Build-time tags for pipelines images and service descriptors

[alanbchristie]

In OpenShift (and Docker), if an existing pipelines image has been deployed re-running the poster image adds the modified or new service descriptors but the underlying image is not necessarily re-pulled.

To solve the problem in OpenShift the imagePullPolicy could be set to Always but this would introduce significant execution delays, especially as pipeline image layers can be substantial.

Anther idea is to use explicit tags on the service descriptor's image reference (the imageName property). And, more importantly, set these at build time. We could have a tag formed from a short-form of the build date. If we expected to produce just one official copy of the pipeline each day the image tag could be 2018-11-14. We set that in the service descriptor imageName value as it's written to the poster image. Finally, we push the corresponding pipelines image using the same tag.

[alanbchristie]

ServiceDiscoveryRouteBuilder now processes headers, specifically: -

• Image-Pull-Secret
• Image-Registry
• Image-Tag

So, if we use the prevailing TRAVIS_TAG as the Image-Tag then we can version pipelines within the execution environment. The service descriptor container image simply needs a copy of the TRAVIS_TAG (for tagged builds).