refactor: move backend to monorepo

backend/src/middleware/prometheus.ts

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2021 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+import {Logger} from '@openstapps/logger';
+import express_prom_bundle from 'express-prom-bundle';
+import fs from 'fs';
+import path from 'path';
+
+/**
+ * Create and configure a new Express Prometheus Middleware instance
+ *
+ * This function tries to configure the new instance with JSON read from
+ * `./conf/prometheus.json`. When this fails an instance configured with
+ * default options is returned.
+ *
+ * @returns express.Express
+ */
+export function getPrometheusMiddleware(): express_prom_bundle.Middleware {
+  const configFileName = path.join('./config', 'prometheus.json');
+  let options: express_prom_bundle.Opts = {};
+
+  try {
+    options = JSON.parse(fs.readFileSync(configFileName, 'utf8'));
+  } catch (error) {
+    Logger.warn("Couldn't get options from config file for Prometheus Middleware.", error);
+  }
+
+  return express_prom_bundle(options);
+}