Passing parameters as environment variables requires that you set the proper handling of environment variables in your programs.

Overview

Oftentimes you will need to expose an input or a context meta data as an environment variable, in some other situations you might want to skip creating a CLI to run a program and handle the logic based on the environment variables exposed in the system.

Polyaxon exposes the full Kubernetes container specification, which means that you can leverage the env sub-section to expose environment variables:

Example

Let's look at a simple program that just prints some information based on an environment variable:

import os

if __name__ == '__main__':
    print(os.environ.get("INPUT_MESSAGE", "Default message"))

In order to run this program, we can use the following polyaxonfile echo.yaml:

version: 1.1
kind: component
inputs:
- name: message
  type: str
  isOptional: true
  value: "Default message"
run:
  kind: job
  init:
    - file:
        content: |
          import os

          if __name__ == '__main__':
              print(os.environ.get("INPUT_MESSAGE", "Default message"))

        filename: echo.py
  container:
    image: polyaxon/polyaxon-quick-start
    workingDir: "{{ globals.artifacts_path }}"
    command: [python3, -u, echo.py]
    env:
      - name: INPUT_MESSAGE
        value: "{{ message }}"

Now you can run multiple version of this example:

polyaxon run -f echo.yaml -P message="test 1" -l

polyaxon run -f echo.yaml -P message="test 2" -l

Exposing inputs/outputs to env var

N.B: Requires CLI >= v1.12.

To improve the previous process, Polyaxon IO/Params specification has an option to expose the value to an environment variable automatically. Instead of manually using the configuration:

    env:
      - name: INPUT_MESSAGE
        value: "{{ message }}"

It's possible to use the specification toEnv to tell Polyaxon to expose the variable:

inputs:
- name: message
  type: str
  isOptional: true
  value: "Default message"
  toEnv: INPUT_MESSAGE  # <----

toEnv is also available on the params specification, in case the component does not define if the IO should expose the value to an env var, or in case a param is used as context only:

params:
  message:
    value: "New message"
    toEnv: ENV_VAR_MESSAGE  # <----