Multithreading cluster creation is done with `reactive_cache`

app/controllers/projects/clusters_controller.rb

 class Projects::ClustersController < Projects::ApplicationController
-  before_action :cluster
+  before_action :cluster, except: [:login, :index, :new, :create]
   before_action :authorize_google_api, except: [:login]
   # before_action :authorize_admin_clusters! # TODO: Authentication
@@ -11,8 +11,8 @@ class Projects::ClustersController < Projects::ApplicationController
   end
   def index
-    if cluster
-      redirect_to edit_namespace_project_cluster_path(project.namespace, project, cluster.id)
+    if project.clusters.any?
+      redirect_to edit_namespace_project_cluster_path(project.namespace, project, project.clusters.last.id)
     else
       redirect_to action: 'new'
     end
@@ -22,72 +22,36 @@ class Projects::ClustersController < Projects::ApplicationController
   end
   def create
-    # Create a cluster on GKE
-    operation = api_client.projects_zones_clusters_create(
-      params['gcp_project_id'], params['cluster_zone'], params['cluster_name'],
-      cluster_size: params['cluster_size'], machine_type: params['machine_type']
-    )
-
-    # wait_operation_done
-    if operation&.operation_type == 'CREATE_CLUSTER'
-      api_client.wait_operation_done(operation.self_link)
-    else
-      raise "TODO: ERROR"
+    begin
+      Ci::CreateClusterService.new(project, current_user, params)
+                              .create_cluster_on_gke(api_client)
+    rescue Ci::CreateClusterService::UnexpectedOperationError => e
+      puts "#{self.class.name} - #{__callee__}: e: #{e}"
+      # TODO: error
     end
-    # Get cluster details (end point, etc)
-    gke_cluster = api_client.projects_zones_clusters_get(
-      params['gcp_project_id'], params['cluster_zone'], params['cluster_name']
-    )
-    # Get k8s token
-    token = ''
-    KubernetesService.new.tap do |ks|
-      ks.api_url = 'https://' + gke_cluster.endpoint
-      ks.ca_pem = Base64.decode64(gke_cluster.master_auth.cluster_ca_certificate)
-      ks.username = gke_cluster.master_auth.username
-      ks.password = gke_cluster.master_auth.password
-      secrets = ks.read_secrets
-      secrets.each do |secret|
-        name = secret.dig('metadata', 'name')
-        if /default-token/ =~ name
-          token_base64 = secret.dig('data', 'token')
-          token = Base64.decode64(token_base64)
-          break
-        end
+    redirect_to action: 'index'
+  end
+  ##
+  # Return
+  # @status: The current status of the operation.
+  # @status_message: If an error has occurred, a textual description of the error.
+  def creation_status
+    respond_to do |format|
+      format.json do
+        render json: cluster.creation_status(session[GoogleApi::CloudPlatform::Client.token_in_session])
       end
     end
-
-    # Update service
-    kubernetes_service.attributes = service_params(
-        active: true,
-        api_url: 'https://' + gke_cluster.endpoint,
-        ca_pem: Base64.decode64(gke_cluster.master_auth.cluster_ca_certificate),
-        namespace: params['project_namespace'],
-        token: token
-      )
-
-    kubernetes_service.save!
-
-    # Save info
-    project.clusters.create(
-      gcp_project_id: params['gcp_project_id'],
-      cluster_zone: params['cluster_zone'],
-      cluster_name: params['cluster_name'],
-      service: kubernetes_service
-    )
-
-    redirect_to action: 'index'
   end
   def edit
-    # TODO: If on, do we override parameter?
-    # TODO: If off, do we override parameter?
   end
   def update
     cluster.update(enabled: params['enabled'])
     cluster.service.update(active: params['enabled'])
+    # TODO: Do we overwrite KubernetesService parameter?
     render :edit
   end
@@ -99,8 +63,7 @@ class Projects::ClustersController < Projects::ApplicationController
   private
   def cluster
-    # Each project has only one cluster, for now. In the future iteraiton, we'll support multiple clusters
-    @cluster ||= project.clusters.last
+    @cluster ||= project.clusters.find(params[:id])
   end
   def api_client
@@ -112,20 +75,6 @@ class Projects::ClustersController < Projects::ApplicationController
       )
   end
-  def kubernetes_service
-    @kubernetes_service ||= project.find_or_initialize_service('kubernetes')
-  end
-
-  def service_params(active:, api_url:, ca_pem:, namespace:, token:)
-    {
-      active: active,
-      api_url: api_url,
-      ca_pem: ca_pem,
-      namespace: namespace,
-      token: token
-    }
-  end
-
   def authorize_google_api
     unless session[GoogleApi::CloudPlatform::Client.token_in_session]
       redirect_to action: 'login'

