commands_containers.md

Commands Containers

Aladdin allows project-specific commands to be managed and implemented within the project repository. These commands can be run independently/directly, or from within aladdin through aladdin cmd <project name> <command name>. To do this, we will spin up a dedicated commands pod that is specific to each project.

In this template project, we demonstrate a simple status command, which will ping the relevant endpoints for aladdin-demo and print out each of their statuses. Running kubectl get pods should show that aladdin-demo-commands-<hash> is running alongside the other aladdin-demo pods. The status command can be run using aladdin with:

$ aladdin cmd aladdin-demo status

Define Command Functions

We start off by creating a commands_app folder that contains the requirements for the commands that need to be run, and a commands folder that has separate files for each command. In this case, we want to run status, so we create status.py.

The only required function in status.py is a parse_args(sub_parser) function. Aladdin will look for this function when you try to run your command. The command status must be added to the sub_parser, and set_defaults should take a function that points to the function that actually runs.

def parse_args(sub_parser):
    subparser = sub_parser.add_parser("status", help="Report on the status of the application")
    # register the function to be executed when command "status" is called
    subparser.set_defaults(func=print_status)
    
def print_status(arg):
    ...

Create Docker Container

We will also need to create a Dockerfile for this container. The image for this commands container must be inherited from the aladdin commands_base docker image, and copy over the folder containing the command functions as command. We demonstrate this in the Dockerfile.

FROM fivestarsos/commands-base:1.0.0
...
COPY commands_app/commands commands

Update the build docker script to build the commands container as well.

docker_build "aladdin-demo-commands" "app/commands_app/Dockerfile" "app"

Create Kubernetes Deploy File

We create commands/deploy.yaml.

Update lamp.json

Include the commands container image in docker_images.

{
    "name": "aladdin-demo",
    "build_docker": "./build/build_docker.sh",
    "helm_chart": "./helm/aladdin-demo",
    "docker_images": [
        "aladdin-demo",
        "aladdin-demo-commands"
    ]
}