Expose prometheus endpoint per metric in dashboard

Adds a new stage to dashboard processesing step for the
EnvironmentsController::metrics_dashboard endpoint.

Allows the front end to avoid generating the endpoint
unitutive string mutations.

lib/gitlab/metrics/dashboard/base_service.rb

@@ -7,12 +7,13 @@ module Gitlab
     module Dashboard
       class BaseService < ::BaseService
         DASHBOARD_LAYOUT_ERROR = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardLayoutError
+        MISSING_QUERY_ERROR = Gitlab::Metrics::Dashboard::Stages::EndpointInserter::MissingQueryError
 
         def get_dashboard
           return error("#{dashboard_path} could not be found.", :not_found) unless path_available?
 
           success(dashboard: process_dashboard)
-        rescue DASHBOARD_LAYOUT_ERROR => e
+        rescue DASHBOARD_LAYOUT_ERROR, MISSING_QUERY_ERROR => e
           error(e.message, :unprocessable_entity)
         end
 

lib/gitlab/metrics/dashboard/processor.rb

@@ -11,11 +11,13 @@ module Gitlab
         SYSTEM_SEQUENCE = [
           Stages::CommonMetricsInserter,
           Stages::ProjectMetricsInserter,
+          Stages::EndpointInserter,
           Stages::Sorter
         ].freeze
 
         PROJECT_SEQUENCE = [
           Stages::CommonMetricsInserter,
+          Stages::EndpointInserter,
           Stages::Sorter
         ].freeze
 

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

+# frozen_string_literal: true
+
+module Gitlab
+  module Metrics
+    module Dashboard
+      module Stages
+        class EndpointInserter < BaseStage
+          MissingQueryError = Class.new(StandardError)
+
+          def transform!
+            for_metrics do |metric|
+              metric[:prometheus_endpoint_path] = endpoint_for_metric(metric)
+            end
+          end
+
+          private
+
+          def endpoint_for_metric(metric)
+            Gitlab::Routing.url_helpers.prometheus_api_namespace_project_environment_path(
+              project.namespace,
+              project,
+              environment,
+              proxy_path: query_type(metric),
+              query: query_for_metric(metric)
+            )
+          end
+
+          def query_type(metric)
+            metric[:query] ? :query : :query_range
+          end
+
+          def query_for_metric(metric)
+            query = metric[query_type(metric)]
+
+            raise MissingQueryError.new('Missing required metric key: one of :query or :query_range') unless query
+
+            query
+          end
+        end
+      end
+    end
+  end
+end

spec/fixtures/lib/gitlab/metrics/dashboard/schemas/metrics.json

@@ -2,7 +2,8 @@
   "type": "object",
   "required": [
     "unit",
-    "label"
+    "label",
+    "prometheus_endpoint_path"
   ],
   "oneOf": [
     { "required": ["query"] },
@@ -14,7 +15,8 @@
     "query": { "type": "string" },
     "unit": { "type": "string" },
     "label": { "type": "string" },
-    "track": { "type": "string" }
+    "track": { "type": "string" },
+    "prometheus_endpoint_path": { "type": "string" }
   },
   "additionalProperties": false
 }

spec/lib/gitlab/metrics/dashboard/finder_spec.rb

@@ -6,7 +6,7 @@ describe Gitlab::Metrics::Dashboard::Finder, :use_clean_rails_memory_store_cachi
   include MetricsDashboardHelpers
 
   set(:project) { build(:project) }
-  set(:environment) { build(:environment, project: project) }
+  set(:environment) { create(:environment, project: project) }
   let(:system_dashboard_path) { Gitlab::Metrics::Dashboard::SystemDashboardService::SYSTEM_DASHBOARD_PATH}
 
   describe '.find' do
@@ -27,6 +27,17 @@ describe Gitlab::Metrics::Dashboard::Finder, :use_clean_rails_memory_store_cachi
       it_behaves_like 'misconfigured dashboard service response', :unprocessable_entity
     end
 
+    context 'when the dashboard contains a metric without a query' do
+      let(:project) do
+        project_with_dashboard(
+          dashboard_path,
+          { 'panel_groups' => [{ 'panels' => [{ 'metrics' => [{ 'id' => 'mock' }] }] }] }.to_yaml
+        )
+      end
+
+      it_behaves_like 'misconfigured dashboard service response', :unprocessable_entity
+    end
+
     context 'when the system dashboard is specified' do
       let(:dashboard_path) { system_dashboard_path }
 

spec/lib/gitlab/metrics/dashboard/processor_spec.rb

@@ -4,13 +4,19 @@ require 'spec_helper'
 
 describe Gitlab::Metrics::Dashboard::Processor do
   let(:project) { build(:project) }
-  let(:environment) { build(:environment, project: project) }
+  let(:environment) { create(:environment, project: project) }
   let(:dashboard_yml) { YAML.load_file('spec/fixtures/lib/gitlab/metrics/dashboard/sample_dashboard.yml') }
 
   describe 'process' do
     let(:process_params) { [project, environment, dashboard_yml] }
     let(:dashboard) { described_class.new(*process_params).process(insert_project_metrics: true) }
 
+    it 'includes a path for the prometheus endpoint with each metric' do
+      all_metrics.each do |metric|
+        expect(metric).to include(prometheus_endpoint_path: prometheus_path(metric[:query_range]))
+      end
+    end
+
     context 'when dashboard config corresponds to common metrics' do
       let!(:common_metric) { create(:prometheus_metric, :common, identifier: 'metric_a1') }
 
@@ -99,7 +105,15 @@ describe Gitlab::Metrics::Dashboard::Processor do
       query_range: metric.query,
       unit: metric.unit,
       label: metric.legend,
-      metric_id: metric.id
+      metric_id: metric.id,
+      prometheus_endpoint_path: prometheus_path(metric.query)
     }
   end
+
+  def prometheus_path(query)
+    "/#{project.namespace.path}" \
+    "/#{project.name}/environments/" \
+    "#{environment.id}/prometheus/api/v1" \
+    "/query_range?query=#{CGI::escape query}"
+  end
 end

spec/lib/gitlab/metrics/dashboard/project_dashboard_service_spec.rb

@@ -7,7 +7,7 @@ describe Gitlab::Metrics::Dashboard::ProjectDashboardService, :use_clean_rails_m
 
   set(:user) { build(:user) }
   set(:project) { build(:project) }
-  set(:environment) { build(:environment, project: project) }
+  set(:environment) { create(:environment, project: project) }
 
   before do
     project.add_maintainer(user)

spec/lib/gitlab/metrics/dashboard/system_dashboard_service_spec.rb

@@ -6,7 +6,7 @@ describe Gitlab::Metrics::Dashboard::SystemDashboardService, :use_clean_rails_me
   include MetricsDashboardHelpers
 
   set(:project) { build(:project) }
-  set(:environment) { build(:environment, project: project) }
+  set(:environment) { create(:environment, project: project) }
 
   describe 'get_dashboard' do
     let(:dashboard_path) { described_class::SYSTEM_DASHBOARD_PATH }