Use etag caching for environments JSON

For the index view, the environments can now be requested every 15
seconds. Any transition state of a projects environments will trigger a
cache invalidation action.

Fixes gitlab-org/gitlab-ce#31701

app/controllers/projects/environments_controller.rb

@@ -15,6 +15,8 @@ class Projects::EnvironmentsController < Projects::ApplicationController
     respond_to do |format|
       format.html
       format.json do
+        Gitlab::PollingInterval.set_header(response, interval: 15_000)
+
         render json: {
           environments: EnvironmentSerializer
             .new(project: @project, current_user: @current_user)

app/models/environment.rb

@@ -57,6 +57,10 @@ class Environment < ActiveRecord::Base
     state :available
     state :stopped
+
+    after_transition do |environment|
+      environment.expire_etag_cache
+    end
   end
   def predefined_variables
@@ -196,6 +200,13 @@ class Environment < ActiveRecord::Base
     [external_url, public_path].join('/')
   end
+  def expire_etag_cache
+    Gitlab::EtagCaching::Store.new.tap do |store|
+      store.touch(Gitlab::Routing.url_helpers
+        .namespace_project_environments_path(project.namespace, project))
+    end
+  end
+
   private
   # Slugifying a name may remove the uniqueness guarantee afforded by it being

changelogs/unreleased/zj-realtime-env-list.yml

+---
+title: Make environment table realtime
+merge_request: 11333
+author:

lib/gitlab/etag_caching/router.rb

@@ -7,9 +7,10 @@ module Gitlab
       #   - Don't contain a reserved word (expect for the words used in the
       #     regex itself)
       #   - Ending in `noteable/issue/<id>/notes` for the `issue_notes` route
-      #   - Ending in `issues/id`/realtime_changes` for the `issue_title` route
+      #   - Ending in `issues/id`/rendered_title` for the `issue_title` route
       USED_IN_ROUTES = %w[noteable issue notes issues realtime_changes
-                          commit pipelines merge_requests new].freeze
+                          commit pipelines merge_requests new
+                          environments].freeze
       RESERVED_WORDS = DynamicPathValidator::WILDCARD_ROUTES - USED_IN_ROUTES
       RESERVED_WORDS_REGEX = Regexp.union(*RESERVED_WORDS)
       ROUTES = [
@@ -40,6 +41,10 @@ module Gitlab
         Gitlab::EtagCaching::Router::Route.new(
           %r(^(?!.*(#{RESERVED_WORDS})).*/pipelines/\d+\.json\z),
           'project_pipeline'
+        ),
+        Gitlab::EtagCaching::Router::Route.new(
+          %r(^(?!.*(#{RESERVED_WORDS_REGEX})).*/environments\.json\z),
+          'environments'
         )
       ].freeze

spec/lib/gitlab/etag_caching/router_spec.rb

@@ -77,6 +77,16 @@ describe Gitlab::EtagCaching::Router do
     expect(result).to be_blank
   end
+  it 'matches the environments path' do
+    env = build_env(
+      '/my-group/my-project/environments.json'
+    )
+
+    result = described_class.match(env)
+
+    expect(result).to be_blank
+  end
+
   def build_env(path)
     { 'PATH_INFO' => path }
   end

spec/models/environment_spec.rb

 require 'spec_helper'
 describe Environment, models: true do
-  let(:project) { create(:empty_project) }
+  set(:project) { create(:empty_project) }
   subject(:environment) { create(:environment, project: project) }
   it { is_expected.to belong_to(:project) }
@@ -34,6 +34,14 @@ describe Environment, models: true do
     end
   end
+  describe 'state machine' do
+    it 'invalidates the cache after a change' do
+      expect(environment).to receive(:expire_etag_cache)
+
+      environment.stop
+    end
+  end
+
   describe '#nullify_external_url' do
     it 'replaces a blank url with nil' do
       env = build(:environment, external_url: "")