Remove the ability to run multiple commands

[jsvd]

Addresses #1747.
This removes the argument list iteration and spawning of multiple
tasks.
It's still possible to specify aditional arguments but now they're
ignored.

[jordansissel]

I'd love to see runner be implemented as Clamp::Command with subcommands detailed the clamp way, like:

class LogStash::Runner < Clamp::Command
  subcommand "agent", ...
  subcommand "web", ...
  ...
end

[jordansissel]

(my hope for removing the 'multi-subprocess' feature was to do a refactor that didnt' reinvent subcommand stuff)

[electrical]

Would be nice to redo it indeed in the 'right way'

[jsvd]

Is there a benefit to Clamp once we no longer have to support "background" tasks? Maybe simple optparsing the cli options and spawing the command would be enough.

[jordansissel]

Clamp doesn't do background tasks, but we use clamp elsewhere and it is, in my opinion, the most superior CLI library available for Ruby :)

[jordansissel]

Example clamp usage in the new plugin manager: https://github.com/elasticsearch/logstash/blob/master/lib/logstash/pluginmanager/main.rb

[electrical]

Clamp doesn't do background tasks, but we use clamp elsewhere and it is, in my opinion, the most superior CLI library available for Ruby :)

That's a discussion for an other time ;-)

[elasticsearch-release]

💚 Test passed.
Refer to this link for build results: http://build-eu-1.elasticsearch.org/job/Logstash_PR/109/

[jsvd]

I guess I mean the Stud, specially Stud::Task. As for Clamp, no strong opinions there.

[jordansissel]

@electrical hehe. Still! Because we support subcommands already (agent, web, irb, etc), we should probably use a library that makes it easy to do. Ruby's optparse is kind of not awesome for that.

[jordansissel]

@jsvd +1, we don't need Stud::Task here

[jsvd]

Well, this PR accomplished the goal of getting the ball rolling ;) Thanks for the input

[jordansissel]

Truth! Sorry if the review I gave sounded a bit short! We can definitely do it in two PRs for sure - one to disable multiple-subproceses, and another to refactor. +1 on doing this.

[jsvd]

I'll try to assess tomorrow if a full refactor "the clamp way" is simple/quick enough. otherwise I'd go with your two-step suggestion. 👍

[jordansissel]

Code LGTM, mostly!

I tested it, one difference is that bin/logstash on master, with no arguments, outputs "No command given" and offers help. With this PR, it exits 0 with no output.

[jordansissel]

Thanks for being so fast on this :)

[jsvd]

Bugger, I'll add that test tomorrow and fix it. ty

[elasticsearch-release]

💚 Test passed.
Refer to this link for build results: http://build-eu-1.elasticsearch.org/job/Logstash_PR/110/

[jordansissel]

This was merged with a new (experimental) tool to help us merge a single PR into multiple branches. Hopefully it doesn't set git on fire. <3

Closing!