diff --git a/app/controllers/concerns/render_service_results.rb b/app/controllers/concerns/render_service_results.rb
new file mode 100644
index 0000000000000000000000000000000000000000..0149a71d9f563a0c5bd5cca491a5714a6aed71ce
--- /dev/null
+++ b/app/controllers/concerns/render_service_results.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module RenderServiceResults
+  extend ActiveSupport::Concern
+
+  def success_response(result)
+    render({
+      status: result[:http_status],
+      json: result[:body]
+    })
+  end
+
+  def continue_polling_response
+    render({
+      status: :no_content,
+      json: {
+        status: _('processing'),
+        message: _('Not ready yet. Try again later.')
+      }
+    })
+  end
+
+  def error_response(result)
+    render({
+      status: result[:http_status] || :bad_request,
+      json: { status: result[:status], message: result[:message] }
+    })
+  end
+end
diff --git a/app/controllers/projects/environments/prometheus_api_controller.rb b/app/controllers/projects/environments/prometheus_api_controller.rb
index 9c6c6513a78a5e72f153192ed21909119c64ece7..e902d218c752e99f1504414d6d1d422d695fec0e 100644
--- a/app/controllers/projects/environments/prometheus_api_controller.rb
+++ b/app/controllers/projects/environments/prometheus_api_controller.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class Projects::Environments::PrometheusApiController < Projects::ApplicationController
+  include RenderServiceResults
+
   before_action :authorize_read_prometheus!
   before_action :environment
 
@@ -12,21 +14,10 @@ class Projects::Environments::PrometheusApiController < Projects::ApplicationCon
       proxy_params
     ).execute
 
-    if result.nil?
-      return render status: :no_content, json: {
-        status: _('processing'),
-        message: _('Not ready yet. Try again later.')
-      }
-    end
-
-    if result[:status] == :success
-      render status: result[:http_status], json: result[:body]
-    else
-      render(
-        status: result[:http_status] || :bad_request,
-        json: { status: result[:status], message: result[:message] }
-      )
-    end
+    return continue_polling_response if result.nil?
+    return error_response(result) if result[:status] == :error
+
+    success_response(result)
   end
 
   private
diff --git a/app/controllers/projects/grafana_api_controller.rb b/app/controllers/projects/grafana_api_controller.rb
new file mode 100644
index 0000000000000000000000000000000000000000..4bdf4c12cac5552ef6031cf91f2ecd2d989ea4e2
--- /dev/null
+++ b/app/controllers/projects/grafana_api_controller.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class Projects::GrafanaApiController < Projects::ApplicationController
+  include RenderServiceResults
+
+  def proxy
+    result = ::Grafana::ProxyService.new(
+      project,
+      params[:datasource_id],
+      params[:proxy_path],
+      query_params.to_h
+    ).execute
+
+    return continue_polling_response if result.nil?
+    return error_response(result) if result[:status] == :error
+
+    success_response(result)
+  end
+
+  private
+
+  def query_params
+    params.permit(:query, :start, :end, :step)
+  end
+end
diff --git a/app/controllers/projects/merge_requests/diffs_controller.rb b/app/controllers/projects/merge_requests/diffs_controller.rb
index 7b694dcdd779def647e14521b3dad0598c861660..1913d7cd580f2709fc564908b9c14cb3edb65d54 100644
--- a/app/controllers/projects/merge_requests/diffs_controller.rb
+++ b/app/controllers/projects/merge_requests/diffs_controller.rb
@@ -7,7 +7,7 @@ class Projects::MergeRequests::DiffsController < Projects::MergeRequests::Applic
   before_action :apply_diff_view_cookie!
   before_action :commit, except: :diffs_batch
   before_action :define_diff_vars, except: :diffs_batch
-  before_action :define_diff_comment_vars, except: :diffs_batch
+  before_action :define_diff_comment_vars, except: [:diffs_batch, :diffs_metadata]
 
   def show
     render_diffs
@@ -37,6 +37,11 @@ class Projects::MergeRequests::DiffsController < Projects::MergeRequests::Applic
     render json: PaginatedDiffSerializer.new(current_user: current_user).represent(diffs, options)
   end
 
+  def diffs_metadata
+    render json: DiffsMetadataSerializer.new(project: @merge_request.project)
+                   .represent(@diffs, additional_attributes)
+  end
+
   private
 
   def preloadable_mr_relations
diff --git a/app/helpers/diff_helper.rb b/app/helpers/diff_helper.rb
index 6aafd856423e290d77f12fe644bbfac8dd7b9a17..52ec2eadf5e833e349847b503ac1e30bfd484c16 100644
--- a/app/helpers/diff_helper.rb
+++ b/app/helpers/diff_helper.rb
@@ -203,8 +203,8 @@ module DiffHelper
     link_to "#{hide_whitespace? ? 'Show' : 'Hide'} whitespace changes", url, class: options[:class]
   end
 
