Incompatibility with selenium-stealth library in multiprocessing on Linux

[raye22]

🐛 Bug Report: Linux-specific incompatibility with selenium-stealth

Summary

When using undetected_chromedriver together with the selenium-stealth library in multiprocessing on Linux, Chrome instances crash with ProtocolError. The exact same code works perfectly on macOS, indicating a Linux-specific issue in how these libraries interact.

macOS: uc + selenium-stealth + multiprocessing = ✅ WORKS
Linux: uc + selenium-stealth + multiprocessing = ❌ CRASHES

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Environment

Working Environment (macOS):

• OS: macOS (Darwin)
• Python: 3.10
• Chrome: 141.0.7390.107
• undetected-chromedriver: 3.5.x
• selenium-stealth: 1.0.6
• Result: ✅ 8 concurrent instances work perfectly

Failing Environment (Linux Server):

• OS: Ubuntu 22.04 LTS (Linux kernel 5.15.0)
• Python: 3.10
• Chrome: 141.0.7390.107
• undetected-chromedriver: 3.5.x (same version)
• selenium-stealth: 1.0.6 (same version)
• Result: ❌ First instance crashes when second starts

System Resources (Not Limited):

• File descriptors: 1,048,576
• Shared memory: 246GB
• RAM: 491GB total
• CPUs: 64

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The Issue

This is a platform-specific incompatibility: the combination of undetected_chromedriver + selenium-stealth only fails on Linux.

Configuration	macOS	Linux
uc alone + multiprocessing	✅ Works	✅ Works
uc + selenium-stealth + single process	✅ Works	✅ Works
uc + selenium-stealth + multiprocessing	✅ WORKS	❌ CRASHES

Since the exact code works on macOS, this suggests platform-specific differences in how undetected_chromedriver patches Chrome on Linux vs macOS, which conflicts with selenium-stealth's patches.

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Code to Reproduce (Fails on Linux, Works on macOS)

import multiprocessing as mp
import os
import time
from selenium.webdriver.chrome.options import Options
import undetected_chromedriver as uc
from selenium_stealth import stealth

def worker(worker_id):
    print(f"[Worker-{worker_id}] Starting (PID: {os.getpid()})")
    
    try:
        opts = Options()
        opts.binary_location = "/usr/bin/google-chrome-stable"  # Linux path
        opts.add_argument("--headless=new")
        opts.add_argument(f"--user-data-dir=/tmp/uc_test_{os.getpid()}")
        opts.add_argument("--no-sandbox")
        opts.add_argument("--disable-dev-shm-usage")
        opts.add_argument(f"--remote-debugging-port={9222 + worker_id}")
        
        driver = uc.Chrome(options=opts, version_main=None)
        
        # Adding selenium-stealth causes crashes on Linux only
        stealth(
            driver,
            languages=["en-US", "en"],
            vendor="Apple Computer, Inc.",
            platform="MacIntel",
            webgl_vendor="Apple Inc.",
        )
        
        driver.get("https://www.google.com")
        print(f"[Worker-{worker_id}] ✓ Success: {driver.title}")
        driver.quit()
        
    except Exception as e:
        print(f"[Worker-{worker_id}] ✗ FAILED: {e}")
        import traceback
        traceback.print_exc()

if __name__ == "__main__":
    mp.set_start_method('spawn', force=True)
    
    p1 = mp.Process(target=worker, args=(1,))
    p2 = mp.Process(target=worker, args=(2,))
    
    p1.start()
    time.sleep(2)
    p2.start()
    
    p1.join()
    p2.join()

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Expected Behavior

Both workers should succeed on both macOS and Linux.

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Actual Behavior

On macOS: ✅ Both workers succeed

On Linux: ❌ First worker crashes

[Worker-1] Starting
[Worker-1] Creating Chrome driver...
[Worker-1] Loading page...
[Worker-2] Starting
[Worker-2] Creating Chrome driver...
[Worker-2] Loading page...
[Worker-1] ✗ FAILED: ProtocolError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))
[Worker-2] ✓ Success: Google

Why selenium-stealth is Needed

Without selenium-stealth, undetected_chromedriver alone works in multiprocessing on Linux, but fails bot detection (all requests timeout at verification challenges). The stealth library is necessary for production use.

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Things Tested (All Failed on Linux)

1. ✅ Different --user-data-dir per instance
2. ✅ Different --remote-debugging-port per instance
3. ✅ Both fork and spawn modes
4. ✅ 60+ second delays between workers
5. ✅ Various Chrome flags
6. ✅ Running as separate processes (not multiprocessing)
7. ✅ Proxies per worker
8. ✅ Verified resource limits are very high

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Impact

This severely limits scalability for Linux production environments:

• AWS/GCP/Azure (all primarily Linux)
• Docker containers (Linux-based)
• Most web scraping servers (Linux)

Many developers test on macOS (works fine) then deploy to Linux (silent failure).

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Request

Could the maintainers:

1. Investigate why the patching mechanism works differently on Linux vs macOS?
2. Test the reproduction code on Linux to verify?
3. Either:
   • Fix the Linux compatibility, or
   • Document the incompatibility clearly

Suggested documentation:

## 🐧 Linux-Specific Issues

**selenium-stealth compatibility:** When using `selenium-stealth` with 
undetected_chromedriver in multiprocessing on Linux, instances may crash.
This works fine on macOS. 

Thank you for this amazing library! Happy to provide additional debugging information or test patches on Linux.

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