Add a wrapper for pipeline statuses

This reads status from redis & stores it in redis if it was missing.

If the project has no HEAD, the cache is deleted

app/models/ci/pipeline_status.rb

+# This class is not backed by a table in the main database.
+# It loads the latest Pipeline for the HEAD of a repository, and caches that
+# in Redis.
+module Ci
+  class PipelineStatus
+    attr_accessor :sha, :status, :project, :loaded
+
+    delegate :commit, to: :project
+
+    def self.load_for_project(project)
+      new(project).tap do |status|
+        status.load_status
+      end
+    end
+
+    def initialize(project, sha: nil, status: nil)
+      @project = project
+      @sha = sha
+      @status = status
+    end
+
+    def has_status?
+      loaded? && sha.present? && status.present?
+    end
+
+    def load_status
+      return if loaded?
+
+      if has_cache?
+        load_from_cache
+      else
+        load_from_commit
+        store_in_cache
+      end
+
+      self.loaded = true
+    end
+
+    def load_from_commit
+      self.sha = commit.sha
+      self.status = commit.status
+    end
+
+    # We only cache the status for the HEAD commit of a project
+    # This status is rendered in project lists
+    def store_in_cache_if_needed
+      return unless sha
+      return delete_from_cache unless commit
+      store_in_cache if commit.sha == self.sha
+    end
+
+    def load_from_cache
+      Gitlab::Redis.with do |redis|
+        self.sha, self.status = redis.hmget(cache_key, :sha, :status)
+      end
+    end
+
+    def store_in_cache
+      Gitlab::Redis.with do |redis|
+        redis.mapped_hmset(cache_key, { sha: sha, status: status })
+      end
+    end
+
+    def delete_from_cache
+      Gitlab::Redis.with do |redis|
+        redis.del(cache_key)
+      end
+    end
+
+    def has_cache?
+      Gitlab::Redis.with do |redis|
+        redis.exists(cache_key)
+      end
+    end
+
+    def loaded?
+      self.loaded
+    end
+
+    def cache_key
+      "projects/#{project.id}/build_status"
+    end
+  end
+end

