Add latest changes from gitlab-org/gitlab@master

1 files changed, 129 insertions, 0 deletions

diff --git a/app/finders/prometheus_metrics_finder.rb b/app/finders/prometheus_metrics_finder.rb
new file mode 100644
index 00000000000..84a071abbd5
--- /dev/null
+++ b/app/finders/prometheus_metrics_finder.rb
@@ -0,0 +1,129 @@
+# frozen_string_literal: true
+
+class PrometheusMetricsFinder
+  ACCEPTED_PARAMS = [
+    :project,
+    :group,
+    :title,
+    :y_label,
+    :identifier,
+    :id,
+    :common,
+    :ordered
+  ].freeze
+
+  # Cautiously preferring a memoized class method over a constant
+  # so that the DB connection is accessed after the class is loaded.
+  def self.indexes
+    @indexes ||= PrometheusMetric
+      .connection
+      .indexes(:prometheus_metrics)
+      .map { |index| index.columns.map(&:to_sym) }
+  end
+
+  def initialize(params = {})
+    @params = params.slice(*ACCEPTED_PARAMS)
+  end
+
+  # @return [PrometheusMetric, PrometheusMetric::ActiveRecord_Relation]
+  def execute
+    validate_params!
+
+    metrics = by_project(::PrometheusMetric.all)
+    metrics = by_group(metrics)
+    metrics = by_title(metrics)
+    metrics = by_y_label(metrics)
+    metrics = by_common(metrics)
+    metrics = by_ordered(metrics)
+    metrics = by_identifier(metrics)
+    metrics = by_id(metrics)
+
+    metrics
+  end
+
+  private
+
+  attr_reader :params
+
+  def by_project(metrics)
+    return metrics unless params[:project]
+
+    metrics.for_project(params[:project])
+  end
+
+  def by_group(metrics)
+    return metrics unless params[:group]
+
+    metrics.for_group(params[:group])
+  end
+
+  def by_title(metrics)
+    return metrics unless params[:title]
+
+    metrics.for_title(params[:title])
+  end
+
+  def by_y_label(metrics)
+    return metrics unless params[:y_label]
+
+    metrics.for_y_label(params[:y_label])
+  end
+
+  def by_common(metrics)
+    return metrics unless params[:common]
+
+    metrics.common
+  end
+
+  def by_ordered(metrics)
+    return metrics unless params[:ordered]
+
+    metrics.ordered
+  end
+
+  def by_identifier(metrics)
+    return metrics unless params[:identifier]
+
+    metrics.for_identifier(params[:identifier])
+  end
+
+  def by_id(metrics)
+    return metrics unless params[:id]
+
+    metrics.id_in(params[:id])
+  end
+
+  def validate_params!
+    validate_params_present!
+    validate_id_params!
+    validate_indexes!
+  end
+
+  # Ensure all provided params are supported
+  def validate_params_present!
+    raise ArgumentError, "Please provide one or more of: #{ACCEPTED_PARAMS}" if params.blank?
+  end
+
+  # Protect against the caller "finding" the wrong metric
+  def validate_id_params!
+    raise ArgumentError, 'Only one of :identifier, :id is permitted' if params[:identifier] && params[:id]
+    raise ArgumentError, ':identifier must be scoped to a :project or :common' if params[:identifier] && !(params[:project] || params[:common])
+  end
+
+  # Protect against unaccounted-for, complex/slow queries.
+  # This is not a hard and fast rule, but is meant to encourage
+  # mindful inclusion of new queries.
+  def validate_indexes!
+    indexable_params = params.except(:ordered, :id, :project).keys
+    indexable_params << :project_id if params[:project]
+    indexable_params.sort!
+
+    raise ArgumentError, "An index should exist for params: #{indexable_params}" unless appropriate_index?(indexable_params)
+  end
+
+  def appropriate_index?(indexable_params)
+    return true if indexable_params.blank?
+
+    self.class.indexes.any? { |index| (index - indexable_params).empty? }
+  end
+end