Eventify

A lightweight python module for building event driven distributed systems.

Installation

pip install eventify

Problem

Developers need a easy and fast way to implement business logic in a modern asynchronous way. Developers should not have to worry about service communication.

Contributing

TBD

Architecture

Tutorial

Below is everything you need to get started using the eventify project.

Minimum Viable Service

Create an Event handler function to receive events. To publish events, use session.emit_event() within the Event handler function. To start your service (and begin listening for events), pass the Event handler function as a callback to run a Service.

#!/usr/bin/env python
"""
Minimal viable microservice
"""
import asyncio
import logging
import sys

from eventify.base_handler import BaseHandler
from eventify.event import Event
from eventify.service import Service


class GoogleCollector:
    """
    Google Specific Collector
    """

    async def collect_vm_data(self):
        print('...collecting data from gce api...')
        await asyncio.sleep(1)

class Collector(BaseHandler, GoogleCollector):
    """
    Generic collector
    """

    async def init(self):
        """
        Service initialization
        """
        print('...service initialized...')


def run():
    """
    Run an eventify service
    """
    Service(
        config_file='config.json',
        handlers=[Collector]
    ).start()

if __name__ == '__main__':
    run()

Minimum Configuration - config.json

Each application (service, microservice, etc.) can publish to 0 or 1 topic and subscribe to 0 or more topics. Thus each application requires its own configuration file which defines its publications & subscriptions. Each configuration file also specifies the location of the transport host.

{
    "_comment": "service configuration",
    "name": "example",
    "image": "example/service",
    "driver": "crossbar",
    "transport_host": "ws://events-server:8080/ws",
    "pub_options": {
        "acknowledge": true,
        "retain": true
    },
    "publish_topic": {
        "topic": "example",
        "timeout": 20,
        "reply_in": 0
    },
    "subscribed_topics": [
        "ui-events"
    ],
    "replay_events": true,
    "replay_type": "event_store"
}

Event History Support

To add event history support add the @event_tracker decorator to any event handler your define.

Environment variables

• EVENT_DB_HOST

Hostname of database server

• EVENT_DB_USER

Username for database server

• EVENT_DB_PASS

Password for username

• EVENT_DB_TYPE

Database driver type - defaults to postgres

• EVENT_DB_POOL_SIZE

Database connection pool size - defaults to 5

• EVENT_TRACKING_HOST

For use with replay functionality - host of in memory cache

Supported Drivers

• Crossbar
• Kafka

Crossbar

Quickest way to get started with crossbar is to use docker; both redis and postgresql are required for a minimal working service.

Running Crossbar

docker run -d -p 8080:8080 -it crossbario/crossbar:latest

Running Kafka

• TBD

Running Redis

docker run -d -p 6379:6379 -t redis:latest

Running Postgresql

docker run --name postgres-container -p 5432:5432 -e POSTGRES_PASSWORD=mysecretpassword -d postgres

Note: This does not have a volume or persistant storage so in a production environment you would want to configure a volume

See More

http://crossbar.io

Pypi

https://pypi.python.org/pypi/eventify

Read The Docs

http://eventify.readthedocs.io/en/latest/