Support dashboard params for metrics dashboard

https://gitlab.com/gitlab-org/gitlab-ce/issues/62971

Adds support to EnvironmentsController#metrics_dashboard
for the following params: group, title, y_label
These params are used to uniquely identify a panel on
the metrics dashboard.

Metrics are stored in several places, so this adds
utilities to find a specific panel from the database
or filesystem depending on the metric specified.

Also moves some shared utilities into separate classes,
notably default values and errors.

20 files changed, 712 insertions, 56 deletions

diff --git a/app/controllers/projects/environments_controller.rb b/app/controllers/projects/environments_controller.rb
index ccd54b369fa..07eb689d031 100644
--- a/app/controllers/projects/environments_controller.rb
+++ b/app/controllers/projects/environments_controller.rb
@@ -165,7 +165,8 @@ class Projects::EnvironmentsController < Projects::ApplicationController
         project,
         current_user,
         environment,
-        embedded: params[:embedded]
+        dashboard_path: params[:dashboard],
+        **dashboard_params.to_h.symbolize_keys
       )
     elsif Feature.enabled?(:environment_metrics_show_multiple_dashboards, project)
       result = dashboard_finder.find(
@@ -233,6 +234,10 @@ class Projects::EnvironmentsController < Projects::ApplicationController
     params.require([:start, :end])
   end
 
+  def dashboard_params
+    params.permit(:embedded, :group, :title, :y_label)
+  end
+
   def dashboard_finder
     Gitlab::Metrics::Dashboard::Finder
   end
diff --git a/app/models/prometheus_metric_enums.rb b/app/models/prometheus_metric_enums.rb
index 6cb22cc69cd..d58f825f222 100644
--- a/app/models/prometheus_metric_enums.rb
+++ b/app/models/prometheus_metric_enums.rb
@@ -9,13 +9,17 @@ module PrometheusMetricEnums
       aws_elb: -3,
       nginx: -4,
       kubernetes: -5,
-      nginx_ingress: -6,
+      nginx_ingress: -6
+    }.merge(custom_groups).freeze
+  end
 
-      # custom/user groups
+  # custom/user groups
+  def self.custom_groups
+    {
       business: 0,
       response: 1,
       system: 2
-    }
+    }.freeze
   end
 
   def self.group_details
@@ -50,16 +54,20 @@ module PrometheusMetricEnums
         group_title: _('System metrics (Kubernetes)'),
         required_metrics: %w(container_memory_usage_bytes container_cpu_usage_seconds_total),
         priority: 5
-      }.freeze,
+      }.freeze
+    }.merge(custom_group_details).freeze
+  end
 
-      # custom/user groups
+  # custom/user groups
+  def self.custom_group_details
+    {
       business: {
         group_title: _('Business metrics (Custom)'),
         priority: 0
       }.freeze,
       response: {
         group_title: _('Response metrics (Custom)'),
-      priority: -5
+        priority: -5
       }.freeze,
       system: {
         group_title: _('System metrics (Custom)'),
diff --git a/app/services/metrics/dashboard/base_embed_service.rb b/app/services/metrics/dashboard/base_embed_service.rb
new file mode 100644
index 00000000000..7a686b740e1
--- /dev/null
+++ b/app/services/metrics/dashboard/base_embed_service.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+# Base class for embed services. Contains a few basic helper
+# methods that the embed services share.
+module Metrics
+  module Dashboard
+    class BaseEmbedService < ::Metrics::Dashboard::BaseService
+      def cache_key
+        "dynamic_metrics_dashboard_#{identifiers}"
+      end
+
+      protected
+
+      def dashboard_path
+        params[:dashboard_path]
+      end
+
+      def group
+        params[:group]
+      end
+
+      def title
+        params[:title]
+      end
+
+      def y_label
+        params[:y_label]
+      end
+
+      def identifiers
+        [dashboard_path, group, title, y_label].join('|')
+      end
+    end
+  end
+end
diff --git a/app/services/metrics/dashboard/base_service.rb b/app/services/metrics/dashboard/base_service.rb
index b331bf51874..8a42675c66d 100644
--- a/app/services/metrics/dashboard/base_service.rb
+++ b/app/services/metrics/dashboard/base_service.rb
@@ -5,17 +5,14 @@
 module Metrics
   module Dashboard
     class BaseService < ::BaseService
-      PROCESSING_ERROR = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardProcessingError
-      NOT_FOUND_ERROR = Gitlab::Template::Finders::RepoTemplateFinder::FileNotFoundError
+      include Gitlab::Metrics::Dashboard::Errors
 
       def get_dashboard
         return error('Insufficient permissions.', :unauthorized) unless allowed?
 
