As a developer who has used both Selenium and Docker a lot in the past, I thought running Selenium with Chromedriver in Docker would be pretty straight-forward. I quickly made a Debian image with Python and Chromedriver installed, and tried to run a few test cases.

The test starts successfully, so I go to grab a lunch.

However, when I come back, I see that the test has failed with the following error:

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INTERNALERROR> selenium.common.exceptions.InvalidSessionIdException: Message: invalid session id

I’ve seen this error in the past. This means Chromedriver was doing its job normally, but Chrome had suddenly crashed for some reason.

After executing the test for a few times and monitoring resource usage, I came to a conclusion that Chrome was simply consuming too much memory.

Solution: don’t use shared memory

Turns out the problem is that the shared memory size in the docker container is too small. The default shared memory size in Docker is 64MB, which is not enough for Chrome to run properly.

Conveniently, Chrome has a start-up option --disable-dev-shm-usage that disables the use of /dev/shm for shared memory. instead, it will use the /tmp directory.

Example Chrome options

Here is a full example of running Chromedriver in a docker container:

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from selenium import webdriver
from selenium.webdriver.remote.webdriver import WebDriver
from selenium.webdriver.support.wait import WebDriverWait

opts = webdriver.ChromeOptions()
opts.add_argument('--headless')
opts.add_argument("--no-sandbox")
opts.add_argument("--disable-setuid-sandbox")
opts.add_argument("--disable-gpu")
opts.add_argument("--disable-dev-shm-usage")
opts.add_argument("--window-size=1920,1080")
service = webdriver.ChromeService(executable_path = '/usr/bin/chromedriver')
driver = webdriver.Chrome(service=service, options=opts)