Add proxy endpoint for grafana proxy

Adds a new endpoint which proxies calls to the grafana endpoint
which proxies calls to any grafana datasource configured to
support it. This will be used as a part of embedding prometheus
metrics in GFM via grafana.

app/controllers/concerns/render_service_results.rb

+# 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

app/controllers/projects/environments/prometheus_api_controller.rb

 # 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

app/controllers/projects/grafana_api_controller.rb

+# 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

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

app/services/grafana/proxy_service.rb

+# 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

changelogs/unreleased/sy-grafana-proxy.yml

+---
+title: Add endpoint to proxy requests to grafana's proxy endpoint
+merge_request: 18210
+author:
+type: added

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.
 

lib/grafana/client.rb

+# 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

spec/controllers/projects/grafana_api_controller_spec.rb

+# 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

spec/lib/grafana/client_spec.rb

+# 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

spec/services/grafana/proxy_service_spec.rb

+# 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