myheats

commit ddb856ee2efeb60577a85cde2e6640d3db2f0312
parent ac298c1e654c5fb1dbec89d842a2228abb443c3c
Author: Andreas Gruhler <andreas.gruhler@adfinis.com>
Date:   Sat, 28 Sep 2024 11:55:01 +0200

fix(api): MaxListenersExceededWarning, manage db sub

This MaxListenersExceededWarning warning occurred when several clients
had a watch on the scores.

MaxListenersExceededWarning: Possible EventEmitter memory leak detected.
11 error listeners added to [Duplex]. MaxListeners is 10. Use
emitter.setMaxListeners() to increase limit at genericNodeError
(node:internal/errors:984:15)

With this fix we create the subscription on the database only once. All
client sockets are passed from the routing/server module to the db
backend and maintained as set. When the client disconnects, it is
removed from the server and the db backend set.

Diffstat:
M
src/api/db.cjs
 | 
27
+++++++++++++++++++++++----
M
src/api/server.cjs
 | 
5
+++--

2 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/src/api/db.cjs b/src/api/db.cjs
@@ -1,4 +1,6 @@
 const postgres = require('postgres');
+const watchers = new Set();
+let scoreSubscription = null
 
 require('dotenv').config({
   // Configure common config files and modes
@@ -339,13 +341,29 @@ async function setScore(heat, athlete, judge, score) {
   }
 }
 
-async function watchScores(clients) {
+async function removeWatcher(sock) {
+  console.log("- Watcher removed")
+  watchers.delete(sock)
+}
+
+// add client to subscription
+async function watchScores(sock) {
+  // add client to watchlist
+  console.log("+ Watcher added")
+  watchers.add(sock);
+
+  if (scoreSubscription !== null) {
+    // we are already subscribed to this publication
+    return scoreSubscription
+  }
+
+  // subscribe to score publication
   try {
-    const { unsubscribe } = await sql.subscribe(
+    scoreSubscription = await sql.subscribe(
       '*:scores',
       (row, { command, relation, key, old }) => {
         // distributed score updates to all connected clients
-        for(let c of clients) {
+        for(let c of watchers) {
           c.send(JSON.stringify({
             "message": "Received new scores",
             "data": row,
@@ -357,7 +375,7 @@ async function watchScores(clients) {
         console.log("~ Watching scores")
       }
     )
-    return unsubscribe
+    return scoreSubscription
   } catch (error) {
     console.error('Error occurred in watchScores:', error);
     throw error
@@ -382,6 +400,7 @@ module.exports = {
   getScore,
   setScore,
   watchScores,
+  removeWatcher,
   addAthleteToHeat,
   addAthlete,
   removeAthlete,
diff --git a/src/api/server.cjs b/src/api/server.cjs
@@ -710,7 +710,7 @@ wss1.on('connection', function connection(sock) {
       console.log('  Uncle roger hears:', msg);
 
       if (msg.method === 'watchScores') {
-        db.watchScores(clients)
+        db.watchScores(sock)
       }
     } catch (error) {
       console.error('x Error:', error.message);
@@ -723,7 +723,8 @@ wss1.on('connection', function connection(sock) {
   sock.on('close', function(event) {
     console.log("  Close event:", event.code);
     console.log("  Close reason:", event.reason);
-    clients.delete(ws);
+    clients.delete(sock);
+    db.removeWatcher(sock);
   });
 
   clients.add(sock);