First pass at an Resmon reporter for CLGR

lib/Core/ChefLastGoodRun.pm

+package Core::ChefLastGoodRun;
+
+use strict;
+use warnings;
+
+use base 'Resmon::Module';
+
+
+=pod
+
+=head1 NAME
+
+Core::ChefLastGoodRun
+
+=head1 SYNOPSIS
+
+ Core::ChefLastGoodRun {
+    local : report_path => /var/chef/reports/last_good_run.json
+ }
+
+=head1 DESCRIPTION
+
+This module reads a JSON file deposited whenever chef-solo runs to successful completion.
+
+=head1 CONFIGURATION
+
+=over
+
+=item check_name
+
+Arbitrary name of the check.
+
+=item report_path
+
+Optional path to the report JSON file.
+
+=back
+
+=head1 METRICS
+
+=over
+
+=item age (integer, seconds since last run)
+
+=back
+
+=head1 METRICS AVAILABLE WITH REPORT PARSING
+
+If you have the JSON and File::Slurp perl modules installed, the following are also provided:
+
+=over
+
+=item elapsed (float, time last run took)
+
+=item change_count (integer, number of changes)
+
+=back
+
+=cut
+
+my $MODS_LOADED;
+
+sub handler {
+    my $self = shift;
+    my $config = $self->{'config'};
+    my $report_path = $config->{'report_path'} || '/var/chef/reports/last_good_run.json';
+
+    unless (-e $report_path) { return {} }
+
+    # Age metric
+    my %metrics;
+    $metrics{age} = [ time() - (stat($report_path))[9], 'I' ];
+
+    # Try to load JSON module
+    unless ($MODS_LOADED) {
+        eval "use JSON; use File::Slurp;";
+        if ($@) {
+            return \%metrics;
+        } else {
+            $MODS_LOADED = 1;
+        }
+    }
+
+    my $report = File::Slurp::readfile($report_path);
+    $report = decode_json($report);
+
+    $metrics{elapsed} = [ $report->{elapsed_time}, 'F' ];
+    $metrics{change_count} = [ scalar(@{$report->{updated_resources}}), 'I' ];
+
+    return \%metrics;
+};
+
+1;