spec/models/ci/pipeline_status_spec.rb

+require 'spec_helper'
+
+describe Ci::PipelineStatus do
+  let(:project) { create(:project) }
+  let(:pipeline_status) { described_class.new(project) }
+
+  describe '.load_for_project' do
+    it "loads the status" do
+      expect_any_instance_of(described_class).to receive(:load_status)
+
+      described_class.load_for_project(project)
+    end
+  end
+
+  describe '#has_status?' do
+    it "is false when the status wasn't loaded yet" do
+      expect(pipeline_status.has_status?).to be_falsy
+    end
+
+    it 'is true when all status information was loaded' do
+      fake_commit = double
+      allow(fake_commit).to receive(:status).and_return('failed')
+      allow(fake_commit).to receive(:sha).and_return('failed424d1b73bc0d3cb726eb7dc4ce17a4d48552f8c6')
+      allow(pipeline_status).to receive(:commit).and_return(fake_commit)
+      allow(pipeline_status).to receive(:has_cache?).and_return(false)
+
+      pipeline_status.load_status
+
+      expect(pipeline_status.has_status?).to be_truthy
+    end
+  end
+
+  describe '#load_status' do
+    it 'loads the status from the cache when there is one' do
+      expect(pipeline_status).to receive(:has_cache?).and_return(true)
+      expect(pipeline_status).to receive(:load_from_cache)
+
+      pipeline_status.load_status
+    end
+
+    it 'loads the status from the project commit when there is no cache' do
+      allow(pipeline_status).to receive(:has_cache?).and_return(false)
+
+      expect(pipeline_status).to receive(:load_from_commit)
+
+      pipeline_status.load_status
+    end
+
+    it 'stores the status in the cache when it loading it from the project' do
+      allow(pipeline_status).to receive(:has_cache?).and_return(false)
+      allow(pipeline_status).to receive(:load_from_commit)
+
+      expect(pipeline_status).to receive(:store_in_cache)
+
+      pipeline_status.load_status
+    end
+
+    it 'sets the state to loaded' do
+      pipeline_status.load_status
+
+      expect(pipeline_status).to be_loaded
+    end
+
+    it 'only loads the status once' do
+      expect(pipeline_status).to receive(:has_cache?).and_return(true).exactly(1)
+      expect(pipeline_status).to receive(:load_from_cache).exactly(1)
+
+      pipeline_status.load_status
+      pipeline_status.load_status
+    end
+  end
+
+  describe "#load_from_commit" do
+    let!(:pipeline) { create(:ci_pipeline, :success, project: project, sha: project.commit.sha) }
+
+    it 'reads the status from the pipeline for the commit' do
+      pipeline_status.load_from_commit
+
+      expect(pipeline_status.status).to eq('success')
+      expect(pipeline_status.sha).to eq(project.commit.sha)
+    end
+  end
+
+  describe "#store_in_cache", :redis do
+    it "sets the object in redis" do
+      pipeline_status.sha = '123456'
+      pipeline_status.status = 'failed'
+
+      pipeline_status.store_in_cache
+      read_sha, read_status = Gitlab::Redis.with { |redis| redis.hmget("projects/#{project.id}/build_status", :sha, :status) }
+
+      expect(read_sha).to eq('123456')
+      expect(read_status).to eq('failed')
+    end
+  end
+
+  describe '#store_in_cache_if_needed', :redis do
+    it 'stores the state in the cache when the sha is the HEAD of the project' do
+      create(:ci_pipeline, :success, project: project, sha: project.commit.sha)
+      build_status = described_class.load_for_project(project)
+
+      build_status.store_in_cache_if_needed
+      sha, status = Gitlab::Redis.with { |redis| redis.hmget("projects/#{project.id}/build_status", :sha, :status) }
+
+      expect(sha).not_to be_nil
+      expect(status).not_to be_nil
+    end
+
+    it "doesn't store the status in redis when the sha is not the head of the project" do
+      other_status = described_class.new(project, sha: "123456", status: "failed")
+
+      other_status.store_in_cache_if_needed
+      sha, status = Gitlab::Redis.with { |redis| redis.hmget("projects/#{project.id}/build_status", :sha, :status) }
+
+      expect(sha).to be_nil
+      expect(status).to be_nil
+    end
+
+    it "deletes the cache if the repository doesn't have a head commit" do
+      empty_project = create(:empty_project)
+      Gitlab::Redis.with { |redis| redis.mapped_hmset("projects/#{empty_project.id}/build_status", { sha: "sha", status: "pending" }) }
+      other_status = described_class.new(empty_project, sha: "123456", status: "failed")
+
+      other_status.store_in_cache_if_needed
+      sha, status = Gitlab::Redis.with { |redis| redis.hmget("projects/#{empty_project.id}/build_status", :sha, :status) }
+
+      expect(sha).to be_nil
+      expect(status).to be_nil
+    end
+  end
+
+  describe "with a status in redis", :redis do
+    let(:status) { 'success' }
+    let(:sha) { '424d1b73bc0d3cb726eb7dc4ce17a4d48552f8c6' }
+
+    before do
+      Gitlab::Redis.with { |redis| redis.mapped_hmset("projects/#{project.id}/build_status", { sha: sha, status: status }) }
+    end
+
+    describe '#load_from_cache' do
+      it 'reads the status from redis' do
+        pipeline_status.load_from_cache
+
+        expect(pipeline_status.sha).to eq(sha)
+        expect(pipeline_status.status).to eq(status)
+      end
+    end
+
+    describe '#has_cache?' do
+      it 'knows the status is cached' do
+        expect(pipeline_status.has_cache?).to be_truthy
+      end
+    end
+
+    describe '#delete_from_cache' do
+      it 'deletes values from redis'  do
+        pipeline_status.delete_from_cache
+
+        key_exists = Gitlab::Redis.with { |redis| redis.exists("projects/#{project.id}/build_status") }
+
+        expect(key_exists).to be_falsy
+      end
+    end
+  end
+end