Microserv

JSON-RPC over websocket with multicast service discovery with a browser compatible client

Installation

npm install --save microserv

Usage

Service A

const { Server, Service } = require('microserv')
 
const server = new Server('my-app', { port: 3000 })
const msgService = new Service('message')
 
msgService.register('getMessage', () => {
    return 'Hello, world!'
})
 
server.addService(msgService)
server.listen()
server.announce()

Service B

const http = require('http')
const { Server, Service } = require('microserv')
 
const server = new Server('my-app', { port: 3001 })
const mathService = new Service('math')
 
mathService.register('add', (a, b) => {
    return a + b
})
 
server.addService(mathService)
 
// Wait for the message service to be ready
server.need('message')
    .then(([ message ]) => {
        const app = http.createServer((req, res) => {
            res.statusCode = 200
            res.setHeader('Content-Type', 'text/plain')
 
            // Call the message service `getMessage` method
            message.getMessage()
                .then(msg => {
                    res.end(msg)
                    // { type: 'string', data: 'Hello, world!' }
                })
        })
 
        app.listen(8080, '127.0.0.1')
    })
 
server.listen()
server.announce()

Client

const { Client } = require('microserv')
 
const client = new Client()
 
client.need('message', 'math')
    .then(([ message, math ]) => {
        message
            .getMessage()
            .then(msg => console.log(msg))
 
        math
            .add(1, 2)
            .then(sum => console.log(sum))
    })
 
client.connect('ws://localhost:3000')
client.connect('ws://localhost:3001')

Server

const server = new Server('my-app', { port: 3001 })

new Server(namespace[,options]) -> Client

Instantiate a client

Parameters:

• address {String}: The service namespace. Only services in the same namespace can connect to each other.
• options {Object}: Websocket options
  • port {Number}: Websocket port
  • interval {Number}: How often to announce the service (in ms). Defaults to 5000.
  • sever {http.Server|https.server}: A server to use as the websocket server. If set, will override port.
  • secure {Boolean}: Use secure websockets. Defaults to false.
  • serviceTransform {Function}: A function to transform the data returned from an rpc call. Defaults to noop.
  • authorization {Any}: Credentials to pass to Server when connecting
  • authorizeClient {Function}: A sync or async function to authorize a Client. Function is passed the Client's authorization credentials
  • dns {Object}: dns-discovery options

server.addService(service) -> Server

Add a service to the server, and announce the service to connected peers

Parameters:

• service {Service}: A Service instance

server.need(...services) -> Promise

List required services. Resolves with each of the required services of type ClientService

Parameters:

• services {String}: Service names

server.listen() -> Server

Begin listening for peers

server.announce() -> Server

Announce the service on the network. Will reannounce the service at the interval provided via opts.

Event: 'error'

Emitted when there is an error on the server

Event: 'connection_reset'

Emitted when a connected socket is reset

Service

const service = new Service('my-service')

new Service(name) -> Service

Instantiate a new Service

Parameters:

• name {String}: The service name that will be announced to peers

service.register(method, cb[, resultType]) -> Service

Register an rpc method with the service

Parameters:

• method {String}: The name of the method
• cb {Function}: The function to invoke when the rpc method is called
• resultType {String}: The type of data returned by the method. Defaults to typeof result

service.emit(name, data)

Emits an event via the websocket

Parameters:

• name {String}: The event name
• data {*}: The event data

ClientService

Returned from server.need(). This should not be instantiated direclty.

clientService.subscribe(name, cb)

Subscribe to a service event

Parameters:

• name {String}: The name of the event
• cb {Function}: The event callback

clientService.service_method(*) -> Object

Each method registered with the service is exposed a method of the client service. Returns and object with data and type properties.

Event: 'close'

Emitted when the connection to the service is lost

Event: 'reopen'

Emitted when the connection to a lost service is reestablished

Client

const client = new Client()

new Client([opts, rpcOpts]) -> Client

Instantiate a new Client

Parameters:

• opts {Object}: Options
  • serviceTransform {Function}: A function to transform the data returned from an rpc call. Defaults to noop.
  • authorization {Any}: Credentials to pass to Server when connecting
• rpcOpts {Object}: Options for rpc-websockets

client.connect(connection) -> Websocket

Connect to a specific websocket server

Parameters:

• connection {String}: The server connection string (eg. ws://localhost:3001)

client.need(...service) -> Promise

List required services. Resolves with each of the required services of type ClientService

Parameters:

• services {String}: Service names

Event: 'close'

Emitted when the connection to a service is closed

Event: 'error'

Event: 'unauthorized'

Emitted when the client fails authorization

Tests

npm run test

License

MIT License