After battling with this problem for quite some time, we finally found a solution that worked for us. Hoping to share our success story here in case it can benefit others.

It turns out the root of our issue was memory-related. Our testing environment runs within a docker container, and we discovered that the default dev/shm size in Docker is only 64mb. Increasing this allocation solved the pesky "no such session" error for us.

We utilize docker compose for our setup, so we simply modified the docker-compose.yml file by adding shm_size: 256M to address the problem.

Recently, I came across a similar exception as well. Initially, it seemed to be unpredictable, but upon closer examination, I discovered that it occurs consistently when ChromeDriver.Close() is called before attempting to FindElement.

In my scenario, the ChromeDriver.Close() method was invoked in an exception handler of a previous test due to a timing issue. This issue only impacted the subsequent test, giving the impression that it was unreliable. However, thorough investigation confirmed its deterministic nature.

Based on my findings, this is how I encountered and resolved the error. It's possible that your situation may differ...

This particular error message...

WebDriverError: no session found
  (Details: chromedriver=a.b.c (36d3d07f660ff2bc1bf28a75d1cdabed0983e7c4),platform=Mac OS X 10.11.5 x86_64)

...suggests that the ChromeDriver encountered difficulties while communicating with the established Browsing Context, specifically the Chrome Browser session.

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We have thoroughly discussed and analyzed this issue in the ongoing conversation Issue 732: No such session error - inconsistent problem occurring during prolonged test runs. Typically, this error manifests after an extended period of running the Test Suite as shown below:

[0127/105308:ERROR:nacl_helper_linux.cc(289)] NaCl helper process is running without a sandbox!
Likely due to incorrect SUID sandbox configuration.
[489.849][INFO]: RESPONSE FindElements unknown error: session deleted because of page crash
from tab crashed
  (Session info: chrome=p.q.r.s)
[489.849][DEBUG]: Log type 'driver' lost 0 entries upon destruction
[489.849][DEBUG]: Log type 'browser' lost 9 entries upon destruction

The definition of this error can be found in nacl_helper_linux.cc:

// If Zygote has started handling requests, we should be sandboxed via
// the setuid sandbox.
if (!IsSandboxed()) {
  LOG(ERROR) << "NaCl helper process is running without a sandbox!\n"
    << "Most likely you need to configure your SUID sandbox "
    << "correctly";

The method FindElement(s) specifically FAILED due to a sandbox issue leading to a Page Crash caused by session deletion.

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Solution

This error could be triggered by various reasons, and potential solutions include:

• To resolve this error, initiate the Chrome session by configuring the ChromeDriver with the argument --disable-impl-side-painting
  • In addition, consider adding the argument --enable-gpu-rasterization which allows heuristics to determine when a layer tile should be drawn using the Skia GPU backend. This is valid only with GPU accelerated compositing + impl-side painting.
  • You may also consider adding the argument --force-gpu-rasterization which always utilizes the Skia GPU backend for drawing layer tiles. Valid only with GPU accelerated compositing + impl-side painting. Overrides the kEnableGpuRasterization flag.

• This error might also occur if the server fails to recognize the unique session identifier. This usually happens when the session has been deleted or if the session ID is invalid due to either of the following reasons:

  • Explicit session deletion: A WebDriver session is explicitly terminated when invoking the quit() method as shown:

    from selenium import webdriver
    from selenium.common.exceptions import InvalidSessionIdException
    
    driver = webdriver.Chrome(executable_path=r'C:\Utility\BrowserDrivers\chromedriver.exe')
    print("Current session is {}".format(driver.session_id))
    driver.quit()
    try:
        driver.get("https://www.google.com/")
    except Exception as e:
        print(e.message)
    
    #Console Output:
    Current session is a9272550-c4e5-450f-883d-553d337eed48
    No active session with ID a9272550-c4e5-450f-883d-553d337eed48
    

  • Implicit session deletion: A WebDriver session is implicitly ended when closing the last window or tab using the close() method as demonstrated:

    driver = webdriver.Chrome(executable_path=r'C:\Utility\BrowserDrivers\chromedriver.exe')
    print("Current session is {}".format(driver.session_id))
    # closes current window/tab
    driver.close()
    try:
        driver.get("https://www.google.com/")
    except Exception as e:
        print(e.message)
    
    #Console Output:
    Current session is a9272550-c4e5-450f-883d-553d337eed48
    No active session with ID a9272550-c4e5-450f-883d-553d337eed48
    

• You might need to include the argument --no-sandbox

• Chrome often crashes within Docker containers on certain pages due to insufficient space in /dev/shm. To fix this issue, ensure proper sizing of /dev/shm.

• One possible solution:

  sudo mount -t tmpfs -o rw,nosuid,nodev,noexec,relatime,size=512M tmpfs /dev/shm
  

• Alternatively, use the -v /dev/shm:/dev/shm option to share the host /dev/shm

• An additional approach would be to add chrome_options with --disable-dev-shm-usage. This forces Chrome to utilize the /tmp directory instead. Note that this may slow down execution since disk storage will be utilized rather than memory.

  chrome_options.add_argument('--disable-dev-shm-usage')        
  

---

Reference

For further insights, refer to these detailed discussions:

• selenium.common.exceptions.WebDriverException: Message: invalid session id using Selenium with ChromeDriver and Chrome through Python
• unknown error: session deleted because of page crash from unknown error: cannot determine loading status from tab crashed with ChromeDriver Selenium
• org.openqa.selenium.SessionNotCreatedException: session not created exception from tab crashed error when executing from Jenkins CI server

At times, we tend to overcomplicate things by delving too deep into a problem's complexity, when the solution may actually be quite simple and straightforward.

I encountered this issue while using browser.close() as an exception handler in my logout() method. This action ended the session, causing subsequent protractor tests to fail with an error.

By removing browser.close() and opting to throw an error instead, I was able to successfully resolve the problem.