http.ClientRequest ignores incomplete chunked http response

[bjarketrux]

When fetching a file via http with header Transfer-Encoding: chunked a prematurely disrupted connection (socket) is not handled properly.

According to the MDN a chunked response is terminated by a 0-length chunk at the end.

Example code

var http = require("http");

const server = http.createServer((req, res) => {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.write("chunk-1");

    setTimeout(() => res.write("chunk-2"), 2000);
    setTimeout(() => res.socket.destroy(), 4000);
    // Normally the response would look like this
    // setTimeout(() => res.write("chunk-3"), 4000);
    // setTimeout(() => res.end(), 6000);
});

server.listen(8000);

var req = http.get("http://localhost:8000", res => {
    console.log("Status code:", res.statusCode);

    res.on("data", data => {
        console.log("Received chunk:", data.toString());
    });

    res.on("end", () => console.log("Ended"));
});

req.on("error", error => {
    console.log("Request error:", error);
});

Observed behavior

Executing the example code will output:

Status code: 200
Received chunk: chunk-1
Received chunk: chunk-2
Ended

Expected behavior

I would expect the following output:

Status code: 200
Received chunk: chunk-1
Received chunk: chunk-2
Request error: ERR_INCOMPLETE_CHUNKED_ENCODING

Note: The code ERR_INCOMPLETE_CHUNKED_ENCODING is what Chrome will write when navigating to http://localhost:8000, but I imagine node.js will have another code.

Note 2: Data is not called with the 0-size termination message.

Alternative behavior:
The end event is called with an error or message saying that the underlying socket was closed but the chunked message was not terminated.

If the observed behavior is expected, what can I do to detect an incomplete message? Note that I want to pipe the response into a file so I will not implement the on('data') handler.

• Version: v8.12.0
• Platform: MacOS Mojave 10.14.2

[akshayarise]

@bjarketrux

According to MDN

At the beginning of each chunk you need to explicitly add the length of the current chunk in hexadecimal format, followed by '\r\n' and then the chunk itself, followed by another '\r\n'. The terminating chunk is a regular chunk, with the exception that its length is zero. It is followed by the trailer, which consists of a (possibly empty) sequence of entity header fields.

[bjarketrux]

@akshayarise
The message send from the server already has this format. The problem is detecting (from the client) if all chunks has been received or if the underlying socket was closed prematurely.

[bjarketrux]

Any update?

[lpinca]

@bjarketrux you can use https://nodejs.org/api/http.html#http_message_complete

res.on('end', function() {
  console.log(this.complete);
})

[bjarketrux]

@lpinca If you look at the observed and expected behavior sections in the original post you can see that I already use the 'end' event but this is not the issue.

This issue is that I cannot distinguish between a normal stream and an abrupted connection which is exactly what I want.

[lpinca]

I can't see where message.complete is used in your example code. When the 'end' event is emitted you can check the complete attribute. This allows you to know if the response is complete (whether or not all chunks have been received).

[bjarketrux]

Whoops, I should have read the answer instead of complaining about you not reading the question :-D

Works absolutely! 🥇