Better Shipit TASK_ID integration (deployment_id)

Closes Shopify#136

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## next
 
+*Enhancements*
+- Uses `TASK_ID` environment variable as the `deployment_id` when rendering resource templates for better Shipit integration.
+
 *Bug fixes*
 - Attempting to deploy from a directory that only contains `secrets.ejson` will no longer fail deploy ([#416](https://github.com/Shopify/kubernetes-deploy/pull/416))
 

README.md

@@ -108,6 +108,7 @@ offical compatibility chart below.
 
 - `$REVISION` **(required)**: the SHA of the commit you are deploying. Will be exposed to your ERB templates as `current_sha`.
 - `$KUBECONFIG`  **(required)**: points to one or multiple valid kubeconfig files that include the context you want to deploy to. File names are separated by colon for Linux and Mac, and semi-colon for Windows.
+- `$TASK_ID`: used as the ID of the deployment for resource naming.
 - `$ENVIRONMENT`: used to set the deploy directory to `config/deploy/$ENVIRONMENT`. You can use the `--template-dir=DIR` option instead if you prefer (**one or the other is required**).
 - `$GOOGLE_APPLICATION_CREDENTIALS`: points to the credentials for an authenticated service account (required if your kubeconfig `user`'s auth provider is GCP)
 
@@ -130,7 +131,7 @@ Each app's templates are expected to be stored in a single directory. If this is
 All templates must be YAML formatted. You can also use ERB. The following local variables will be available to your ERB templates by default:
 
 * `current_sha`: The value of `$REVISION`
-* `deployment_id`:  A randomly generated identifier for the deploy. Useful for creating unique names for task-runner pods (e.g. a pod that runs rails migrations at the beginning of deploys).
+* `deployment_id`: The value of `$TASK_ID`, or in its absence, a randomly generated identifier for the deploy. Useful for creating unique names for task-runner pods (e.g. a pod that runs rails migrations at the beginning of deploys).
 
 You can add additional variables using the `--bindings=BINDINGS` option which can be formated as comma separated string, JSON string or path to a JSON or YAML file. Complex JSON or YAML data will be converted to a Hash for use in templates. To load a file the argument should include the relative file path prefixed with an `@` sign. An argument error will be raised if the string argument cannot be parsed, the referenced file does not include a valid extension (`.json`, `.yaml` or `.yml`) or the referenced file does not exist.
 

lib/kubernetes-deploy/renderer.rb

@@ -24,7 +24,11 @@ def initialize(current_sha:, template_dir:, logger:, bindings: {})
       @logger = logger
       @bindings = bindings
       # Max length of podname is only 63chars so try to save some room by truncating sha to 8 chars
-      @id = current_sha[0...8] + "-#{SecureRandom.hex(4)}" if current_sha
+      @id = if ENV["TASK_ID"]
+        ENV["TASK_ID"]
+      elsif current_sha
+        current_sha[0...8] + "-#{SecureRandom.hex(4)}"
+      end
     end
 
     def render_template(filename, raw_template)