BrowserWebDriverContainer does not start if shared memory not set under WSL2

[romanboehm]

Hi there,

I've been trying to run my UI Tests under Windows out of curiosity. If I use the old Docker engine for Windows, everything works fine (as does under "real" Linux, for that matter). When employing the WSL2 based engine, the tests fail because the container for the web driver (image selenium/standalone-firefox-debug:3.141.59) does not start.

I've been creating the container like so:

private BrowserWebDriverContainer<?> container = new BrowserWebDriverContainer<>()
            .withCapabilities(new FirefoxOptions());

If I try to run the tests with WSL 2-based Docker -- no matter if from the IDE or with mvn -- I get the following Exception:
com.github.dockerjava.api.exception.InternalServerErrorException: {"message":"error while creating mount source path '/dev/shm': mkdir /dev/shm: file exists"}

The same happens if I issue docker run -d -p 4444:4444 -v /dev/shm:/dev/shm selenium/standalone-firefox from Powershell. It does NOT happen if I issue it under WSL 2's Bash.

FYI: As a workaround, I manually set shared memory on container instantiation:

private BrowserWebDriverContainer<?> container = new BrowserWebDriverContainer<>()
            .withSharedMemorySize(2147483648L)
            .withCapabilities(new FirefoxOptions());

When preemptively setting shm I can bypass the bind creation in BrowserWebDriverContainer:

if (this.getShmSize() == null) {
    this.getBinds().add(new Bind("/dev/shm", new Volume("/dev/shm"), AccessMode.rw));
}

Now, I'm not sure whether this presents as something you can or even want to fix as it seems like it's WSL 2-backed Docker's fault. But here we are. ;)

Besides that, thanks for Testcontainers, it's been nothing but great so far.

Cheers,
rmnbhm

---

WSL Version: 2
WSL Distro: Ubuntu 18.04
Docker Engine Version: 19.03.8
Windows 10 Version: 2004 (Build 19041.173)
TestContainers Version: 1.12.5
Image used: selenium/standalone-firefox-debug:3.141.59

[kiview]

Hey @rmnbhm,
thanks for bringing this to our attention. I can confirm this and wonder why I didn't stumble upon this when I first tried out WSL2.
Your workaround of course works, but we should provide a better OOTB experience for users here.

[kiview]

Although the linked issue was fixed in Docker, we still seem to have a somewhat related problem on WSL2 with the Chrome image.
Configuring the ChromeOptions as follows seems to mitigate the problem:

new ChromeOptions().addArguments("--disable-dev-shm-usage")

The proposed workaround by @rmnbhm also still works for Chrome, but is not necessary on Firefox anymore (probably because of the changes to Docker in WSL2):

.withSharedMemorySize(2147483648L)