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[api] Limit Nagle batching for log messages to reduce LWIP buffer pressure (#13439)

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This commit is contained in:
J. Nick Koston
2026-01-22 08:09:14 -10:00
committed by GitHub
parent 4ac7fe84b4
commit ddb762f8f5
2 changed files with 46 additions and 40 deletions
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esphome/components/api/api_connection.cpp
+2 -17
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@@ -1844,23 +1844,8 @@ bool APIConnection::send_buffer(ProtoWriteBuffer buffer, uint8_t message_type) {
return false;
}
// Toggle Nagle's algorithm based on message type to prevent log messages from
// filling the TCP send buffer and crowding out important state updates.
//
// This honors the `no_delay` proto option - SubscribeLogsResponse is the only
// message with `option (no_delay) = false;` in api.proto, indicating it should
// allow Nagle coalescing. This option existed since 2019 but was never implemented.
//
// - Log messages: Enable Nagle (NODELAY=false) so small log packets coalesce
// into fewer, larger packets. They flush naturally via TCP delayed ACK timer
// (~200ms), buffer filling, or when a state update triggers a flush.
//
// - All other messages (state updates, responses): Disable Nagle (NODELAY=true)
// for immediate delivery. These are time-sensitive and should not be delayed.
//
// This must be done proactively BEFORE the buffer fills up - checking buffer
// state here would be too late since we'd already be in a degraded state.
this->helper_->set_nodelay(!is_log_message);
// Set TCP_NODELAY based on message type - see set_nodelay_for_message() for details
this->helper_->set_nodelay_for_message(is_log_message);
APIError err = this->helper_->write_protobuf_packet(message_type, buffer);
if (err == APIError::WOULD_BLOCK)