harcon-radiation

Harcon-Radiation - An extension to the harcon library to automatically expose services through REST and/or Websocket using Harcon and JsonRPC message formats.

================ harcon-radiation is a small tool extending the harcon library to provide a REST-, and Websocket-based interface. Following your configuration, your services within your entities will be exposed through REST / Websocket automatically.

Every time you publish or revoke an object-based entity, the harcon-radiation reacts to the changes and maintain the interfaces transparently.

!Note: From version 8.0.0, harcon supports only Node v8 and await functions. For callback-based version please use v7 or below.

Installation

$ npm install harcon-radiation

Quick setup

var harcon = new Harcon( { ... } )
await harcon.init( function (err) {} )
var radiation = new Radiation( harcon, { ... } )
await radiation.init( )
var rest = require('connect-rest')
var connect = require('connect')
...
var app = connect()
...
app.use( await radiation.rester( rest, options ) ) // Activates the REST services
...
server = http.createServer(app)
io = radiation.io( io.listen( server ) ) // Activates the Websocket services
...
harcon.addicts( {
	name: 'julie',
	context: 'book',
	rest: true,
	websocket: true,
	log: async function( data ){
		return 'Done.'
	}
} )

The example shows how you can attach the radiation to a connect/express instance and link to your harcon instance. You can activate the REST and Websocket interfaces. Any object-based entities published to harcon possessing attributes 'rest' and 'websocket' will be exposed through those interfaces automatically.

Regulate publishing process

The default behavior is to publish all services. However, one can define rules to make exceptions. By setting the option hideInnerServices, harcon-radiation will hide inner services and won't publish them

var radiation = new Radiation( harcon, { hideInnerServices: true } )

harcon-radiation ignores a service in 2 cases:

• its name starts with a given prefix

	var radiation = new Radiation( harcon, { hideInnerServices: true, innerServicesPrefix: '_' } )

• its name matches to a given pattern

	var radiation = new Radiation( harcon, { hideInnerServices: true, innerServicesFn: function(name){
		return name.startsWith('inner') || name.startsWith('sys')
	} } )

Call REST

There are 3 options to expose services through REST-like interface:

• RESTful: each service will be exposed on different URI according the name of the division, context/entity and service...
• JSON-RPC 2.0: one single URI acccepting JSON-RPC 2.0 calls
• Harcon RPC: one single URI accepting a harcon JSON

By default, option 1 is turned on, and the rest options are passive.

RESTful

RESTful interface means a POST service using the addressing logic implemented in harcon. To address a service exposed, you have to compose a URI using the name of the division[, context], entity and service. By calling the following URI:

post -> 'http://localhost:8080/Harcon/book/log'

with a body of

{ params: [ 'Hello!'] }

will address the service 'log' of the component 'book' in the division 'Harcon'. The of the entity will be sent as JSON.

JSON-RPC 2.0

harcon-radiation supports JSON-RPC 2.0 if you create the instace as follows:

	var radiation = new Radiation( harcon, rest: { jsonrpcPath: '/RPCTwo' } )

This will accept POST request on the path '/RPCTwo' respecting the JSON-RPC 2.0 standard.

Note: be aware the limitations of JSON-RPC. It does not support orchestration like divisions or contexts, therefore addressing should be limited to entityname.service, subdomains/subcontexts cannot be addressed.

Harcon-RPC

The following settings will activate the Harcon-RPC option on URI '/Harcon':

	var radiation = new Radiation( harcon, { rest: { harconrpcPath: '/Harcon' } } )

By sending the following JSON to the address, you can address the method 'terminus' of the entity 'marie' in the division 'King.charming':

	{ division: 'King.charming', event: 'marie.terminus', params: ['Szióka!'] }

Websockets

Using Websockets is also straightforward. By default, the URI will be the name of your Harcon instance. You can override it by the following config:

	var radiation = new Radiation( harcon, { websocket: { harconPath: '/Socket' } } )

Send packet to that address:

var socket = ioclient( 'http://localhost:8080/Socket' )
socket.emit('ignite', { id: '10', division: 'Inflicter', event: 'book.log', params: [ 'Helloka!' ] } )

This will send the JS object to the room 'Socket'. By sending an 'ignite' message and passing the communication object you want to deliver will call the function.

