Jenkins Pipeline launches Protractor Selenium server, then freezes forever - linux

Question

I'm trying to launch Protractor tests in a Jenkins Pipeline job.
I get a success message, but then the job hangs forever.
I'm running the build on an Ubuntu machine.
The build's logs...
[Bac à sable pipeline] Running shell script
+ sudo webdriver-manager update
[17:46:51] I/update - chromedriver: file exists /usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/chromedriver_2.29.zip
[17:46:51] I/update - chromedriver: unzipping chromedriver_2.29.zip
[17:46:52] I/update - chromedriver: setting permissions to 0755 for /usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/chromedriver_2.29
[17:46:52] I/update - chromedriver: chromedriver_2.29 up to date
[17:46:52] I/update - selenium standalone: file exists /usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/selenium-server-standalone-3.4.0.jar
[17:46:52] I/update - selenium standalone: selenium-server-standalone-3.4.0.jar up to date
[17:46:53] I/update - geckodriver: file exists /usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/geckodriver-v0.16.1.tar.gz
[17:46:53] I/update - geckodriver: unzipping geckodriver-v0.16.1.tar.gz
[17:46:53] I/update - geckodriver: setting permissions to 0755 for /usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/geckodriver-v0.16.1
[17:46:53] I/update - geckodriver: geckodriver-v0.16.1 up to date
[Pipeline] sh
[Bac à sable pipeline] Running shell script
+ webdriver-manager start --seleniumPort 4445
[17:46:56] I/start - java -Djava.security.egd=file:///dev/./urandom -Dwebdriver.chrome.driver=/usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/chromedriver_2.29 -Dwebdriver.gecko.driver=/usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/geckodriver-v0.16.1 -jar /usr/lib/node_modules/protractor/node_modules/webdriver-manager/selenium/selenium-server-standalone-3.4.0.jar -port 4445
[17:46:56] I/start - seleniumProcess.pid: 20154
17:46:58.246 INFO - Selenium build info: version: '3.4.0', revision: 'unknown'
17:46:58.247 INFO - Launching a standalone Selenium Server
2017-05-22 17:46:58.383:INFO::main: Logging initialized #1398ms to org.seleniumhq.jetty9.util.log.StdErrLog
17:46:58.669 INFO - Driver provider org.openqa.selenium.ie.InternetExplorerDriver registration is skipped:
registration capabilities Capabilities [{ensureCleanSession=true, browserName=internet explorer, version=, platform=WINDOWS}] does not match the current platform LINUX
17:46:58.687 INFO - Driver provider org.openqa.selenium.edge.EdgeDriver registration is skipped:
registration capabilities Capabilities [{browserName=MicrosoftEdge, version=, platform=WINDOWS}] does not match the current platform LINUX
17:46:58.687 INFO - Driver class not found: com.opera.core.systems.OperaDriver
17:46:58.688 INFO - Driver provider com.opera.core.systems.OperaDriver registration is skipped:
Unable to create new instances on this machine.
17:46:58.688 INFO - Driver class not found: com.opera.core.systems.OperaDriver
17:46:58.691 INFO - Driver provider com.opera.core.systems.OperaDriver is not registered
17:46:58.701 INFO - Driver provider org.openqa.selenium.safari.SafariDriver registration is skipped:
registration capabilities Capabilities [{browserName=safari, version=, platform=MAC}] does not match the current platform LINUX
2017-05-22 17:46:58.964:INFO:osjs.Server:main: jetty-9.4.3.v20170317
2017-05-22 17:46:59.226:INFO:osjsh.ContextHandler:main: Started o.s.j.s.ServletContextHandler#475530b9{/,null,AVAILABLE}
2017-05-22 17:46:59.353:INFO:osjs.AbstractConnector:main: Started ServerConnector#393c0317{HTTP/1.1,[http/1.1]}{0.0.0.0:4445}
2017-05-22 17:46:59.356:INFO:osjs.Server:main: Started #2371ms
17:46:59.356 INFO - Selenium Server is up and running
EDIT:
Here are the Jenkins logs
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.335 INFO - Started org.openqa.jetty.jetty.servlet.ServletHandler#22345313
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.336 INFO - Started HttpContext[/wd,/wd]
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.336 INFO - Started HttpContext[/selenium-server/driver,/selenium-server/driver]
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.336 INFO - Started HttpContext[/,/]
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.340 INFO - Started SocketListener on 0.0.0.0:4444
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.344 INFO - Started org.openqa.jetty.jetty.Server#6eb7407d
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.375 INFO - Starting auto registration thread. Will try to register every 5000 ms.
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.376 INFO - Registering the node to the hub: http://mydomain.foobar:9093/grid/register
May 23, 2017 9:10:19 AM jenkins.model.Jenkins <init>
INFO: 09:10:19.431 INFO - The node is registered to the hub and ready to use
And the Jenkins Selenium Plugin logs:
May 23, 2017 9:10:19 AM org.openqa.grid.internal.Registry add
INFO: Registered a node http://172.17.0.1:4444
May 23, 2017 9:16:01 AM org.openqa.grid.internal.Registry add
INFO: Registered a node http://172.17.0.1:9095
This one, or this one, didn't help. Any ideas?

Answer 1

I managed to run the task without hang using this command:
xvfb-run -a webdriver-manager start --seleniumPort 4445 &
-a makes xvfb run on the first available display, and & makes this task run in the background.