diff --git a/libs/client-api/src/ws/client.rs b/libs/client-api/src/ws/client.rs
index 5967c44a..d0b8367e 100644
--- a/libs/client-api/src/ws/client.rs
+++ b/libs/client-api/src/ws/client.rs
@@ -50,7 +50,8 @@ pub trait WSClientHttpSender: Send + Sync {
   async fn send_ws_msg(&self, device_id: &str, message: Message) -> Result<(), WSError>;
 }
 
-type ChannelByObjectId = HashMap<String, Weak<WebSocketChannel<CollabMessage>>>;
+type WeakChannel = Weak<WebSocketChannel<CollabMessage>>;
+type ChannelByObjectId = HashMap<String, Vec<WeakChannel>>;
 pub type WSConnectStateReceiver = Receiver<ConnectState>;
 
 pub struct WSClient {
@@ -167,30 +168,21 @@ impl WSClient {
                   RealtimeMessage::Collab(collab_msg) => {
                     if let Some(collab_channels) = weak_collab_channels.upgrade() {
                       let object_id = collab_msg.object_id().to_owned();
-                      let is_channel_dropped =
-                        if let Some(channel) = collab_channels.read().get(&object_id) {
+
+                      // Iterate all channels and send the message to them.
+                      if let Some(channels) = collab_channels.read().get(&object_id) {
+                        for channel in channels.iter() {
                           match channel.upgrade() {
                             None => {
                               // when calling [WSClient::subscribe], the caller is responsible for keeping
                               // the channel alive as long as it wants to receive messages from the websocket.
                               warn!("channel is dropped");
-                              true
                             },
                             Some(channel) => {
                               trace!("receive remote message: {}", collab_msg);
-                              channel.forward_to_stream(collab_msg);
-                              false
+                              channel.forward_to_stream(collab_msg.clone());
                             },
                           }
-                        } else {
-                          false
-                        };
-
-                      // Try to remove the channel if it is dropped. If failed, will try again next time.
-                      if is_channel_dropped {
-                        if let Some(mut w) = collab_channels.try_write() {
-                          trace!("remove channel: {}", object_id);
-                          let _ = w.remove(&object_id);
                         }
                       }
                     } else {
@@ -267,10 +259,18 @@ impl WSClient {
     object_id: String,
   ) -> Result<Arc<WebSocketChannel<CollabMessage>>, WSError> {
     let channel = Arc::new(WebSocketChannel::new(&object_id, self.sender.clone()));
-    self
-      .collab_channels
-      .write()
-      .insert(object_id, Arc::downgrade(&channel));
+    let mut collab_channels_guard = self.collab_channels.write();
+
+    // remove the dropped channels
+    if let Some(channels) = collab_channels_guard.get_mut(&object_id) {
+      channels.retain(|channel| channel.upgrade().is_some());
+    }
+
+    collab_channels_guard
+      .entry(object_id)
+      .or_default()
+      .push(Arc::downgrade(&channel));
+
     Ok(channel)
   }
 
