Fix "session deleted because of page crash" when using Selenium Grid and Docker

17 March 2021 — Written by Joel

Recently I created a CI pipeline that stands up a local selenium grid and then pipeline jobs run WebdriverIO tests against that selenium grid.

I noticed that when I ran more than a single feature file in parallel, that the first process for the first feature file would succeed, but all others would fail with the following error saying something about the page crashing:

[0-5] 2021-03-16T18:49:58.094Z WARN webdriver: Request failed with status 500 due to unknown error: session deleted because of page crash                                     
from unknown error: cannot determine loading status                                                                                                                           
from tab crashed                                                                                                                                                              
  (Session info: chrome=89.0.4389.82)                                                                                                                                         
[0-5] 2021-03-16T18:49:58.103Z ERROR webdriver: Request failed with status 404 due to invalid session id: invalid session id

From then on, WebDriver would log that it was trying to connect to the session but not finding the session id and timing out.

[0-5] 2021-03-16T18:49:58.118Z WARN webdriver: Request failed with status 500 due to Session [cdc0c2a1ee9d791bd13827a53754de91] was terminated due to BROWSER_TIMEOUT         
[0-5] 2021-03-16T18:49:58.124Z WARN webdriver: Request failed with status 500 due to Session [cdc0c2a1ee9d791bd13827a53754de91] was terminated due to BROWSER_TIMEOUT         
[0-5] 2021-03-16T18:49:58.129Z ERROR webdriver: Request failed with status 500 due to unknown error: Session [cdc0c2a1ee9d791bd13827a53754de91] was terminated due to BROWSER_
TIMEOUT

The selenium grid was configured to allow 20 concurrent sessions, as was the single Chrome node, so I was perplexed!

selenium_hub:
  image: selenium/hub
  ports:
    - 4444
  environment:
    - SE_OPTS=-debug
    - GRID_MAX_SESSION=20
    - GRID_BROWSER_TIMEOUT=10000
    - GRID_TIMEOUT=10000
chrome:
  image: selenium/node-chrome
  depends_on:
    - selenium_hub
  environment: 
    - NODE_MAX_SESSION=20
    - NODE_MAX_INSTANCES=20
    - HUB_HOST=selenium_hub
    - HUB_PORT=4444

I was looking into this with a coworker when I googled the error message and came across this StackOverflow answer, which pointed me to this github issue which tipped me off that, "... recent version(s) of Chrome seem to crash in Docker containers, on certain pages, due to too small /dev/shm."

Given this limitation, there were a few ways to handle this

Increase the size of /dev/shm with the --shm-size option (I believe shm stands for shared memory)
Mount /dev/shm:/dev/shm from the host to the container
Disable /dev/shm via the --disable-dev-shm-usage option so that the disk is used instead of memory, which can make things slower.

I decided to go with the 3rd option since memory is also limited in the CI context. I might change it in the future, but for now it works.

The StackOverflow answer also suggests adding the --no-sandbox option, which should be fine as long as you trust the websites your browser will be visiting.

In the context of WebdriverIO, I added these in the capabilities for Chrome:

capabilities: [
  {
    browserName: 'chrome',
    'goog:chromeOptions': {
      args: [
        '--no-sandbox',
        '--disable-dev-shm-usage',
        '--disable-gpu',
        '--window-size=1920,1080',
      ],
    },
  }
...
]

Once I added these options, it worked! 🎉

This should also be true if you're using some other WebDriver-based framework or using another language since this is ultimately related to running the Chrome browser in the context of a Docker container.

Hopefully this helps someone else out there running into this.

Fix "session deleted because of page crash" when using Selenium Grid and Docker

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