DAG-type workflow specification¶

A DAG (directed acyclic graph) workflow is a series of tasks that are scheduled to run after their dependencies have finished. See DAG-type workflows result for the result of a DAG workflow.

Specification¶

A DAG-type workflow (element of workflows) has specification

spec_type (string): specification type, must be dag
name, version, description and registration: see Common specification
tasks (array[object]): array of workflow activity tasks to be run during execution, see ScheduleActivityTaskDecisionAttributes
- id (string): task ID, must be unique within a workflow execution and without :, /, |, arn or any control character
- type (object): activity type, with name (str, activity name) and version (str, activity version)
- input (object): activity input definition, see Input
- heartbeat (int or “NONE”): optional, task heartbeat time-out (seconds), or "NONE" for unlimited
- timeout (int): optional, task time-out (seconds), or "None" for unlimited
- task_list (string): optional, task-list to schedule task on
- priority (int): optional, task priority
- dependencies (array[string]): optional, IDs of task’s dependents

Input¶

There are multiple options when defining activity task input. In the task input specification (aka input-spec), type can have one of the following values:

none: no value will be passed as input, meaning there will be no input key in the poll-for-activity-task response provided to the worker.
```
input:
  type: none
```

constant: the activity will be passed value in the input-spec, which can be any valid type.

input:
  type: constant
  value: 42

input:
  type: constant
  value:
    spam:
      - foo: bar
        eggs: 42
      - null
    swallow: false

workflow-input: the activity will be passed a portion of the workflow input, according to path in the input-spec (see Basic single-valued JSONPath for its syntax). path can be omitted, defaulting to "$" (the entire workflow input). Specify default to allow missing values, instead using the value of default
```
input:
  type: workflow-input
```
```
id: foo
input:
  type: workflow-input
  path: $.foo
```
```
input:
  type: workflow-input
  path: $.spam[0].eggs.swallow[2]
```
dependency-result: the activity will be passed a portion of one of its dependencies’ results, with the dependency acitivity task with ID id in the input-spec, according to path in the input-spec (see Basic single-valued JSONPath for its syntax). path can be omitted, defaulting to "$" (the entire dependency result). Specify default to allow missing values, instead using the value of default
```
dependencies:
  - foo
  - bar
input:
  type: dependency-result
  id: bar
```
```
dependencies:
  - foo
  - bar
input:
  type: dependency-result
  id: bar
  path: $.swallow[2]
```

object: you can have seddy build an object to be passed to the activity, with the value of each key being specified by its own input specification, as defined by items in the input-spec. This can be done recursively.

dependencies:
  - foo
  - bar
input:
  type: object
  items:
    spam:
      type: dependency-result
      id: foo
      path: $.swallow[2]
    eggs:
      type: object
      items:
        cheese:
          type: constant
          value: null
        pie:
          type: workflow-input
          path: $.spam[0].eggs.swallow[2]
        gravy:
          type: dependency-result
          id: bar
    ham:
      type: constant
      value: 42

Example¶

spec_type: dag
name: spam
version: "1.0"
description: A workflow with spam, spam, eggs and spam.
registration:
  active: true
  task_timeout: 5
  execution_timeout: 3600
  task_list: coffee
tasks:
  - id: foo
    type:
      name: spam-foo
      version: "0.3"
    input:
      type: workflow-input
      value: $.foo
    timeout: 10
    task_list: eggs
    priority: 1
  - id: bar
    type:
      name: spam-foo
      version: "0.4"
    input:
      type: constant
      value: 42
    timeout: 10
    task_list: eggs
    dependencies:
    - foo