app/models/ci/cluster.rb

 module Ci
   class Cluster < ActiveRecord::Base
     extend Gitlab::Ci::Model
+    include ReactiveCaching
+
+    self.reactive_cache_key = ->(cluster) { [cluster.class.model_name.singular, cluster.project_id, cluster.id] }
     belongs_to :project
     belongs_to :owner, class_name: 'User'
     belongs_to :service
+    # after_save :clear_reactive_cache!
+
+    def creation_status(access_token)
+      with_reactive_cache(access_token) do |operation|
+        {
+          status: operation[:status],
+          status_message: operation[:status_message]
+        }
+      end
+    end
+
+    def calculate_reactive_cache(access_token)
+      return { status: 'INTEGRATED' } if service # If it's already done, we don't need to continue the following process
+
+      api_client = GoogleApi::CloudPlatform::Client.new(access_token, nil)
+      operation = api_client.projects_zones_operations(gcp_project_id, cluster_zone, gcp_operation_id)
+
+      if operation&.status == 'DONE'
+        # Get cluster details (end point, etc)
+        gke_cluster = api_client.projects_zones_clusters_get(
+          gcp_project_id, cluster_zone, cluster_name
+        )
+
+        # Get k8s token
+        token = ''
+        KubernetesService.new.tap do |ks|
+          ks.api_url = 'https://' + gke_cluster.endpoint
+          ks.ca_pem = Base64.decode64(gke_cluster.master_auth.cluster_ca_certificate)
+          ks.username = gke_cluster.master_auth.username
+          ks.password = gke_cluster.master_auth.password
+          secrets = ks.read_secrets
+          secrets.each do |secret|
+            name = secret.dig('metadata', 'name')
+            if /default-token/ =~ name
+              token_base64 = secret.dig('data', 'token')
+              token = Base64.decode64(token_base64)
+              break
+            end
+          end
+        end
+
+        # k8s endpoint, ca_cert
+        endpoint = 'https://' + gke_cluster.endpoint
+        cluster_ca_certificate = Base64.decode64(gke_cluster.master_auth.cluster_ca_certificate)
+
+        # Update service
+        kubernetes_service.attributes = {
+          active: true,
+          api_url: endpoint,
+          ca_pem: cluster_ca_certificate,
+          namespace: project_namespace,
+          token: token
+        }
+
+        kubernetes_service.save!
+
+        # Save info in cluster record
+        update(
+          enabled: true,
+          service: kubernetes_service,
+          username: gke_cluster.master_auth.username,
+          password: gke_cluster.master_auth.password,
+          token: token,
+          ca_cert: cluster_ca_certificate,
+          end_point: endpoint,
+        )
+      end
+
+      puts "#{self.class.name} - #{__callee__}: operation.to_json: #{operation.to_json}"
+      operation.to_h
+    end
+
+    def kubernetes_service
+      @kubernetes_service ||= project.find_or_initialize_service('kubernetes')
+    end
   end
 end

app/services/ci/create_cluster_service.rb

+module Ci
+  class CreateClusterService < BaseService
+    UnexpectedOperationError = Class.new(StandardError)
+
+    def create_cluster_on_gke(api_client)
+      # Create a cluster on GKE
+      operation = api_client.projects_zones_clusters_create(
+        params['gcp_project_id'], params['cluster_zone'], params['cluster_name'],
+        cluster_size: params['cluster_size'], machine_type: params['machine_type']
+      )
+
+      if operation&.status != ('RUNNING' || 'PENDING')
+        raise UnexpectedOperationError
+      end
+
+      api_client.parse_self_link(operation.self_link).tap do |project_id, zone, operation_id|
+        project.clusters.create(owner: current_user,
+                                gcp_project_id: params['gcp_project_id'],
+                                cluster_zone: params['cluster_zone'],
+                                cluster_name: params['cluster_name'],
+                                project_namespace: params['project_namespace'],
+                                gcp_operation_id: operation_id).tap do |cluster|
+          # Start status polling. When the operation finish, create KubernetesService.
+          cluster.creation_status(api_client.access_token)
+        end
+      end
+    end
+  end
+end