         success(dashboard: process_dashboard)
-      rescue NOT_FOUND_ERROR
-        error("#{dashboard_path} could not be found.", :not_found)
-      rescue PROCESSING_ERROR => e
-        error(e.message, :unprocessable_entity)
+      rescue StandardError => e
+        handle_errors(e)
       end
 
       # Summary of all known dashboards for the service.
diff --git a/app/services/metrics/dashboard/custom_metric_embed_service.rb b/app/services/metrics/dashboard/custom_metric_embed_service.rb
new file mode 100644
index 00000000000..094a8091409
--- /dev/null
+++ b/app/services/metrics/dashboard/custom_metric_embed_service.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+# Responsible for returning a dashboard containing a specified
+# custom metric. Creates panels based on the matching metric
+# stored in the database.
+#
+# Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
+module Metrics
+  module Dashboard
+    class CustomMetricEmbedService < ::Metrics::Dashboard::BaseEmbedService
+      include Gitlab::Metrics::Dashboard::Defaults
+
+      # Returns a new dashboard with only the matching
+      # metrics from the system dashboard, stripped of
+      # group info.
+      #
+      # Note: This overrides the method #raw_dashboard,
+      # which means the result will not be cached. This
+      # is because we are inserting DB info into the
+      # dashboard before post-processing. This ensures
+      # we aren't acting on deleted or out-of-date metrics.
+      #
+      # @return [Hash]
+      def raw_dashboard
+        panels_not_found!(identifiers) if panels.empty?
+
+        { 'panel_groups' => [{ 'panels' => panels }] }
+      end
+
+      private
+
+      # Generated dashboard panels for each metric which
+      # matches the provided input.
+      # @return [Array<Hash>]
+      def panels
+        @panels ||= metrics.map { |metric| panel_for_metric(metric) }
+      end
+
+      # Metrics which match the provided inputs.
+      # @return [ActiveRecordRelation<PromtheusMetric>]
+      def metrics
+        project.prometheus_metrics.select do |metric|
+          metric.group == group_key &&
+          metric.title == title &&
+          metric.y_label == y_label
+        end
+      end
+
+      # Returns a symbol representing the group that
+      # the dashboard's group title belongs to.
+      # It will be one of the keys found under
+      # PrometheusMetricEnums.custom_groups.
+      #
+      # @return [String]
+      def group_key
+        PrometheusMetricEnums
+          .group_details
+          .find { |_, details| details[:group_title] == group }
+          &.first
+          &.to_s
+      end
+
+      # Returns a representation of a PromtheusMetric
+      # as a dashboard panel. As the panel is generated
+      # on the fly, we're using the default values for
+      # info we can't get from the DB.
+      #
+      # @return [Hash]
+      def panel_for_metric(metric)
+        {
+          type: DEFAULT_PANEL_TYPE,
+          weight: DEFAULT_PANEL_WEIGHT,
+          title: metric.title,
+          y_label: metric.y_label,
+          metrics: [metric.queries.first.merge(metric_id: metric.id)]
+        }
+      end
+    end
+  end
+end
diff --git a/app/services/metrics/dashboard/default_embed_service.rb b/app/services/metrics/dashboard/default_embed_service.rb
index 8b01b44fc98..147037fa284 100644
--- a/app/services/metrics/dashboard/default_embed_service.rb
+++ b/app/services/metrics/dashboard/default_embed_service.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 # Responsible for returning a filtered system dashboard
-# containing only the default embedded metrics. In future,
-# this class may be updated to support filtering to
-# alternate metrics/panels.
+# containing only the default embedded metrics. This class
+# operates by selecting metrics directly from the system
+# dashboard.
 #
 # Why isn't this filtering in a processing stage? By filtering
 # here, we ensure the dynamically-determined dashboard is cached.
@@ -11,7 +11,7 @@
 # Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
 module Metrics
   module Dashboard
-    class DefaultEmbedService < ::Metrics::Dashboard::BaseService
+    class DefaultEmbedService < ::Metrics::Dashboard::BaseEmbedService
       # For the default filtering for embedded metrics,
       # uses the 'id' key in dashboard-yml definition for
       # identification.
@@ -33,10 +33,6 @@ module Metrics
         { 'panel_groups' => [{ 'panels' => panels }] }
       end
 
-      def cache_key
-        "dynamic_metrics_dashboard_#{metric_identifiers.join('_')}"
-      end
-
       private
 