-  def render_overflow_warning?(diff_files)
-    diffs = @merge_request_diff.presence || diff_files
+  def render_overflow_warning?(diffs_collection)
+    diffs = @merge_request_diff.presence || diffs_collection.diff_files
 
     diffs.overflow?
   end
diff --git a/app/models/grafana_integration.rb b/app/models/grafana_integration.rb
index 668b9dafd7d0785aba17213fcad8f7fe3a014109..51cc398394d7320a3131ede182c812ca26821bbb 100644
--- a/app/models/grafana_integration.rb
+++ b/app/models/grafana_integration.rb
@@ -13,4 +13,8 @@ class GrafanaIntegration < ApplicationRecord
             addressable_url: { enforce_sanitization: true, ascii_only: true }
 
   validates :token, :project, presence: true
+
+  def client
+    @client ||= ::Grafana::Client.new(api_url: grafana_url.chomp('/'), token: token)
+  end
 end
diff --git a/app/models/repository_language.rb b/app/models/repository_language.rb
index e6867f905e2083d652a35adab7a9c244bd74fafb..e468d7162391ad7e3147e3ec290cb4a605cd85f8 100644
--- a/app/models/repository_language.rb
+++ b/app/models/repository_language.rb
@@ -7,7 +7,7 @@ class RepositoryLanguage < ApplicationRecord
   default_scope { includes(:programming_language) }
 
   validates :project, presence: true
-  validates :share, inclusion: { in: 0..100, message: "The share of a lanuage is between 0 and 100" }
+  validates :share, inclusion: { in: 0..100, message: "The share of a language is between 0 and 100" }
   validates :programming_language, uniqueness: { scope: :project_id }
 
   delegate :name, :color, to: :programming_language
diff --git a/app/serializers/diff_file_metadata_entity.rb b/app/serializers/diff_file_metadata_entity.rb
new file mode 100644
index 0000000000000000000000000000000000000000..500a844b1702e8203a8e5cf5562057693951e898
--- /dev/null
+++ b/app/serializers/diff_file_metadata_entity.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class DiffFileMetadataEntity < Grape::Entity
+  expose :added_lines
+  expose :removed_lines
+  expose :new_path
+  expose :old_path
+  expose :new_file?, as: :new_file
+  expose :deleted_file?, as: :deleted_file
+end
diff --git a/app/serializers/diffs_entity.rb b/app/serializers/diffs_entity.rb
index 1763fe5b6ab70b01180ab7f9c20b322558954ea1..19875a1287cf0d6d7f911ddb96d786118abd03ce 100644
--- a/app/serializers/diffs_entity.rb
+++ b/app/serializers/diffs_entity.rb
@@ -53,7 +53,7 @@ class DiffsEntity < Grape::Entity
   # rubocop: enable CodeReuse/ActiveRecord
 
   expose :render_overflow_warning do |diffs|
-    render_overflow_warning?(diffs.diff_files)
+    render_overflow_warning?(diffs)
   end
 
