mudb

mudb

A database for real-time server-client applications.

A mudb application has one MuServer and several MuClients. Each node consists of one or more protocols which define different behaviors.

A protocol is essentially a collection of event handlers. To define a protocol, typically you need to specify

• a protocol schema
• a server protocol
• a client protocol

example

Here is a minimal chat room demo, heavily documented to show how to define a protocol using mudb.

schema.js The first step of creating any applications with mudb is to specify a protocol schema using muschema, defining the data structures of different messages that all parties agree on.

var muschema = require('muschema')
var MuStruct = muschema.MuStruct
var MuString = muschema.MuString

// define a protocol schema, which always contains a `server` and a `client` property
exports.ChatSchema = {
    // define data structures of messages sent to client
    client: {
        // each `chat` message contains a record with
        // a `name` property of string type
        // a `text` property of string type
        // both should always be present
        chat: new MuStruct({
            name: new MuString(),
            text: new MuString(),
        }),
    },
    // define data structures of messages sent to server
    server: {
        // each `say` message contains a string
        say: new MuString(),
    },
}

server.js

function randomName () {
    return Math.random().toString(36).substr(2, 11)
}

// `server` should be a `MuServer`
module.exports = function (server) {
    // create a protocol and add it to `server`
    var serverProtocol = server.protocol(require('./schema').ChatSchema)

    // a dictionary of clients' displayed names
    var clientNames = {}

    // configure protocol by specifying handlers
    serverProtocol.configure({
        // handlers for client messages
        message: {
            // whenever a client sends a `say` message (i.e. clientProtocol.server.message.say()),
            // server should broadcast the content to everyone, along with sender's displayed name
            say: function (client, content) {
                // fist argument of every client message handler is a reference
                // to client who sent the message

                // broadcast sender's name and text content, both of which are strings contained in a record,
                // as described in `ChatSchema.client.chat`, to all connected clients in a `chat` message
                serverProtocol.broadcast.chat({
                    name: clientNames[client.sessionId],
                    text: content,
                })
            },
        },
        // when a client connects, server should inform everyone
        connect: function (client) {
            // set client's displayed name to a random string
            clientNames[client.sessionId] = randomName()
            // also broadcast a `chat` message to all connected clients
            // except this time the message is from server
            serverProtocol.broadcast.chat({
                name: 'server',
                text: clientNames[client.sessionId] + ' joined the channel',
            })
        },
        // when a client disconnects, server should also inform everyone
        disconnect: function (client) {
            serverProtocol.broadcast.chat({
                name: 'server',
                text: clientNames[client.sessionId] + ' left',
            })
            // stop tracking client's displayed name
            delete clientNames[client.sessionId]
        },
    })

    // launch server after creating and configuring all protocols
    server.start()
}

client.js

// `client` should be a `MuClient`
module.exports = function (client) {
    var messageDiv = document.createElement('div')
    var textLabel = document.createElement('label')
    var textInput = document.createElement('input')

    // create a protocol and add it to `client`
    var clientProtocol = client.protocol(require('./schema').ChatSchema)

    messageDiv.style.overflow = 'auto'
    messageDiv.style.width = '400px'
    messageDiv.style.height = '300px'

    textLabel.textContent = 'message: '

    textInput.type = 'text'
    textInput.style.width = '400px'
    textInput.style.padding = '0px'
    textInput.style.margin = '0px'

    document.body.appendChild(messageDiv)
    document.body.appendChild(document.createElement('br'))
    document.body.appendChild(textLabel)
    document.body.appendChild(textInput)

    // configure protocol by specifying handlers
    clientProtocol.configure({
        // when client is ready to handle messages
        ready: function () {
            textInput.addEventListener('keydown', function (ev) {
                // when pressing `enter` on the input box
                if (ev.keyCode === 13) {
                    // send a `say` message to server
                    // the message being sent contains the text in the input box,
                    // a string, as described by `ChatSchema.server.say`
                    clientProtocol.server.message.say(textInput.value)
                    // empty input box
                    textInput.value = ''
                }
            })
        },
        // handlers for server messages
        message: {
            // whenever server sends a `chat` message (e.g. serverProtocol.broadcast.chat()),
            chat: function (data) {
                // which contains name of whoever said something and the content
                var name = data.name
                var text = data.text

