Running cypress in headless mode should not use xvfb

[mrmeku]

Current behavior

Currently, when I use cypress in headless mode via cypress run, xvfb is still invoked. Consequently, sometimes this can make my cypress tests error out due to an error.

For example:
Cypress: Fatal IO error 11 (Resource temporarily unavailable) on X server :105.

Desired behavior

When running in headless mode, there is no need to spawn xvfb at all. This should only be done when using cypress run to run a browser in headed mode.

Versions

All versions of cypress up to 7.3.0

[mrmeku]

I believe the fix for this bug can be done within

cypress/cli/lib/exec/xvfb.js

Line 60 in 56234e5

isNeeded () {

If the isNeeded function where to accept an argument of whether or not the browser is running in headless mode then we could have it return false immediately. There might be a better place to make the fix though.

I would love to make a PR to fix this bug, but I'd like a little input from the maintainers as to the shape of the fix they are most comfortable with.

[flotwig]

@mrmeku that sounds like the right path. Does Electron still require X to run though?

[mrmeku]

That's debatable. Chrome and chromium no longer need XVFB to run any more (see https://developers.google.com/web/updates/2017/04/headless-chrome)

Electron's docs, on the other hand, makes the opposite claim (https://www.electronjs.org/docs/tutorial/testing-on-headless-ci)

I suspect that the electron docs are merely out of date.

Electron would need to be launched using the --headless flag to avoid the need for xvfb, but I think if that requirement is met there's no reason I know of that it would need a display server at all

[mrmeku]

Running electron with the ELECTRON_RUN_AS_NODE environment variable might also be part of the magic here: https://www.electronjs.org/docs/api/environment-variables#electron_run_as_node

[mrmeku]

I did some experimenting with ELECTRON_RUN_AS_NODE and it seems like that strategy could pan out. The only other requirement is that when using ELECTRON_RUN_AS_NODE you can no longer require the electron package. So within packages/server, logic will need to be added to deal with that reality.

You could interact with electron via a helper file packages/server/electron which tries to require electron and if it fails, provides a mocked out version of the APIs the server tries to interact with.

Anyway, the change is definitely slightly more involved that I had hoped since electron itself doesn't expose the same display server less headless mode that chromium does.

[wrslatz]

We've run into this all of a sudden over the past couple of days (combo of this, cypress-io/xvfb#98, and cypress-io/cypress-docker-images#54).

[mrmeku]

I'll keep hacking on my PR, I just got side tracked

[wrslatz]

Happy to help test any changes if I can

[wrslatz]

For now it seems like the xvfb-run -a workaround described in cypress-io/cypress-docker-images#54 is holding 🤞🏻 The issue is intermittent so it's hard to tell.

[sec0ndhand]

Would also love to resolve this, I haven't contributed much, but this would also help support people trying to utilise cypress on heroku ci here.

[cypress-bot]

The code for this is done in cypress-io/cypress#16537, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[mrmeku]

@jennifer-shehane @flotwig Would it be possible for someone to build a cypress binary for linux now that this change has been merged so I can test out the changes in my own projects to better exercise edge cases?

[bahmutov]

@mrmeku see cf689dd#commitcomment-53273920

[cypress-bot]

Released in 8.0.0.

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