1 files changed, 40 insertions, 0 deletions
diff --git a/lib/gitlab/health_checks/prometheus_text_format.rb b/lib/gitlab/health_checks/prometheus_text_format.rb
new file mode 100644
index 00000000000..b3c759b4730
--- /dev/null
+++ b/lib/gitlab/health_checks/prometheus_text_format.rb
@@ -0,0 +1,40 @@
+module Gitlab
+  module HealthChecks
+    class PrometheusTextFormat
+      def marshal(metrics)
+        "#{metrics_with_type_declarations(metrics).join("\n")}\n"
+      end
+
+      private
+
+      def metrics_with_type_declarations(metrics)
+        type_declaration_added = {}
+
+        metrics.flat_map do |metric|
+          metric_lines = []
+
+          unless type_declaration_added.key?(metric.name)
+            type_declaration_added[metric.name] = true
+            metric_lines << metric_type_declaration(metric)
+          end
+
+          metric_lines << metric_text(metric)
+        end
+      end
+
+      def metric_type_declaration(metric)
+        "# TYPE #{metric.name} gauge"
+      end
+
+      def metric_text(metric)
+        labels = metric.labels&.map { |key, value| "#{key}=\"#{value}\"" }&.join(',') || ''
+
+        if labels.empty?
+          "#{metric.name} #{metric.value}"
+        else
+          "#{metric.name}{#{labels}} #{metric.value}"
+        end
+      end
+    end
+  end
+end