Procedure of a Wharf container step

Sample .wharf-ci.yml:

myStage:
  myStep:
    container:
      image: mcr.microsoft.com/dotnet/sdk:latest
      cmds:
        - dotnet run

Then you run something like

wharf build kubernetes --namespace build

Here’s a comparison of procedures between running in Kubernetes and locally via Docker:

Kubernetes

1. Start pod

   • name: wharf-container-12345
     • emptyDir volume
     • initcontainer:
       • mount emptyDir at /emptyDir
       • image: alpine/git:latest
       • cmd: git clone "${REPO}" /emptyDir/repo
     • container:
       • image: ${myStage.myStep.container.image}
       • cmd: ${myStage.myStep.container.shell} (Just to make the container sit and wait for input that we’re never going to give it)
       • tty: true
       • working dir: /emptyDir/repo

2. Wait until initcontainer is done and container has started

3. Run the commands remotely

   • Alternative A:

     1. Write the commands into a file and add the leading shebang. Ex:

        #!${myStage.myStep.container.shell}
        ${myStage.myStep.container.cmds}

     2. Get that file over to the container. For example like how kubectl cp does it. (This would require having tar installed though).

        Could use a ConfigMap or Secret here and set the configMap.defaultMode to 777.¹

     3. Run the script. Use something equivalent to

        kubectl exec -ti "${podName}" /path/to/script

   • Alternative B:

     1. Run the commands by assuming the shell got a -c flag:

        kubectl exec -ti "${podName}" \
          "${myStage.myStep.container.shell}" \
          -c "${myStage.myStep.container.cmds}"

   • Alternative C:

     1. Feed init container with the command and then let it place that inside the emptyDir. Example:

        git clone "${REPO}" /emptyDir/repo
        
        cat <<'WHARF_CONTAINER_SCRIPT' > /emptyDir/script
        #!${myStage.myStep.container.shell}
        ${myStage.myStep.container.cmds}
        WHARF_CONTAINER_SCRIPT
        
        chmod +x /emptyDir/script

     2. Run the script. Use something equivalent to

        kubectl exec -ti "${podName}" /emptyDir/script

Local via Docker

1. Write the commands to a temporary file. Ex:

   mkdir -p /tmp/wharf/build/12345
   
   cat <<'WHARF_CONTAINER_SCRIPT' > /tmp/wharf/build/12345/script
   #!${myStage.myStep.container.shell}
   ${myStage.myStep.container.cmds}
   WHARF_CONTAINER_SCRIPT
   
   chmod +x /tmp/wharf/build/12345/script

2. Copy the repo

   cp -r . /tmp/wharf/build/12345/repo

3. Run the command via docker

   # Assuming the repo is at pwd
   docker run --rm -it \
     --volume /tmp/wharf/build/12345:/wharf \
     --workdir /wharf/repo \
     --entrypoint "${myStage.myStep.container.shell}" \
     "${myStage.myStep.container.image}" \
     /wharf/script