spring-river

Disclaimer

This library is my attempt to make a javascript version of Fred George's (@fredgeorge) RapidsRivers following Zeit's Micro simple bootstrap approach. This is just an experiment at this point.

For more information on the Rapids/Rivers/Ponds paradigm, please refer to the links at the bottom of this file.

Usage

If you learn by looking at code first, check out examples directory.

Now onto the step-by-step:

First, you need to install spring-river as a runtime dependency:

``shell
npm install spring-river --save
`

This library requires an amqp-compatible queue. RabbitMQ works perfectly. In order to configure the queue address, you can either set the environment variable ADDRESS or add the --address (or -a) flag when starting your services and set the address as amqp://….

$3

If your microservice is the one generating "solutions", add a {"start": "river"} script, like the following, to your package.json:

`json
{
"main": "index.js",
"name": "my-microservice-river",
"scripts": {
"start": "river"
}
}
`

Your index.js will look like the following. It accepts a packet, which is, for all purposes, a plain javascript object with the packet's contents, and a publish function, which can be used to publish conclusions back to the rapids.

`javascript
module.exports = (packet, publish) => {
packet.solution = 10;
publish(packet);
};
`

To get you service running, all you need to do is to run:

`shell
npm start
`

$3

If your microservice is the one generating "needs", add a {"start": "spring"} script, like the following, to your package.json:

`json
{
"main": "index.js",
"name": "my-microservice-spring",
"scripts": {
"start": "spring"
}
}
`

Your index.js will look like the following. It accepts a publish function, which can be used to publish conclusions (a need is a conclusion) to the rapids.

`javascript
module.exports = (publish) => {
setInterval(() => {
publish({need: 'rental_car_offer'});
}, 5000)
};
`

To get you service running, all you need to do is to run:

`shell
npm start
`

$3

By definition, your exported function will be called whenever a packet arrives (this is so we can keep the bus a dumb pipe). In order to filter out and focus only on interesting packets, you can use decorators around your to-be-exported function. E.g.:

`javascript
const myFilter = require('./my-filter');

module.exports = myFilter((packet, publish) => {
packet.solution = 10;
publish(packet);
});
`

Where my-filter.js could be something that filters only packets that have {need: 'rental_car_offer'}:

`javascript
module.exports = (next) => (packet, publish) => {
if (packet.need === 'rental_car_offer') {
next(packet, publish);
}
}
`

This library ships with a few built-in predicates that you might find useful (perhaps these are candidates to be moved out into their own modules, as these are just very simple functions).

#### Usage

The following example is interested in packets that contain the {need: 'rental_car_offer'} key-value pair and does not have a solution key:

`javascript
const predicates = require('spring-river/predicates');
const {requireValues, forbidKeys} = predicates;

module.exports = predicates(
requireValues({need: 'rental_car_offer'}),
forbidKeys('solution')
)((packet, publish) => {
packet.solution = 10;
publish(packet);
});

`

Credits

First and foremost, everything here is built based on Fred George's (@fredgeorge) Rapids/Rivers/Ponds paradigm, so here's a list of resources if you want to get more familiar with this idea:

* https://vimeo.com/79866979
* https://youtu.be/2rKEveL55TY
* https://github.com/fredgeorge/rapids_rivers
* https://github.com/fredgeorge/microservice_workshop
* https://www.infoq.com/news/2016/02/not-just-microservices

The structure of this module was inspired by Zeit's Micro, so bin/index.js` borrows a lot from it.

License

This software is licensed under the MIT license.

---