This is for internal use by the PaaS team. Public-facing documentation is located at docs.cloud.service.gov.uk.

ADR034: Continuously deploy platform CF applications

Context

As part of GOV.UK PaaS we have a number of applications that we consider to be an essential part of the platform deployed as cloud foundry apps. These include:

• paas-admin
• paas-billing
• paas-accounts

Prior to July 2019 the versions of these applications were pinned in paas-cf, and they were only deployed along with the whole platform. This had a couple of negative consequences:

• Following a change to an app’s source and a passing build an additional manual change to paas-cf was required to deploy it
• Deploying apps required waiting for unrelated slow bits of the pipeline to complete (e.g. terraform apply, bosh deploy, cf acceptance tests), despite the fact that a change to an app could not possibly affect or be affected by these steps

There were also some advantages of specifying the version of applications explicitly:

• There’s an record of which versions of the applications work with which versions of the platform.
• Merges to paas-cf require a signed merge commit to be deployed, so we can be explicit about the set of people who are allowed to deploy changes

Decision

We will update the pipeline to:

• Require GPG signatures on git commits before deploying applications in staging and production
• Automatically deploy every build of the master branch of the applications to staging
• In staging: tag the application repo when a deployment passes its acceptance tests
• In production: automatically deploy any build which has been tagged by staging

Status

Accepted

Consequences

• Deployments to paas-admin, paas-billing and paas-accounts will take minutes instead of hours
• We will continue to enforce that all production code requires a signed commit to deploy
• We will no longer have a single record of which version of the applications were deployed with which version of the platform