Add rake file to generate sample metrics

Interpolate metric queries

Use yml for sample metric output to easily convert hash

Create a file for each metric

Replace metrics endpoint if using sample data

Need to create sample_metrics directory to run test

Moveing logic out of the controller

Insert live endpoint

Add specs for SampleMetricsService

Cleaning up controller specs

Return 404 instead of 500 when file is not found

app/controllers/projects/environments/sample_metrics_controller.rb

+# frozen_string_literal: true
+
+class Projects::Environments::SampleMetricsController < Projects::ApplicationController
+  def query
+    result = Metrics::SampleMetricsService.new(params[:identifier]).query
+
+    if result
+      render json: { "status": "success", "data": { "resultType": "matrix", "result": result } }
+    else
+      render_404
+    end
+  end
+end

app/services/metrics/sample_metrics_service.rb

+# frozen_string_literal: true
+
+module Metrics
+  class SampleMetricsService
+    DIRECTORY = "sample_metrics"
+
+    attr_reader :identifier
+
+    def initialize(identifier)
+      @identifier = identifier
+    end
+
+    def query
+      return unless identifier && File.exist?(file_location)
+
+      YAML.load_file(File.expand_path(file_location, __dir__))
+    end
+
+    private
+
+    def file_location
+      sanitized_string = identifier.gsub(/[^0-9A-Za-z_]/, '')
+      File.join(Rails.root, DIRECTORY, "#{sanitized_string}.yml")
+    end
+  end
+end

changelogs/unreleased/generate-test-prometheus-data.yml

+---
+title: Genereate a set of sample prometheus metrics and route to the sample metrics
+  when enabled
+merge_request: 19987
+author:
+type: added

config/routes/project.rb

@@ -232,6 +232,8 @@ constraints(::Constraints::ProjectUrlConstrainer.new) do
             get '/terminal.ws/authorize', to: 'environments#terminal_websocket_authorize', format: false
 
             get '/prometheus/api/v1/*proxy_path', to: 'environments/prometheus_api#proxy', as: :prometheus_api
+
+            get '/sample_metrics', to: 'environments/sample_metrics#query' if ENV['USE_SAMPLE_METRICS']
           end
 
           collection do

doc/raketasks/generate_sample_prometheus_data.md

+# Generate Sample Prometheus Data
+
+This command will run Prometheus queries for each of the metrics of a specific environment
+for a default time interval of 7 days ago to now. The results of each of query are stored
+under a `sample_metrics` directory as a yaml file named by the metric's `identifier`.
+When the environmental variable `USE_SAMPLE_METRICS` is set, the Prometheus API query is
+re-routed to `Projects::Environments::SampleMetricsController` which loads the appropriate
+data set if it is present within the `sample_metrics` directory.
+
+- This command requires an id from an Environment with an available Prometheus installation.
+
+**Example:**
+
+```
+bundle exec rake gitlab:generate_sample_prometheus_data[21]
+```

lib/gitlab/metrics/dashboard/stages/endpoint_inserter.rb

@@ -16,12 +16,20 @@ module Gitlab
           private
 
           def endpoint_for_metric(metric)
-            Gitlab::Routing.url_helpers.prometheus_api_project_environment_path(
-              project,
-              params[:environment],
-              proxy_path: query_type(metric),
-              query: query_for_metric(metric)
-            )
+            if ENV['USE_SAMPLE_METRICS']
+              Gitlab::Routing.url_helpers.sample_metrics_project_environment_path(
+                project,
+                params[:environment],
+                identifier: metric[:id]
+              )
+            else
+              Gitlab::Routing.url_helpers.prometheus_api_project_environment_path(
+                project,
+                params[:environment],
+                proxy_path: query_type(metric),
+                query: query_for_metric(metric)
+              )
+            end
           end
 
           def query_type(metric)

lib/tasks/gitlab/generate_sample_prometheus_data.rake

+namespace :gitlab do
+  desc "GitLab | Generate Sample Prometheus Data"
+  task :generate_sample_prometheus_data, [:environment_id] => :gitlab_environment do |_, args|
+    environment = Environment.find(args[:environment_id])
+    metrics = PrometheusMetric.where(project_id: [environment.project.id, nil])
+    query_variables = Gitlab::Prometheus::QueryVariables.call(environment)
+
+    sample_metrics_directory_name = Metrics::SampleMetricsService::DIRECTORY
+    FileUtils.mkdir_p(sample_metrics_directory_name)
+
+    metrics.each do |metric|
+      query = metric.query % query_variables
+      result = environment.prometheus_adapter.prometheus_client.query_range(query, start: 7.days.ago)
+
+      next unless metric.identifier
+
+      File.write("#{sample_metrics_directory_name}/#{metric.identifier}.yml", result.to_yaml)
+    end
+  end
+end

