Significant Slowdown in Requests When Using ProxyAgent

[hamdallah90]

Hello,

I'm experiencing a significant slowdown in request performance when using ProxyAgent with the undici library. The same requests without a proxy are much faster. Below are the details of my setup and the observed behavior.

Steps to Reproduce:

1. Set up a basic HTTP client using undici:

import {
  Client,
  Dispatcher,
  request,
  ProxyAgent,
  getGlobalDispatcher,
} from "undici";
import { Readable, Writable } from "stream";
import { IncomingHttpHeaders } from "undici/types/header";
import { createGunzip } from "zlib";
import { promisify } from "util";
import { Buffer } from "buffer";

const pipeline = promisify(require("stream").pipeline);

export class HttpClient {
  private baseURL: string;
  private defaultHeaders: Record<string, string> = {};
  private proxy: string | undefined;
  private timeout: number = 30000;
  private dispatcher: Dispatcher;

  constructor(baseURL: string, proxyneeded: boolean = true, timeout?: number) {
    this.baseURL = baseURL;

    if (timeout) {
      this.timeout = timeout;
    }

    if (proxyneeded) {
      this.proxy = "http://127.0.0.1:3128";
      this.dispatcher = new ProxyAgent(this.proxy);
    } else {
      this.dispatcher = getGlobalDispatcher();
    }
  }

  public get<T = any>(
    url: string,
    config?: RequestInit & { params?: Record<string, any> }
  ): Promise<T> {
    return this.request<T>({
      ...config,
      method: "GET",
      path: this.buildUrl(url, config?.params),
    });
  }

  public post<T = any>(
    url: string,
    data?: any,
    config?: RequestInit
  ): Promise<T> {
    return this.request<T>({
      ...config,
      method: "POST",
      path: url,
      body: data,
    });
  }

  public put<T = any>(
    url: string,
    data?: any,
    config?: RequestInit
  ): Promise<T> {
    return this.request<T>({ ...config, method: "PUT", path: url, body: data });
  }

  public delete<T = any>(
    url: string,
    config?: RequestInit & { params?: Record<string, any> }
  ): Promise<T> {
    return this.request<T>({
      ...config,
      method: "DELETE",
      path: this.buildUrl(url, config?.params),
    });
  }

  public request<T = any>(
    config: RequestInit & { path: string }
  ): Promise<T> {
    const { method, path, body, headers } = config;

    if (!method) {
      return Promise.reject(new Error("HTTP method is required"));
    }

    const url = !path.startsWith("/") ? `/${path}` : path;

    return request(this.baseURL + url, {
      method: method as Dispatcher.HttpMethod,
      body: body ? JSON.stringify(body) : undefined,
      headers: {
        ...this.defaultHeaders,
        ...headers,
      } as
        | IncomingHttpHeaders
        | string[]
        | Iterable<[string, string | string[] | undefined]>
        | null,
      headersTimeout: this.timeout,
      dispatcher: this.dispatcher,
    } as any)
      .then(({ statusCode, headers, trailers, body }: any) => {
        return this.getResponseBody(headers, body);
      })
      .then(responseContent => {
        return { data: responseContent } as T;
      });
  }

  public setHeader(name: string, value: string): void {
    this.defaultHeaders[name] = value;
  }

  public removeHeader(name: string): void {
    delete this.defaultHeaders[name];
  }

  private buildUrl(url: string, params?: Record<string, any>): string {
    if (!params) {
      return url;
    }

    const urlObj = new URL(url, this.baseURL);
    Object.keys(params).forEach((key) =>
      urlObj.searchParams.append(key, params[key])
    );
    return urlObj.toString();
  }

  private getResponseBody(
    headers: IncomingHttpHeaders,
    response: Dispatcher.BodyMixin
  ): Promise<any> {
    const buffers: Uint8Array[] = [];
    return new Promise((resolve, reject) => {
      (async () => {
        try {
          for await (const chunk of response as any) {
            buffers.push(chunk);
          }
          const buffer = Buffer.concat(buffers);

          if (headers["content-encoding"] === "gzip") {
            this.decompressGzip(buffer).then(resolve).catch(reject);
          } else {
            resolve(this.parseResponse(buffer));
          }
        } catch (err) {
          reject(err);
        }
      })();
    });
  }

  private decompressGzip(buffer: Buffer): Promise<any> {
    const gunzip = createGunzip();
    const decompressedBuffers: Buffer[] = [];
    return new Promise((resolve, reject) => {
      pipeline(
        Readable.from([buffer]),
        gunzip,
        new Writable({
          write(chunk, encoding, callback) {
            decompressedBuffers.push(chunk);
            callback();
          },
        })
      )
        .then(() => {
          const decompressed = Buffer.concat(decompressedBuffers);
          resolve(this.parseResponse(decompressed));
        })
        .catch(reject);
    });
  }

  private parseResponse(buffer: Buffer): any {
    const responseText = buffer.toString();
    try {
      return JSON.parse(responseText);
    } catch {
      return responseText;
    }
  }
}

3. Compare the response time when using ProxyAgent versus without using any proxy.

Thank you for your attention to this issue. Any insights or fixes would be greatly appreciated.

