apso-domain-events (Python)

Transactional outbox + delivery for Apso services, built on SQLAlchemy 2.0 with an optional FastAPI integration. Implements the cross-language CONTRACT.md.

state change ─(same DB txn)→ DomainEvent row (capture)
                                   │
                       relay drains pending rows (poller)
                                   │
                       fan out to active destination(s) (delivery)

Install

pip install apso-domain-events            # webhook delivery needs no extra dep
pip install apso-domain-events[kafka]     # confluent-kafka
pip install apso-domain-events[aws]       # boto3 (sqs / eventbridge)
pip install apso-domain-events[fastapi]   # FastAPI integration

Wire it

from apso_domain_events import register_domain_events
from myapp.models import Product, Order  # the CLI-emitted manifest

register_domain_events(
    engine,                      # Engine or sessionmaker
    entities=[Product, Order],   # only these emit; never hardcoded in the lib
    poll_interval=5.0,
    app=app,                     # optional FastAPI app → startup/shutdown poller
)

Create the events table from Base.metadata (or your migration tool):

from apso_domain_events import Base
Base.metadata.create_all(engine)

Delivery

The active destination(s) are chosen at runtime from EVENTS_DESTINATION (comma-separated → fan-out):

At-least-once: fan-out re-sends to ALL destinations on retry. Consumers MUST dedupe on event.id.

The webhook adapter signs requests per Standard Webhooks (webhook-id, webhook-timestamp, webhook-signature: v1,...).