Support sidecars

[michaelsauter]

Tekton tasks may specify sidecars, see https://tekton.dev/vault/pipelines-v0.16.3/tasks/#specifying-sidecars. One use case for sidecars is to run a database for use with integration tests. To support this, our builder tasks (ods-build-go and friends) would need to be able to run a sidecar.

However, it seems like sidecars cannot be configured from a pipeline, only from within a task. This is problematic as we don't want to run a sidecar all the time, nor do we want that every user who wants to use a sidecar needs to create a custom task.

One idea I have is to automatically generate a "sidecar companion task": based on ods-build-go, generate a ods-build-go-with-sidecar task. This task also has a few parameters which allow to specify the image to use and the script to execute.

Other ideas?

FYI @felipecruz91 @renedupont

[felipecruz91]

This is problematic as we don't want to run a sidecar all the time, nor do we want that every user who wants to use a sidecar needs to create a custom task.

Fully agree. In my view ods-pipeline should provide an additional task with support for sidecar containers.

One idea I have is to automatically generate a "sidecar companion task"

Yes, I guess we have no other option at the moment. The only drawback I see for now is maintainability (we'll now have twice the number of tasks per every builder task).

Perhaps you can elaborate a bit more on how to automatically generate the task? I'd like to have some make command that injects the sidecar container in a list of predefined tasks and the tasks generated (manifests) are then applied to the cluster, so we don't necessarily have to create them manually one by one.

[michaelsauter]

The idea would be:

1. Read the normal builder task from cluster
2. Inject the sidecar and additional parameters
3. Install the task with the sidecar in the cluster

That way we do not need to maintain two tasks. However the tests should verify that the sidecar works as expected.

Example:

Original task:

apiVersion: tekton.dev/v1beta1
kind: ClusterTask
metadata:
  name: ods-build-go
spec:
  description: Builds Go (module) applications.
  params:
    - name: enable-cgo
      description: Whether to enable CGO. When not enabled the build will set `CGO_ENABLED=0`.
      type: string
      default: "false"
  steps:
    - name: build-go-binary
      image: build/package/Dockerfile.go-toolset
      resources: {}
      script: go build
      workingDir: $(workspaces.source.path)
  workspaces:
    - name: source

Modified task with sidecar:

apiVersion: tekton.dev/v1beta1
kind: ClusterTask
metadata:
  name: ods-build-go
spec:
  description: Builds Go (module) applications.
  params:
    - name: enable-cgo
      description: Whether to enable CGO. When not enabled the build will set `CGO_ENABLED=0`.
      type: string
      default: "false"
    - name: sidecar-image
      description: Image to use for sidecar
      type: string
    - name: sidecar-script
      description: Image to use for sidecar
      type: string
      default: ''
  steps:
    - name: build-go-binary
      image: build/package/Dockerfile.go-toolset
      resources: {}
      script: go build
      workingDir: $(workspaces.source.path)
  sidecars:
  - image: $(params.sidecar-image)
    name: sidecar
    script: $(params.sidecar-script)
  workspaces:
    - name: source