The response will be sent as 'done' or 'error' message depending on the result.

Note: The ID is highly recommended to be passed to differentiate the incoming answer packets.

JSON-RPC 2.0 over Websocket

This service can be turned on by the following configuration:

	var radiation = new Radiation( harcon, { websocket: { jsonrpcPath: '/SocketRPC' } } )

It will accept and send JSON-RPC JSON packets...

Emit message to websocket listeners

You can send out / broadcast messages to connected listeners if your business entity calls the method 'shifted', which is a built-in service of harcon letting entities to inform the system about state changes. harcon-radiation uses this mechanism to send out those messages to the websocket listeners.

	this.shifted( { mood: 'happy' } )

That will send the message 'mood' to the connected clients with the data 'happy'. All properties of the object sent will be turned into separate messages to be broadcasted. And the payload of the messages will be set by the value of the given property.

Note: Considering the nature of the JSON-RPC 2.0, this level of service is available only for the 'normal' websockets clients.

Distinguish websocket clients

By default, the function 'shifted' emits message to all listeners connected. Some business cases desire more focused approach, targeting a defined group of clients. During the 'ignite' message processing, harcon-radiation allows you to have a injected service which is performed when the results are about to send back to the caller.

THe configuration file might define the following attribute:

assignSocket: function (event) {
	return async function ( terms, res, socket ) {
		return res
	}
}

The function 'assignSocket' is called as a final step of message processing. It requires a function as a return value answering the event just processed. By default, it is the same function doing nothing. You can extend this to inject your logic to mark sockets as below:

assignSocket: function (event) {
	return async function ( terms, name, socket ) {
		if (event === 'Julie.login') {
			socket.name = name[0]
			socket.join( name[0] )
			resolve( name )
		}
		else resolve( res )
	}
}

This definition tells the harcon-radiation to use another function for events 'Julie.login'. If the login was successful, the name is associated to the socket connected.

Using sockets, you have 2 ways to walk on:

• associate sockets to rooms
• add custom attributes to socket instances

You can use one of them or both, as you wish.

Either way, you can identify clients easily by specifying selection expression in function 'shift' as below:

this.shifted( { mood: 'Pour toi, Claire' }, 'Claire' )

This solution identifies the room 'Claire' targeting all sockets within.

this.shifted( { mood: 'C\'est fini, Marie' }, {name: 'Marie'} )

This solution identifies all sockets possessing the given attributes and values.

Security

harcon-radiation is using connect-rest inside and allows you to use the security features of that REST lib. Your components might possess a protector function which should retrieve protector function used by the connect-rest when it is called. The service parameter can be used to differentiate the different security aspects your services cover.

harcon.addicts( {
	name: 'julie',
	rest: true,
	security: {
		protector: function(service){
			return async function( req, res, pathname, path ){
				throw new Error('Something is fishy')
			}
		}
	}
} )

About the protector functions, please find the description here.

Note: this feature is valid only for REST option 1.

Shield

harcon-radiation allows you to define a shield function in the config file in order to protect the system against unwanted addressing or reaching restricted area:

var harcon = new Harcon( {
	...
	shield: function (division, event) {
		return false
	}
} )

Should that function return 'true', the incoming message should be rejected with an error: 'Message has been blocked'

Nimesis

Nimesis is a built-in entity of harcon-radiation providing one single service:

mimic: function( entityDef ){

It accepts harcon entity definitions as string and converts them to entity definitions then publishes it according its configuration. By default, all services will be exposed through REST and Websockets as well. Serves well when dynamic extension or ability to publish services on-the-fly is a requirement. The Nimesis Will hold only 1 definition as reference. When a new definition incomes, the previous one will be destructed.

Calling the function 'reshape' will remove the published entity.

Note: this feature is serving special purposes, use it with adequate caution.

License

(The MIT License)

Copyright (c) 2016 Imre Fazekas

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Bugs

See https://github.com/imrefazekas/harcon-radiation/issues.