       # Returns an array of the panels groups on the
@@ -51,11 +47,11 @@ module Metrics
       # the panel is in the list of identifiers to collect.
       def matching_panel?(panel)
         panel['metrics'].any? do |metric|
-          metric_identifiers.include?(metric['id'])
+          identifiers.include?(metric['id'])
         end
       end
 
-      def metric_identifiers
+      def identifiers
         DEFAULT_EMBEDDED_METRICS_IDENTIFIERS
       end
     end
diff --git a/app/services/metrics/dashboard/dynamic_embed_service.rb b/app/services/metrics/dashboard/dynamic_embed_service.rb
new file mode 100644
index 00000000000..927efe37a80
--- /dev/null
+++ b/app/services/metrics/dashboard/dynamic_embed_service.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+# Responsible for returning a filtered project dashboard
+# containing only the request-provided metrics. The result
+# is then cached for future requests. Metrics are identified
+# based on a combination of identifiers for now, but the ideal
+# would be similar to the approach in DefaultEmbedService, but
+# a single unique identifier is not currently available across
+# all metric types (custom, project-defined, cluster, or system).
+#
+# Use Gitlab::Metrics::Dashboard::Finder to retrive dashboards.
+module Metrics
+  module Dashboard
+    class DynamicEmbedService < ::Metrics::Dashboard::BaseEmbedService
+      include Gitlab::Utils::StrongMemoize
+
+      # Returns a new dashboard with only the matching
+      # metrics from the system dashboard, stripped of groups.
+      # @return [Hash]
+      def get_raw_dashboard
+        not_found! if panels.empty?
+
+        { 'panel_groups' => [{ 'panels' => panels }] }
+      end
+
+      private
+
+      def panels
+        strong_memoize(:panels) do
+          not_found! unless base_dashboard
+          not_found! unless groups = base_dashboard['panel_groups']
+          not_found! unless matching_group = find_group(groups)
+          not_found! unless all_panels = matching_group['panels']
+
+          find_panels(all_panels)
+        end
+      end
+
+      def base_dashboard
+        strong_memoize(:base_dashboard) do
+          Gitlab::Metrics::Dashboard::Finder.find_raw(project, dashboard_path: dashboard_path)
+        end
+      end
+
+      def find_group(groups)
+        groups.find do |candidate_group|
+          candidate_group['group'] == group
+        end
+      end
+
+      def find_panels(all_panels)
+        all_panels.select do |panel|
+          panel['title'] == title && panel['y_label'] == y_label
+        end
+      end
+
+      def not_found!
+        panels_not_found!(identifiers)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics/dashboard/defaults.rb b/lib/gitlab/metrics/dashboard/defaults.rb
new file mode 100644
index 00000000000..3c39a7c6911
--- /dev/null
+++ b/lib/gitlab/metrics/dashboard/defaults.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# Central point for managing default attributes from within
+# the metrics dashboard module.
+module Gitlab
+  module Metrics
+    module Dashboard
+      module Defaults
+        DEFAULT_PANEL_TYPE = 'area-chart'
+        DEFAULT_PANEL_WEIGHT = 0
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics/dashboard/errors.rb b/lib/gitlab/metrics/dashboard/errors.rb
new file mode 100644
index 00000000000..1739a4e6738
--- /dev/null
+++ b/lib/gitlab/metrics/dashboard/errors.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+# Central point for managing errors from within the metrics
+# dashboard module. Handles errors from dashboard retrieval
+# and processing steps, as well as defines shared error classes.
+module Gitlab
+  module Metrics
+    module Dashboard
+      module Errors
+        PanelNotFoundError = Class.new(StandardError)
+
+        PROCESSING_ERROR = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardProcessingError
+        NOT_FOUND_ERROR = Gitlab::Template::Finders::RepoTemplateFinder::FileNotFoundError
+
+        def handle_errors(error)
+          case error
+          when PROCESSING_ERROR
+            error(error.message, :unprocessable_entity)
+          when NOT_FOUND_ERROR
+            error("#{dashboard_path} could not be found.", :not_found)
+          when PanelNotFoundError
+            error(error.message, :not_found)
+          else
+            raise error
+          end
+        end
+
+        def panels_not_found!(opts)
+          raise PanelNotFoundError.new("No panels matching properties #{opts}")
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics/dashboard/finder.rb b/lib/gitlab/metrics/dashboard/finder.rb
index 1373830844b..66c4d662a6c 100644
--- a/lib/gitlab/metrics/dashboard/finder.rb
+++ b/lib/gitlab/metrics/dashboard/finder.rb
@@ -12,21 +12,37 @@ module Gitlab
           # @param project [Project]
           # @param user [User]
           # @param environment [Environment]
-          # @param opts - dashboard_path [String] Path at which the
-          #         dashboard can be found. Nil values will
-          #         default to the system dashboard.
-          # @param opts - embedded [Boolean] Determines whether the
+          # @param options - embedded [Boolean] Determines whether the
           #         dashboard is to be rendered as part of an
           #         issue or location other than the primary
           #         metrics dashboard UI. Returns only the
           #         Memory/CPU charts of the system dash.
+          # @param options - dashboard_path [String] Path at which the
+          #         dashboard can be found. Nil values will
+          #         default to the system dashboard.
+          # @param options - group [String] Title of the group
+          #         to which a panel might belong. Used by
+          #         embedded dashboards.
+          # @param options - title [String] Title of the panel.
+          #         Used by embedded dashboards.
+          # @param options - y_label [String] Y-Axis label of
+          #         a panel. Used by embedded dashboards.
           # @return [Hash]
-          def find(project, user, environment, dashboard_path: nil, embedded: false)
-            service_for_path(dashboard_path, embedded: embedded)
-              .new(project, user, environment: environment, dashboard_path: dashboard_path)
+          def find(project, user, environment, options = {})
+            service_for(options)
+              .new(project, user, options.merge(environment: environment))
               .get_dashboard
           end
 
