", array("replicaSet" => "myReplSetName"));

    // Using multiple servers as the seed list
    $m = new MongoClient("mongodb://,", array("replicaSet" => "myReplSetName"));

    The PHP driver will query the database server(s)
    listed to determine the primary. So long as it can connect to at
    least one host listed and find a primary, the connection will
    succeed. If it cannot make a connection to any servers listed or
    cannot find a primary, a MongoConnectionException will be thrown.


    You should always provide a seed list with more
    than one member of the ReplicaSet. For highest availability you
    should seed with at least one server from each of your


    The host names that you specify in the seed list
    must match the host names in the replica
    set configuration. This is because the driver only uses the host
    names in the replica set configuration to create the hash for its
    persistent connections.

    For example, if an IP address is used in the seed
    list and the replica set is configured with host names, the driver
    will discard any seed list connection(s) that differ from the
    canonical host names reported by the replica set. Effectively,
    these non-canonical seed list connections will be recreated on each
    request, greatly reducing the benefit of using persistent


    The driver does not
    support connecting to different replica sets with the same name.
    This extends beyond one script so make sure to have separate names
    for each of your replica sets. That also means that you can
    not do this:

    Example #2 Wrong replica set name

    = new MongoClient("mongodb://devserver1,devserver2,devserver3/?replicaSet=repset");
    $m = new MongoClient("mongodb://prodserver1,prodserver2,prodserver3/?replicaSet=repset");

    Instead, you need to have two different names for
    your replica sets:

    Example #3 Correct use of two replica set

    = new MongoClient("mongodb://devserver1,devserver2,devserver3/?replicaSet=devset");
    $m = new MongoClient("mongodb://prodserver1,prodserver2,prodserver3/?replicaSet=prodset");

    If the primary becomes unavailable, an election
    will take place and a secondary will be promoted to the role of
    primary (unless a majority vote cannot be established). During this
    time (» 20-60 seconds), the
    connection will not be able to perform any write operations and
    attempts to do so will result in an exception. Connections to
    secondaries will still be able to perform reads.


    The default Read Preference is to only read from the primary.
    During the election process there is no primary, and all read will
    therefore fail.

    It is recommended to use
    Read Preference for applications that require high availability for
    reads, as reads will only be executed on the secondaries when there
    simply isn’t a primary available.

    Once a primary is elected, attempting to perform a
    read or write will allow the driver to detect the new primary. The
    driver will make this its primary database connection and continue
    operating normally.

    The health and state of a secondary is checked
    every 5 seconds (configurable with mongo.ping_interval) or when the next operation occurs
    after 5 seconds. It will also recheck the configuration when the
    driver has a problem reaching a server.

    Replica set failovers are checked every 60 seconds
    (configurable with mongo.is_master_interval), and whenever a write
    operation fails when using acknowledged writes.


    Secondaries may be behind the primary in
    operations, so your application must be able to handle out-of-date
    data when using Read Preferences other then

    For more information on replica sets, see the
    » core documentation.


    Version Description
    1.0.9 Added support for connecting to ReplicaSet and automatic