fix(backend): send nodeId in ws message on connection open

Oak doesn't set headers correctly when upgrading to the ws protocol.

Author: RichardDorian

backend/src/middleware/cluster.ts

@@ -1,6 +1,14 @@
 import { Middleware } from '@oak/oak';
 
-const nodeId = crypto.randomUUID();
+import { fromEnv } from '../utils/fromEnv.ts';
+
+export const nodeId = crypto.randomUUID();
+
+export const inCluster = fromEnv('CLUSTER', {
+  defaultValue: false,
+  allowDefaultValueInProd: true,
+  type: Boolean,
+});
 
 export default function (): Middleware {
   return async (ctx, next) => {

backend/src/routes/v1/canvas/gateway.ts

@@ -9,6 +9,7 @@ import {
 } from '../../../db/canvas.ts';
 import { auth } from '../../../middleware/index.ts';
 import { httpError } from '../../../utils/httpError.ts';
+import { inCluster, nodeId } from '../../../middleware/cluster.ts';
 
 const connections = new Set<WebSocket>();
 
@@ -36,6 +37,14 @@ function gateway(ctx: Context) {
 
   ws.onopen = () => {
     connections.add(ws);
+
+    if (inCluster)
+      ws.send(
+        JSON.stringify({
+          type: 'cluster',
+          servedBy: nodeId,
+        })
+      );
   };
 
   ws.onmessage = async (event) => {