JavaScript

1: nodeJS GRPC Producer
2: nodeJS GRPC Consumer

This section will walk you through how to use FactCast from an application programmers perspective.

Please note, that this is a low-level API. If you’re a Java Programmer and want to use a higher-level API or explore what you can do with FactCast in a more approachable way first, you should have a look at the Factus section.

1 - nodeJS GRPC Producer

Producing Facts via nodeJS is very simple due to the available gRPC NPM Module. It will generate a stub constructor called RemoteFactStore from our proto file.

const uuidV4 = require("uuid/v4");
const grpc = require("grpc");
const protoDescriptor = grpc.load("./FactStore.proto");
const RemoteFactStore =
	protoDescriptor.org.factcast.grpc.api.gen.RemoteFactStore;

// store allows us to publish, subscribe and fetchById (see proto file)
const store = new RemoteFactStore(
	"localhost:9090",
	grpc.credentials.createInsecure()
);

store.publish(
	[
		{
			header: JSON.stringify({
				id: uuidV4(),
				ns: "myapp",
			}),
			payload: JSON.stringify({
				foo: Date.now(),
			}),
		},
	],
	(err, feature) => {
		if (err) {
			console.log(err);
		}
	}
);

See the Facts page for detailed information about all possible and required header fields.

2 - nodeJS GRPC Consumer

const grpc = require("grpc");
const protoDescriptor = grpc.load("./FactStore.proto");
const RemoteFactStore =
	protoDescriptor.org.factcast.grpc.api.gen.RemoteFactStore;

const store = new RemoteFactStore(
	"localhost:9090",
	grpc.credentials.createInsecure()
);

const subscription = store.subscribe({
	json: JSON.stringify({
		continuous: true,
		specs: [
			{
				ns: "myapp",
			},
		],
	}),
});

subscription.on("data", (fact) => {
	console.log(fact);
});