+          # Returns a dashboard without any supplemental info.
+          # Returns only full, yml-defined dashboards.
+          # @return [Hash]
+          def find_raw(project, dashboard_path: nil)
+            service_for(dashboard_path: dashboard_path)
+              .new(project, nil, dashboard_path: dashboard_path)
+              .raw_dashboard
+          end
+
           # Summary of all known dashboards.
           # @return [Array<Hash>] ex) [{ path: String,
           #                              display_name: String,
@@ -46,13 +62,6 @@ module Gitlab
 
           private
 
-          def service_for_path(dashboard_path, embedded:)
-            return embed_service if embedded
-            return system_service if system_dashboard?(dashboard_path)
-
-            project_service
-          end
-
           def system_service
             ::Metrics::Dashboard::SystemDashboardService
           end
@@ -61,12 +70,8 @@ module Gitlab
             ::Metrics::Dashboard::ProjectDashboardService
           end
 
-          def embed_service
-            ::Metrics::Dashboard::DefaultEmbedService
-          end
-
-          def system_dashboard?(filepath)
-            !filepath || system_service.system_dashboard?(filepath)
+          def service_for(options)
+            Gitlab::Metrics::Dashboard::ServiceSelector.call(options)
           end
         end
       end
diff --git a/lib/gitlab/metrics/dashboard/service_selector.rb b/lib/gitlab/metrics/dashboard/service_selector.rb
new file mode 100644
index 00000000000..7ebd8187906
--- /dev/null
+++ b/lib/gitlab/metrics/dashboard/service_selector.rb
@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+# Responsible for determining which dashboard service should
+# be used to fetch or generate a dashboard hash.
+# The services can be considered in two categories - embeds
+# and dashboards. Embeds are all portions of dashboards.
+module Gitlab
+  module Metrics
+    module Dashboard
+      class ServiceSelector
+        SERVICES = ::Metrics::Dashboard
+
+        class << self
+          include Gitlab::Utils::StrongMemoize
+
+          # Returns a class which inherits from the BaseService
+          # class that can be used to obtain a dashboard.
+          # @return [Gitlab::Metrics::Dashboard::Services::BaseService]
+          def call(params)
+            return SERVICES::CustomMetricEmbedService if custom_metrics_embed?(params)
+            return SERVICES::DynamicEmbedService if all_embed_params_present?(params)
+            return SERVICES::DefaultEmbedService if params[:embedded]
+            return SERVICES::SystemDashboardService if system_dashboard?(params[:dashboard_path])
+            return SERVICES::ProjectDashboardService if params[:dashboard_path]
+
+            default_service
+          end
+
+          private
+
+          def default_service
+            SERVICES::SystemDashboardService
+          end
+
+          def system_dashboard?(filepath)
+            SERVICES::SystemDashboardService.system_dashboard?(filepath)
+          end
+
+          # Custom metrics are added to the system dashboard
+          # in ProjectMetricsInserter, so we consider them
+          # to be a part of the system dashboard, even though
+          # they are exclustely stored in the database.
+          def custom_metrics_embed?(params)
+            all_embed_params_present?(params) &&
+              system_dashboard?(params[:dashboard_path]) &&
+              custom_metrics_group?(params[:group])
+          end
+
+          def custom_metrics_group?(group)
+            custom_metrics_group_titles.include?(group)
+          end
+
+          # These are the attributes required to uniquely
+          # identify a panel on a dashboard for embedding.
+          def all_embed_params_present?(params)
+            [
+              params[:embedded],
+              params[:dashboard_path],
+              params[:group],
+              params[:title],
+              params[:y_label]
+            ].all?
+          end
+
+          def custom_metrics_group_titles
+            strong_memoize(:custom_metrics_group_titles) do
+              PrometheusMetricEnums
+                .custom_group_details
+                .map { |_, details| details[:group_title] }
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics/dashboard/stages/base_stage.rb b/lib/gitlab/metrics/dashboard/stages/base_stage.rb
index 0db7b176e8d..514ed50e58d 100644
--- a/lib/gitlab/metrics/dashboard/stages/base_stage.rb
+++ b/lib/gitlab/metrics/dashboard/stages/base_stage.rb
@@ -5,11 +5,11 @@ module Gitlab
     module Dashboard
       module Stages
         class BaseStage
+          include Gitlab::Metrics::Dashboard::Defaults
+
           DashboardProcessingError = Class.new(StandardError)
           LayoutError = Class.new(DashboardProcessingError)
 
