fix: improve MySQL connection handling and cleanup on server start

app/api/socketio/route.js

@@ -9,19 +9,21 @@ const QUEUE_THRESHOLD = parseInt(process.env.QUEUE_THRESHOLD || "100", 10)
 const CONCURRENT_ACTIVE = parseInt(process.env.CONCURRENT_ACTIVE || "50", 10)
 const TOKEN_TTL_SECONDS = parseInt(process.env.TOKEN_TTL_SECONDS || `${15 * 60}`, 10)
 
-// MySQL kapcsolat
-let db = null
-
+// MySQL kapcsolat - minden híváskor új connection
 async function getDbConnection() {
-  if (!db && process.env.MYSQL_HOST) {
-    db = await mysql.createConnection({
+  if (!process.env.MYSQL_HOST) return null
+  try {
+    const connection = await mysql.createConnection({
       host: process.env.MYSQL_HOST,
       user: process.env.MYSQL_USER,
       password: process.env.MYSQL_PASSWORD,
       database: process.env.MYSQL_DATABASE,
     })
+    return connection
+  } catch (error) {
+    console.error('MySQL connection error:', error)
+    return null
   }
-  return db
 }
 
 function ensureEvent(eventId) {
@@ -137,6 +139,15 @@ async function evaluateQueue(eventId, io) {
   // If queue no longer needed, clear it
   if (ev.sockets.size < QUEUE_THRESHOLD) ev.queueOn = false
 
+  // Close database connection
+  if (connection) {
+    try {
+      await connection.end()
+    } catch (error) {
+      console.error('Error closing DB connection:', error)
+    }
+  }
+
   // broadcast
   broadcastUpdate(eventId, io)
 }
@@ -165,12 +176,12 @@ export async function GET(req) {
     global.io = io
 
     // Clean up all expired sessions on server start
-    const connection = await getDbConnection()
-    if (connection) {
+    const startupConnection = await getDbConnection()
+    if (startupConnection) {
       try {
-        const [result] = await connection.execute('DELETE FROM active_sessions WHERE expires_at < NOW()')
+        const [result] = await startupConnection.execute('DELETE FROM active_sessions WHERE expires_at < NOW()')
         console.log(`Server startup: Cleaned ${result.affectedRows} expired sessions`)
-        await connection.end()
+        await startupConnection.end()
       } catch (error) {
         console.error('Cleanup error on startup:', error)
       }
@@ -276,6 +287,15 @@ export async function GET(req) {
           position: pos === -1 ? null : pos + 1,
           estimatedWait: pos === -1 ? null : (ev.active.size + pos) * TOKEN_TTL_SECONDS,
         })
+
+        // Close database connection
+        if (connection) {
+          try {
+            await connection.end()
+          } catch (error) {
+            console.error('Error closing DB connection:', error)
+          }
+        }
       })
 
       socket.on("disconnect", () => {