container.yml Reference

container.yml Reference

The container.yml file defines a Brane package — its metadata, dependencies, files, entrypoint, and available functions.

Full Example

name: data_processor
version: 2.1.0
kind: ecu

dependencies:
  - python3
  - python3-pip
  - python3-numpy

files:
  - src/processor.py
  - src/utils.py
  - requirements.txt

entrypoint:
  kind: task
  exec: src/processor.py

actions:
  'preprocess':
    command:
      args:
      - preprocess
    input:
    - name: dataset_path
      type: string
    - name: normalize
      type: boolean
    output:
    - name: result_path
      type: string

  'analyze':
    command:
      args:
      - analyze
    input:
    - name: data
      type: string
    - name: threshold
      type: real
    output:
    - name: summary
      type: string
    - name: score
      type: real

Fields

name (required)

Package identifier. Must be unique within the registry.

name: my_package

version (required)

Semantic version string.

version: 1.0.0

kind (required)

Package type. Currently supported:

Kind	Description
ecu	Executable Code Unit — arbitrary code in a container

kind: ecu

dependencies

System packages to install via apt in the container.

dependencies:
  - python3
  - python3-pip
  - libssl-dev

files

Files and directories to copy into the container. Paths are relative to the container.yml location.

files:
  - script.py
  - lib/
  - data/config.json

entrypoint

Defines how the container starts.

entrypoint:
  kind: task     # 'task' for synchronous execution
  exec: script.py

actions

Defines the functions the package exposes.

actions:
  'function_name':
    command:
      args:
      - function_name      # Passed as CLI arguments
    input:
    - name: param_name
      type: string         # string, integer, real, boolean
    output:
    - name: result_name
      type: string

Input/Output Types

Type	Description	YAML Example
string	Text value	key: "value"
integer	Whole number	key: 42
real	Floating point	key: 3.14
boolean	True/false	key: true

How Functions Are Called

When Brane executes a function:

1. Input values are set as environment variables (variable name = parameter name)
2. The command.args are passed as command-line arguments to the entrypoint
3. The function must print its output to stdout as YAML
4. The YAML keys must match the declared output parameter names

Example Flow

For a function call preprocess("data.csv", true):

Environment:
  dataset_path=data.csv
  normalize=true

Command:
  python3 src/processor.py preprocess

Expected stdout:
  result_path: "/output/cleaned.csv"