Deploying an app with multiple buildpacks is not supported by eirini-staging

stoyanr commented 4 years ago

Description

Deploying an app with multiple buildpacks as described in How Buildpacks Work in CFAR is not really supported by eirini-staging.

Steps to reproduce

Deploy an app with multiple buildpacks specified in its manifest. In my case, I have an app with one standard buildpack (java_buildpack) and one custom buldpack:

- buildpacks:
  - uas_dataflow_server_buildpack
  - java_buildpack

What was expected to happen

The sequence of interactions as specified in No Buildpack Detection. In this case , the supply script of the first buildpack should be invoked, and then the application should start with the second buildpack.

What actually happened

Depending on whether or not the first buildpack has a detect script that returns 0, one of the following outcomes:

If the first buildpack has a `detect`` script that returns 0, this buildpack is "detected" and the second buildpack is ignored. The app fails to start.
If the first buildpack doesn't have a detect script or it returns 1, this buildpack is simply ignored. The app starts with the second buildpack, but since the supply script of the first buildpack was never called, the app doesn't work as expected.

Suggested fix (optional)

The bug is in https://github.com/cloudfoundry-incubator/eirini-staging/blob/ae1327186284f350673df0d5e3b4f21045fd71fa/builder/config.go#L48-L55 . The skipDetect flag is never set if len(buildpacks) > 0. To fix this issue, this flag should be set if len(buildpacks) > 0 and the skipDetect flags of all buildpacks are true.