NAME

DBD::Multi - Manage Multiple Data Sources with Failover and Load Balancing

SYNOPSIS

  use DBI;

  my $dbh = DBI->connect( 'dbi:Multi:', undef, undef, {
      dsns => [ # in priority order
          10 => [ 'dbi:SQLite:read_one.db', '', '' ],
          10 => [ 'dbi:SQLite:read_two.db', '', '' ],
          20 => [ 'dbi:SQLite:master.db',   '', '' ],
      ],
      # optional
      failed_max    => 1,     # short credibility
      failed_expire => 60*60, # long memory
  });

DESCRIPTION

This software manages multiple database connections for the purposes of load balancing and simple failover procedures. It acts as a proxy between your code and your available databases.

Although there is some code intended for read/write operations, this should be considered EXPIREMENTAL. This module is primary intended for read-only operations (where some other application is being used to handle replication).

The interface is nearly the same as other DBI drivers with one notable exception.

Configuring DSNs

Specify an attribute to the connect() constructor, dsns. This is a list of DSNs to configure. The configuration is given in pairs. First comes the priority of the DSN, lowest is tried first. Second is the DSN.

The second parameter can either be a DBI object or a list of parameters to pass to the DBI connect() instructor.

Configuring Failures

By default a data source will not be tried again after it has failed three times. After five minutes that failure status will be removed and the data source may be tried again for future requests.

To change the maximum number of failures allowed before a data source is deemed failed, set the failed_max parameter. To change the amount of time we remember a data source as being failed, set the failed_expire parameter in seconds.

SEE ALSO

DBD::Multiplex, DBI, perl.

AUTHOR

Initially written by Casey West for pair Networks, Inc. (www.pair.com)

Maintained by Dan Wright for pair Networks, Inc. <DWRIGHT@CPAN.ORG>.