diff --git a/libs/realtime-entity/src/collab_msg.rs b/libs/realtime-entity/src/collab_msg.rs
index 4a4190ee..305fd9f3 100644
--- a/libs/realtime-entity/src/collab_msg.rs
+++ b/libs/realtime-entity/src/collab_msg.rs
@@ -299,8 +299,8 @@ impl From<ServerInit> for CollabMessage {
 impl Display for ServerInit {
   fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
     f.write_fmt(format_args!(
-      "server init: [uid:{:?}|oid:{}|msg_id:{:?}|len:{}]",
-      self.origin.client_user_id(),
+      "server init: [origin:{}|oid:{}|msg_id:{:?}|len:{}]",
+      self.origin,
       self.object_id,
       self.msg_id,
       self.payload.len(),
@@ -372,8 +372,8 @@ impl From<UpdateSync> for CollabMessage {
 impl Display for UpdateSync {
   fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
     f.write_fmt(format_args!(
-      "client update sync: [uid:{:?}|oid:{}|msg_id:{:?}|len:{}]",
-      self.origin.client_user_id(),
+      "client update sync: [origin:{}|oid:{}|msg_id:{:?}|len:{}]",
+      self.origin,
       self.object_id,
       self.msg_id,
       self.payload.len(),
@@ -424,8 +424,8 @@ impl From<CollabAck> for CollabMessage {
 impl Display for CollabAck {
   fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
     f.write_fmt(format_args!(
-      "ack: [uid:{:?}|oid:{}|msg_id:{:?}|{}|len:{}]",
-      self.origin.client_user_id(),
+      "ack: [origin:{}|oid:{}|msg_id:{:?}|{}|len:{}]",
+      self.origin,
       self.object_id,
       self.source.msg_id,
       self.source.sync_verbose,
diff --git a/libs/realtime/src/collaborate/retry.rs b/libs/realtime/src/collaborate/retry.rs
index 76469aed..ef5c7649 100644
--- a/libs/realtime/src/collaborate/retry.rs
+++ b/libs/realtime/src/collaborate/retry.rs
@@ -248,7 +248,7 @@ where
                 .read()
                 .await
                 .values()
-                .map(|value| value.origin.client_user_id())
+                .map(|value| value.origin.to_string())
                 .collect::<Vec<_>>(),
             );
           }
diff --git a/libs/realtime/src/collaborate/server.rs b/libs/realtime/src/collaborate/server.rs
index 86fff3d1..fe8e177a 100644
--- a/libs/realtime/src/collaborate/server.rs
+++ b/libs/realtime/src/collaborate/server.rs
@@ -16,7 +16,7 @@ use tokio::time::interval;
 
 use tokio_stream::wrappers::{BroadcastStream, ReceiverStream};
 use tokio_stream::StreamExt;
-use tracing::{error, info, trace};
+use tracing::{error, event, info, instrument, trace};
 
 use crate::client::ClientWSSink;
 use crate::collaborate::group::CollabGroupCache;
@@ -228,6 +228,7 @@ async fn broadcast_message<U>(
 }
 
 /// Remove the user from the group and remove the group from the cache if the group is empty.
+#[instrument(level = "debug", skip_all)]
 async fn remove_user_from_group<S, U, AC>(
   user: &U,
   groups: &Arc<CollabGroupCache<S, U, AC>>,
@@ -237,15 +238,33 @@ async fn remove_user_from_group<S, U, AC>(
   U: RealtimeUser,
   AC: CollabAccessControl,
 {
+  groups.remove_user(&editing.object_id, user).await;
   if let Some(group) = groups.get_group(&editing.object_id).await {
-    info!("Remove subscriber: {}", editing.origin);
-    group.subscribers.write().await.remove(user);
+    event!(
+      tracing::Level::INFO,
+      "Remove group subscriber: {}",
+      editing.origin
+    );
+
+    event!(
+      tracing::Level::DEBUG,
+      "{}: Group member: {}. member ids: {:?}",
+      &editing.object_id,
+      group.subscribers.read().await.len(),
+      group
+        .subscribers
+        .read()
+        .await
+        .values()
+        .map(|value| value.origin.to_string())
+        .collect::<Vec<_>>(),
+    );
 
     // Destroy the group if the group is empty
     let should_remove = group.is_empty().await;
     if should_remove {
       group.flush_collab();
-      info!("Remove group: {}", editing.object_id);
+      event!(tracing::Level::INFO, "Remove group: {}", editing.object_id);
       groups.remove_group(&editing.object_id).await;
     }
   }
diff --git a/src/biz/collab/access_control.rs b/src/biz/collab/access_control.rs
index b28a494b..c4342f82 100644
--- a/src/biz/collab/access_control.rs
+++ b/src/biz/collab/access_control.rs
@@ -79,7 +79,7 @@ impl CollabAccessControlImpl {
     }
   }
 
-  #[inline]
+  #[instrument(level = "trace", skip(self), err)]
   async fn get_user_collab_access_level(
     &self,
     uid: &i64,
@@ -314,7 +314,7 @@ where
   CollabAC: CollabAccessControl,
   WorkspaceAC: WorkspaceAccessControl,
 {
-  #[instrument(level = "trace", skip_all, err)]
+  #[instrument(level = "trace", skip(self), err)]
   async fn get_collab_access_level(&self, uid: &i64, oid: &str) -> Result<AFAccessLevel, AppError> {
     self
       .collab_access_control