Avoid running erb-renderer with ruby 1.9.3.

[allomov]

Hi, all.

Here is a problem that I've met several times. First time I say it yesterday, when I tried to help in IRC channel (link to the discussion). The problem was that running bosh-init failed and produced the following output:

Command 'deploy' failed:
  Deploying:
    Building state for instance 'bosh/0':
      Rendering job templates for instance 'bosh/0':
        Rendering templates for job 'director/06a47e4bffdad38c76c6f1069d1f477635800a5e':
          Rendering template src: director.yml.erb.erb, dst: config/director.yml.erb:
            Rendering template src: /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/bosh-init-release261922766/extracted_jobs/director/templates/director.yml.erb.erb, dst: /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/rendered-jobs773245294/config/director.yml.erb:
              Running ruby to render templates:
                Running command: 'ruby /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/erb-renderer551137540/erb-render.rb /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/erb-renderer551137540/erb-context.json /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/bosh-init-release261922766/extracted_jobs/director/templates/director.yml.erb.erb /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/rendered-jobs773245294/config/director.yml.erb', stdout: '', stderr: '/home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/erb-renderer551137540/erb-render.rb:180:in `rescue in render': Error filling in template '/home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/bosh-init-release261922766/extracted_jobs/director/templates/director.yml.erb.erb' for director/0 (line 134: #<JSON::GeneratorError: only generation of JSON objects or arrays allowed>) (RuntimeError)
        from /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/erb-renderer551137540/erb-render.rb:166:in `render'
        from /home/ubuntu/.bosh_init/installations/a0c38fbf-18e2-4bb8-4ccd-d16a2e4860ca/tmp/erb-renderer551137540/erb-render.rb:191:in `<main>'
':

Taking a closer look on this problem I found out that it happens because bosh-init uses host version of Ruby. And different versions of ruby have different behaviour for YAML.dump method, that is called in templates of BOSH release in several places (here for example).

In Ruby 2.0+ you can run YAML.dump on strings and booleans without any problems:

2.1.5 :001 > require 'json'
 => true
2.1.5 :002 > JSON.dump(false)
 => "false"

Still in case of Ruby 1.9.3 an exception is raised because JSON.dump expects an array or hash as a parameter:

1.9.3-p551 :001 > require 'json'
 => true
1.9.3-p551 :002 > JSON.dump(false)
JSON::GeneratorError: only generation of JSON objects or arrays allowed
    from /Users/allomov/.rvm/rubies/ruby-1.9.3-p551/lib/ruby/1.9.1/json/common.rb:216:in `generate'
    from /Users/allomov/.rvm/rubies/ruby-1.9.3-p551/lib/ruby/1.9.1/json/common.rb:216:in `generate'
    from /Users/allomov/.rvm/rubies/ruby-1.9.3-p551/lib/ruby/1.9.1/json/common.rb:352:in `dump'
    from (irb):2
    from /Users/allomov/.rvm/rubies/ruby-1.9.3-p551/bin/irb:12:in `<main>'

The message that people see in the current stacktrace does not reflects an actual root of the problem. So I decided to place an exception with according message in case when ruby version is wrong. As far as I can see this is the easiest way to cope with this issue.

This issue is aggravated by the fact that standard Ubuntu goes with Ruby 1.9.3 pre-installed and new comers can easily face it.

[cfdreddbot]

Hey allomov!

Thanks for submitting this pull request! I'm here to inform the recipients of the pull request that you've already signed the CLA.

[cppforlife]

I've created: https://www.pivotaltracker.com/story/show/104923910 to fix deployment of the Director with 1.9.3 ruby.

[allomov]

That sounds like a solution for this particular case. I am wondering if there is a way to prevent such issues in future.

bosh-director switched to Ruby 2 starting from 1.2657.0 (link), but at the same time bosh-init supports bosh starting with 1.2915.0 (due problems with stemcell).

Because of this facts I thought, that deprecating ruby 1.9.3 is an easier way to overcome this issue.

[cppforlife]

Unfortunately there are still people out there using ruby 1.9.3 as system ruby which makes it annoying for them to get things running.

[allomov]

Support your point of view.