Containers

Say what runs and how it starts. The same image, command, and settings run on your machine and on the cluster.

You declareThe platform generates

compose.yaml

services:
  web:
    image: my-app:local # (1)!
    entrypoint: [python] # (2)!
    command: [manage.py, runserver, "0.0.0.0:8000"] # (3)!
    working_dir: /app
    environment:
      LOG_LEVEL: info # (4)!

1. What runs.
2. The program that starts. It replaces the one of the image.
3. What the program receives. It replaces the command of the image.
4. Public settings. Credentials go in Secrets.

Generated on every release. You never write this file or see it.

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    com.docker.compose.project: my-app
    com.docker.compose.service: web
  name: web
  namespace: my-app
spec:
  replicas: 1 # (1)!
  selector:
    matchLabels:
      com.docker.compose.project: my-app
      com.docker.compose.service: web
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        com.docker.compose.project: my-app
        com.docker.compose.service: web
        com.docker.compose.network.default: 'true'
    spec:
      containers:
      - args: # (2)!
        - manage.py
        - runserver
        - 0.0.0.0:8000
        command: # (3)!
        - python
        env: # (4)!
        - name: LOG_LEVEL
          value: info
        image: my-app:local
        imagePullPolicy: IfNotPresent
        name: web
        workingDir: /app # (5)!

1. One copy. Resources and replicas changes it.
2. Your command.
3. Your entrypoint.
4. Your environment.
5. Your working_dir.

Fields

Field	Required	Values
image	Yes	The image to run
entrypoint	No	The program that starts, in place of the one of the image
command	No	What the program receives, in place of the command of the image
working_dir	No	The directory where the program starts
environment	No	Public settings. Every variable has a value

What you get

On your machine

Docker starts one container for the service, with your image, command, and settings.

On the cluster

The platform starts the service with the same image, command, and settings, and keeps it running. You write no manifest.

A private image needs nothing from you: the platform holds the credential to download it.

Rules

Rule	Detail
A field outside the contract is rejected	It is never ignored in silence
Every variable has a value	A variable declared without a value is rejected
The project has a name	name, in lowercase letters, digits, and hyphens. It starts with a letter. Up to 63 characters
A service name is short	Lowercase letters, digits, and hyphens. Up to 52 characters