Merge pull request #2269 from alphagov/custom-prometheus-metrics

Push fact check metrics to prometheus

Gemfile

@@ -33,6 +33,7 @@ gem "mousetrap-rails"
 gem "nested_form", git: "https://github.com/alphagov/nested_form.git", branch: "add-wrapper-class"
 gem "null_logger"
 gem "plek"
+gem "prometheus-client"
 gem "rails_autolink"
 gem "rest-client", require: false
 gem "select2-rails", "~> 3.5.9" # Updating this will mean updating the styling as 4 & > have a new approach to class names.

Gemfile.lock

@@ -611,6 +611,8 @@ GEM
       ast (~> 2.4.1)
       racc
     plek (5.2.0)
+    prometheus-client (4.2.3)
+      base64
     prometheus_exporter (2.1.1)
       webrick
     pry (0.14.1)
@@ -872,6 +874,7 @@ DEPENDENCIES
   nested_form!
   null_logger
   plek
+  prometheus-client
   pry-byebug
   rack
   rails (= 7.0.8.3)

app/lib/fact_check_email_handler.rb

@@ -9,8 +9,9 @@
 class FactCheckEmailHandler
   attr_accessor :fact_check_config
 
-  def initialize(fact_check_config)
+  def initialize(fact_check_config, unprocessed_emails_gauge)
     @fact_check_config = fact_check_config
+    @unprocessed_emails_gauge = unprocessed_emails_gauge
   end
 
   def process_message(message)
@@ -35,7 +36,7 @@ def process
       unprocessed_emails_count += 1
     end
 
-    GovukStatsd.gauge("unprocessed_emails.count", unprocessed_emails_count)
+    @unprocessed_emails_gauge.set(unprocessed_emails_count)
   rescue StandardError => e
     # Occasionally, there is an error when connecting to the mailbox in production.
     # It seems a very transient error, and since the job is run every few minutes isn't really a problem, but if the

script/mail_fetcher

@@ -20,7 +20,12 @@ end
 
 Rails.logger.info "Running MailFetcher in #{Rails.env} mode - #{Time.zone.now.utc}"
 
-handler = FactCheckEmailHandler.new(Publisher::Application.fact_check_config)
+registry = Prometheus::Client.registry
+gauge = registry.gauge(
+  :publisher_fact_check_unprocessed_emails_total,
+  docstring: "Number of unprocessed fact check emails",
+)
+handler = FactCheckEmailHandler.new(Publisher::Application.fact_check_config, gauge)
 
 # The lock is created and belongs to this process for as long as the `life`.
 # When the block has finished executing, the lock is explicitly released.
@@ -50,3 +55,7 @@ rescue StandardError => e
 end
 
 Rails.logger.info "Finished running MailFetcher in #{Rails.env} mode - #{Time.zone.now.utc}"
+Prometheus::Client::Push.new(
+  job: "publisher-metrics",
+  gateway: ENV.fetch("PROMETHEUS_PUSHGATEWAY_URL"),
+).add(registry)

test/integration/fact_check_email_test.rb

@@ -27,7 +27,7 @@ def assert_correct_state(key, value, state)
     message[key] = value
 
     Mail.stubs(:all).yields(message)
-    FactCheckEmailHandler.new(fact_check_config).process
+    FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set)).process
 
     answer.reload
     assert answer.public_send("#{state}?")
@@ -41,7 +41,7 @@ def assert_correct_state(key, value, state)
 
     answer.destroy!
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
     handler.process
 
     assert message.is_marked_for_delete?
@@ -53,7 +53,7 @@ def assert_correct_state(key, value, state)
     message = fact_check_mail_for(answer)
     Mail.stubs(:all).yields(message)
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
     handler.process
 
     answer.reload
@@ -71,7 +71,7 @@ def assert_correct_state(key, value, state)
 
     Mail.stubs(:all).yields(fact_check_mail_for(answer))
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
     handler.process
 
     answer.reload
@@ -96,7 +96,7 @@ def assert_correct_state(key, value, state)
       fact_check_mail_for(answer1, body: "Third Message"),
     )
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
     handler.process
 
     answer1.reload
@@ -122,7 +122,7 @@ def assert_correct_state(key, value, state)
 
     Mail.stubs(:all).yields(message)
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
     handler.process
 
     assert_not message.is_marked_for_delete?
@@ -139,7 +139,7 @@ def assert_correct_state(key, value, state)
 
     Mail.stubs(:all).multiple_yields(message_cc, message_bcc)
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
     handler.process
 
     assert message_cc.is_marked_for_delete?
@@ -152,7 +152,7 @@ def assert_correct_state(key, value, state)
 
     Mail.stubs(:all).yields(message)
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
     handler.process_message(message)
     assert message.is_marked_for_delete?
   end
@@ -163,7 +163,7 @@ def assert_correct_state(key, value, state)
 
     Mail.stubs(:all).yields(message)
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
 
     handler.process_message(message)
     assert message.is_marked_for_delete?
@@ -182,7 +182,7 @@ def assert_correct_state(key, value, state)
       fact_check_mail_for(answer2, body: "Second Message"),
     )
 
-    handler = FactCheckEmailHandler.new(fact_check_config)
+    handler = FactCheckEmailHandler.new(fact_check_config, stub.stubs(:set))
 
     invocations = 0
     handler.process do

test/unit/lib/fact_check_email_handler_test.rb

@@ -1,29 +1,34 @@
 require "test_helper"
 
 class FactCheckEmailHandlerTest < ActiveSupport::TestCase
+  setup do
+    @gauge = stub
+  end
+
   def handler
-    FactCheckEmailHandler.new(Publisher::Application.fact_check_config)
+    FactCheckEmailHandler.new(Publisher::Application.fact_check_config, @gauge)
   end
 
   test "#process ignores 'out of office' emails" do
     out_of_office_message = Mail.new { subject("Automatic reply: out of office") }
     Mail.stubs(:all).yields(out_of_office_message)
+    @gauge.expects(:set).with(0)
     handler.process
     assert out_of_office_message.is_marked_for_delete?
   end
 
-  test "#process sends count of unprocessed emails to Graphite" do
+  test "#process sends count of unprocessed emails to Prometheus" do
     processed_message = Mail.new { subject("Automatic reply: out of office") }
     unprocessed_message = Mail.new { subject("Any other subject") }
-    GovukStatsd.expects(:gauge).with("unprocessed_emails.count", 1)
+    @gauge.expects(:set).with(1)
     Mail.stubs(:all).multiple_yields(processed_message, unprocessed_message)
 
     handler.process
   end
 
-  test "#process does not send count of unprocessed emails to Graphite when emails cannot be retrieved" do
+  test "#process does not send count of unprocessed emails to Prometheus when emails cannot be retrieved" do
     Mail.stubs(:all).raises(StandardError)
-    GovukStatsd.expects(:gauge).never
+    @gauge.expects(:set).never
 
     handler.process
   end