   expose :email_patch_path, if: -> (*) { merge_request } do |diffs|
diff --git a/app/serializers/diffs_metadata_entity.rb b/app/serializers/diffs_metadata_entity.rb
new file mode 100644
index 0000000000000000000000000000000000000000..c82c686e8ef5ef9471639cd70bbed98b3adc96d1
--- /dev/null
+++ b/app/serializers/diffs_metadata_entity.rb
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+class DiffsMetadataEntity < DiffsEntity
+  unexpose :diff_files
+  expose :diff_files, using: DiffFileMetadataEntity
+end
diff --git a/app/serializers/diffs_metadata_serializer.rb b/app/serializers/diffs_metadata_serializer.rb
new file mode 100644
index 0000000000000000000000000000000000000000..9f3ba7b778d92daaebdde82d450d2aa23e3c482d
--- /dev/null
+++ b/app/serializers/diffs_metadata_serializer.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class DiffsMetadataSerializer < BaseSerializer
+  entity DiffsMetadataEntity
+end
diff --git a/app/services/grafana/proxy_service.rb b/app/services/grafana/proxy_service.rb
new file mode 100644
index 0000000000000000000000000000000000000000..74fcdc750b0156ac8d3e3d00b336780bd6a6eb7c
--- /dev/null
+++ b/app/services/grafana/proxy_service.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+# Proxies calls to a Grafana-integrated Prometheus instance
+# through the Grafana proxy API
+
+# This allows us to fetch and render metrics in GitLab from a Prometheus
+# instance for which dashboards are configured in Grafana
+module Grafana
+  class ProxyService < BaseService
+    include ReactiveCaching
+
+    self.reactive_cache_key = ->(service) { service.cache_key }
+    self.reactive_cache_lease_timeout = 30.seconds
+    self.reactive_cache_refresh_interval = 30.seconds
+    self.reactive_cache_worker_finder = ->(_id, *args) { from_cache(*args) }
+
+    attr_accessor :project, :datasource_id, :proxy_path, :query_params
+
+    # @param project_id [Integer] Project id for which grafana is configured.
+    #
+    # See #initialize for other parameters.
+    def self.from_cache(project_id, datasource_id, proxy_path, query_params)
+      project = Project.find(project_id)
+
+      new(project, datasource_id, proxy_path, query_params)
+    end
+
+    # @param project [Project] Project for which grafana is configured.
+    # @param datasource_id [String] Grafana datasource id for Prometheus instance
+    # @param proxy_path [String] Path to Prometheus endpoint; EX) 'api/v1/query_range'
+    # @param query_params [Hash<String, String>] Supported params: [query, start, end, step]
+    def initialize(project, datasource_id, proxy_path, query_params)
+      @project = project
+      @datasource_id = datasource_id
+      @proxy_path = proxy_path
+      @query_params = query_params
+    end
+
+    def execute
+      return cannot_proxy_response unless client
+
+      with_reactive_cache(*cache_key) { |result| result }
+    end
+
+    def calculate_reactive_cache(*)
+      return cannot_proxy_response unless client
+
+      response = client.proxy_datasource(
+        datasource_id: datasource_id,
+        proxy_path: proxy_path,
+        query: query_params
+      )
+
+      success(http_status: response.code, body: response.body)
+    rescue ::Grafana::Client::Error => error
+      service_unavailable_response(error)
+    end
+
+    # Required for ReactiveCaching; Usage overridden by
+    # self.reactive_cache_worker_finder
+    def id
+      nil
+    end
+
+    def cache_key
+      [project.id, datasource_id, proxy_path, query_params]
+    end
+
+    private
+
+    def client
+      project.grafana_integration&.client
+    end
+
+    def service_unavailable_response(exception)
+      error(exception.message, :service_unavailable)
+    end
+
+    def cannot_proxy_response
+      error('Proxy support for this API is not available currently')
+    end
+  end
+end
diff --git a/app/views/projects/diffs/_diffs.html.haml b/app/views/projects/diffs/_diffs.html.haml
index 2dba3fcd6649fb06dab5e54ac37c5c635b983d8c..cf7fe36af9d64a3450d03788640a0f602dc9159b 100644
--- a/app/views/projects/diffs/_diffs.html.haml
+++ b/app/views/projects/diffs/_diffs.html.haml
@@ -21,7 +21,7 @@
         = parallel_diff_btn
     = render 'projects/diffs/stats', diff_files: diff_files
 
-- if render_overflow_warning?(diff_files)
+- if render_overflow_warning?(diffs)
   = render 'projects/diffs/warning', diff_files: diffs
 
 .files{ data: { can_create_note: can_create_note } }
diff --git a/changelogs/unreleased/28781-migrate-pages-metadata-in-background.yml b/changelogs/unreleased/28781-migrate-pages-metadata-in-background.yml
new file mode 100644
index 0000000000000000000000000000000000000000..171fd8ff554d0e7fd6384b476e2be36609c26e79
--- /dev/null
+++ b/changelogs/unreleased/28781-migrate-pages-metadata-in-background.yml
@@ -0,0 +1,5 @@
+---
+title: Schedule background migration to populate pages metadata
+merge_request: 17993
+author:
+type: added
diff --git a/changelogs/unreleased/feature-default-cluster-to-vpc-enabled.yml b/changelogs/unreleased/feature-default-cluster-to-vpc-enabled.yml
new file mode 100644
index 0000000000000000000000000000000000000000..feb000554a833f32e633f114a9ddc9ae9053a817
--- /dev/null
+++ b/changelogs/unreleased/feature-default-cluster-to-vpc-enabled.yml
@@ -0,0 +1,5 @@
+---
+title: Create clusters with VPC-Native enabled
+merge_request: 18284
+author:
+type: changed
diff --git a/changelogs/unreleased/osw-diffs-metadata-endpoint.yml b/changelogs/unreleased/osw-diffs-metadata-endpoint.yml
new file mode 100644
index 0000000000000000000000000000000000000000..c8da00249f1346810487678f42b5a490b4d546fe
--- /dev/null
+++ b/changelogs/unreleased/osw-diffs-metadata-endpoint.yml
@@ -0,0 +1,5 @@
+---
+title: Introduce a lightweight diffs_metadata endpoint
+merge_request: 18104
+author:
+type: added
diff --git a/changelogs/unreleased/sy-grafana-proxy.yml b/changelogs/unreleased/sy-grafana-proxy.yml
new file mode 100644
index 0000000000000000000000000000000000000000..2c2a3959bff6c7bc063da5c1bae859d7d56c32e1
--- /dev/null
+++ b/changelogs/unreleased/sy-grafana-proxy.yml
@@ -0,0 +1,5 @@
+---
+title: Add endpoint to proxy requests to grafana's proxy endpoint
+merge_request: 18210
+author:
+type: added
diff --git a/config/routes/project.rb b/config/routes/project.rb
index f9331a22bc86be6eaf07936860c35fca05082f3e..7d51cfd6dee26fabd56a620593d13bbfae77913c 100644
--- a/config/routes/project.rb
+++ b/config/routes/project.rb
@@ -186,6 +186,10 @@ constraints(::Constraints::ProjectUrlConstrainer.new) do
 
