From eb99a036bcfa1f1013a67a13ef070d68d0376340 Mon Sep 17 00:00:00 2001
From: Charlie Hsieh <gasbomb_tw@hotmail.com>
Date: Fri, 17 Jan 2025 16:53:18 +0800
Subject: [PATCH 1/2] feat: queue up ydoc sync task

---
 src/y-socket-io/y-socket-io.js | 55 +++++++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 10 deletions(-)

diff --git a/src/y-socket-io/y-socket-io.js b/src/y-socket-io/y-socket-io.js
index 2993fd0..877cbfc 100644
--- a/src/y-socket-io/y-socket-io.js
+++ b/src/y-socket-io/y-socket-io.js
@@ -90,6 +90,12 @@ export class YSocketIO {
    */
   namespaceMap = new Map()
 
+  /**
+   * @type {Promise<void>[]}
+   * @private
+   */
+  syncQueue = []
+
   /**
    * YSocketIO constructor.
    * @constructor
@@ -157,16 +163,26 @@ export class YSocketIO {
       this.initAwarenessListeners(socket)
       this.initSocketListeners(socket)
 
-      const doc = await this.client.getDoc(namespace, 'index')
-
-      if (
-        api.isSmallerRedisId(doc.redisLastId, socket.user.initialRedisSubId)
-      ) {
-        // our subscription is newer than the content that we received from the api
-        // need to renew subscription id and make sure that we catch the latest content.
-        this.subscriber.ensureSubId(stream, doc.redisLastId)
-      }
-      this.startSynchronization(socket, doc)
+      /**
+       * @type {Promise<void>}
+       */
+      const task = new Promise((resolve) => {
+        assert(this.client)
+        this.client.getDoc(namespace, 'index').then((doc) => {
+          assert(socket.user)
+          assert(this.subscriber)
+          if (
+            api.isSmallerRedisId(doc.redisLastId, socket.user.initialRedisSubId)
+          ) {
+            // our subscription is newer than the content that we received from the api
+            // need to renew subscription id and make sure that we catch the latest content.
+            this.subscriber.ensureSubId(stream, doc.redisLastId)
+          }
+          this.startSynchronization(socket, doc)
+          resolve()
+        })
+      })
+      this.queueUpSyncTask(task)
     })
 
     return { client, subscriber }
@@ -336,6 +352,25 @@ export class YSocketIO {
     }
   }
 
+  /**
+   * @private
+   * @param {Promise<void>} task
+   */
+  queueUpSyncTask (task) {
+    const len = this.syncQueue.push(task)
+    if (len === 1) this.consumeSyncQueue()
+  }
+
+  /**
+   * @private
+   */
+  async consumeSyncQueue () {
+    if (this.syncQueue.length === 0) return
+    const task = this.syncQueue.shift()
+    await task
+    this.consumeSyncQueue()
+  }
+
   /**
    * @param {Namespace} namespace
    */

From 847c7e68ad8db77192acc3ca47bf364309a09e02 Mon Sep 17 00:00:00 2001
From: Charlie Hsieh <gasbomb_tw@hotmail.com>
Date: Fri, 17 Jan 2025 17:03:26 +0800
Subject: [PATCH 2/2] feat: delay client sync step until server is ready

---
 src/y-socket-io/client.js      | 2 +-
 src/y-socket-io/y-socket-io.js | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/y-socket-io/client.js b/src/y-socket-io/client.js
index ebeacde..d93a18c 100644
--- a/src/y-socket-io/client.js
+++ b/src/y-socket-io/client.js
@@ -157,7 +157,7 @@ export class SocketIOProvider extends Observable {
 
     this.doc.on('update', this.onUpdateDoc)
 
-    this.socket.on('connect', () => this.onSocketConnection(resyncInterval))
+    this.socket.once('ready-for-sync', () => this.onSocketConnection(resyncInterval))
 
     this.socket.on('disconnect', (event) => this.onSocketDisconnection(event))
 
diff --git a/src/y-socket-io/y-socket-io.js b/src/y-socket-io/y-socket-io.js
index 877cbfc..1779033 100644
--- a/src/y-socket-io/y-socket-io.js
+++ b/src/y-socket-io/y-socket-io.js
@@ -171,6 +171,7 @@ export class YSocketIO {
         this.client.getDoc(namespace, 'index').then((doc) => {
           assert(socket.user)
           assert(this.subscriber)
+          socket.emit('ready-for-sync')
           if (
             api.isSmallerRedisId(doc.redisLastId, socket.user.initialRedisSubId)
           ) {