scaling: include padId in socketio query string

src/static/js/pad.js

@@ -218,7 +218,14 @@ const sendClientReady = (isReconnect, messageType) => {
 };
 
 const handshake = () => {
+  let padId = document.location.pathname.substring(document.location.pathname.lastIndexOf('/') + 1);
+  // unescape neccesary due to Safari and Opera interpretation of spaces
+  padId = decodeURIComponent(padId);
+
+  // padId is used here for sharding / scaling.  We prefix the padId with padId: so it's clear
+  // to the proxy/gateway/whatever that this is a pad connection and should be treated as such
   socket = pad.socket = socketio.connect(exports.baseURL, '/', {
+    query: {padId},
     reconnectionAttempts: 5,
     reconnection: true,
     reconnectionDelay: 1000,

src/static/js/timeslider.js

@@ -52,7 +52,7 @@ const init = () => {
       Cookies.set('token', token, {expires: 60});
     }
 
-    socket = socketio.connect(exports.baseURL);
+    socket = socketio.connect(exports.baseURL, '/', {query: {padId}});
 
     // send the ready message once we're connected
     socket.on('connect', () => {

src/tests/backend/specs/socketio.js

@@ -52,12 +52,13 @@ const connect = async (res) => {
       ([name, cookie]) => `${name}=${encodeURIComponent(cookie.value)}`).join('; ');
 
   logger.debug('socket.io connecting...');
+  const padId = res.req.path.split('/p/')[1];
   const socket = io(`${common.baseUrl}/`, {
     forceNew: true, // Different tests will have different query parameters.
     path: '/socket.io',
     // socketio.js-client on node.js doesn't support cookies (see https://git.io/JU8u9), so the
     // express_sid cookie must be passed as a query parameter.
-    query: {cookie: reqCookieHdr},
+    query: {cookie: reqCookieHdr, padId},
   });
   try {
     await getSocketEvent(socket, 'connect');