-          DEFAULT_PANEL_TYPE = 'area-chart'
-
           attr_reader :project, :environment, :dashboard
 
           def initialize(project, environment, dashboard)
diff --git a/spec/controllers/projects/environments_controller_spec.rb b/spec/controllers/projects/environments_controller_spec.rb
index 8872e8d38e7..b3852355d77 100644
--- a/spec/controllers/projects/environments_controller_spec.rb
+++ b/spec/controllers/projects/environments_controller_spec.rb
@@ -518,10 +518,10 @@ describe Projects::EnvironmentsController do
       end
     end
 
-    shared_examples_for 'the default dynamic dashboard' do
+    shared_examples_for 'specified dashboard embed' do |expected_titles|
       it_behaves_like '200 response'
 
-      it 'contains only the Memory and CPU charts' do
+      it 'contains only the specified charts' do
         get :metrics_dashboard, params: environment_params(dashboard_params)
 
         dashboard = json_response['dashboard']
@@ -531,10 +531,14 @@ describe Projects::EnvironmentsController do
         expect(dashboard['dashboard']).to be_nil
         expect(dashboard['panel_groups'].length).to eq 1
         expect(panel_group['group']).to be_nil
-        expect(titles).to eq ['Memory Usage (Total)', 'Core Usage (Total)']
+        expect(titles).to eq expected_titles
       end
     end
 
+    shared_examples_for 'the default dynamic dashboard' do
+      it_behaves_like 'specified dashboard embed', ['Memory Usage (Total)', 'Core Usage (Total)']
+    end
+
     shared_examples_for 'dashboard can be specified' do
       context 'when dashboard is specified' do
         let(:dashboard_path) { '.gitlab/dashboards/test.yml' }
@@ -551,7 +555,7 @@ describe Projects::EnvironmentsController do
         end
 
         context 'when the specified dashboard is the default dashboard' do
-          let(:dashboard_path) { ::Metrics::Dashboard::SystemDashboardService::SYSTEM_DASHBOARD_PATH }
+          let(:dashboard_path) { system_dashboard_path }
 
           it_behaves_like 'the default dashboard'
         end
@@ -564,12 +568,40 @@ describe Projects::EnvironmentsController do
 
         it_behaves_like 'the default dynamic dashboard'
 
-        context 'when the dashboard is specified' do
-          let(:dashboard_params) { { format: :json, embedded: true, dashboard: '.gitlab/dashboards/fake.yml' } }
+        context 'when incomplete dashboard params are provided' do
+          let(:dashboard_params) { { format: :json, embedded: true, title: 'Title' } }
+
+          # The title param should be ignored.
+          it_behaves_like 'the default dynamic dashboard'
+        end
+
+        context 'when invalid params are provided' do
+          let(:dashboard_params) { { format: :json, embedded: true, metric_id: 16 } }
 
