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These deployment helper scripts where originally created to help with the deployment process of Arethusa on Perseids servers.

The idea is to easily reference a production and a staging build with the ability to roll back and forth between them and having access to several versioned builds of the software.

Let's say we have a folder hierarchy which we use to store versioned builds of our application.

app/
  v1/
  v2/
  v3/

and another folder called server, which contains files that are exposed to the internet.

We first export an environmental variable, so that the helper scripts know where to work.

export DEPLOYMENT_HELPER_TARGET="server"

We launch the setup script to build up the initial set of links we need in future steps. The first argument of the script is the name of the application, we go for app in this example.

depl-help-setup app

This will create a couple of files in the server folder

server/
  app -> app-prod-1
  app-staging -> app-dev-1
  app-prod-1
  app-prod-2
  app-prod-3
  app-dev-1
  app-dev-2
  app-dev-3

app links to app-prod-1, app-staging links to app-dev-1. The other files will be used to link to the actual directories that contain our builds.

depl-help-deploy app app/v1 dev

will create a link from app-dev-1 to the app/v1 folder. Remember that the tip of the dev link hierarchy is also referenced by app-staging.

Let's repeat the process and add a reference to app/v2, also in the dev environment.

depl-help-deploy app app/v2 dev

app-dev-1 now links to app/v2. The former reference of app-dev-1 was pushed down the link chain and can now be found in app-dev-2, which will then lead to app/v1.

If we are happy with our staged version, we can declare it as our most recent production version.

depl-help-release app

The reference in app-dev-1 will be copied to app-prod-1, which is also accessible through the pure app link.

We can also deploy a new version directly to the production link hierarchy.

depl-help-deploy app app/v3 prod

app-prod-1 will now link to app/v3, app-prod-2 will contain a reference to the former production version sitting in app/v1.

If we encounter problems with the most current version, which users might access through a route that goes to our app link, we can easily roll back to an older version.

depl-help-rollback app prod

This will set back app-prod-1 to what app-prod-2 linked to - in our case this means that app-prod-1 - and therefore app itself - will link to app/v1 again.