Firefox randomly failing to start in CI

Current behavior:

When running tests with Firefox in CI (GitHub Actions), it randomly fails to start with this error:

Cypress could not connect to Firefox.

An unexpected error was received from Marionette connection:

Error: cannot open socket

To avoid this error, ensure that there are no other instances of Firefox launched by Cypress running.

It may be linked to #6504 , but because the environment seems to be different, I think a new issue is more appropriate.

Desired behavior:

Cypress runs reliably everytime.

Test code to reproduce

Repository: https://github.com/Seb-C/test-cypress-action CI script: https://github.com/Seb-C/test-cypress-action/blob/master/.github/workflows/tests.yml (all tests are the default one when we first do cypress open in a new project)

Runs history (showing the randomness): https://github.com/Seb-C/test-cypress-action/actions Logs of a failed run: https://github.com/Seb-C/test-cypress-action/runs/625344325?check_suite_focus=true

Versions

• GitHub actions
• Ubuntu 18.04.4 LTS
• Firefox 74.0.1
• Cypress 4.4.1

[flotwig]

Yeah, so the initial connection timeout was only 2.5 seconds, which seems way too short. 20 seconds still occasionally timed out, but 50 seconds seems to be a good sweet spot from my testing (failures are unrelated to this issue): https://github.com/flotwig/test-cypress-action/commits/master

Opened a PR: #7372

[flotwig]

@jennifer-shehane This can be reopened, it seems like #6392 is distinctly about an issue on Windows when launching the second spec via Firefox, and this issue is more about an issue intermittently launching Firefox which can happen on any system.