refactor(grpc): bind TCP listener before etcd registration to prevent connection issues

- Change tokio-stream dependency to include net feature for TcpListenerStream
- Move TCP listener binding before etcd registry initialization in main function
- Pass pre-bound TcpListener to gRPC server instead of just SocketAddr
- Update gRPC server to use serve_with_incoming with TcpListenerStream
- Prevent peers from attempting connections before gRPC server is ready
- Ensure proper error handling for TCP binding failures during startup

Cargo.toml

@@ -49,7 +49,7 @@ tonic-prost = "0.14"
 tonic-health = "0.14.6"
 url = "2.5"
 etcd-client = { version = "0.18", features = ["tls"] }
-tokio-stream = "0.1"
+tokio-stream = { version = "0.1", features = ["net"] }
 async-nats = "0.49"
 futures-util = "0.3"
 utoipa = { version = "5", features = ["uuid","chrono","actix_extras","decimal","macros"]}

grpc/mod.rs

@@ -27,6 +27,7 @@ use crate::service::AppService;
 
 pub async fn start_grpc_server(
     addr: SocketAddr,
+    listener: tokio::net::TcpListener,
     service: AppService,
 ) -> Result<(), Box<dyn std::error::Error>> {
     let token_svc = auth::TokenGrpcService::new(service.internal_auth.clone());
@@ -60,7 +61,7 @@ pub async fn start_grpc_server(
         .add_service(VoiceServiceServer::new(cs.voice))
         .add_service(StageServiceServer::new(cs.stage))
         .add_service(ChannelAuditServiceServer::new(cs.channel_audit))
-        .serve(addr)
+        .serve_with_incoming(tokio_stream::wrappers::TcpListenerStream::new(listener))
         .await?;
 
     Ok(())

main.rs

@@ -37,6 +37,17 @@ async fn main() -> AppResult<()> {
     let cache = Arc::new(AppCache::from_config(&config).await?);
     let storage = AppS3Storage::from_config(&config).await?;
 
+    let rpc_host = config.get_env_or::<String>("APP_RPC_SELF_HOST", "0.0.0.0".to_string())?;
+    let rpc_port = config.get_env_or::<u16>("APP_RPC_SELF_PORT", 50050)?;
+    let rpc_addr: std::net::SocketAddr = format!("{rpc_host}:{rpc_port}").parse()
+        .map_err(|e| appks::error::AppError::Config(format!("invalid gRPC address: {e}")))?;
+
+    // Bind the TCP listener FIRST so the port is reserved before etcd registration.
+    // This prevents peers from trying to connect before the gRPC server is ready.
+    let rpc_listener = tokio::net::TcpListener::bind(rpc_addr)
+        .await
+        .map_err(|e| appks::error::AppError::Config(format!("gRPC bind failed on {rpc_addr}: {e}")))?;
+
     let registry = Arc::new(EtcdRegistry::connect(&config).await?);
     registry.start_discovery().await?;
     registry
@@ -57,13 +68,9 @@ async fn main() -> AppResult<()> {
     )
     .await;
 
-    let rpc_host = config.get_env_or::<String>("APP_RPC_SELF_HOST", "0.0.0.0".to_string())?;
-    let rpc_port = config.get_env_or::<u16>("APP_RPC_SELF_PORT", 50050)?;
-    let rpc_addr: std::net::SocketAddr = format!("{rpc_host}:{rpc_port}").parse()
-        .map_err(|e| appks::error::AppError::Config(format!("invalid gRPC address: {e}")))?;
     let grpc_service = service.clone();
     tokio::spawn(async move {
-        if let Err(e) = appks::grpc::start_grpc_server(rpc_addr, grpc_service).await {
+        if let Err(e) = appks::grpc::start_grpc_server(rpc_addr, rpc_listener, grpc_service).await {
             tracing::error!(error = %e, "gRPC server failed");
         }
     });