-          # The dashboard param should be ignored.
+          # The superfluous param should be ignored.
           it_behaves_like 'the default dynamic dashboard'
         end
+
+        context 'when the dashboard is correctly specified' do
+          let(:dashboard_params) do
+            {
+              format: :json,
+              embedded: true,
+              dashboard: system_dashboard_path,
+              group: business_metric_title,
+              title: 'title',
+              y_label: 'y_label'
+            }
+          end
+
+          it_behaves_like 'error response', :not_found
+
+          context 'and exists' do
+            let!(:metric) { create(:prometheus_metric, project: project) }
+
+            it_behaves_like 'specified dashboard embed', ['title']
+          end
+        end
       end
     end
 
diff --git a/spec/fixtures/lib/gitlab/metrics/dashboard/schemas/metrics.json b/spec/fixtures/lib/gitlab/metrics/dashboard/schemas/metrics.json
index 33393805464..9c1be32645a 100644
--- a/spec/fixtures/lib/gitlab/metrics/dashboard/schemas/metrics.json
+++ b/spec/fixtures/lib/gitlab/metrics/dashboard/schemas/metrics.json
@@ -16,7 +16,8 @@
     "unit": { "type": "string" },
     "label": { "type": "string" },
     "track": { "type": "string" },
-    "prometheus_endpoint_path": { "type": "string" }
+    "prometheus_endpoint_path": { "type": "string" },
+    "metric_id": { "type": "number" }
   },
   "additionalProperties": false
 }
diff --git a/spec/lib/gitlab/metrics/dashboard/defaults_spec.rb b/spec/lib/gitlab/metrics/dashboard/defaults_spec.rb
new file mode 100644
index 00000000000..420b246b3f5
--- /dev/null
+++ b/spec/lib/gitlab/metrics/dashboard/defaults_spec.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Metrics::Dashboard::Defaults do
+  it { is_expected.to be_const_defined(:DEFAULT_PANEL_TYPE) }
+  it { is_expected.to be_const_defined(:DEFAULT_PANEL_WEIGHT) }
+end
diff --git a/spec/lib/gitlab/metrics/dashboard/finder_spec.rb b/spec/lib/gitlab/metrics/dashboard/finder_spec.rb
index e57c7326320..ce1bb49f5c9 100644
--- a/spec/lib/gitlab/metrics/dashboard/finder_spec.rb
+++ b/spec/lib/gitlab/metrics/dashboard/finder_spec.rb
@@ -5,10 +5,9 @@ require 'spec_helper'
 describe Gitlab::Metrics::Dashboard::Finder, :use_clean_rails_memory_store_caching do
   include MetricsDashboardHelpers
 
-  set(:project) { build(:project) }
+  set(:project) { create(:project) }
   set(:user) { create(:user) }
   set(:environment) { create(:environment, project: project) }
-  let(:system_dashboard_path) { ::Metrics::Dashboard::SystemDashboardService::SYSTEM_DASHBOARD_PATH}
 
   before do
     project.add_maintainer(user)
@@ -52,9 +51,80 @@ describe Gitlab::Metrics::Dashboard::Finder, :use_clean_rails_memory_store_cachi
     end
 
     context 'when the dashboard is expected to be embedded' do
-      let(:service_call) { described_class.find(project, user, environment, dashboard_path: nil, embedded: true) }
+      let(:service_call) { described_class.find(project, user, environment, **params) }
+      let(:params) { { embedded: true } }
 
       it_behaves_like 'valid embedded dashboard service response'
+
+      context 'when params are incomplete' do
+        let(:params) { { embedded: true, dashboard_path: system_dashboard_path } }
+
+        it_behaves_like 'valid embedded dashboard service response'
+      end
+
+      context 'when the panel is specified' do
+        context 'as a custom metric' do
+          let(:params) do
+            { embedded: true,
+              dashboard_path: system_dashboard_path,
+              group: business_metric_title,
+              title: 'title',
+              y_label: 'y_label' }
+          end
+
+          it_behaves_like 'misconfigured dashboard service response', :not_found
+
+          context 'when the metric exists' do
+            before do
+              create(:prometheus_metric, project: project)
+            end
+
+            it_behaves_like 'valid embedded dashboard service response'
+          end
+        end
+
+        context 'as a project-defined panel' do
+          let(:dashboard_path) { '.gitlab/dashboard/test.yml' }
+          let(:params) do
+            { embedded: true,
+              dashboard_path: dashboard_path,
+              group: 'Group A',
+              title: 'Super Chart A1',
+              y_label: 'y_label' }
+          end
+
+          it_behaves_like 'misconfigured dashboard service response', :not_found
+
+          context 'when the metric exists' do
+            let(:project) { project_with_dashboard(dashboard_path) }
+
+            it_behaves_like 'valid embedded dashboard service response'
+          end
+        end
+      end
+    end
+  end
+
+  describe '.find_raw' do
+    let(:dashboard) { YAML.load_file(Rails.root.join('config', 'prometheus', 'common_metrics.yml')) }
+    let(:params) { {} }
+
+    subject { described_class.find_raw(project, **params) }
+
+    it { is_expected.to eq dashboard }
+
+    context 'when the system dashboard is specified' do
+      let(:params) { { dashboard_path: system_dashboard_path } }
+
+      it { is_expected.to eq dashboard }
+    end
+
+    context 'when an existing project dashboard is specified' do
+      let(:dashboard) { YAML.safe_load(fixture_file('lib/gitlab/metrics/dashboard/sample_dashboard.yml')) }
+      let(:params) { { dashboard_path: '.gitlab/dashboards/test.yml' } }
+      let(:project) { project_with_dashboard(params[:dashboard_path]) }
+
+      it { is_expected.to eq dashboard }
     end
   end
 
