December 3, 2011

Day 3 - Share skills and permissions with code

This was written by Jordan Sissel (

Last year, I said, "Don't be a human keyboard," and recommended avoiding this situation by building a dashboard for others to consume instead of consuming your time and energy. Going deeper, why not stem 'human keyboard' requests by providing a very simple terminal- or web-based tool?

Before we dive into solutions, we need to go over some of the problems. What are some common reasons someone might invoke you as their computer interface? In general, you probably have something that this person does not, such as skills or permissions.

Both skills and permissions problems can be solved in the same way. You can codify these things into a tool or application that someone other than yourself can use: turn your knowledge and access into a tool usable by others!

The simplest of these tools could be a script in the terminal or a button in the web browser. Buttons are an important interface element in this situation because of exactly the skill mismatch that I mentioned above - not everyone has the skill to use the terminal (ssh, ssh keys, the shell, etc). Going with the 'button' idea, there are nice options for those in the terminal with tools like dialog:


dialog --yesno "Do you want to do this?" 0 0

if [ $result -eq 0 ] ; then
  # Do your thing here...
  echo "Doing it."
  echo "Cancelled"
  exit 1

Running this script will give you a nice simple terminal tool. This kind of terminal interface is good for some situations, but not all. The dialog tool itself has many more features I won't discuss here, but you will benefit from at least playing with this tool. Anyway, despite this kind of visual interface in the terminal, the permissions problem isn't solved since this script is targeted at users other than you, and you might need to share your permissions.

Permissions are more easily shared over remote interfaces because many access control models lack the detail to express what you want to allow. In a human keyboard situation, the 'server' is you and the 'client' is the person asking for action, which maps pretty well to something like HTTP, so how about exposing permissions and skills through the web browser?

One caveat with doing this with the web is the number of technologies required to make it happen. In the terminal, a button was as easy as a simple dialog invocation, but you'll need a web server, html, and some code to make it happen. Luckily there's lots of open source tools available to make building this quicker.

I'll start with a simple example that has a button restart Apache. I chose Ruby, Sinatra and Bootstrap for this, but you can use any tool that helps you get the job done.

require "rubygems"
require "sinatra"
require "logger"

logger =

# The main page
get "/" do
  haml :index

# Handle form submission
post "/" do"Bouncing apache by request from #{request.ip}")

  # Should use Ruby's Open3 here, but let's keep it simple.
  @output = system("sudo apachectl graceful 2>&1")
  exitcode = $?.exitstatus
  @status = (exitcode == 0) ? "success" : "error"

  # Render it.
  haml :result

There are support files (the templates and such) for this available here.

The above is pretty short in terms of code. Serve up the button (get "/") and handle the form submission (post "/"). The deployment scenario for this is that since your permissions are what are needed, it should run as your user (or as something with appropriate permissions if you are shipping it to production).

The results look something like this:

Main page

Main page

A success after clicking the button

A success after clicking the button

A failure after clicking the button

A failure after clicking the button

Keep in mind the point of all of this is to code your way out of the human keyboard situation. Don't know ruby? There's hope! Ruby, Python, Perl, and other communities have lots of ways to serve the web. Beyond that, you probably have a friend who can help you build the parts you aren't able. Lastly, there's lots of resource online for learning how to build simple web applications like this.

Of course, a simple button is just the start. With slightly more effort, you could build a simple interface that allows users to, for example, pick a database backup to restore to their own dev database, or perhaps exposing a one-click 'silence all active nagios alerts for 30 minutes' feature for your on-call folks?

A complex, real-world example of a skills and permissions sharing tool is Etsy's Deployinator. Deployment in many organizations is a complex mixing of different teams, skills, permissions, and goals. A tool like Deployinator allows the operations team to expose deployment functionality outside the operations team while hiding the necessary complexities of the infrastructure. This allows ops to share its permissions and skills by putting those in code and exposing it in the web browser. Because of this, deployments no longer require the full attention of the operations team, development doesn't block on operations, and no one is used as a human keyboard.

Definitely a brilliant win-win situation for everyone.

Proxying permissions and embedding your skills into code allows other people to act with your permissions and skills in a controlled and repeatable way without the burden of knowledge or complex access controls. Reducing the knowledge required to perform a task will greatly reduce the amount of documentation you need to write, too, since you can reduce most things to "If this, then click this button" instead of documenting the complicated orchestra of steps and knowledge.

Further Reading

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