         resource :import, only: [:new, :create, :show]
         resource :avatar, only: [:show, :destroy]
+
+        get 'grafana/proxy/:datasource_id/*proxy_path',
+            to: 'grafana_api#proxy',
+            as: :grafana_api
       end
       # End of the /-/ scope.
 
@@ -282,6 +286,7 @@ constraints(::Constraints::ProjectUrlConstrainer.new) do
             get :pipelines
             get :diffs, to: 'merge_requests/diffs#show'
             get :diffs_batch, to: 'merge_requests/diffs#diffs_batch'
+            get :diffs_metadata, to: 'merge_requests/diffs#diffs_metadata'
             get :widget, to: 'merge_requests/content#widget'
             get :cached_widget, to: 'merge_requests/content#cached_widget'
           end
diff --git a/db/post_migrate/20191002031332_schedule_pages_metadata_migration.rb b/db/post_migrate/20191002031332_schedule_pages_metadata_migration.rb
new file mode 100644
index 0000000000000000000000000000000000000000..0cd24da50d0c854d3d44d9b5e993ac36233755e7
--- /dev/null
+++ b/db/post_migrate/20191002031332_schedule_pages_metadata_migration.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+class SchedulePagesMetadataMigration < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  BATCH_SIZE = 10_000
+  MIGRATION = 'MigratePagesMetadata'
+
+  disable_ddl_transaction!
+
+  class Project < ActiveRecord::Base
+    include ::EachBatch
+
+    self.table_name = 'projects'
+  end
+
+  def up
+    say "Scheduling `#{MIGRATION}` jobs"
+
+    # At the time of writing there are ~10_669_292 records to be inserted for GitLab.com,
+    # batches of 10_000 with delay interval of 2 minutes gives us an estimate of close to 36 hours.
+    queue_background_migration_jobs_by_range_at_intervals(Project, MIGRATION, 2.minutes, batch_size: BATCH_SIZE)
+  end
+
+  def down
+    # no-op
+  end
+end
diff --git a/lib/google_api/cloud_platform/client.rb b/lib/google_api/cloud_platform/client.rb
index eaf94708282b631e7e581b82f349195d76815404..9085835dee6e9e46e090847937136c43e649bb39 100644
--- a/lib/google_api/cloud_platform/client.rb
+++ b/lib/google_api/cloud_platform/client.rb
@@ -96,6 +96,9 @@ module GoogleApi
             legacy_abac: {
               enabled: legacy_abac
             },
+            ip_allocation_policy: {
+              use_ip_aliases: true
+            },
             addons_config: enable_addons.each_with_object({}) do |addon, hash|
               hash[addon] = { disabled: false }
             end
diff --git a/lib/grafana/client.rb b/lib/grafana/client.rb
new file mode 100644
index 0000000000000000000000000000000000000000..0765630f9bb41f917caae1287f03f15096135ef1
--- /dev/null
+++ b/lib/grafana/client.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+module Grafana
+  class Client
+    Error = Class.new(StandardError)
+
+    # @param api_url [String] Base URL of the Grafana instance
+    # @param token [String] Admin-level API token for instance
+    def initialize(api_url:, token:)
+      @api_url = api_url
+      @token = token
+    end
+
+    # @param datasource_id [String] Grafana ID for the datasource
+    # @param proxy_path [String] Path to proxy - ex) 'api/v1/query_range'
+    def proxy_datasource(datasource_id:, proxy_path:, query: {})
+      http_get("#{@api_url}/api/datasources/proxy/#{datasource_id}/#{proxy_path}", query: query)
+    end
+
+    private
+
+    def http_get(url, params = {})
+      response = handle_request_exceptions do
+        Gitlab::HTTP.get(url, **request_params.merge(params))
+      end
+
+      handle_response(response)
+    end
+
+    def request_params
+      {
+        headers: {
+          'Authorization' => "Bearer #{@token}",
+          'Accept' => 'application/json',
+          'Content-Type' => 'application/json'
+        },
+        follow_redirects: false
+      }
+    end
+
+    def handle_request_exceptions
+      yield
+    rescue Gitlab::HTTP::Error
+      raise_error 'Error when connecting to Grafana'
+    rescue Net::OpenTimeout
+      raise_error 'Connection to Grafana timed out'
+    rescue SocketError
+      raise_error 'Received SocketError when trying to connect to Grafana'
