Sample Capistrano Deployment Script

For now, this script is based on SVN conventions

The primary purpose of this script, besides automating deployment is:

• Automated tagging of releases
• Deployment of tests to testing servers (for A/B testing)
• Deployment of latest release to staging environment
• Notification with commit comments, diffs, etc. for each new release

Background

I've recently began setting up automated deployment for my various PHP apps to testing, staging & development servers. Namely, sites such as WhiteFence.com, ElectricityTexas.com and several other client sites.

I'm moving all of my projects to Git, so this script will be modified accordingly.

How it works

There are 3 files involved with deployment:

• deploy

  Defines the repositores, servers, and notification email, as well as how logging is handled.

• deployment.py

  Class that actually performs the deployment. This is highly based on convention.

• capistrano.sh

  An expect script that performed many of the SVN operations. This is because various SVN commands sent false EOF signals to Python (most likely because of child processes spawning) and had to be caught via expect.

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How to use it

Setup SVN Project Structure

Many of the commands from the script are based on folder structure, which should be as follows:

my-project/
    trunk/
    branches/
    tags/
    tests/

Configure deployment.py

*todo*

Deploy

Typical Deployment

# deploy my-project

Deploy to staging environment

# deploy --stage my-project

Deploy tests to testing tier

# deploy --tests my-project

Deploy tests to staging tier

# deploy --tests --stage my-project

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What's going on behind the scenes?

When deploying to production/stage

1. Script checks latest revision of my-project, trunk, and latest tag.
2. If the trunk has been modified since last tag, a new tag is made at that revision.
3. Script decides testing tier based on the presence of --stage switch.
4. Capistrano script is created for deploying the latest tag to the proper tier.
5. Capistrano script is ran:
   1. Remote deployment folder is initialized.
   2. Old releases are cleaned up.
   3. New release is exported to /releases & symlinked to /current folder on tier.
6. If there is an error, Capistrano performs a --rollback.
7. Finished.

When deploying tests...

The process is the same as above, except that:

• Tests in the /tests folder are not tagged, and are simply deployed as-is.
• Tests are spread across the testing tier. For example, if there are 2 tests and 4 servers, Test A will be placed on servers 1 & 2, while Test B will be placed on servers 3 & 4.