diff --git a/spec/lib/gitlab/metrics/dashboard/service_selector_spec.rb b/spec/lib/gitlab/metrics/dashboard/service_selector_spec.rb
new file mode 100644
index 00000000000..6c6079f6091
--- /dev/null
+++ b/spec/lib/gitlab/metrics/dashboard/service_selector_spec.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Metrics::Dashboard::ServiceSelector do
+  include MetricsDashboardHelpers
+
+  describe '#call' do
+    let(:arguments) { {} }
+
+    subject { described_class.call(arguments) }
+
+    it { is_expected.to be Metrics::Dashboard::SystemDashboardService }
+
+    context 'when just the dashboard path is provided' do
+      let(:arguments) { { dashboard_path: '.gitlab/dashboards/test.yml' } }
+
+      it { is_expected.to be Metrics::Dashboard::ProjectDashboardService }
+
+      context 'when the path is for the system dashboard' do
+        let(:arguments) { { dashboard_path: system_dashboard_path } }
+
+        it { is_expected.to be Metrics::Dashboard::SystemDashboardService }
+      end
+    end
+
+    context 'when the embedded flag is provided' do
+      let(:arguments) { { embedded: true } }
+
+      it { is_expected.to be Metrics::Dashboard::DefaultEmbedService }
+
+      context 'when an incomplete set of dashboard identifiers are provided' do
+        let(:arguments) { { embedded: true, dashboard_path: '.gitlab/dashboards/test.yml' } }
+
+        it { is_expected.to be Metrics::Dashboard::DefaultEmbedService }
+      end
+
+      context 'when all the dashboard identifiers are provided' do
+        let(:arguments) do
+          {
+            embedded: true,
+            dashboard_path: '.gitlab/dashboards/test.yml',
+            group: 'Important Metrics',
+            title: 'Total Requests',
+            y_label: 'req/sec'
+          }
+        end
+
+        it { is_expected.to be Metrics::Dashboard::DynamicEmbedService }
+      end
+
+      context 'with a system dashboard and "custom" group' do
+        let(:arguments) do
+          {
+            embedded: true,
+            dashboard_path: system_dashboard_path,
+            group: business_metric_title,
+            title: 'Total Requests',
+            y_label: 'req/sec'
+          }
+        end
+
+        it { is_expected.to be Metrics::Dashboard::CustomMetricEmbedService }
+      end
+    end
+  end
+end
diff --git a/spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb b/spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb
new file mode 100644
index 00000000000..a1ad5b48ca5
--- /dev/null
+++ b/spec/services/metrics/dashboard/custom_metric_embed_service_spec.rb
@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Metrics::Dashboard::CustomMetricEmbedService do
+  include MetricsDashboardHelpers
+
+  set(:project) { build(:project) }
+  set(:user) { create(:user) }
+  set(:environment) { create(:environment, project: project) }
+
+  before do
+    project.add_maintainer(user)
+  end
+
+  describe '#get_dashboard' do
+    let(:dashboard_path) { system_dashboard_path }
+    let(:group) { business_metric_title }
+    let(:title) { 'title' }
+    let(:y_label) { 'y_label' }
+
+    let(:service_params) do
+      [
+        project,
+        user,
+        {
+          environment: environment,
+          dashboard_path: dashboard_path,
+          group: group,
+          title: title,
+          y_label: y_label
+        }
+      ]
+    end
+
+    let(:service_call) { described_class.new(*service_params).get_dashboard }
+
+    it_behaves_like 'misconfigured dashboard service response', :not_found
+    it_behaves_like 'raises error for users with insufficient permissions'
+
+    context 'the custom metric exists' do
+      let!(:metric) { create(:prometheus_metric, project: project) }
+
+      it_behaves_like 'valid embedded dashboard service response'
+
+      it 'does not cache the unprocessed dashboard' do
+        expect(Gitlab::Metrics::Dashboard::Cache).not_to receive(:fetch)
+
+        described_class.new(*service_params).get_dashboard
+      end
+
+      context 'multiple metrics meet criteria' do
+        let!(:metric_2) { create(:prometheus_metric, project: project, query: 'avg(metric_2)') }