+    rescue OpenSSL::SSL::SSLError
+      raise_error 'Grafana returned invalid SSL data'
+    rescue Errno::ECONNREFUSED
+      raise_error 'Connection refused'
+    rescue => e
+      raise_error "Grafana request failed due to #{e.class}"
+    end
+
+    def handle_response(response)
+      return response if response.code == 200
+
+      raise_error "Grafana response status code: #{response.code}"
+    end
+
+    def raise_error(message)
+      raise Client::Error, message
+    end
+  end
+end
diff --git a/spec/controllers/projects/grafana_api_controller_spec.rb b/spec/controllers/projects/grafana_api_controller_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..352a364295b5a31b13f9791f4e6fbbc0d2b3e730
--- /dev/null
+++ b/spec/controllers/projects/grafana_api_controller_spec.rb
@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Projects::GrafanaApiController do
+  let_it_be(:project) { create(:project) }
+  let_it_be(:user) { create(:user) }
+
+  before do
+    project.add_reporter(user)
+    sign_in(user)
+  end
+
+  describe 'GET #proxy' do
+    let(:proxy_service) { instance_double(Grafana::ProxyService) }
+    let(:params) do
+      {
+        namespace_id: project.namespace.full_path,
+        project_id: project.name,
+        proxy_path: 'api/v1/query_range',
+        datasource_id: '1',
+        query: 'rate(relevant_metric)',
+        start: '1570441248',
+        end: '1570444848',
+        step: '900'
+      }
+    end
+
+    before do
+      allow(Grafana::ProxyService).to receive(:new).and_return(proxy_service)
+      allow(proxy_service).to receive(:execute).and_return(service_result)
+    end
+
+    shared_examples_for 'error response' do |http_status|
+      it "returns #{http_status}" do
+        get :proxy, params: params
+
+        expect(response).to have_gitlab_http_status(http_status)
+        expect(json_response['status']).to eq('error')
+        expect(json_response['message']).to eq('error message')
+      end
+    end
+
+    context 'with a successful result' do
+      let(:service_result) { { status: :success, body: '{}' } }
+
+      it 'returns a grafana datasource response' do
+        get :proxy, params: params
+
+        expect(Grafana::ProxyService)
+          .to have_received(:new)
+          .with(project, '1', 'api/v1/query_range',
+                params.slice(:query, :start, :end, :step).stringify_keys)
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(json_response).to eq({})
+      end
+    end
+
+    context 'when the request is still unavailable' do
+      let(:service_result) { nil }
+
+      it 'returns 204 no content' do
+        get :proxy, params: params
+
+        expect(response).to have_gitlab_http_status(:no_content)
+        expect(json_response['status']).to eq('processing')
+        expect(json_response['message']).to eq('Not ready yet. Try again later.')
+      end
+    end
+
+    context 'when an error has occurred' do
+      context 'with an error accessing grafana' do
+        let(:service_result) do
+          {
+            http_status: :service_unavailable,
+            status: :error,
+            message: 'error message'
+          }
+        end
+
+        it_behaves_like 'error response', :service_unavailable
+      end
+
+      context 'with a processing error' do
+        let(:service_result) do
+          {
+            status: :error,
+            message: 'error message'
+          }
+        end
+
+        it_behaves_like 'error response', :bad_request
+      end
+    end
+  end
+end
diff --git a/spec/controllers/projects/merge_requests/diffs_controller_spec.rb b/spec/controllers/projects/merge_requests/diffs_controller_spec.rb
index 302de3246c2ead6fa730db6d6f9768b1c70aafce..e677e836145fc26514273692d32d3eab9aac379d 100644
--- a/spec/controllers/projects/merge_requests/diffs_controller_spec.rb
+++ b/spec/controllers/projects/merge_requests/diffs_controller_spec.rb
@@ -100,6 +100,136 @@ describe Projects::MergeRequests::DiffsController do
     it_behaves_like 'persisted preferred diff view cookie'
   end
 
