Difference between revisions of "Design Specs: Database Connectivity"
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Revision as of 14:55, 17 February 2010
Objectives
Part of the WormBase::API. Needs to be able to connect to multiple databases (multiple instances of the same database in some cases). Should be fault tolerant if a server or database crashes.
Resources
The current connectivity code is part of the API. The API, in turn, is inside of the lib directory of the WormBase mercurial repository:
http://bitbucket.org/tharris/wormbase/src/tip/lib/WormBase/API/Service/
Currently, each database is a "Service". When the API is instantiated, connections are made to each required service. Database handles are cached. When a database handle is needed, the service first checks to see if it is live, if not it refreshes the connection. This would probably be the ideal location to implement failover -- check the current connection, if dead, try a different database server.
http://bitbucket.org/tharris/wormbase/src/9009075c4c5a/lib/WormBase/API/Role/Service/gff.pm
around 'dbh' => sub { my $orig = shift; my $self = shift; my $species = $self->species; # Do we already have a dbh? HOW TO TEST THIS WITH HASH REF? if ($self->has_dbh) { $self->log->debug(" gff-dbh for $species exists and is alive!"); return $self->$orig; } else { $self->log->debug(" gff-dbh for $species doesn't exist yet; trying to connect"); my $dbh = $self->connect($species); } };
Note also that these Services use Moose "Roles" to define shared methods and variables like connect().
Here's the acedb service:
http://bitbucket.org/tharris/wormbase/src/tip/lib/WormBase/API/Service/acedb.pm
The acedb service "consumes" the generic Service role:
http://bitbucket.org/tharris/wormbase/src/9009075c4c5a/lib/WormBase/API/Role/Service.pm
This nomenclature and structure is a bit confusing and probably needs to be streamlined/refined!!