1 files changed, 83 insertions, 0 deletions
diff --git a/lib/gitlab/metrics/sli.rb b/lib/gitlab/metrics/sli.rb
new file mode 100644
index 00000000000..de73db0755d
--- /dev/null
+++ b/lib/gitlab/metrics/sli.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Metrics
+    class Sli
+      SliNotInitializedError = Class.new(StandardError)
+
+      COUNTER_PREFIX = 'gitlab_sli'
+
+      class << self
+        INITIALIZATION_MUTEX = Mutex.new
+
+        def [](name)
+          known_slis[name] || initialize_sli(name, [])
+        end
+
+        def initialize_sli(name, possible_label_combinations)
+          INITIALIZATION_MUTEX.synchronize do
+            sli = new(name)
+            sli.initialize_counters(possible_label_combinations)
+            known_slis[name] = sli
+          end
+        end
+
+        def initialized?(name)
+          known_slis.key?(name) && known_slis[name].initialized?
+        end
+
+        private
+
+        def known_slis
+          @known_slis ||= {}
+        end
+      end
+
+      attr_reader :name
+
+      def initialize(name)
+        @name = name
+        @initialized_with_combinations = false
+      end
+
+      def initialize_counters(possible_label_combinations)
+        @initialized_with_combinations = possible_label_combinations.any?
+        possible_label_combinations.each do |label_combination|
+          total_counter.get(label_combination)
+          success_counter.get(label_combination)
+        end
+      end
+
+      def increment(labels:, success:)
+        total_counter.increment(labels)
+        success_counter.increment(labels) if success
+      end
+
+      def initialized?
+        @initialized_with_combinations
+      end
+
+      private
+
+      def total_counter
+        prometheus.counter(total_counter_name.to_sym, "Total number of measurements for #{name}")
+      end
+
+      def success_counter
+        prometheus.counter(success_counter_name.to_sym, "Number of successful measurements for #{name}")
+      end
+
+      def total_counter_name
+        "#{COUNTER_PREFIX}:#{name}:total"
+      end
+
+      def success_counter_name
+        "#{COUNTER_PREFIX}:#{name}:success_total"
+      end
+
+      def prometheus
+        Gitlab::Metrics
+      end
+    end
+  end
+end