+  describe 'GET diffs_metadata' do
+    def go(extra_params = {})
+      params = {
+        namespace_id: project.namespace.to_param,
+        project_id: project,
+        id: merge_request.iid,
+        format: 'json'
+      }
+
+      get :diffs_metadata, params: params.merge(extra_params)
+    end
+
+    context 'when not authorized' do
+      let(:another_user) { create(:user) }
+
+      before do
+        sign_in(another_user)
+      end
+
+      it 'returns 404 when not a member' do
+        go
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+
+      it 'returns 404 when visibility level is not enough' do
+        project.add_guest(another_user)
+
+        go
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+
+    context 'when diffable does not exists' do
+      it 'returns 404' do
+        go(diff_id: 9999)
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+
+    context 'with valid diff_id' do
+      it 'returns success' do
+        go(diff_id: merge_request.merge_request_diff.id)
+
+        expect(response).to have_gitlab_http_status(200)
+      end
+
+      it 'serializes diffs metadata with expected arguments' do
+        expected_options = {
+          environment: nil,
+          merge_request: merge_request,
+          merge_request_diff: merge_request.merge_request_diff,
+          merge_request_diffs: merge_request.merge_request_diffs,
+          start_version: nil,
+          start_sha: nil,
+          commit: nil,
+          latest_diff: true
+        }
+
+        expect_next_instance_of(DiffsMetadataSerializer) do |instance|
+          expect(instance).to receive(:represent)
+            .with(an_instance_of(Gitlab::Diff::FileCollection::MergeRequestDiff), expected_options)
+            .and_call_original
+        end
+
+        go(diff_id: merge_request.merge_request_diff.id)
+      end
+    end
+
+    context 'with MR regular diff params' do
+      it 'returns success' do
+        go
+
+        expect(response).to have_gitlab_http_status(200)
+      end
+
+      it 'serializes diffs metadata with expected arguments' do
+        expected_options = {
+          environment: nil,
+          merge_request: merge_request,
+          merge_request_diff: merge_request.merge_request_diff,
+          merge_request_diffs: merge_request.merge_request_diffs,
+          start_version: nil,
+          start_sha: nil,
+          commit: nil,
+          latest_diff: true
+        }
+
+        expect_next_instance_of(DiffsMetadataSerializer) do |instance|
+          expect(instance).to receive(:represent)
+            .with(an_instance_of(Gitlab::Diff::FileCollection::MergeRequestDiff), expected_options)
+            .and_call_original
+        end
+
+        go
+      end
+    end
+
+    context 'with commit param' do
+      it 'returns success' do
+        go(commit_id: merge_request.diff_head_sha)
+
+        expect(response).to have_gitlab_http_status(200)
+      end
+
+      it 'serializes diffs metadata with expected arguments' do
+        expected_options = {
+          environment: nil,
+          merge_request: merge_request,
+          merge_request_diff: nil,
+          merge_request_diffs: merge_request.merge_request_diffs,
+          start_version: nil,
+          start_sha: nil,
+          commit: merge_request.diff_head_commit,
+          latest_diff: nil
+        }
+
+        expect_next_instance_of(DiffsMetadataSerializer) do |instance|
+          expect(instance).to receive(:represent)
+            .with(an_instance_of(Gitlab::Diff::FileCollection::Commit), expected_options)
+            .and_call_original
+        end
+
+        go(commit_id: merge_request.diff_head_sha)
+      end
+    end
+  end
+
   describe 'GET diff_for_path' do
     def diff_for_path(extra_params = {})
       params = {
diff --git a/spec/lib/google_api/cloud_platform/client_spec.rb b/spec/lib/google_api/cloud_platform/client_spec.rb
index 2253feb376dfb421bd3d49c8242b319f2d0801ce..91b076c31d608f2fe68685e95dd9c2f2213732eb 100644
--- a/spec/lib/google_api/cloud_platform/client_spec.rb
+++ b/spec/lib/google_api/cloud_platform/client_spec.rb
@@ -102,6 +102,9 @@ describe GoogleApi::CloudPlatform::Client do
           legacy_abac: {
             enabled: legacy_abac
           },
+          ip_allocation_policy: {
+            use_ip_aliases: true
+          },
           addons_config: addons_config
         }
       }
diff --git a/spec/lib/grafana/client_spec.rb b/spec/lib/grafana/client_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..bd93a3c59a26f0e715c7d0e1d10ae8b2538472ba
--- /dev/null
+++ b/spec/lib/grafana/client_spec.rb
@@ -0,0 +1,107 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Grafana::Client do
+  let(:grafana_url) { 'https://grafanatest.com/-/grafana-project' }
+  let(:token) { 'test-token' }
+
+  subject(:client) { described_class.new(api_url: grafana_url, token: token) }
+
+  shared_examples 'calls grafana api' do
+    let!(:grafana_api_request) { stub_grafana_request(grafana_api_url) }
