Merge branch 'add-pipeline-metrics-worker' into 'master'

Add Pipeline metrics worker

## What does this MR do?
Creating a new Merge Request metrics is time consuming, because we need to access repository.

This makes this operation asynchronous, thus non-blocking for updating pipeline.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !6896

5 files changed, 92 insertions, 22 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 38765b347d0..9d28227f960 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ Please view this file on the master branch, on stable branches it's out of date.
   - Change user & group landing page routing from /u/:username to /:username
   - Prevent running GfmAutocomplete setup for each diff note !6569
   - Added documentation for .gitattributes files
+  - Move Pipeline Metrics to separate worker
   - AbstractReferenceFilter caches project_refs on RequestStore when active
   - Replaced the check sign to arrow in the show build view. !6501
   - Add a /wip slash command to toggle the Work In Progress status of a merge request. !6259 (tbalthazar)
diff --git a/app/models/ci/pipeline.rb b/app/models/ci/pipeline.rb
index 4fdb5fef4fb..c7b9d6cc223 100644
--- a/app/models/ci/pipeline.rb
+++ b/app/models/ci/pipeline.rb
@@ -49,6 +49,10 @@ module Ci
         transition any => :canceled
       end
 
+      # IMPORTANT
+      # Do not add any operations to this state_machine
+      # Create a separate worker for each new operation
+
       before_transition [:created, :pending] => :running do |pipeline|
         pipeline.started_at = Time.now
       end
@@ -62,13 +66,11 @@ module Ci
       end
 
       after_transition [:created, :pending] => :running do |pipeline|
-        MergeRequest::Metrics.where(merge_request_id: pipeline.merge_requests.map(&:id)).
-          update_all(latest_build_started_at: pipeline.started_at, latest_build_finished_at: nil)
+        pipeline.run_after_commit { PipelineMetricsWorker.perform_async(id) }
       end
 
       after_transition any => [:success] do |pipeline|
-        MergeRequest::Metrics.where(merge_request_id: pipeline.merge_requests.map(&:id)).
-          update_all(latest_build_finished_at: pipeline.finished_at)
+        pipeline.run_after_commit { PipelineMetricsWorker.perform_async(id) }
       end
 
       after_transition [:created, :pending, :running] => :success do |pipeline|
diff --git a/app/workers/pipeline_metrics_worker.rb b/app/workers/pipeline_metrics_worker.rb
new file mode 100644
index 00000000000..7bb92df3bbd
--- /dev/null
+++ b/app/workers/pipeline_metrics_worker.rb
@@ -0,0 +1,30 @@
+class PipelineMetricsWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: :default
+
+  def perform(pipeline_id)
+    Ci::Pipeline.find_by(id: pipeline_id).try do |pipeline|
+      update_metrics_for_active_pipeline(pipeline) if pipeline.active?
+      update_metrics_for_succeeded_pipeline(pipeline) if pipeline.success?
+    end
+  end
+
+  private
+
+  def update_metrics_for_active_pipeline(pipeline)
+    metrics(pipeline).update_all(latest_build_started_at: pipeline.started_at, latest_build_finished_at: nil)
+  end
+
+  def update_metrics_for_succeeded_pipeline(pipeline)
+    metrics(pipeline).update_all(latest_build_started_at: pipeline.started_at, latest_build_finished_at: pipeline.finished_at)
+  end
+
+  def metrics(pipeline)
+    MergeRequest::Metrics.where(merge_request_id: merge_requests(pipeline))
+  end
+
+  def merge_requests(pipeline)
+    pipeline.merge_requests.map(&:id)
+  end
+end
diff --git a/spec/models/ci/pipeline_spec.rb b/spec/models/ci/pipeline_spec.rb
index 550a890797e..163c0b5c516 100644
--- a/spec/models/ci/pipeline_spec.rb
+++ b/spec/models/ci/pipeline_spec.rb
@@ -187,33 +187,24 @@ describe Ci::Pipeline, models: true do
       end
     end
 
-    describe "merge request metrics" do
+    describe 'merge request metrics' do
       let(:project) { FactoryGirl.create :project }
       let(:pipeline) { FactoryGirl.create(:ci_empty_pipeline, status: 'created', project: project, ref: 'master', sha: project.repository.commit('master').id) }
       let!(:merge_request) { create(:merge_request, source_project: project, source_branch: pipeline.ref) }
 
-      context 'when transitioning to running' do
-        it 'records the build start time' do
-          time = Time.now
-          Timecop.freeze(time) { build.run }
-
-          expect(merge_request.reload.metrics.latest_build_started_at).to be_within(1.second).of(time)
-        end
-
-        it 'clears the build end time' do
-          build.run
+      before do
+        expect(PipelineMetricsWorker).to receive(:perform_async).with(pipeline.id)
+      end
 
-          expect(merge_request.reload.metrics.latest_build_finished_at).to be_nil
+      context 'when transitioning to running' do
+        it 'schedules metrics workers' do
+          pipeline.run
         end
       end
 
       context 'when transitioning to success' do
-        it 'records the build end time' do
-          build.run
-          time = Time.now
-          Timecop.freeze(time) { build.success }
-
-          expect(merge_request.reload.metrics.latest_build_finished_at).to be_within(1.second).of(time)
+        it 'schedules metrics workers' do
+          pipeline.succeed
         end
       end
     end
diff --git a/spec/workers/pipeline_metrics_worker_spec.rb b/spec/workers/pipeline_metrics_worker_spec.rb
new file mode 100644
index 00000000000..f58df3f0d6e
--- /dev/null
+++ b/spec/workers/pipeline_metrics_worker_spec.rb
@@ -0,0 +1,46 @@
+require 'spec_helper'
+
+describe PipelineMetricsWorker do
+  let(:project) { create(:project) }
+  let!(:merge_request) { create(:merge_request, source_project: project, source_branch: pipeline.ref) }
+
+  let(:pipeline) do
+    create(:ci_empty_pipeline,
+           status: status,
+           project: project,
+           ref: 'master',
+           sha: project.repository.commit('master').id,
+           started_at: 1.hour.ago,
+           finished_at: Time.now)
+  end
+
+  describe '#perform' do
+    subject { described_class.new.perform(pipeline.id) }
+
+    context 'when pipeline is running' do
+      let(:status) { 'running' }
+
+      it 'records the build start time' do
+        subject
+
+        expect(merge_request.reload.metrics.latest_build_started_at).to eq(pipeline.started_at)
+      end
+
+      it 'clears the build end time' do
+        subject
+
+        expect(merge_request.reload.metrics.latest_build_finished_at).to be_nil
+      end
+    end
+
+    context 'when pipeline succeeded' do
+      let(:status) { 'success' }
+
+      it 'records the build end time' do
+        subject
+
+        expect(merge_request.reload.metrics.latest_build_finished_at).to eq(pipeline.finished_at)
+      end
+    end
+  end
+end