Add a module to do generic postgres checks.

This module is meant to be generic enough that it can do any query based check against postgres. You just need to add the entry to %queries for it to be available.

lib/Core/Postgres.pm

+package Core::Postgres;
+
+use strict;
+use warnings;
+
+use base 'Resmon::Module';
+use DBI;
+
+=pod
+
+=head1 NAME
+
+Core::Postgres - check Postgres
+
+=head1 SYNOPSIS
+
+Core::Postgres {
+   check_name: host => 'localhost', port => 5432, user => 'someuser', pass => 'somepass', params => ['10 seconds']
+}
+
+=head1 DESCRIPTION
+
+This module checks Postgres.
+
+=head1 CONFIGURATION
+
+=over
+
+=item check_name
+
+The check to run.
+
+=item host
+
+The host to connect to
+
+=item port
+
+The port that the service listens on.  This defaults to 5432.
+
+=item user
+
+The username to connect as.
+
+=item pass
+
+The password to connect with.
+
+=item params
+
+An array ref of params to pass to the query.
+
+=back
+
+=head1 METRICS
+
+This check returns the metrics from the selected check.
+
+=cut
+
+=head1 NOTES
+
+None.
+
+=cut
+
+my %checks = (
+    slave_lag => {
+        query => q[select
+    extract(epoch from lag) as slave_lag,
+    extract(epoch from max_lag) as max_slave_lag,
+    coalesce(lag <= max_lag + coalesce($1::interval,'0 seconds'::interval),true) as ok
+from
+    (select
+        now() - pg_last_xact_replay_timestamp() as lag,
+        greatest((nullif(current_setting('max_standby_streaming_delay'),'-1'))::interval,(nullif(current_setting('max_standby_archive_delay'),'-1'))::interval) as max_lag)],
+        param_count => 1
+    },
+);
+
+sub handler
+{
+    my $self = shift;
+    my $config = $self->{'config'};
+
+    my $query = $checks{ $self->{'check_name'} }{'query'};
+    my $param_count = $checks{ $self->{'check_name'} }{'param_count'};
+    my $host = $self->{'host'} || 'localhost';
+    my $port = $config->{'port'} || 5432;
+    my $user = $config->{'user'} || 'postgres';
+    my $pass = $config->{'pass'};
+    my @params = ();
+
+    if (defined($config->{'params'}) and ref($config->{'params'}) eq "ARRAY")
+    {
+        @params = @{ $config->{'params'} };
+    }
+
+    if (scalar(@params) < $param_count)
+    {
+        push @params, (undef) x ($param_count - scalar(@params));
+    }
+
+    my $dbh = DBI->connect("DBI:Pg:host=$host;port=$port", $user, $pass);
+
+    my $sth = $dbh->prepare($query);
+    $sth->execute(@params);
+
+    my $metrics = $sth->fetchrow_hashref();
+
+    return $metrics;
+};
+
+1;