                // print name and content out in message box
                var textNode = document.createTextNode(name + ": " + text)
                messageDiv.appendChild(textNode)
                messageDiv.appendChild(document.createElement('br'))
            }
        }
    })

    // open client after creating and configuring all protocols
    client.start()
}

To run the demo,

• cd into the directory containing the three files above
• npm i mudo
• mudo --socket websocket --open

table of contents

• 1 install
• 2 api
  • 2.1 interfaces
    • 2.1.1 MuSocket
      • 2.1.1.1 sessionId:string
      • 2.1.1.2 open:boolean
      • 2.1.1.3 start(spec)
      • 2.1.1.4 send(data:Uint8Array|string, unreliable?:boolean)
      • 2.1.1.5 close()
    • 2.1.2 MuSocketServer
      • 2.1.2.1 clients:MuSocket[]
      • 2.1.2.2 open:boolean
      • 2.1.2.3 start(spec)
      • 2.1.2.4 close()
  • 2.2 MuServer(socketServer:MuSocketServer)
    • 2.2.1 protocol(schema:ProtocolSchema) : MuServerProtocol
    • 2.2.2 start(spec?)
    • 2.2.3 destroy()
  • 2.3 MuServerProtocol
    • 2.3.1 broadcast:TableOf<DispatchFn>
    • 2.3.2 configure(spec)
  • 2.4 MuRemoteClient
    • 2.4.1 sessionId
    • 2.4.2 message:TableOf<DispatchFn>
    • 2.4.3 sendRaw:SendRawFn
    • 2.4.4 close()
  • 2.5 MuClient(socket:MuSocket)
    • 2.5.1 protocol(schema:ProtocolSchema) : MuClientProtocol
    • 2.5.2 start(spec?)
    • 2.5.3 destroy()
  • 2.6 MuClientProtocol
    • 2.6.1 server:MuRemoteServer
    • 2.6.2 configure(spec)
  • 2.7 MuRemoteServer
    • 2.7.1 message:TableOf<DispatchFn>
• 3 usage tips
• 4 helpful modules
• 5 more examples
• 6 TODO

1 install

npm i mudb muweb-socket mulocal-socket

2 api

2.1 interfaces

Purely instructive types used to describe the API:

• TableOf<T>: { [messageName:string]:T } | {}
• ProtocolSchema: { server:TableOf<AnyMuSchema>, client:TableOf<AnyMuSchema> }
• DispatchFn: (data, unreliable?:boolean) => undefined
• SendRawFn: (data:Uint8Array|string, unreliable?:boolean) => undefined
• ClientMessageHandler: (client:MuRemoteClient, data, unreliable?:boolean) => undefined
• ServerMessageHandler: (data, unreliable:boolean) => undefined

To create a mudb application, a socket (i.e. a MuSocket instance) and a corresponding socket server (i.e. a MuSocketServer instance) are required. We try to make mudb extensible by allowing you to use a customized socket-server implementation.

A few socket modules are provided out of the box alongside mudb (e.g. muweb-socket). Make sure that you have checked those out before trying to create your own socket modules.

2.1.1 MuSocket

MuSockets are bidirectional sockets. They support both reliable, ordered streams and unreliable optimistic packet transfer. Any mudb sockets should implement the MuSocket interface as described below.

2.1.1.1 sessionId:string

Required property, a unique session id identifying the socket

2.1.1.2 open:boolean

Required property, a flag determining whether the socket is open

2.1.1.3 start(spec)

Required method, can be used to establish a connection to the server from the client side

• spec:{ ready, message, close }
  • ready() should be called when the connection is ready
  • message(data:Uint8Array|string, unreliable:boolean) should be called when receiving messages
  • close(error?) should be called when the connection is closed

2.1.1.4 send(data:Uint8Array|string, unreliable?:boolean)

Required method, used to send messages to the other end of the connection

2.1.1.5 close()

Required method, used to close the connection

2.1.2 MuSocketServer

A MuSocketServer handles client communications coming through the corresponding MuSockets. Any mudb socket servers should implement the MuSocketServer interface as described below.

