aws / aws/aws-lambda-nodejs-runtime-interface-client

HttpResponseStream doesn't work when `end`ing the stream without a `write`

Abierto
#97 1 comentario 2 reacciones 0 asignados Ver en GitHub
Lenguaje dominante
TypeScript
Estrellas
224
Forks
60
Métricas de merge de PR
Sin PR fusionados en 30 d

Descripción

When using `HttpResponseStream` to set the status code and headers on a streaming response, I noticed that if I never call `write` on the stream, the custom status code and headers don't work.

Example repro:

```js
export const handler = awslambda.streamifyResponse(
async (event, responseStream, context) => {
const metadata = {
statusCode: 404,
headers: { "Content-Type": "text/plain", "X-Foo": "Bar" }
};
responseStream = awslambda.HttpResponseStream.from(responseStream, metadata);
// This will cause a 502 with no custom response headers:
responseStream.end("Not Found");
// This will cause a 200 with no custom response headers:
responseStream.end();
}
);
```

I believe this is because `HttpResponseStream` relies on the `onBeforeFirstWrite` callback:

https://github.com/aws/aws-lambda-nodejs-runtime-interface-client/blob/7374a4e338fc3b070811d55ee337740f3f6cb382/src/HttpResponseStream.js#L22-L27

`onBeforeFirstWrite` is implemented by overriding http.ClientRequest stream's `write`:

```js
// https://github.com/aws/aws-lambda-base-images/tree/nodejs18.x -> /var/runtime/index.mjs
req.write = function(chunk, encoding, callback) {
vvverbose("ResponseStream::write", chunk.length, "callback:", typeof callback);
if (typeof chunk !== "string" && !Buffer.isBuffer(chunk) && chunk?.constructor !== Uint8Array) {
chunk = JSON.stringify(chunk);
}
if (status === STATUS_READY && typeof this._onBeforeFirstWrite === "function") {
this._onBeforeFirstWrite((ch) => origWrite(ch));
}
const ret = origWrite(chunk, encoding, callback);
// [snip]
```

But turns out Node's `ClientRequest` doesn't call `write` when `end`ing the stream with a final `chunk` of data, it calls an internal `write_` instead:

https://github.com/nodejs/node/blob/544cfc5ef151bca8d625fbccc581200a77b00bc0/lib/_http_outgoing.js#L1106

I guess this could also be considered a Node bug, because their documentation for [`ClientRequest.end`](https://nodejs.org/docs/latest/api/http.html#requestenddata-encoding-callback) says:

> If `data` is specified, it is equivalent to calling [`request.write(data, encoding)`](https://nodejs.org/docs/latest/api/http.html#requestwritechunk-encoding-callback) followed by `request.end(callback)`.

But even if it did implement that contract correctly, there's still the case of ending the stream with no data, i.e., `responseStream.end()`.

Guía de contribución

Abrir la guía de contribución

Evaluación

Este issue todavía no se ha evaluado.

Recibe los nuevos issues en tu correo

Un resumen breve de issues de GitHub para principiantes.