+
+    it 'calls grafana api' do
+      subject
+
+      expect(grafana_api_request).to have_been_requested
+    end
+  end
+
+  shared_examples 'no redirects' do
+    let(:redirect_to) { 'https://redirected.example.com' }
+    let(:other_url) { 'https://grafana.example.org' }
+
+    let!(:redirected_req_stub) { stub_grafana_request(other_url) }
+
+    let!(:redirect_req_stub) do
+      stub_grafana_request(
+        grafana_api_url,
+        status: 302,
+        headers: { location: redirect_to }
+      )
+    end
+
+    it 'does not follow redirects' do
+      expect { subject }.to raise_exception(
+        Grafana::Client::Error,
+        'Grafana response status code: 302'
+      )
+
+      expect(redirect_req_stub).to have_been_requested
+      expect(redirected_req_stub).not_to have_been_requested
+    end
+  end
+
+  shared_examples 'handles exceptions' do
+    exceptions = {
+      Gitlab::HTTP::Error => 'Error when connecting to Grafana',
+      Net::OpenTimeout => 'Connection to Grafana timed out',
+      SocketError => 'Received SocketError when trying to connect to Grafana',
+      OpenSSL::SSL::SSLError => 'Grafana returned invalid SSL data',
+      Errno::ECONNREFUSED => 'Connection refused',
+      StandardError => 'Grafana request failed due to StandardError'
+    }
+
+    exceptions.each do |exception, message|
+      context "#{exception}" do
+        before do
+          stub_request(:get, grafana_api_url).to_raise(exception)
+        end
+
+        it do
+          expect { subject }
+            .to raise_exception(Grafana::Client::Error, message)
+        end
+      end
+    end
+  end
+
+  describe '#proxy_datasource' do
+    let(:grafana_api_url) do
+      'https://grafanatest.com/-/grafana-project/' \
+        'api/datasources/proxy/' \
+        '1/api/v1/query_range' \
+        '?query=rate(relevant_metric)' \
+        '&start=1570441248&end=1570444848&step=900'
+    end
+
+    subject do
+      client.proxy_datasource(
+        datasource_id: '1',
+        proxy_path: 'api/v1/query_range',
+        query: {
+          query: 'rate(relevant_metric)',
+          start: 1570441248,
+          end: 1570444848,
+          step: 900
+        }
+      )
+    end
+
+    it_behaves_like 'calls grafana api'
+    it_behaves_like 'no redirects'
+    it_behaves_like 'handles exceptions'
+  end
+
+  private
+
+  def stub_grafana_request(url, body: {}, status: 200, headers: {})
+    stub_request(:get, url)
+      .to_return(
+        status: status,
+        headers: { 'Content-Type' => 'application/json' }.merge(headers),
+        body: body.to_json
+      )
+  end
+end
diff --git a/spec/migrations/schedule_pages_metadata_migration_spec.rb b/spec/migrations/schedule_pages_metadata_migration_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..100ed520a3242da55d73c52904db3fa350c7c4ee
--- /dev/null
+++ b/spec/migrations/schedule_pages_metadata_migration_spec.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20191002031332_schedule_pages_metadata_migration')
+
+describe SchedulePagesMetadataMigration, :migration, :sidekiq do
+  let(:namespaces) { table(:namespaces) }
+  let(:projects) { table(:projects) }
+
+  before do
+    stub_const("#{described_class.name}::BATCH_SIZE", 1)
+
+    namespaces.create!(id: 11, name: 'gitlab', path: 'gitlab-org')
+    projects.create!(id: 111, namespace_id: 11, name: 'Project 111')
+    projects.create!(id: 114, namespace_id: 11, name: 'Project 114')
+  end
+
+  it 'schedules pages metadata migration' do
+    Sidekiq::Testing.fake! do
+      Timecop.freeze do
+        migrate!
+
+        expect(described_class::MIGRATION).to be_scheduled_delayed_migration(2.minutes, 111, 111)
+        expect(described_class::MIGRATION).to be_scheduled_delayed_migration(4.minutes, 114, 114)
+        expect(BackgroundMigrationWorker.jobs.size).to eq(2)
+      end
+    end
+  end
+end
diff --git a/spec/serializers/diffs_metadata_entity_spec.rb b/spec/serializers/diffs_metadata_entity_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..aaca393ec272a33eacccad63910a2bd9667bcaa4
--- /dev/null
+++ b/spec/serializers/diffs_metadata_entity_spec.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe DiffsMetadataEntity do
+  let(:user) { create(:user) }
+  let(:project) { create(:project, :repository) }
+  let(:request) { EntityRequest.new(project: project, current_user: user) }
+  let(:merge_request) { create(:merge_request_with_diffs, target_project: project, source_project: project) }
+  let(:merge_request_diffs) { merge_request.merge_request_diffs }
+  let(:merge_request_diff) { merge_request_diffs.last }
+
+  let(:entity) do
+    described_class.new(merge_request_diff.diffs,
+                        request: request,
+                        merge_request: merge_request,
+                        merge_request_diffs: merge_request_diffs)
+  end
+
+  context 'as json' do
+    subject { entity.as_json }
+
+    it 'contain only required attributes' do
