5 Mistakes That Make LLM Streaming Break on a Flaky Network
Your chat UI looks fine on the office Wi-Fi. Then someone joins from a train, the SSE connection drops mid-sentence, and either the answer restarts from scratch or the model keeps burning tokens while nobody is listening. Same feature, different network. I spent a stretch of time turning a "works in demos" stream into something that survives reconnects. The full working project (ASP.NET Core 10,…
The article titled "5 Mistakes That Make LLM Streaming Break on a Flaky Network" outlines common issues that arise when implementing live language model streaming over unreliable networks. Five key mistakes are identified and explained:
1. Tying generation to the HTTP request - Generating responses should be separated from the HTTP request. Starting generation in a registry and returning a 202 response with a stream ID allows generation to continue even if the subscriber disconnects. This prevents wasted computation when the connection is lost and the model restarts.
2. Lack of sequence IDs - Without unique sequence IDs, reconnecting causes the client to restart the entire generation process. Including an append-only stream log with sequence numbers enables clients to replay only the missed events after reconnecting.
3. Naming error events - Using "error" as an event name can cause confusion with the default EventSource error handler. The article recommends using a distinct "failed" event name with a user-friendly error message and an errorId for debugging.
4. Silent streams and lack of a stop button - Proxies and load balancers can leave SSE connections idle, leading to disconnections. Implementing heartbeats while work is in progress and providing a cancellation endpoint allows users to cancel the model generation and prevents unnecessary token usage.
5. Incomplete API implementation - The "quick stream" implementation provided is not suitable for production. The article lists several additional features and best practices for a robust streaming API, including sequence IDs, cancellation, heartbeats, owner authentication, sticky sessions, and the use of HTTP/2 or HTTP/3.
The article emphasizes that flaky networks are not an edge case and recommends implementing a complete resumable streaming solution before considering a project complete. The author provides the complete source code and detailed implementation in a separate package available to subscribers.
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