refactor: 更优雅地处理客户端断开连接

改进对 WebSocket 客户端断开连接的处理，以防止日志中出现大量错误。

主要变更：
- 将关闭 channel 导致的发送失败日志级别从 error 降为 debug，因为客户端断开是正常操作。
- 在尝试发送消息（包括实时事件和历史事件）之前，主动检查客户端 channel 是否已关闭。
- 当检测到 channel 关闭时，及时终止发送任务，以确保资源被迅速清理并防止任务卡死。

src/nostr/messages.rs

@@ -1,5 +1,5 @@
 use crate::nostr::NostrEvent;
-use log::error;
+use log::{debug, error};
 use serde_json;
 use tokio::sync::mpsc;
 pub struct RelayMessage;
@@ -41,7 +41,8 @@ impl RelayMessage {
         match to_client_msg_tx.send(msg).await {
             Ok(_) => Ok(()),
             Err(e) => {
-                error!("Failed to send EVENT message (sub_id: {}): {}", sub_id, e);
+                // Channel closed 是正常的客户端断连，使用 debug 级别
+                debug!("Failed to send EVENT message (sub_id: {}): {}", sub_id, e);
                 Err(anyhow!(
                     "Failed to send EVENT message (sub_id: {}): {}",
                     sub_id,
@@ -57,7 +58,8 @@ impl RelayMessage {
         match to_client_msg_tx.send(msg).await {
             Ok(_) => Ok(()),
             Err(e) => {
-                error!("Failed to send EOSE message (sub_id: {}): {}", sub_id, e);
+                // Channel closed 是正常的客户端断连，使用 debug 级别
+                debug!("Failed to send EOSE message (sub_id: {}): {}", sub_id, e);
                 Err(anyhow!(
                     "Failed to send EOSE message (sub_id: {}): {}",
                     sub_id,
@@ -77,7 +79,8 @@ impl RelayMessage {
         match to_client_msg_tx.send(msg).await {
             Ok(_) => Ok(()),
             Err(e) => {
-                error!("Failed to send CLOSED message (sub_id: {}): {}", sub_id, e);
+                // Channel closed 是正常的客户端断连，使用 debug 级别
+                debug!("Failed to send CLOSED message (sub_id: {}): {}", sub_id, e);
                 Err(anyhow!(
                     "Failed to send CLOSED message (sub_id: {}): {}",
                     sub_id,
@@ -96,7 +99,8 @@ impl RelayMessage {
         match to_client_msg_tx.send(msg).await {
             Ok(_) => Ok(()),
             Err(e) => {
-                error!(
+                // Channel closed 是正常的客户端断连，使用 debug 级别
+                debug!(
                     "Failed to send NOTICE message (message: {}): {}",
                     message, e
                 );

src/ws_logic.rs

@@ -75,13 +75,21 @@ pub async fn handle_ws_connection(
                 Ok(event_msg) = event_rx.recv() => {
                     let event: NostrEvent = serde_json::from_str(&event_msg).unwrap(); // 假设广播的消息总是有效的 NostrEvent
                     let conn = client_conn_for_send.read().await;
+
+                    // 检查 channel 是否已关闭，如果关闭则立即退出
+                    if conn.sender.is_closed() {
+                        info!("Client {} channel closed, stopping send task", client_id);
+                        break;
+                    }
+
                     for (sub_id, subscription) in &conn.subscriptions {
                         if subscription.filters.iter().any(|filter| filter.matches(&event)) {
                             match RelayMessage::send_event(&event, sub_id, &conn.sender).await {
                                 Ok(()) => debug!("Sent event to client {}", client_id),
-                                Err(e) => {
-                                    error!("Failed to send event to client {}: {}", client_id, e);
-                                    break;
+                                Err(_) => {
+                                    // Channel 已关闭，立即退出整个循环
+                                    info!("Client {} channel closed during event send, stopping send task", client_id);
+                                    return;
                                 },
                             }
                         }
@@ -254,16 +262,29 @@ pub async fn handle_message(
                 );
             }
 
+            // 检查 channel 是否已关闭
+            if to_client_msg_tx.is_closed() {
+                debug!("Client channel closed before sending historical events for sub_id: {}", sub_id);
+                return Ok(());
+            }
+
             // 查询历史事件并发送
             for filter in &filters {
                 let events = filter.select(pool).await?; // 使用 FilterExt
                 for event in events {
+                    // 在发送每个事件前检查 channel 状态，避免大量失败尝试
+                    if to_client_msg_tx.is_closed() {
+                        debug!("Client channel closed during historical event sending for sub_id: {}", sub_id);
+                        return Ok(());
+                    }
                     RelayMessage::send_event(&event, &sub_id, to_client_msg_tx).await?;
                 }
             }
 
             // 发送 EOSE 消息，表示历史事件已发送完毕
-            RelayMessage::send_eose(&sub_id, to_client_msg_tx).await?;
+            if !to_client_msg_tx.is_closed() {
+                RelayMessage::send_eose(&sub_id, to_client_msg_tx).await?;
+            }
             Ok(())
         }