Add jobs requesting API

lib/api/entities.rb

@@ -697,5 +697,43 @@ module API
       expose :id, :message, :starts_at, :ends_at, :color, :font
       expose :active?, as: :active
     end
+
+    class ArtifactFile < Grape::Entity
+      expose :filename, :size
+    end
+
+    class JobCredentials < Grape::Entity
+      expose :type, :url, :username, :password
+    end
+
+    class JobResponse < Grape::Entity
+      expose :id, :ref, :tag, :sha, :status
+      expose :name, :token, :stage
+      expose :project_id
+      expose :project_name
+      expose :artifacts_file, using: ArtifactFile, if: ->(build, _) { build.artifacts? }
+    end
+
+    class RequestJobResponse < JobResponse
+      expose :commands
+      expose :repo_url
+      expose :before_sha
+      expose :allow_git_fetch
+      expose :token
+      expose :artifacts_expire_at, if: ->(build, _) { build.artifacts? }
+
+      expose :options do |model|
+        model.options
+      end
+
+      expose :timeout do |model|
+        model.timeout
+      end
+
+      expose :variables
+      expose :depends_on_builds, using: JobResponse
+
+      expose :credentials, using: JobCredentials
+    end
   end
 end

lib/api/helpers/runner.rb

 module API
   module Helpers
     module Runner
+      UPDATE_RUNNER_EVERY = 10 * 60
+
       def runner_registration_token_valid?
         ActiveSupport::SecurityUtils.variable_size_secure_compare(params[:token],
                                                                   current_application_settings.runners_registration_token)
@@ -18,6 +20,32 @@ module API
       def current_runner
         @runner ||= ::Ci::Runner.find_by_token(params[:token].to_s)
       end
+
+      def update_runner_info
+        return unless update_runner?
+
+        current_runner.contacted_at = Time.now
+        current_runner.assign_attributes(get_runner_version_from_params)
+        current_runner.save if current_runner.changed?
+      end
+
+      def update_runner?
+        # Use a random threshold to prevent beating DB updates.
+        # It generates a distribution between [40m, 80m].
+        #
+        contacted_at_max_age = UPDATE_RUNNER_EVERY + Random.rand(UPDATE_RUNNER_EVERY)
+
+        current_runner.contacted_at.nil? ||
+            (Time.now - current_runner.contacted_at) >= contacted_at_max_age
+      end
+
+      def build_not_found!
+        if headers['User-Agent'].to_s.match(/gitlab(-ci-multi)?-runner \d+\.\d+\.\d+(~beta\.\d+\.g[0-9a-f]+)? /)
+          no_content!
+        else
+          not_found!
+        end
+      end
     end
   end
 end

lib/api/runner.rb

@@ -48,5 +48,44 @@ module API
         Ci::Runner.find_by_token(params[:token]).destroy
       end
     end
+
+    resource :jobs do
+      desc 'Request a job' do
+        success Entities::RequestJobResponse
+      end
+      params do
+        requires :token, type: String, desc: %q(Runner's authentication token)
+      end
+      post '/request' do
+        authenticate_runner!
+        not_found! unless current_runner.active?
+        update_runner_info
+
+        if current_runner.is_runner_queue_value_latest?(params[:last_update])
+          header 'X-GitLab-Last-Update', params[:last_update]
+          Gitlab::Metrics.add_event(:build_not_found_cached)
+          return build_not_found!
+        end
+
+        new_update = current_runner.ensure_runner_queue_value
+        result = ::Ci::RegisterBuildService.new(current_runner).execute
+
+        if result.valid?
+          if result.build
+            Gitlab::Metrics.add_event(:build_found,
+                                      project: result.build.project.path_with_namespace)
+            present result.build, with: Entities::RequestJobResponse
+          else
+            Gitlab::Metrics.add_event(:build_not_found)
+            header 'X-GitLab-Last-Update', new_update
+            build_not_found!
+          end
+        else
+          # We received build that is invalid due to concurrency conflict
+          Gitlab::Metrics.add_event(:build_invalid)
+          conflict!
+        end
+      end
+    end
   end
 end