Re-add Prometheus metrics

app.js

@@ -87,7 +87,7 @@ const Admiral = new Fleet({
     }
   },
   services: [
-    //{ name: "prometheus", path: path.join(__dirname, "./utils/services/prometheus.js") },
+    { name: "prometheus", path: path.join(__dirname, "./utils/services/prometheus.js") },
     { name: "image", path: path.join(__dirname, "./utils/services/image.js")}
   ]
 });

utils/services/prometheus.js

@@ -0,0 +1,57 @@
+const { BaseServiceWorker } = require("eris-fleet");
+const http = require("http");
+const logger = require("../logger.js");
+const database = require("../database.js");
+
+class PrometheusWorker extends BaseServiceWorker {
+  constructor(setup) {
+    super(setup);
+
+    if (process.env.METRICS !== "" && process.env.METRICS !== undefined) {
+      this.httpServer = http.createServer(async (req, res) => {
+        if (req.method !== "GET") {
+          res.statusCode = 405;
+          return res.end("GET only");
+        }
+        res.write(`# HELP command_count Number of times a command has been run
+# TYPE command_count counter
+`);
+        if (process.env.API === "true") {
+          const servers = await this.ipc.command("image", { type: "stats" }, true);
+          res.write(`# HELP connected_workers Number of workers connected
+# TYPE connected_workers gauge
+connected_workers ${servers.length}
+# HELP running_jobs Number of running jobs on this worker
+# TYPE running_jobs gauge
+# HELP queued_jobs Number of queued jobs on this worker
+# TYPE queued_jobs gauge
+# HELP max_jobs Number of max allowed jobs on this worker
+# TYPE max_jobs gauge
+`);
+          for (const [i, w] of servers.entries()) {
+            res.write(`running_jobs{worker="${i}"} ${w.runningJobs}\n`);
+            res.write(`queued_jobs{worker="${i}"} ${w.queued}\n`);
+            res.write(`max_jobs{worker="${i}"} ${w.max}\n`);
+          }
+        }
+        const counts = await database.getCounts();
+        for (const [i, w] of Object.entries(counts)) {
+          res.write(`command_count{command="${i}"} ${w}\n`);
+        }
+        res.end();
+      });
+      this.httpServer.listen(process.env.METRICS, () => {
+        logger.log("info", `Serving metrics at ${process.env.METRICS}`);
+      });
+    }
+
+    this.serviceReady();
+  }
+
+  shutdown(done) {
+    this.httpServer.close();
+    done();
+  }
+}
+
+module.exports = PrometheusWorker;