How do I limit the bandwidth of a HTTP request in Node?

Question

I am trying to limit the bandwidth (download / upload speed) that a HTTP request uses. I'm using the NPM package stream-throttle. I created a custom HTTP agent to pipe the socket through an instance of Throttle and have timed the speed at which a 5MB file downloads.

const http = require("http");
const net = require("net");
const {Throttle, ThrottleGroup} = require("stream-throttle");

const maxBandwidth = 100;
// an example 5MB file of random data
const str = "http://212.183.159.230/5MB.zip";


// this pipes an instance of Throttle
class SlowAgent extends http.Agent {
    createConnection(options, callback){
        const socket = new net.Socket(options);
        socket.pipe(new Throttle({rate: maxBandwidth}));
        socket.connect(options);
        return socket;
    }
}

const options = {
    // this should slow down the request
    agent: new SlowAgent()
};

const time = Date.now();
const req = http.request(str, options, (res) => {
    res.on("data", () => {
    });
    res.on('end', () => {
        console.log("Done! Elapsed time: " + (Date.now() - time) + "ms");
    });
});

req.on('error', (e) => {
    console.error(`problem with request: ${e.message}`);
});

req.on("end", () => {
    console.log("done");
});

console.log("Request started");
req.end();

Regardless of the value of maxBandwidth or whether SlowAgent is used at all (I have tried commenting out agent: new SlowAgent()), I notice no difference in the elapsed time (about 4000 milliseconds). How can I fix my SlowAgent class? Do I not understand socket.pipe? Or is there something else I need to do?

freakish pointed out to change SlowAgent to be this:

// this pipes an instance of Throttle
class SlowAgent extends http.Agent {
    createConnection(options, callback){
        const socket = new net.Socket(options);
        socket.connect(options);
        return socket.pipe(new Throttle({rate: 10}));
    }
}

but that causes this problem:

problem with request: Parse Error: Expected HTTP/ Error: Parse Error: Expected HTTP/
    at Throttle.socketOnData (_http_client.js:456:22)
    at Throttle.emit (events.js:209:13)
    at addChunk (_stream_readable.js:305:12)
    at readableAddChunk (_stream_readable.js:286:11)
    at Throttle.Readable.push (_stream_readable.js:220:10)
    at Throttle.Transform.push (_stream_transform.js:150:32)
    at /home/max/Documents/Personal/node-projects/proxy/node_modules/stream-throttle/src/throttle.js:37:14
    at processTicksAndRejections (internal/process/task_queues.js:75:11) {
  bytesParsed: 0,
  code: 'HPE_INVALID_CONSTANT',
  reason: 'Expected HTTP/',
  rawPacket: <Buffer 47>
}

Answer 1

我设法通过取消自定义agent并使用createConnection内部http.request选项来使其工作：

const options = {
    createConnection(options) {
        const socket = new net.Socket();
        return socket.connect({host: options.host, port: options.port});
    },
    hostname: "212.183.159.230",
    path: "/5MB.zip"
};

const time = Date.now();

const req = http.request(options, (res) => {

    res.pipe(new Throttle({rate: 200 * 1024}))
        .on("data", (chunk) => {
            console.log(chunk.length);
        })

    res.on("end", () => {
        console.log("Done! Elapsed time: " + (Date.now() - time) + "ms");
    });
});