app/views/projects/clusters/_form.html.haml

 Create a new cluster
 %br
-= link_to "Create on Google Container Engine", namespace_project_clusters_path(@project.namespace, @project, cluster_name: "gke-test-creation42", gcp_project_id: 'gitlab-internal-153318', cluster_zone: 'us-central1-a', cluster_size: '1', project_namespace: 'aaa', machine_type: '???'), method: :post
+= link_to "Create on Google Container Engine", namespace_project_clusters_path(@project.namespace, @project, cluster_name: "gke-test-creation#{Random.rand(100)}", gcp_project_id: 'gitlab-internal-153318', cluster_zone: 'us-central1-a', cluster_size: '1', project_namespace: 'aaa', machine_type: '???'), method: :post
 -# gke-test-creation#{Random.rand(100)}

app/views/projects/clusters/edit.html.haml

@@ -5,3 +5,4 @@ edit/show cluster
 = link_to "Enable", namespace_project_cluster_path(@project.namespace, @project, @cluster.id, enabled: 'true'), method: :put
 = link_to "Disable", namespace_project_cluster_path(@project.namespace, @project, @cluster.id, enabled: 'false'), method: :put
 = link_to "Soft-delete the cluster", namespace_project_cluster_path(@project.namespace, @project, @cluster.id), method: :delete
+= link_to 'Check status', creation_status_namespace_project_cluster_path(@cluster.project.namespace, @cluster.project, @cluster.id), :remote => true

config/routes/project.rb

@@ -187,6 +187,10 @@ constraints(ProjectUrlConstrainer.new) do
         collection do
           get :login
         end
+
+        member do
+          get :creation_status, format: :json
+        end
       end
       resources :environments, except: [:destroy] do

db/migrate/20170924094327_create_ci_clusters.rb

@@ -24,6 +24,7 @@ class CreateCiClusters < ActiveRecord::Migration
       t.string :gcp_project_id
       t.string :cluster_zone
       t.string :cluster_name
+      t.string :gcp_operation_id
       t.datetime_with_timezone :created_at, null: false
       t.datetime_with_timezone :updated_at, null: false

db/schema.rb

@@ -281,6 +281,7 @@ ActiveRecord::Schema.define(version: 20170924094327) do
     t.string "gcp_project_id"
     t.string "cluster_zone"
     t.string "cluster_name"
+    t.string "gcp_operation_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
   end

lib/google_api/cloud_platform/client.rb

@@ -40,7 +40,8 @@ module GoogleApi
         begin
           operation = service.create_cluster(project_id, zone, request_body)
         rescue Google::Apis::ClientError, Google::Apis::AuthorizationError => e
-          Rails.logger.error("#{self.class.name}: Could not create cluster #{cluster_name}: #{e}")
+          puts "#{self.class.name} - #{__callee__}: Could not create cluster #{cluster_name}: #{e}"
+          # TODO: Error
         end
         puts "#{self.class.name} - #{__callee__}: operation: #{operation.inspect}"
         operation
@@ -51,23 +52,14 @@ module GoogleApi
         service.authorization = access_token
         operation = service.get_zone_operation(project_id, zone, operation_id)
+        puts "#{self.class.name} - #{__callee__}: operation: #{operation.inspect}"
         operation
       end
-      def wait_operation_done(self_link)
-        running = true
-
+      def parse_self_link(self_link)
         ret = self_link.match(/projects\/(.*)\/zones\/(.*)\/operations\/(.*)/)
-        project_id = ret[1]
-        zone = ret[2]
-        operation_id = ret[3]
-        while running
-          operation = projects_zones_operations(project_id, zone, operation_id)
-          if operation.status != 'RUNNING'
-            running = false
-          end
-        end
+        return ret[1], ret[2], ret[3] # project_id, zone, operation_id
       end
     end
   end