fix websocket subscription performance issue

rpc/src/module/subscription.rs

@@ -1,13 +1,17 @@
 use async_trait::async_trait;
+use broadcast::error::RecvError;
 use ckb_async_runtime::Handle;
 use ckb_jsonrpc_types::Topic;
+use ckb_logger::error;
 use ckb_notify::NotifyController;
 use ckb_stop_handler::new_tokio_exit_rx;
 use futures_util::{stream::BoxStream, Stream};
 use jsonrpc_core::Result;
 use jsonrpc_utils::{pub_sub::PublishMsg, rpc};
 use tokio::sync::broadcast;
 
+const NOTIFY_CHANNEL_SIZE: usize = 128;
+
 /// RPC Module Subscription that CKB node will push new messages to subscribers, support with WebSocket or TCP.
 ///
 /// RPC subscriptions require a full duplex connection. CKB offers such connections in the form of
@@ -211,9 +215,19 @@ impl SubscriptionRpc for SubscriptionRpcImpl {
         };
         let mut rx = tx.subscribe();
         Ok(Box::pin(async_stream::stream! {
-               while let Ok(msg) = rx.recv().await {
-                    yield msg;
-               }
+                loop {
+                    match rx.recv().await {
+                        Ok(msg) => {
+                            yield msg;
+                        }
+                        Err(RecvError::Lagged(cnt)) => {
+                            error!("subscription lagged error: {:?}", cnt);
+                        }
+                        Err(RecvError::Closed) => {
+                            break;
+                        }
+                    }
+                }
         }))
     }
 }
@@ -232,11 +246,11 @@ impl SubscriptionRpcImpl {
         let mut reject_transaction_receiver = handle
             .block_on(notify_controller.subscribe_reject_transaction(SUBSCRIBER_NAME.to_string()));
 
-        let (new_tip_header_sender, _) = broadcast::channel(10);
-        let (new_tip_block_sender, _) = broadcast::channel(10);
-        let (proposed_transaction_sender, _) = broadcast::channel(10);
-        let (new_transaction_sender, _) = broadcast::channel(10);
-        let (new_reject_transaction_sender, _) = broadcast::channel(10);
+        let (new_tip_header_sender, _) = broadcast::channel(NOTIFY_CHANNEL_SIZE);
+        let (new_tip_block_sender, _) = broadcast::channel(NOTIFY_CHANNEL_SIZE);
+        let (proposed_transaction_sender, _) = broadcast::channel(NOTIFY_CHANNEL_SIZE);
+        let (new_transaction_sender, _) = broadcast::channel(NOTIFY_CHANNEL_SIZE);
+        let (new_reject_transaction_sender, _) = broadcast::channel(NOTIFY_CHANNEL_SIZE);
 
         let stop_rx = new_tokio_exit_rx();
         handle.spawn({
@@ -266,7 +280,10 @@ impl SubscriptionRpcImpl {
                         _ = stop_rx.cancelled() => {
                             break;
                         },
-                        else => break,
+                        else => {
+                            error!("SubscriptionRpcImpl tokio::select! unexpected error");
+                            break;
+                        }
                     }
                 }
             }