2.1.2.1 clients:MuSocket[]

Required property, server-side mocks of connected clients

2.1.2.2 open:boolean

Required property, a flag determining whether the socket server is running

2.1.2.3 start(spec)

Required method, used to launch the socket server

• spec:{ ready, connection, close }
  • ready() should be called when the socket server is launched
  • connection(client:MuSocket) should be called when a client connects
  • close(error?) should be called when the socket server is closed

2.1.2.4 close()

Required method, used to shut down the socket server

2.2 MuServer(socketServer:MuSocketServer)

var httpServer = require('http').createServer(/* ... */)
var socketServer = new require('muweb-socket').MuWebSocketServer(httpServer)
var muServer = new require('mudb').MuServer(socketServer)

2.2.1 protocol(schema:ProtocolSchema) : MuServerProtocol

Adds a server protocol, and returns it to be configured.

A MuServer can have multiple protocols. Note that you cannot add any new protocols after the server is started.

2.2.2 start(spec?)

Launches server.

• spec:{ ready?, close? }
  • ready(): called when the underlying socket server is launched
  • close(error?): called when the underlying socket server is closed

2.2.3 destroy()

Shuts down the underlying socket server and terminates all clients. Useful when having multiple instances of mudb.

2.3 MuServerProtocol

2.3.1 broadcast:TableOf<DispatchFn>

An object of methods, each of which broadcasts to all connected clients. Each message (delta encoded) will be handled by a specific handler. For example, the message sent by protocol.broadcast.shower(shampoo, true) will be handled by the shower method on the corresponding client protocol, as shower(shampoo, true). So this is effectively dispatching method calls to a remote object.

broadcastRaw:SendRawFn

A method that broadcasts to all connected clients with "raw" (not processed, contrary to delta) messages. The messages will be handled by the raw message handler of the corresponding client protocol.

2.3.2 configure(spec)

Each protocol should be configured before the server is started and can be configured only once, by specifying the event handlers in spec.

• spec:{ message, ready?, connect?, raw?, disconnect?, close? }
  • message:TableOf<ClientMessageHandler> required
  • ready() called when the underlying socket server is launched
  • connect(client:MuRemoteClient) called when a client connects
  • raw(client:MuRemoteClient, data:Uint8Array|string, unreliable:boolean) called when a "raw" message is received
  • disconnect(client:MuRemoteClient) called when a client disconnects
  • close() called when the underlying socket server is closed

2.4 MuRemoteClient

A MuRemoteClient is the server-side representation of a client, used in the event handlers.

2.4.1 sessionId

A string representing a unique session id identifying the client.

2.4.2 message:TableOf<DispatchFn>

An object of methods, each of which sends messages (delta encoded) to the corresponding client.

2.4.3 sendRaw:SendRawFn

A method that sends "raw" messages to the corresponding client.

2.4.4 close()

Closes the reliable socket.

2.5 MuClient(socket:MuSocket)

var socket = new require('muweb-socket/socket').MuWebSocket(spec)
var muClient = new require('mudb').MuClient(socket)

2.5.1 protocol(schema:ProtocolSchema) : MuClientProtocol

Adds a client protocol, and returns it to be configured.

A MuClient can have multiple protocols. Note that you cannot add any new protocols after the client is started.

2.5.2 start(spec?)

Runs client.

• spec:{ ready?, close? }
  • ready(error?:string) called when the client is ready to handle messages
  • close(error?:string) called when all sockets are closed

2.5.3 destroy()

Closes all sockets.

2.6 MuClientProtocol

2.6.1 server:MuRemoteServer

The client-side representation of the server.

2.6.2 configure(spec)

Each protocol should be configured before the client is started and can be configured only once, by specifying the event handlers in spec.

• spec:{ message, ready?, raw?, close? }
  • message:TableOf<ServerMessageHandler> required
  • ready() called when the client is ready to handle messages
  • raw(data:Uint8Array|string, unreliable:boolean) called when receiving a "raw" message
  • close() called when all sockets are closed

2.7 MuRemoteServer

2.7.1 message:TableOf<DispatchFn>

An object of methods, each of which sends specific messages (delta encoded) to the server.

sendRaw:SendRawFn

A method that sends "raw" messages to the server.

3 usage tips

4 helpful modules

5 more examples

6 TODO

• more test cases

credits

Development supported by Shenzhen DianMao Digital Technology Co., Ltd.

Written in Shenzhen, China.

(c) 2017 Mikola Lysenko, Shenzhen DianMao Digital Technology Co., Ltd.