branching_and_dependencies.yml

# This example workflow demonstrates how to use the "direct" workflow type
# in Mistral to build up a chain of jobs with dependencies. If you run this
# workflow, you should see an initial python job, and then three running in
# parallel, and then a final python job after those three are done.
#
# Workflows in the Civis Platform are written in YAML and a workflow DSL
# (domain specific language) called Mistral.
#
# See this website, https://docs.ansible.com/ansible/latest/reference_appendices/YAMLSyntax.html,
# for an introduction to YAML.
#
# See the Mistral documentation, https://docs.openstack.org/mistral/train/user/wf_lang_v2.html,
# for a description of the Mistral DSL.

version: '2.0'  # you always need this key to specify version 2 of the mistral DSL

branching_and_dependencies:  # the name of the workflow can be anything, but Platform ignores it
  tasks:  # all tasks for the workflow go here

    python_init:
      action: civis.scripts.python3
      input:
        name: python init
        source: print("Hello from Python! We are just getting started!")
      # This key indicates which tasks to run after this task succeeds.
      # There are many possible options. See the mistral docs for details.
      # Here we are listing all tasks to run in a list.
      on-success:
        - python_task_a
        - python_task_b
        - python_task_c

    python_task_a:
      action: civis.scripts.python3
      input:
        name: python task a
        # some fancy YAML for multiline strings
        source: |
          import time

          print("Python Task A greets you!", flush=True)
          time.sleep(30)
      # After this task finishes, it launches the final task.
      on-success:
        - python_final

    python_task_b:
      action: civis.scripts.python3
      input:
        name: python task b
        source: |
          import time

          print("Python Task B greets you!", flush=True)
          time.sleep(30)
      on-success:
        - python_final

    python_task_c:
      action: civis.scripts.python3
      input:
        name: python task c
        source: |
          import time

          print("Python Task C greets you!", flush=True)
          time.sleep(30)
      on-success:
        - python_final

    python_final:
      action: civis.scripts.python3
      input:
        name: python final
        source: print("The final Python script greets you!")
      # The join key tells Mistral that this task should wait for all tasks
      # pointing to it (via the on-success keys above) before starting this
      # task.
      join: all