Allow way to check if instance is ready before starting agent

[andyshinn]

I am doing some post-boot stuff with cloud-init and startup scripts to prepare my instance for Jenkins (mounting NVMe disks and post-boot Ansible playbook). I'm actually wanting to store Jenkins workspace data on the NVMe SSD for performance reasons which means I need to wait for this to complete before the plugin can copy and start the agent.jar.

In 3.0.0 I was able to hack around this by creating a custom /usr/local/bin/java script that was picked up when the instance installer first checked output of java -version. The wrapper script would artificially hang until the Ansible playbook had completed (to Jenkins it just appears that the command returns very slowly).

This issue is a feature request to have a way to wait for the instance to be ready via external method. The simple fix to enable the hack again is to just move the java -version check before the agent.jar copy. But I actually think longer term it might make sense to add a check for the cloud-init Final stage using cloud-init status --wait or the /var/lib/cloud/instance/boot-finished file. This would likely account for my scenario and others where people bootstrap instances using cloud-init where there might be stuff required before the agent can actually run jobs.

[stephenashank]

Thanks for submitting this! I like the idea of waiting for cloud-init. In the meantime, I've created #105 to restore the previous functionality.

[andyshinn]

Thanks!

A slight amendment to my initial research about cloud-init. I am actually using the google-startup-script unit and it runs after cloud-init (I assumed it would be part of cloud-init). Implementation details should take into account the startup-script service as well.

[rachely3n]

I've cut a release 3.3.0 that has #105 included. Please try it out and let us know how it goes.

[craigdbarber]

Closing this with the release of 3.3.0. Please feel free to re-open if the issue persists.

[kishorviswanathan]

After one year, I am here looking for the exact same feature. Creating a custom image with java just for Jenkins agent is an overkill. So I ended up using the hack mentioned by @andyshinn by adding cloud-init status --wait in the wrapper script. It would be really helpful if the plugin could wait for the cloud-init completion before checking for Java.

Please reopen this issue.