Fix slow noise handshake by reading multiple messages per loop (#9130)

esphome/components/api/api_connection.cpp

@@ -28,6 +28,12 @@
 namespace esphome {
 namespace api {
 
+// Read a maximum of 5 messages per loop iteration to prevent starving other components.
+// This is a balance between API responsiveness and allowing other components to run.
+// Since each message could contain multiple protobuf messages when using packet batching,
+// this limits the number of messages processed, not the number of TCP packets.
+static constexpr uint8_t MAX_MESSAGES_PER_LOOP = 5;
+
 static const char *const TAG = "api.connection";
 static const int ESP32_CAMERA_STOP_STREAM = 5000;
 
@@ -109,12 +115,16 @@ void APIConnection::loop() {
     return;
   }
 
+  const uint32_t now = App.get_loop_component_start_time();
   // Check if socket has data ready before attempting to read
   if (this->helper_->is_socket_ready()) {
+    // Read up to MAX_MESSAGES_PER_LOOP messages per loop to improve throughput
+    for (uint8_t message_count = 0; message_count < MAX_MESSAGES_PER_LOOP; message_count++) {
       ReadPacketBuffer buffer;
       err = this->helper_->read_packet(&buffer);
       if (err == APIError::WOULD_BLOCK) {
-      // pass
+        // No more data available
+        break;
       } else if (err != APIError::OK) {
         on_fatal_error();
         if (err == APIError::SOCKET_READ_FAILED && errno == ECONNRESET) {
@@ -127,7 +137,7 @@ void APIConnection::loop() {
         }
         return;
       } else {
-      this->last_traffic_ = App.get_loop_component_start_time();
+        this->last_traffic_ = now;
         // read a packet
         if (buffer.data_len > 0) {
           this->read_message(buffer.data_len, buffer.type, &buffer.container[buffer.data_offset]);
@@ -138,6 +148,7 @@ void APIConnection::loop() {
           return;
       }
     }
+  }
 
   // Process deferred batch if scheduled
   if (this->deferred_batch_.batch_scheduled &&
@@ -152,7 +163,6 @@ void APIConnection::loop() {
 
   static uint8_t max_ping_retries = 60;
   static uint16_t ping_retry_interval = 1000;
-  const uint32_t now = App.get_loop_component_start_time();
   if (this->sent_ping_) {
     // Disconnect if not responded within 2.5*keepalive
     if (now - this->last_traffic_ > (KEEPALIVE_TIMEOUT_MS * 5) / 2) {

esphome/components/api/api_frame_helper.cpp

@@ -274,12 +274,21 @@ APIError APINoiseFrameHelper::init() {
 }
 /// Run through handshake messages (if in that phase)
 APIError APINoiseFrameHelper::loop() {
+  // During handshake phase, process as many actions as possible until we can't progress
+  // socket_->ready() stays true until next main loop, but state_action() will return
+  // WOULD_BLOCK when no more data is available to read
+  while (state_ != State::DATA && this->socket_->ready()) {
     APIError err = state_action_();
     if (err != APIError::OK && err != APIError::WOULD_BLOCK) {
       return err;
     }
+    if (err == APIError::WOULD_BLOCK) {
+      break;
+    }
+  }
+
   if (!this->tx_buf_.empty()) {
-    err = try_send_tx_buf_();
+    APIError err = try_send_tx_buf_();
     if (err != APIError::OK && err != APIError::WOULD_BLOCK) {
       return err;
     }