Support for connecting to external databases for custom Reports/Plugins

Netdisco/lib/App/Netdisco/Configuration.pm

@@ -33,6 +33,13 @@ if (ref {} eq ref setting('database')) {
         schema_class => 'App::Netdisco::DB',
     };
 
+    foreach my $c (@{setting('external_databases')}) {
+        my $schema = delete $c->{tag} or next;
+        next if $schema eq 'netdisco';
+        setting('plugins')->{DBIC}->{$schema} = $c;
+        setting('plugins')->{DBIC}->{$schema}->{schema_class}
+          ||= 'App::Netdisco::GenericDB';
+    }
 }
 
 # defaults for workers

Netdisco/lib/App/Netdisco/GenericDB.pm

@@ -0,0 +1,10 @@
+use utf8;
+package App::Netdisco::GenericDB;
+
+use strict;
+use warnings;
+
+use base 'DBIx::Class::Schema';
+__PACKAGE__->load_namespaces();
+
+1;

Netdisco/lib/App/Netdisco/GenericDB/Result/Virtual/GenericReport.pm

@@ -0,0 +1,13 @@
+package App::Netdisco::GenericDB::Result::Virtual::GenericReport;
+
+use strict;
+use warnings;
+
+use base 'DBIx::Class::Core';
+
+__PACKAGE__->table_class('DBIx::Class::ResultSource::View');
+__PACKAGE__->table("generic_report");
+__PACKAGE__->result_source_instance->is_virtual(1);
+__PACKAGE__->result_source_instance->view_definition(q{});
+
+1;

Netdisco/lib/App/Netdisco/Manual/Configuration.pod

@@ -80,6 +80,27 @@ Additional library paths for the application (both web frontend and backend
 poller daemons). You can also use a colon-separated list in the
 "C<NETDISCO_INC>" environment variable.
 
+=head3 C<external_databases>
+
+Value: List of Database Configuration Hashes. Default: None.
+
+The Plugins and User Reports features of Netdisco can gather data from
+external databases. You need to install the Perl database driver for the
+target database platform, and configure this setting appropriately. For
+example:
+
+ external_databases:
+   - tag: externaldb
+     dsn: 'dbi:Pg:dbname=myexternaldb;host=192.0.2.1'
+     user: oliver
+     password: letmein
+     options:
+       pg_enable_utf8: true
+
+Note that C<tag> is I<required> and maps to the C<database> key if you use the
+Generic Reports feature (see "L</reports>", below), or becomes the Dancer
+database schema name if you program the Plugin directly.
+
 =head2 Web Frontend
 
 =head3 C<domain_suffix>

Netdisco/lib/App/Netdisco/Manual/WritingPlugins.pod

@@ -330,6 +330,32 @@ C<port_control>:
 Take care over the subtle differences in syntax, especially the placement of
 the fat comma ("C<< => >>").
 
+=head1 Database Connections
+
+The Netdisco database is available via the C<netdisco> schema key, as below.
+You can also use the C<external_databases> configuration item to set up
+connections to other databases.
+
+ # possibly install another database driver
+ ~netdisco/bin/localenv cpanm --notest DBD::mysql
+ 
+ # deployment.yml
+ external_databases:
+   - tag: externaldb
+     dsn: 'dbi:mysql:dbname=myexternaldb;host=192.0.2.1'
+     user: oliver
+     password: letmein
+ 
+ # plugin code
+ use Dancer::Plugin::DBIC;
+ 
+ schema('netdisco')->resultset('Devices')->search({vendor => 'cisco'});
+ schema('externaldb')->resultset('MyTable')->search({field => 'foobar'});
+
+You'll need to install a L<DBIx::Class> Schema and also set C<schema_class> to
+its name within the C<external_databases> setting, for the second example
+above.
+
 =head1 Templates
 
 All of Netdisco's web page templates are stashed away in its distribution,

Netdisco/lib/App/Netdisco/Web/GenericReport.pm

@@ -26,7 +26,9 @@ foreach my $report (@{setting('reports')}) {
       # TODO: this should be done by creating a new Virtual Result class on
       # the fly (package...) and then calling DBIC register_class on it.
 
-      my $rs = schema('netdisco')->resultset('Virtual::GenericReport')->result_source;
+      my $schema = ($report->{database} || 'netdisco');
+      my $rs = schema($schema)->resultset('Virtual::GenericReport')->result_source;
+
       $rs->view_definition($report->{query});
       $rs->remove_columns($rs->columns);
       $rs->add_columns( exists $report->{query_columns}
@@ -34,7 +36,7 @@ foreach my $report (@{setting('reports')}) {
         : (map {keys %{$_}} @{$report->{columns}})
       );
 
-      my $set = schema('netdisco')->resultset('Virtual::GenericReport')
+      my $set = schema($schema)->resultset('Virtual::GenericReport')
         ->search(undef, {
           result_class => 'DBIx::Class::ResultClass::HashRefInflator',
           ( (exists $report->{bind_params})