Random errors : cannot start Firefox/FirefoxHeadless

Firefox : v67.0.3 OS : Ubuntu 19.04 and Windows 10 Karma : v4.1.0 Firefox launcher : v1.1.0 Node.js : v12.4.0

I’ve some projects whose Karma tests work as expected when I’m using the Chrome launcher. But when I use the Firefox launcher, I get the following error:

0 06 2019 19:37:21.060:INFO [karma-server]: Karma v4.1.0 server started at http://0.0.0.0:9876/
20 06 2019 19:37:21.062:INFO [launcher]: Launching browsers Firefox with concurrency unlimited
20 06 2019 19:37:21.067:INFO [launcher]: Starting browser Firefox
20 06 2019 19:37:21.124:ERROR [launcher]: Cannot start Firefox
	
20 06 2019 19:37:21.124:ERROR [launcher]: Firefox stdout: 
20 06 2019 19:37:21.124:ERROR [launcher]: Firefox stderr: 
20 06 2019 19:37:21.127:INFO [launcher]: Trying to start Firefox again (1/2).
20 06 2019 19:37:21.181:ERROR [launcher]: Cannot start Firefox
	
20 06 2019 19:37:21.181:ERROR [launcher]: Firefox stdout: 
20 06 2019 19:37:21.181:ERROR [launcher]: Firefox stderr: 
20 06 2019 19:37:21.183:INFO [launcher]: Trying to start Firefox again (2/2).
20 06 2019 19:37:21.237:ERROR [launcher]: Cannot start Firefox
	
20 06 2019 19:37:21.238:ERROR [launcher]: Firefox stdout: 
20 06 2019 19:37:21.238:ERROR [launcher]: Firefox stderr: 
20 06 2019 19:37:21.239:ERROR [launcher]: Firefox failed 2 times (cannot start). Giving up.
[19:37:21] 'test:browser' errored after 585 ms
[19:37:21] Error: karma: 1
    at ChildProcess.<anonymous> (/repo/js/enum.js/gulpfile.esm.js:93:40)
    at ChildProcess.emit (events.js:200:13)
    at ChildProcess.EventEmitter.emit (domain.js:494:23)
    at maybeClose (internal/child_process.js:1021:16)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:283:5)

This error seems to be random: on some projects, the launcher works as expected (for example: https://github.com/cedx/lcov.js). On other projects, the launcher triggers the error (for example: https://github.com/cedx/enum.js).

For the projects that fail, it also seems to be random: the error is triggered on Ubuntu 19.04 and Windows 10, but not on TravisCI with Ubuntu 16.04 (for example: https://travis-ci.com/cedx/enum.js/jobs/209733946).

My Karma config (which is the same on the two mentioned projects):

module.exports = config => config.set({
  basePath: require('path').resolve(__dirname, '..'),
  browsers: ['FirefoxHeadless'],
  files: [
    {pattern: 'lib/**/*.js', type: 'module'},
    {pattern: 'test/**/*.js', type: 'module'}
  ],
  frameworks: ['mocha', 'chai'],
  reporters: ['progress'],
  singleRun: true
});

Using Firefox, instead of FirefoxHeadless, does not change anything (i.e. same error).

[birtles]

@sebavan Thanks for confirming. I was planning on digging into the Ubuntu issues in #93 before releasing (assuming I even have the access required to submit a new release) but haven’t had a chance to set up a VM for it yet.

Let me have another look at Ubuntu later this week (I’m currently traveling) and if I can’t fix it easily I’ll try to release another version.

[birtles]

Right, that’s because the browser process will run in the background and on the second time through it will be running when the launcher tries to connect.

Depending on the load on your machine it might connect on the third time or it might fail altogether. With -wait-for-browser it will succeed first time.

I put up PR #95 for this but there seems to be something wrong with the CI for this repository. Looking at other PRs too it looks like no one is maintaining this anymore so I’m not sure if the PR will get merged.