Event Sourcing with Axon Server

This package supports using the Python eventsourcing library with Axon Server.

Installation

Use pip to install the stable distribution from the Python Package Index.

$ pip install eventsourcing-axonserver

Please note, it is recommended to install Python packages into a Python virtual environment.

Getting started

Define aggregates and applications in the usual way. Please note, aggregate sequences in Axon Server start from position 0, so set INITIAL_VERSION on your aggregate classes accordingly.

from eventsourcing.application import Application
from eventsourcing.domain import Aggregate, event
from uuid import uuid5, NAMESPACE_URL


class TrainingSchool(Application):
    def register(self, name):
        dog = Dog(name)
        self.save(dog)

    def add_trick(self, name, trick):
        dog = self.repository.get(Dog.create_id(name))
        dog.add_trick(trick)
        self.save(dog)

    def get_tricks(self, name):
        dog = self.repository.get(Dog.create_id(name))
        return dog.tricks


class Dog(Aggregate):
    INITIAL_VERSION = 0

    @event('Registered')
    def __init__(self, name):
        self.name = name
        self.tricks = []

    @staticmethod
    def create_id(name):
        return uuid5(NAMESPACE_URL, f'/dogs/{name}')

    @event('TrickAdded')
    def add_trick(self, trick):
        self.tricks.append(trick)

Configure the application to use Axon Server. Set environment variable PERSISTENCE_MODULE to 'eventsourcing_axonserver', and set AXONSERVER_URI to the host and port of your Axon Server.

school = TrainingSchool(env={
    "PERSISTENCE_MODULE": "eventsourcing_axonserver",
    "AXONSERVER_URI": "localhost:8124",
})

The application's methods may be then called, from tests and user interfaces.

school.register('Fido')
school.add_trick('Fido', 'roll over')
school.add_trick('Fido', 'play dead')
tricks = school.get_tricks('Fido')
assert tricks == ['roll over', 'play dead']

For more information, please refer to the Python eventsourcing library and the Axon Server project.

Developers

Clone the project repository, set up a virtual environment, and install dependencies.

Use your IDE (e.g. PyCharm) to open the project repository. Create a Poetry virtual environment, and then update packages.

$ make update-packages

Alternatively, use the make install command to create a dedicated Python virtual environment for this project.

$ make install

Start Axon Server.

$ make start-axon-server

Run tests.

$ make test

Add tests in ./tests. Add code in ./eventsourcing_axonserver.

Check the formatting of the code.

$ make lint

Reformat the code.

$ make fmt

Add dependencies in pyproject.toml and then update installed packages.

$ make update-packages

Stop Axon Server.

$ make stop-axon-server