oamg/leapp-repository/leapp-actor-dev

Developing Leapp Actors

Actor structure

Every actor follows layout:

repos/system_upgrade/<leapp_repo_dir>/actors/<actor_name>/
├── actor.py              # Actor class (thin wrapper)
├── libraries/
│   └── <actor_name>.py   # Implementation logic
└── tests/
    └── test_<actor_name>.py

Keep actor.py minimal — delegate the real implementation to the library for testability:

from leapp.actors import Actor
from leapp.libraries.actor import <actor_name>
from leapp.models import <ConsumedModel>, <ProducedModel>
from leapp.tags import <PhaseTag>, IPUWorkflowTag
class MyActor(Actor):
    """Brief description of what this actor does."""
    name = '<actor_name>'
    consumes = (<ConsumedModel>,)
    produces = (<ProducedModel>,)
    tags = (IPUWorkflowTag, <PhaseTag>)
    def process(self):
        <actor_name>.process()

Phase selection

Common multi-actor patterns

Inhibiting an incompatible system (2 actors):

1. Scanner in FactsCollectionPhase — produces a facts message.
2. Checker in ChecksPhase — consumes facts, creates report / inhibits.

Modifying incompatible config (3 actors):

1. Scanner in FactsCollectionPhase — collects info.
2. Checker in ChecksPhase — decides and reports planned change.
3. Modifier in ApplicationsPhase — performs the change.

Placement rules

• Reusable across upgrade paths → repos/system_upgrade/common/
• Specific to one path → repos/system_upgrade/el8toel9/ or el9toel10/
• Same rule applies to models and shared libraries.

Before writing new code

• Search existing actors/models/libraries — reuse before creating.
• Check if a model already provides the message you need (search model class names in repos/).
• Discover repos/system_upgrade/common/libraries/ for shared utilities.
• Prefer using stdlib functions over shell commands.
• If introduce envars, use LEAPP and LEAPP_DEVEL.
• Write unit-testable code (see skills/leapp-unit-tests/).

Key constraints

• Avoid running code on a module level to avoid slow downs during this load phase
• Never use subprocess — use leapp.libraries.stdlib.run() instead.
• Never interact with the system during ChecksPhase.
• Do not introduce new dependencies, unless it's strongly justified.

Python compatibility

Reference

• How to write an Actor for Leapp Upgrade
• Phases of the Upgrade Workflow
• Coding guidelines
• Best Practices for actor development