rabbit-eventstore


rabbit-eventstore
=================

This is an event sourcing CQRS framework for nodejs and rabbitmq.
It consists of:

* A server listening to a RabbitMQ queue for event messages. Each event message
will get a "position number" (which is an uniqe incremental id) and be
appended to a log/storage file. After properly numbered and stored, the event
message will be re-published (with the position number) to an AMQP fanout
exchange.
* A javascript module for publishing new events. ("The command.")
* A javascript module for fetching events. ("The listener.")

some generic principles
-----------------------

* The event messages must be JSON.

the server
----------

$3

To download all events messages, just make an HTTP request to the server!
(We don't check HTTP method, path or anything. Just make a request!)

The event messages are JSON blobs separated by line break.

the listener
------------

The listener will fetch historic events from the position you give, and listen
to new events. They will come in strict order!

``javascript
const listener = require('rabbit-eventstore/listener');

// Start fetching events from position 50:
listener.listen(50, msg => {
console.log('Incoming event:', msg);
});

// Start fetching events from the beginning of time:
listener.listen(0, msg => {
console.log('Incoming event:', msg);
});

// Just fetch new events (from now on):
listener.listen(msg => {
console.log('Incoming event:', msg);
});
`

If you are returning a promise from them listen callback, the next message will
not be fetched until you resolve the promise.


environment vars
----------------

$3

* AMQPHOST - The domain/hostname/ip to connect to. Default is localhost.
* DEBUG - Set to something truthy to output debug messages to stdout.
* EXCHANGENAME - The AMQP exchange to publish to. Default is events.
* QUEUENAME - The AMQP queue to consume. Default is events.

$3

* PORT - Listen on this port for http requests. Default is 80.
* STORAGEFILE - The file path to save event messages to. Default is ./storage.

$3

* HISTORYURL - Url to the http interface of the server (to get historic
events). Default is http://localhost/`.

roadmap
-------

* Different AMQP servers for the consuming queue and the fanout. (For future
scaling.)
* Rotation of the storage file. Maybe pushing old storage files to AWS S3 or
such services.