♻️ Make the namespacing independent of the branding.

backend/src/app/metrics.clj

@@ -0,0 +1,181 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; This Source Code Form is "Incompatible With Secondary Licenses", as
+;; defined by the Mozilla Public License, v. 2.0.
+;;
+;; Copyright (c) 2020 UXBOX Labs SL
+
+(ns app.metrics
+  (:require
+   [clojure.tools.logging :as log]
+   [cuerdas.core :as str])
+  (:import
+   io.prometheus.client.CollectorRegistry
+   io.prometheus.client.Counter
+   io.prometheus.client.Gauge
+   io.prometheus.client.Summary
+   io.prometheus.client.exporter.common.TextFormat
+   io.prometheus.client.hotspot.DefaultExports
+   java.io.StringWriter))
+
+(defn- create-registry
+  []
+  (let [registry (CollectorRegistry.)]
+    (DefaultExports/register registry)
+    registry))
+
+(defonce registry (create-registry))
+(defonce cache (atom {}))
+
+(defmacro with-measure
+  [sym expr teardown]
+  `(let [~sym (System/nanoTime)]
+     (try
+       ~expr
+       (finally
+         (let [~sym (/ (- (System/nanoTime) ~sym) 1000000)]
+           ~teardown)))))
+
+(defn make-counter
+  [{:keys [id help] :as props}]
+  (let [instance (doto (Counter/build)
+                   (.name id)
+                   (.help help))
+        instance (.register instance registry)]
+    (reify
+      clojure.lang.IDeref
+      (deref [_] instance)
+
+      clojure.lang.IFn
+      (invoke [_ cmd]
+        (.inc ^Counter instance))
+
+      (invoke [_ cmd val]
+        (case cmd
+          :wrap (fn
+                  ([a]
+                   (.inc ^Counter instance)
+                   (val a))
+                  ([a b]
+                   (.inc ^Counter instance)
+                   (val a b))
+                  ([a b c]
+                   (.inc ^Counter instance)
+                   (val a b c)))
+
+          (throw (IllegalArgumentException. "invalid arguments")))))))
+
+(defn counter
+  [{:keys [id] :as props}]
+  (or (get @cache id)
+      (let [v (make-counter props)]
+        (swap! cache assoc id v)
+        v)))
+
+(defn make-gauge
+  [{:keys [id help] :as props}]
+  (let [instance (doto (Gauge/build)
+                   (.name id)
+                   (.help help))
+        instance (.register instance registry)]
+    (reify
+      clojure.lang.IDeref
+      (deref [_] instance)
+
+      clojure.lang.IFn
+      (invoke [_ cmd]
+        (case cmd
+          :inc (.inc ^Gauge instance)
+          :dec (.dec ^Gauge instance))))))
+
+(defn gauge
+  [{:keys [id] :as props}]
+  (or (get @cache id)
+      (let [v (make-gauge props)]
+        (swap! cache assoc id v)
+        v)))
+
+(defn make-summary
+  [{:keys [id help] :as props}]
+  (let [instance (doto (Summary/build)
+                   (.name id)
+                   (.help help)
+                   (.quantile 0.5 0.05)
+                   (.quantile 0.9 0.01)
+                   (.quantile 0.99 0.001))
+        instance  (.register instance registry)]
+    (reify
+      clojure.lang.IDeref
+      (deref [_] instance)
+
+      clojure.lang.IFn
+      (invoke [_ val]
+        (.observe ^Summary instance val))
+
+      (invoke [_ cmd val]
+        (case cmd
+          :wrap (fn
+                  ([a]
+                   (with-measure $$
+                     (val a)
+                     (.observe ^Summary instance $$)))
+                  ([a b]
+                   (with-measure $$
+                     (val a b)
+                     (.observe ^Summary instance $$)))
+                  ([a b c]
+                   (with-measure $$
+                     (val a b c)
+                     (.observe ^Summary instance $$))))
+
+          (throw (IllegalArgumentException. "invalid arguments")))))))
+
+(defn summary
+  [{:keys [id] :as props}]
+  (or (get @cache id)
+      (let [v (make-summary props)]
+        (swap! cache assoc id v)
+        v)))
+
+(defn wrap-summary
+  [f props]
+  (let [sm (summary props)]
+    (sm :wrap f)))
+
+(defn wrap-counter
+  [f props]
+  (let [cnt (counter props)]
+    (cnt :wrap f)))
+
+(defn instrument-with-counter!
+  [{:keys [var] :as props}]
+  (let [cnt  (counter props)
+        vars (if (var? var) [var] var)]
+    (doseq [var vars]
+      (alter-var-root var (fn [root]
+                            (let [mdata (meta root)
+                                  original (::counter-original mdata root)]
+                              (with-meta
+                                (cnt :wrap original)
+                                (assoc mdata ::counter-original original))))))))
+
+(defn instrument-with-summary!
+  [{:keys [var] :as props}]
+  (let [sm (summary props)]
+    (alter-var-root var (fn [root]
+                          (let [mdata (meta root)
+                                original (::summary-original mdata root)]
+                            (with-meta
+                              (sm :wrap original)
+                              (assoc mdata ::summary-original original)))))))
+
+(defn dump
+  [& args]
+  (let [samples (.metricFamilySamples ^CollectorRegistry registry)
+        writer  (StringWriter.)]
+    (TextFormat/write004 writer samples)
+    {:headers {"content-type" TextFormat/CONTENT_TYPE_004}
+     :body (.toString writer)}))
+