+
+        it_behaves_like 'valid embedded dashboard service response'
+
+        it 'includes both metrics' do
+          result = service_call
+          included_queries = all_queries(result[:dashboard])
+
+          expect(included_queries).to include('avg(metric_2)', 'avg(metric)')
+        end
+      end
+    end
+
+    context 'when the metric exists in another project' do
+      let!(:metric) { create(:prometheus_metric, project: create(:project)) }
+
+      it_behaves_like 'misconfigured dashboard service response', :not_found
+    end
+  end
+
+  private
+
+  def all_queries(dashboard)
+    dashboard[:panel_groups].flat_map do |group|
+      group[:panels].flat_map do |panel|
+        panel[:metrics].map do |metric|
+          metric[:query_range]
+        end
+      end
+    end
+  end
+end
diff --git a/spec/services/metrics/dashboard/dynamic_embed_service_spec.rb b/spec/services/metrics/dashboard/dynamic_embed_service_spec.rb
new file mode 100644
index 00000000000..bf5e90f20f4
--- /dev/null
+++ b/spec/services/metrics/dashboard/dynamic_embed_service_spec.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Metrics::Dashboard::DynamicEmbedService, :use_clean_rails_memory_store_caching do
+  include MetricsDashboardHelpers
+
+  set(:project) { build(:project) }
+  set(:user) { create(:user) }
+  set(:environment) { create(:environment, project: project) }
+
+  before do
+    project.add_maintainer(user)
+  end
+
+  describe '#get_dashboard' do
+    let(:dashboard_path) { '.gitlab/dashboards/test.yml' }
+    let(:group) { 'Group A' }
+    let(:title) { 'Super Chart A1' }
+    let(:y_label) { 'y_label' }
+
+    let(:service_params) do
+      [
+        project,
+        user,
+        {
+          environment: environment,
+          dashboard_path: dashboard_path,
+          group: group,
+          title: title,
+          y_label: y_label
+        }
+      ]
+    end
+
+    let(:service_call) { described_class.new(*service_params).get_dashboard }
+
+    context 'when the dashboard does not exist' do
+      it_behaves_like 'misconfigured dashboard service response', :not_found
+    end
+
+    context 'when the dashboard is exists' do
+      let(:project) { project_with_dashboard(dashboard_path) }
+
+      it_behaves_like 'valid embedded dashboard service response'
+      it_behaves_like 'raises error for users with insufficient permissions'
+
+      it 'caches the unprocessed dashboard for subsequent calls' do
+        expect(YAML).to receive(:safe_load).once.and_call_original
+
+        described_class.new(*service_params).get_dashboard
+        described_class.new(*service_params).get_dashboard
+      end
+
+      context 'when the specified group is not present on the dashboard' do
+        let(:group) { 'Group Not Found' }
+
+        it_behaves_like 'misconfigured dashboard service response', :not_found
+      end
+
+      context 'when the specified title is not present on the dashboard' do
+        let(:title) { 'Title Not Found' }
+
+        it_behaves_like 'misconfigured dashboard service response', :not_found
+      end
+
+      context 'when the specified y-axis label is not present on the dashboard' do
+        let(:y_label) { 'Y-Axis Not Found' }
+
+        it_behaves_like 'misconfigured dashboard service response', :not_found
+      end
+    end
+  end
+end
diff --git a/spec/support/helpers/metrics_dashboard_helpers.rb b/spec/support/helpers/metrics_dashboard_helpers.rb
index 1511a2f6b49..0e86b6dfda7 100644
--- a/spec/support/helpers/metrics_dashboard_helpers.rb
+++ b/spec/support/helpers/metrics_dashboard_helpers.rb
@@ -18,6 +18,14 @@ module MetricsDashboardHelpers
     project.repository.refresh_method_caches([:metrics_dashboard])
   end
 
+  def system_dashboard_path
+    Metrics::Dashboard::SystemDashboardService::SYSTEM_DASHBOARD_PATH
+  end
+
+  def business_metric_title
+    PrometheusMetricEnums.group_details[:business][:group_title]
+  end
+
   shared_examples_for 'misconfigured dashboard service response' do |status_code|
     it 'returns an appropriate message and status code' do
       result = service_call