Automatically embed metrics for gitlab alerts

Inserts a link to a metrics embed in the description of issues
created as a result of alerts from prometheus, for which the
alerting rules were configured through the GitLab UI.

If the alerting rule did not originate from GitLab, no changes
will occur in incident issues.

app/presenters/projects/prometheus/alert_presenter.rb

@@ -53,7 +53,7 @@ module Projects
           #### Summary
 
           #{metadata_list}
-          #{alert_details}
+          #{alert_details}#{metric_embed_for_alert}
         MARKDOWN
       end
 
@@ -118,6 +118,10 @@ module Projects
       def host_links
         Array(hosts.value).join(' ')
       end
+
+      def metric_embed_for_alert; end
     end
   end
 end
+
+Projects::Prometheus::AlertPresenter.prepend_if_ee('EE::Projects::Prometheus::AlertPresenter')

changelogs/unreleased/sy-auto-embed-alert.yml

+---
+title: Automatically include embedded metrics for GitLab alert incidents
+merge_request: 25277
+author:
+type: added

doc/user/incident_management/index.md

@@ -105,3 +105,5 @@ Incident Management features can be easily enabled & disabled via the Project se
 #### Auto-creation
 
 GitLab Issues can automatically be created as a result of an Alert notification. An Issue created this way will contain error information to help you further debug the error.
+
+For [GitLab-managed alerting rules](../project/integrations/prometheus.md#setting-up-alerts-for-prometheus-metrics-ultimate), the issue will include an embedded chart for the query corresponding to the alert. The chart will show an hour of data surrounding the starting point of the incident, 30 minutes before and after.

ee/app/presenters/ee/projects/prometheus/alert_presenter.rb

+# frozen_string_literal: true
+
+module EE
+  module Projects
+    module Prometheus
+      module AlertPresenter
+        extend ::Gitlab::Utils::Override
+
+        METRIC_TIME_WINDOW = 30.minutes
+
+        override :metric_embed_for_alert
+        def metric_embed_for_alert
+          return unless gitlab_alert
+
+          time = starts_at ? Time.rfc3339(starts_at) : Time.current
+          url = metrics_dashboard_project_prometheus_alert_url(
+            project,
+            gitlab_alert.prometheus_metric_id,
+            environment_id: environment.id,
+            start: format_embed_timestamp(time - METRIC_TIME_WINDOW),
+            end: format_embed_timestamp(time + METRIC_TIME_WINDOW)
+          )
+
+          "\n[](#{url})"
+        end
+
+        def format_embed_timestamp(timestamp)
+          timestamp.utc.strftime('%FT%TZ')
+        end
+      end
+    end
+  end
+end

ee/spec/presenters/ee/projects/prometheus/alert_presenter_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Projects::Prometheus::AlertPresenter do
+  let_it_be(:project) { create(:project) }
+
+  let(:presenter) { described_class.new(alert) }
+  let(:payload) { {} }
+  let(:alert) { create(:alerting_alert, project: project, payload: payload) }
+
+  describe '#issue_summary_markdown' do
+    let(:markdown_line_break) { '  ' }
+
+    subject { presenter.issue_summary_markdown }
+
+    context 'with gitlab alert' do
+      let(:gitlab_alert) { create(:prometheus_alert, project: project) }
+      let(:metric_id) { gitlab_alert.prometheus_metric_id }
+      let(:env_id) { gitlab_alert.environment_id }
+      let(:starts_at) { '2018-03-12T09:06:00Z' }
+
+      let(:expected_markdown) do
+        <<~MARKDOWN.chomp
+        #### Summary
+
+        **Start time:** #{presenter.starts_at}#{markdown_line_break}
+        **full_query:** `avg(metric) > 1.0`
+
+        [](http://localhost/#{project.full_path}/prometheus/alerts/#{metric_id}/metrics_dashboard?end=2018-03-12T09%3A36%3A00Z&environment_id=#{env_id}&start=2018-03-12T08%3A36%3A00Z)
+        MARKDOWN
+      end
+
+      before do
+        payload['labels'] = { 'gitlab_alert_id' => metric_id }
+      end
+
+      context 'without a starting time available' do
+        around do |example|
+          Timecop.freeze(starts_at) { example.run }
+        end
+
+        it { is_expected.to eq(expected_markdown) }
+      end
+
+      context 'with a starting time available' do
+        before do
+          payload['startsAt'] = starts_at
+        end
+
+        it { is_expected.to eq(expected_markdown) }
+      end
+    end
+  end
+end