Best regards,

[metcoder95]

👋
Can you provide an
Minimum Reproducible Example with plain JS to support you better?

[hamdallah90]

node httpClientExample.mjs

Making 100 requests without Proxy...
Total time without Proxy: 10058.17 ms
Average time without Proxy: 100.57 ms

Making 100 requests with Proxy...
Total time with Proxy: 45844.97 ms
Average time with Proxy: 458.43 ms

this is the code

import { request, ProxyAgent, getGlobalDispatcher } from "undici";
import { createGunzip } from "zlib";
import { pipeline, Readable, Writable } from "stream";
import { promisify } from "util";
import { Buffer } from "buffer";

const pipelinePromise = promisify(pipeline);


const baseURL = "https://jsonplaceholder.typicode.com";
const proxyURL = "http://127.0.0.1:3128"; // Change this to your actual proxy URL
const timeout = 30000;
const numberOfRequests = 100;

async function fetchWithUndici(url, useProxy = false) {
  const dispatcher = useProxy ? new ProxyAgent(proxyURL) : getGlobalDispatcher();

  const { statusCode, headers, body } = await request(`${baseURL}${url}`, {
    method: 'GET',
    dispatcher,
    headersTimeout: timeout
  });

  const responseBody = await getResponseBody(headers, body);
  return { statusCode, headers, responseBody };
}

async function getResponseBody(headers, body) {
  const buffers = [];
  for await (const chunk of body) {
    buffers.push(chunk);
  }
  const buffer = Buffer.concat(buffers);

  if (headers['content-encoding'] === 'gzip') {
    return decompressGzip(buffer);
  }
  return parseResponse(buffer);
}

function decompressGzip(buffer) {
  const gunzip = createGunzip();
  const decompressedBuffers = [];

  return new Promise((resolve, reject) => {
    pipelinePromise(
      Readable.from([buffer]),
      gunzip,
      new Writable({
        write(chunk, encoding, callback) {
          decompressedBuffers.push(chunk);
          callback();
        }
      })
    )
      .then(() => {
        const decompressed = Buffer.concat(decompressedBuffers);
        resolve(parseResponse(decompressed));
      })
      .catch(reject);
  });
}

function parseResponse(buffer) {
  const responseText = buffer.toString();
  try {
    return JSON.parse(responseText);
  } catch {
    return responseText;
  }
}

async function measureRequests(useProxy) {
  const times = [];
  const startTotal = process.hrtime();

  for (let i = 0; i < numberOfRequests; i++) {
    const start = process.hrtime();
    await fetchWithUndici("/posts/1", useProxy);
    const end = process.hrtime(start);
    const timeInMs = end[0] * 1000 + end[1] / 1e6;
    times.push(timeInMs);
  }

  const endTotal = process.hrtime(startTotal);
  const totalTime = endTotal[0] * 1000 + endTotal[1] / 1e6;
  const averageTime = times.reduce((a, b) => a + b, 0) / times.length;

  return { totalTime, averageTime };
}

(async () => {
  console.log(`Making ${numberOfRequests} requests without Proxy...`);
  const { totalTime: totalTimeWithoutProxy, averageTime: averageTimeWithoutProxy } = await measureRequests(false);
  console.log(`Total time without Proxy: ${totalTimeWithoutProxy.toFixed(2)} ms`);
  console.log(`Average time without Proxy: ${averageTimeWithoutProxy.toFixed(2)} ms`);

  console.log(`Making ${numberOfRequests} requests with Proxy...`);
  const { totalTime: totalTimeWithProxy, averageTime: averageTimeWithProxy } = await measureRequests(true);
  console.log(`Total time with Proxy: ${totalTimeWithProxy.toFixed(2)} ms`);
  console.log(`Average time with Proxy: ${averageTimeWithProxy.toFixed(2)} ms`);
})();

[hamdallah90]

this is when using axios

node httpClientExample.mjs

Making 100 requests without Proxy...
Total time without Proxy: 10229.93 ms
Average time without Proxy: 102.29 ms

Making 100 requests with Proxy...
Total time with Proxy: 20142.50 ms
Average time with Proxy: 201.41 ms

---

This is when using axios with Promise.all

node httpClientExample.mjs
Making 100 requests without Proxy...
Total time without Proxy: 535.43 ms
Average time without Proxy: 407.45 ms
Making 100 requests with Proxy...
Total time with Proxy: 628.32 ms
Average time with Proxy: 428.96 ms

---

This is when using undici with Promise.all

❯ node httpClientExample.mjs
Making 100 requests without Proxy...
Total time without Proxy: 499.42 ms
Average time without Proxy: 373.25 ms
Making 100 requests with Proxy...
Total time with Proxy: 16655.35 ms
Average time with Proxy: 7610.46 ms

[mcollina]

Looks like there is a bug somewhere, good spot!

What would be good is to have a complete way to reproduce your problem. I recommend you to create a repository and include everything, so we can reproduce this benchmark locally.

(yes, it should include a target server and the proxy).