Introduction to the inventory model, it's role and purpose in the CI/CD process.

• Inventory Structure and Content
• Inventory Entry Format
• Inventory Workflow
  • CI writes
  • Promotion
• Use Cases

Inventory model keeps track of the following information:

• Details of the built artifact (pipeline run, commit SHA).
• Signature of the built artifact.
• The artifact that is to be deployed.

Based on this data, we can keep track of related evidence during the artifact build and deployment lifecycle.

The Inventory is stored in a git repo as git helps to keep track of the changes ensuring auditability.

The main branch (master) is updated by the CI pipeline, while other branches are used for the various target deployment environments.

The Inventory contains an Inventory entry for every artifact that participates in a deployment.

One Inventory entry points to a single artifact.

Inventory entries are JSON files, see the format below. The file name is the entry name, it can be structured in folders.

The Entry type represents the schema of the Inventory entry (using typescript syntax but it's fairly easy to translate it to eg. JSON Schema):

interface Entry {
  repository_url: string;
  artifact: string;
  build_number: number;
  commit_sha: string;
  name: string;
  pipeline_run_id: string;
  version: string;
  signature: string;
}

{
  "repository_url": "https://us-south.git.cloud.ibm.com/user/java-spring-app.git",
  "artifact": "binary-20210318042338.tar.gz",
  "build_number": 2,
  "commit_sha": "218913eb78b3c1b8cde2573a66998ac04848f529",
  "name": "java-spring-app",
  "pipeline_run_id": "96fc6b5e-d491-43bc-ada5-e03e17538c0a",
  "version": "v1",
  "signature": "3cb49a1f235e81a11a6abab55713172a" 
}

The master branch is populated from CI builds. The last commit in the master branch has all the metadata related to the build and its output.

Promoting to a target branch happens by creating a pull request. The PR contents will fill the Change Request fields for change management service if they are integrated. When the PR is reviewed, the promotion PR can be merged.

0. Set up inventory.
1. CI pipelines fill the master branch with Inventory entries
2. CD pipeline starts:
   • Pipeline will tag the latest commit with the Pipeline Run ID
   • Pipeline picks up the content of the master branch from that tag
   • Since this is a first promotion to a new target, deployment will contain all items and will attempt to deploy.

1. If there a problem, a deployed application has to be rolled back to a previous version on prod
2. DevOps pick a point in the Inventory to roll back to.
3. All the commits are reverted until that point and promoted as a PR
4. The Rollback Promotion PR get merged
5. CD pipeline starts:
   • Pipeline picks up the contents of the prod branch from the tag and will attempt to deploy.