express: New `httpUptime` metric

CHANGELOG.md

@@ -26,7 +26,8 @@
 * Database performance is significantly improved.
 * Admin UI now has test coverage in CI. (The tests are not enabled by default;
   see `settings.json`.)
-* New stats: `activePads`, `lastDisconnected`, `memoryUsageHeap`.
+* New stats/metrics: `activePads`, `httpUptime`, `lastDisconnected`,
+  `memoryUsageHeap`.
 * For plugin authors:
   * New `callAllSerial()` function that invokes hook functions like `callAll()`
     except it supports asynchronous hook functions.

src/node/hooks/express.js

@@ -17,6 +17,7 @@ const logger = log4js.getLogger('http');
 let serverName;
 const sockets = new Set();
 const socketsEvents = new events.EventEmitter();
+let startTime = null;
 
 exports.server = null;
 
@@ -49,6 +50,7 @@ const closeServer = async () => {
 };
 
 exports.createServer = async () => {
+  stats.gauge('httpUptime', () => startTime == null ? 0 : new Date() - startTime);
   console.log('Report bugs at https://github.com/ether/etherpad-lite/issues');
 
   serverName = `Etherpad ${settings.getGitCommit()} (https://etherpad.org)`;
@@ -215,6 +217,8 @@ exports.restartServer = async () => {
     });
   });
   await util.promisify(exports.server.listen).bind(exports.server)(settings.port, settings.ip);
+  startTime = new Date();
+  logger.info('HTTP server listening for connections');
 };
 
 exports.shutdown = async (hookName, context) => {