Endocrine System: Edge

This is the Endocrine System Core that connects several Endocrine System Edges with each other. For a better understanding also check out the Readme of the Egde.

The main tasks of the Core are:

• Exchanging hormones and definitions
• Access control

At the moment the core depends on MongoDB for clustering purposes. This shall be improved in later versions.

Example

While running this example you should start several instances of the Endocrine System Edge.

"use strict";

const mdns = require( 'es-discovery-mdns' );
const ES = require( './lib/es.js' );

let es = new ES( {
  keyPath: 'server.key',
  certPath: 'server.crt',
  caPath: 'ca.crt',
  mongo: { url: 'mongodb://localhost:27017/es' },
  advertisements: [ mdns.advertisement() ],
  accessControl: {
    in: ( client, name ) => {
      // The hormone name must match with the CN of the client certificate
      let cn = client.subject.CN;
      if( name.substr( 0, cn.length ) == cn ) return Promise.resolve();
      else return Promise.reject();
    },
    out: ( client, name ) => {
      // All hormones are sent to every connected client
      return Promise.resolve();
    }
  }
} );

es.on( 'inRejected', ( client, topic ) => {
  // Notify that we just rejected someone's published message
  let ip = client.connection.stream.remoteAddress;
  console.error( "Publish rejected from " + ip + " on topic " + topic );
} );

API

The Endocrine System Core system can be required as follows. The API description refers to ES.

const ES = require( 'es-core' );

Endocrine System Core

let es = ES( options );

Offers a broker for Endocrine System Edge and returns a broker handle.

options can be:

• certPath: Path to the PEM client certificate.
• keyPath: Path to the PEM client key.
• caPath: Path to the PEM certificate authority that signed the client certificate.
• port: (optional) Port to listen on. Default: 8883.
• advertisements: (optional) Array of advertisement services. They will make the Core discoverable.
• mongo: MongoDB configuration:
  • url: URL to the MongoDB server.
• accessControl: Callback functions for deciding whether or not a message shall pass. If not specified the core will reject by default.
  • in: Callback method called for every incoming hormone. Interface: ( cert, hormoneName ) => {} expecting a promise.
  • out: Callback method called for every outgoing hormone. Interface: ( cert, hormoneName ) => {} expecting a promise.
  • inOther: Callback method called for every MQTT message not related to the endocrine system. Interface: ( cert, topic ) => {} expecting a promise.
  • outOther: Callback method called for every MQTT message not related to the endocrine system. Interface: ( cert, topic ) => {} expecting a promise.

Class: Endocrine System Core

The connection handle es offers some events and methods:

Event: ready

es.on( 'ready', () => { ... } );

Emitted when the server is able to accept incoming connections.

Event: inRejected

es.on( 'inRejected', ( client, topic ) => { ... } );

Emitted if an incoming message is rejected.

Event: outRejected

es.on( 'outRejected', ( client, topic ) => { ... } );

Emitted if an outgoing message is rejected.

Event: inPassed

es.on( 'inPassed', ( client, topic ) => { ... } );

Emitted if an incoming message passed.

Event: outPassed

es.on( 'outPassed', ( client, topic ) => { ... } );

Emitted if an outgoing message passed.

Method: shutdown

es.shutdown();

Shuts down the endorcine system. A promise is returned, that will be resolved if the system has been successfully shut down.