Added basic Good Job collectors

README.md

@@ -627,6 +627,17 @@ PrometheusExporter::Instrumentation::Resque.start
 | Gauge | `resque_workers`        | Total number of Resque workers running |
 | Gauge | `resque_working`        | Total number of Resque workers working |
 
+### GoodJob metrics
+
+The metrics are generated from the database using the relevant scopes. To start monitoring your GoodJob
+installation, you'll need to start the instrumentation:
+
+```ruby
+# e.g. config/initializers/good_job.rb
+require 'prometheus_exporter/instrumentation'
+PrometheusExporter::Instrumentation::GoodJob.start
+```
+
 ### Unicorn process metrics
 
 In order to gather metrics from unicorn processes, we use `rainbows`, which exposes `Rainbows::Linux.tcp_listener_stats` to gather information about active workers and queued requests. To start monitoring your unicorn processes, you'll need to know both the path to unicorn PID file and the listen address (`pid_file` and `listen` in your unicorn config file)

lib/prometheus_exporter/instrumentation/good_job.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# collects stats from GoodJob
+module PrometheusExporter::Instrumentation
+  class GoodJob < PeriodicStats
+    def self.start(client: nil, frequency: 30)
+      good_job_collector = new
+      client ||= PrometheusExporter::Client.default
+
+      worker_loop do
+        client.send_json(good_job_collector.collect)
+      end
+
+      super
+    end
+
+    def collect
+      {
+        type: "good_job",
+        scheduled: ::GoodJob::Job.scheduled.size,
+        retried: ::GoodJob::Job.retried.size,
+        queued: ::GoodJob::Job.queued.size,
+        running: ::GoodJob::Job.running.size,
+        finished: ::GoodJob::Job.finished.size,
+        succeeded: ::GoodJob::Job.succeeded.size,
+        discarded: ::GoodJob::Job.discarded.size
+      }
+    end
+  end
+end

lib/prometheus_exporter/server.rb

@@ -19,3 +19,4 @@
 require_relative "server/active_record_collector"
 require_relative "server/shoryuken_collector"
 require_relative "server/resque_collector"
+require_relative "server/good_job_collector"

lib/prometheus_exporter/server/collector.rb

@@ -23,6 +23,7 @@ def initialize(json_serializer: nil)
       register_collector(ActiveRecordCollector.new)
       register_collector(ShoryukenCollector.new)
       register_collector(ResqueCollector.new)
+      register_collector(GoodJobCollector.new)
     end
 
     def register_collector(collector)

lib/prometheus_exporter/server/good_job_collector.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module PrometheusExporter::Server
+  class GoodJobCollector < TypeCollector
+    MAX_GOOD_JOB_METRIC_AGE = 30
+    GOOD_JOB_GAUGES = {
+      scheduled: "Total number of scheduled GoodJob jobs.",
+      retried: "Total number of retried GoodJob jobs.",
+      queued: "Total number of queued GoodJob jobs.",
+      running: "Total number of running GoodJob jobs.",
+      finished: "Total number of finished GoodJob jobs.",
+      succeeded: "Total number of succeeded GoodJob jobs.",
+      discarded: "Total number of discarded GoodJob jobs."
+    }
+
+    def initialize
+      @good_job_metrics = []
+      @gauges = {}
+    end
+
+    def type
+      "good_job"
+    end
+
+    def metrics
+      return [] if good_job_metrics.length == 0
+
+      good_job_metrics.map do |metric|
+        labels = metric.fetch("custom_labels", {})
+
+        GOOD_JOB_GAUGES.map do |name, help|
+          gauge = gauges[name] ||= PrometheusExporter::Metric::Gauge.new("good_job_#{name}", help)
+          gauge.observe(metric.fetch(name.to_s), labels)
+        end
+      end
+
+      gauges.values
+    end
+
+    def collect(object)
+      now = ::Process.clock_gettime(::Process::CLOCK_MONOTONIC)
+
+      object["created_at"] = now
+      good_job_metrics.delete_if { |metric| metric["created_at"] + MAX_GOOD_JOB_METRIC_AGE < now }
+      good_job_metrics << object
+    end
+
+    private
+
+    attr_reader :good_job_metrics, :gauges
+  end
+end