spec/controllers/projects/environments/sample_metrics_controller_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Projects::Environments::SampleMetricsController do
+  include StubENV
+
+  let_it_be(:project) { create(:project) }
+  let_it_be(:environment) { create(:environment, project: project) }
+  let_it_be(:user) { create(:user) }
+
+  before(:context) do
+    RSpec::Mocks.with_temporary_scope do
+      stub_env('USE_SAMPLE_METRICS', 'true')
+      Rails.application.reload_routes!
+    end
+  end
+
+  after(:context) do
+    Rails.application.reload_routes!
+  end
+
+  before do
+    project.add_reporter(user)
+    sign_in(user)
+  end
+
+  describe 'GET #query' do
+    context 'when the file is not found' do
+      before do
+        get :query, params: environment_params
+      end
+
+      it 'returns a 404' do
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+
+    context 'when the sample data is found' do
+      before do
+        allow_next_instance_of(Metrics::SampleMetricsService) do |service|
+          allow(service).to receive(:query).and_return([])
+        end
+        get :query, params: environment_params
+      end
+
+      it 'returns JSON with a message and a 200 status code' do
+        expect(json_response.keys).to contain_exactly('status', 'data')
+        expect(response).to have_gitlab_http_status(:ok)
+      end
+    end
+  end
+
+  private
+
+  def environment_params(params = {})
+    {
+      id: environment.id.to_s,
+      namespace_id: project.namespace.full_path,
+      project_id: project.name,
+      identifier: 'sample_metric_query_result'
+    }.merge(params)
+  end
+end

spec/fixtures/gitlab/sample_metrics/sample_metric_query_result.yml

+---
+- metric: {}
+  values:
+  - - 1573560714.209
+    - '0.02361297607421875'
+  - - 1573560774.209
+    - '0.02361297607421875'
+  - - 1573560834.209
+    - '0.02362823486328125'
+  - - 1573560894.209
+    - '0.02361297607421875'
+  - - 1573560954.209
+    - '0.02385711669921875'
+  - - 1573561014.209
+    - '0.02361297607421875'
+  - - 1573561074.209
+    - '0.02361297607421875'
+  - - 1573561134.209
+    - '0.02362060546875'
+  - - 1573561194.209
+    - '0.02362060546875'
+  - - 1573561254.209
+    - '0.02362060546875'
+  - - 1573561314.209
+    - '0.02362060546875'
+  - - 1573561374.209
+    - '0.023624420166015625'
+  - - 1573561434.209
+    - '0.023651123046875'
+  - - 1573561494.209
+    - '0.02362060546875'
+  - - 1573561554.209
+    - '0.0236358642578125'
+  - - 1573561614.209
+    - '0.02362060546875'
+  - - 1573561674.209
+    - '0.02362060546875'
+  - - 1573561734.209
+    - '0.02362060546875'
+  - - 1573561794.209
+    - '0.02362060546875'
+  - - 1573561854.209
+    - '0.02362060546875'
+  - - 1573561914.209
+    - '0.023651123046875'
+  - - 1573561974.209
+    - '0.02362060546875'
+  - - 1573562034.209
+    - '0.02362060546875'
+  - - 1573562094.209
+    - '0.02362060546875'
+  - - 1573562154.209
+    - '0.02362060546875'
+  - - 1573562214.209
+    - '0.023624420166015625'
+  - - 1573562274.209
+    - '0.02362060546875'
+  - - 1573562334.209
+    - '0.023868560791015625'
+  - - 1573562394.209
+    - '0.02374267578125'
+  - - 1573562454.209
+    - '0.02362060546875'
+  - - 1573562514.209
+    - '0.02362060546875'
+  - - 1573562574.209
+    - '0.02362060546875'
+  - - 1573562634.209
+    - '0.02362060546875'
+  - - 1573562694.209
+    - '0.023639678955078125'
+  - - 1573562754.209
+    - '0.0236358642578125'
+  - - 1573562814.209
+    - '0.02362060546875'
+  - - 1573562874.209
+    - '0.0236358642578125'
+  - - 1573562934.209
+    - '0.023651123046875'
+  - - 1573562994.209
+    - '0.02362060546875'
+  - - 1573563054.209
+    - '0.023624420166015625'
+  - - 1573563114.209
+    - '0.02362060546875'
+  - - 1573563174.209
+    - '0.02362060546875'
+  - - 1573563234.209
+    - '0.02362060546875'
+  - - 1573563294.209
+    - '0.02362060546875'
+  - - 1573563354.209
+    - '0.02362060546875'
+  - - 1573563414.209
+    - '0.023651123046875'
+  - - 1573563474.209
+    - '0.023651123046875'
+  - - 1573563534.209
+    - '0.023651123046875'
+  - - 1573563594.209
+    - '0.023773193359375'
+  - - 1573563654.209
+    - '0.023681640625'
+  - - 1573563714.209
+    - '0.023895263671875'
+  - - 1573563774.209
+    - '0.023651123046875'
+  - - 1573563834.209
+    - '0.023651123046875'
+  - - 1573563894.209
+    - '0.023651123046875'
+  - - 1573563954.209
+    - '0.0236663818359375'
+  - - 1573564014.209
+    - '0.023651123046875'
+  - - 1573564074.209
+    - '0.023681640625'
+  - - 1573564134.209
+    - '0.0236663818359375'
+  - - 1573564194.209
+    - '0.0236663818359375'
+  - - 1573564254.209
+    - '0.023651123046875'
+  - - 1573564314.209
+    - '0.023651123046875'
+  - - 1573564374.209
+    - '0.023651123046875'
+  - - 1573564434.209
+    - '0.023773193359375'
+  - - 1573564494.209
+    - '0.023651123046875'
+  - - 1573564554.209
+    - '0.023681640625'
+  - - 1573564614.209
+    - '0.023773193359375'
+  - - 1573564674.209
+    - '0.023651123046875'
+  - - 1573564734.209
+    - '0.023651123046875'
+  - - 1573564794.209
+    - '0.023651123046875'
+  - - 1573564854.209
+    - '0.023651123046875'
+  - - 1573564914.209
+    - '0.023651123046875'
+  - - 1573564974.209
+    - '0.023651123046875'
+  - - 1573565034.209
+    - '0.023651123046875'
+  - - 1573565094.209
+    - '0.023895263671875'
\ No newline at end of file

