Copyright (c) 2022 by Fred George
@author Fred George fredgeorge@acm.org
Licensed under the MIT License; see LICENSE file in root.
A TypeScript implementation of Rapids/Rivers framework using RabbitMQ for the event bus. This also supports JavaScript implementation of services (using TypeScript engine).
This framework models the Rapids/Rivers/Pond metaphor first proposed by Fred George. It strives to present a relatively simple choreography scheme to allow tiny MicroServices to interact with minimal coupling.
Originally formulated for a workshop conference in Bergen, Norway, in 2014(?), and it has been re-implemented several times, including NAV (Norwegian Welfare Association) in 2019 and Orn Software in 2022 (in C#).
This project is built with:
- WebStorm 2022.2.1 (Professional Edition)
- TypeScript 4.7.4
- jest 28.1.3
- ts-jest 28.0.8
- amqplib 0.10.3 (access to RabbitMQ)
An event bus acts as a rapids, an undifferentiated stream of all messages. Access to the rapids is through an adapter; for RabbitMQ, the adapter is the RabbitMqRapidsConnection.
Messages on the event bus are captured into packets. In TypeScript and JavaScript, you can inspect the received fields directly as properties of the packet. You can also create new packets, and add properties to them that will be rendered into JSON automatically on publishing to the rapids.
Using a set of rules, a subset of the rapids is created as a river. Services are attached to a river, and will receive only packets that conform to the rules.
Two TypeScript sample services are provided:
- Need in TypeScript: service generates a stream of messages on the event bus
- Examine this code for how to create and send a Packet
- Monitor in TypeScript: service logs to the console all messages on the bus
- Examine this code for how to attach to the rapids via a river
- Also note the comments for how to set up rules for the packets you want to process
Two corresponding JavaScript sample services are also provided with the same purposes as the TypeScript versions.
Bring up an instance of RabbitMQ, preferably with the management addition to allow browser inspection of what is happening.
Run the Monitor service. Start the compiler-built monitor.js (not the monitor.ts), and be sure to add the startup parameters identifying the RabbitMQ IP address (localhost if running locally) and port number (default is 5672). You should see a console log announcing its start.
Next, run the Need service by starting the compiler-built need.js. Again, IP and port are required parameters. Need should generate a message very five seconds. Monitor should show this message.
If this is all working, you are ready to write your own, new services!