+      expect(subject.keys).to contain_exactly(
+        # Inherited attributes
+        :real_size, :size, :branch_name,
+        :target_branch_name, :commit, :merge_request_diff,
+        :start_version, :latest_diff, :latest_version_path,
+        :added_lines, :removed_lines, :render_overflow_warning,
+        :email_patch_path, :plain_diff_path,
+        :merge_request_diffs,
+        # Attributes
+        :diff_files
+      )
+    end
+
+    describe 'diff_files' do
+      it 'returns diff files metadata' do
+        payload =
+          DiffFileMetadataEntity.represent(merge_request_diff.diffs.diff_files).as_json
+
+        expect(subject[:diff_files]).to eq(payload)
+      end
+    end
+  end
+end
diff --git a/spec/services/grafana/proxy_service_spec.rb b/spec/services/grafana/proxy_service_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..694d531c9fc86657f749a0ddc2d8030a116b72f8
--- /dev/null
+++ b/spec/services/grafana/proxy_service_spec.rb
@@ -0,0 +1,139 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Grafana::ProxyService do
+  include ReactiveCachingHelpers
+
+  let_it_be(:project) { create(:project) }
+  let_it_be(:grafana_integration) { create(:grafana_integration, project: project) }
+
+  let(:proxy_path) { 'api/v1/query_range' }
+  let(:datasource_id) { '1' }
+  let(:query_params) do
+    {
+      'query' => 'rate(relevant_metric)',
+      'start' => '1570441248',
+      'end' => '1570444848',
+      'step' => '900'
+    }
+  end
+
+  let(:cache_params) { [project.id, datasource_id, proxy_path, query_params] }
+
+  let(:service) do
+    described_class.new(project, datasource_id, proxy_path, query_params)
+  end
+
+  shared_examples_for 'initializes an instance' do
+    it 'initializes an instance of ProxyService class' do
+      expect(subject).to be_an_instance_of(described_class)
+      expect(subject.project).to eq(project)
+      expect(subject.datasource_id).to eq('1')
+      expect(subject.proxy_path).to eq('api/v1/query_range')
+      expect(subject.query_params).to eq(query_params)
+    end
+  end
+
+  describe '.from_cache' do
+    subject { described_class.from_cache(*cache_params) }
+
+    it_behaves_like 'initializes an instance'
+  end
+
+  describe '#initialize' do
+    subject { service }
+
+    it_behaves_like 'initializes an instance'
+  end
+
+  describe '#execute' do
+    subject(:result) { service.execute }
+
+    context 'when grafana integration is not configured' do
+      before do
+        allow(project).to receive(:grafana_integration).and_return(nil)
+      end
+
+      it 'returns error' do
+        expect(result).to eq(
+          status: :error,
+          message: 'Proxy support for this API is not available currently'
+        )
+      end
+    end
+
+    context 'with caching', :use_clean_rails_memory_store_caching do
+      context 'when value not present in cache' do
+        it 'returns nil' do
+          expect(ReactiveCachingWorker)
+            .to receive(:perform_async)
+            .with(service.class, service.id, *cache_params)
+
+          expect(result).to eq(nil)
+        end
+      end
+
+      context 'when value present in cache' do
+        let(:return_value) { { 'http_status' => 200, 'body' => 'body' } }
+
+        before do
+          stub_reactive_cache(service, return_value, cache_params)
+        end
+
+        it 'returns cached value' do
+          expect(ReactiveCachingWorker)
+            .not_to receive(:perform_async)
+            .with(service.class, service.id, *cache_params)
+
+          expect(result[:http_status]).to eq(return_value[:http_status])
+          expect(result[:body]).to eq(return_value[:body])
+        end
+      end
+    end
+
+    context 'call prometheus api' do
+      let(:client) { service.send(:client) }
+
+      before do
+        synchronous_reactive_cache(service)
+      end
+
+      context 'connection to grafana datasource succeeds' do
+        let(:response) { instance_double(Gitlab::HTTP::Response) }
+        let(:status_code) { 400 }
+        let(:body) { 'body' }
+
+        before do
+          allow(client).to receive(:proxy_datasource).and_return(response)
+
+          allow(response).to receive(:code).and_return(status_code)
+          allow(response).to receive(:body).and_return(body)
+        end
+
+        it 'returns the http status code and body from prometheus' do
+          expect(result).to eq(
+            http_status: status_code,
+            body: body,
+            status: :success
+          )
+        end
+      end
+
+      context 'connection to grafana datasource fails' do
+        before do
+          allow(client).to receive(:proxy_datasource)
+            .and_raise(Grafana::Client::Error, 'Network connection error')
+        end
+
+        it 'returns error' do
+          expect(result).to eq(
+            status: :error,
+            message: 'Network connection error',
+            http_status: :service_unavailable
+          )
+        end
+      end
+    end
+  end
+end