spec/services/metrics/sample_metrics_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Metrics::SampleMetricsService do
+  describe 'query' do
+    subject { described_class.new(identifier).query }
+
+    context 'when the file is not found' do
+      let(:identifier) { nil }
+
+      it { is_expected.to be_nil }
+    end
+
+    context 'when the file is found' do
+      let(:identifier) { 'sample_metric_query_result' }
+      let(:source) { File.join(Rails.root, 'spec/fixtures/gitlab/sample_metrics', "#{identifier}.yml") }
+      let(:destination) { File.join(Rails.root, Metrics::SampleMetricsService::DIRECTORY, "#{identifier}.yml") }
+
+      around do |example|
+        FileUtils.mkdir_p(Metrics::SampleMetricsService::DIRECTORY)
+        FileUtils.cp(source, destination)
+
+        example.run
+      ensure
+        FileUtils.rm(destination)
+      end
+
+      subject { described_class.new(identifier).query }
+
+      it 'loads data from the sample file correctly' do
+        expect(subject).to eq(YAML.load_file(source))
+      end
+    end
+
+    context 'when the identifier is for a path outside of sample_metrics' do
+      let(:identifier) { '../config/secrets' }
+
+      it { is_expected.to be_nil }
+    end
+  end
+end

spec/tasks/gitlab/generate_sample_prometheus_data_spec.rb

+# frozen_string_literal: true
+
+require 'rake_helper'
+
+describe 'gitlab:generate_sample_prometheus_data rake task' do
+  let(:cluster) { create(:cluster, :provided_by_user, :project) }
+  let(:environment) { create(:environment, project: cluster.project) }
+  let(:sample_query_file) { File.join(Rails.root, Metrics::SampleMetricsService::DIRECTORY, 'test_query_result.yml') }
+  let!(:metric) { create(:prometheus_metric, project: cluster.project, identifier: 'test_query_result') }
+
+  around do |example|
+    example.run
+  ensure
+    FileUtils.rm(sample_query_file)
+  end
+
+  it 'creates the file correctly' do
+    Rake.application.rake_require 'tasks/gitlab/generate_sample_prometheus_data'
+    allow(Environment).to receive(:find).and_return(environment)
+    allow(environment).to receive_message_chain(:prometheus_adapter, :prometheus_client, :query_range) { sample_query_result }
+    run_rake_task('gitlab:generate_sample_prometheus_data', [environment.id])
+
+    expect(File.exist?(sample_query_file)).to be true
+
+    query_file_content = YAML.load_file(sample_query_file)
+
+    expect(query_file_content).to eq(sample_query_result)
+  end
+end
+
+def sample_query_result
+  file = File.join(Rails.root, 'spec/fixtures/gitlab/sample_metrics', 'sample_metric_query_result.yml')
+  YAML.load_file(File.expand_path(file, __dir__))
+end