Managing Sandboxes

It should take at most two commands to bring up a developer sandbox:

  1. Check out the code from version control
  2. Initialize the sandbox environment

Building and running a program inevitably requires other programs.

For a portable shell script, the environment is simple. Just ensure sh is available.

In most cases, the environment is more complex.

Write a command that installs app dependencies, and keep it in version control.

Once that exists, use it to write a command that creates a working project sandbox. That should also live in version control.

This makes it simple for a new team member to start working.

Making and deploying builds also becomes simpler, paving the way for continuous integration, continuous deployment, and horizontal scaling.

Vagrant automates creating and setting up virtual machines. It's an excellent tool for testing an app in an isolated environment, and thus for creating developer sandboxes.

When testing network services with Vagrant, use DHCP for networking, set the VM's hostname to ${project}-${username}-${id}, and have your provisioner install Avahi, so the VM is reachable by the domain name ${project}-${username}-${id}.local (without requiring network administrators to manage DNS for sandboxes).

The $id variable is a per-user counter set in the Vagrantfile (which supports arbitrary computations by being Ruby). Set it from a per-user seed value that's incremented on sandbox creation.

By running each project's sandbox on a distinct virtual machine connected to the local network, you ensure that they will not interfere with each other. Each virtual machine publishes its own network services, which will only impact machines that choose to interact with them, and non-network processes on the virtual machine cannot impact other machines on the network.

Thus, this approach makes it possible to have effectively infinite sandboxes, given sufficient computational resources.

By contrast, any approach that opens ports or runs processes directly on the developer's physical machine will eventually result in conflicts, thus requiring the developer to think about her sandbox.

By giving infinite sandboxes to anyone on the network, it becomes easy to help teammates debug their sandboxes, run impromptu demos, and even to let stakeholders try a commit while a developer continues work on the branch.

Since Vagrantfiles are just Ruby, you can also support custom domain names via environment variables. When used, it's on the developer to avoid conflicts.

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