Add docker swarm join-tokens as facts

[oschusler]

Fix for issue #638.

This PR adds 2 facts to PuppetDB (worker_join_token and manager_join_token). The puppet agent will have to be run twice, once to setup the docker manager, and a second time to send the updated fact to PuppetDB. Combined with the following snippet, a docker cluster can be started up, unsupervised:

node 'manager' {
  docker::swarm {'cluster_manager':
    init           => true,
    advertise_addr => "${::ipaddress}",
    listen_addr    => "${::ipaddress}",
    require        => Class['docker'],
  }

  @@docker::swarm {'cluster_worker':
    join           => true,
    manager_ip     => "${ipaddress}",
    token          => "${worker_join_token}",
    tag            => "cluster_join_command",
    require        => Class['docker'],
  }
}

node 'worker' {
  Docker::Swarm<<| tag == 'cluster_join_command' |>> {
    advertise_addr => "${ipaddress}",
    listen_addr    => "${ipaddress}",
  }
}

[oschusler]

Travis seems to time out only on PUPPET_GEM_VERSION="~> 6.0" CHECK=parallel_spec. It claims not to have received any output in the last 10 minutes, while the output has finished ("Finished in 6 minutes 19 seconds (files took 5 minutes 4 seconds to load)")

[david22swan]

@oschusler Took a quick look at your pr and it all looks fine but would need some changes before it can be merged in. For a PR such as this both updated test's and docs would be needed, to ensure that the functionality works as is intended and make it so that people can easily understand it's function.
If you can get both of those done I don't see a reason why this should not be merged.

[oschusler]

@david22swan thank you for your comments. I will add the documentation and tests. Could you however perhaps explain to me why Travis is failing? I complains that it didn't receive any logging in the last 10 minutes, while the last log statement was that all tests passed.

[codecov-commenter]

Codecov Report

Merging #651 into main will decrease coverage by 3.27%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##             main     #651      +/-   ##
==========================================
- Coverage   25.64%   22.37%   -3.28%     
==========================================
  Files          20       20              
  Lines         741      751      +10     
==========================================
- Hits          190      168      -22     
- Misses        551      583      +32     

Impacted Files	Coverage Δ
lib/facter/docker.rb	42.66% <70.00%> (-40.42%)	⬇️

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[david22swan]

@oschusler From what I know there was a problem with our code coverage tool that was causing it to hang indefinitely. A fix has gone in though so there should be no more problems.

[oschusler]

@david22swan I think the PR is ready, could you have a look at it?

[david22swan]

@oschusler Apologies for the wait, taking a look through I would say I am happy with what you have done and feel good about merging it.
Thanks for the work :)