Logux Server

Logux is a client-server communication protocol. It synchronizes actions between clients and server logs.

This framework helps you to write Logux server and define back-end callbacks for each client’s event type.

Getting Started

Installation

Create new Node.js project:

mkdir PROJECT_NAME
cd PROJECT_NAME
npm init

Install Logux Server:

npm install --save logux-server logux-core

Create Main File

Create server.js with this boilerplate:

const Server = require('logux-server').Server

const app = new Server(
  Server.loadOptions(process, {
    subprotocol: '1.0.0',
    supports: '1.x',
    root: __dirname
  })
)

app.auth((userId, token) => {
  // TODO Check token and return a Promise with true or false.
})

app.listen()

Write Business Logic

Logux is a communication protocol. It doesn’t know anything about your database. You need to write custom logic inside your action callbacks.

app.type('CHANGE_NAME', {
  access (action, meta, creator) {
    return action.user === creator.userId
  },
  process (action) {
    return users.find({ id: action.user }).then(user => {
      user.update({ name: action.name })
    })
  }
})

Read logux-core docs for app.log API.

If you already have business logic written in PHP, Ruby, Java — don’t worry. You can do whatever you want in the action listener. For one, you may just call the legacy REST API:

  process (action) {
    request.put(`http://example.com/users/${action.user}`).form({
      name: action.name
    })
  }

Control Data Access

By default other clients will not receive new actions.

There are 3 ways to send new action to client.

Set nodeIds: ['10:h40vj5'] in action’s metadata.
Set users: ['10'] in action’s metadata.
Using channels.

Before using channel, you need to define it:

app.channel('user/:id', (params, action, meta, creator) => {
  if (params.id !== creator.userId) {
    // Access denied
    return false
  } else {
    // Sending initial state
    db.loadUser(params.id).then(user => {
      app.log.add(
        { type: 'USER_NAME', name: user.name },
        {
          nodeIds: [creator.nodeId],
          time: user.nameChangedAt * 1000
        })
    })
    return true
  }
})

Then server or clients could create actions with channels: ['user/10'] in action’s metadata.

logux/subscribe action will subscribe client to a channel:

client.log.add({ type: 'logux/subscribe', channel: 'user/10' })

To send action to channel, add channels metadata:

client.log.add(
  { type: 'CHANGE_NAME', name: 'New', user: 10 },
  { channels: ['user/10'] }
)

Note, that everyone could send actions to a channel. If you don’t want it, check metadata in access() callbacks inside type() definition.

Test Your Logic Locally

You can run your server with:

npm start

Use ws://localhost:1337 URL in Logux Client.

Get SSL Certificate

Logux uses WebSockets for communicating between client and server. Without SSL, old proxies and firewalls can block WebSockets connection. Also, SSL will obviously help to prevent many attacks against your server.

Probably the best way to get a free SSL certificate is Let’s Encrypt.

Save certificate PEM-files to cert.pem and key.pem in your project directory or change listen() options to correct certificate paths.

Start Production Server

Use your favorite DevOps tools to start Logux server in production mode:

NODE_ENV=production npm start

You DevOps tools could set Logux Server options via arguments or environment variables:

Command-line	Environment	Description
`-h`, `--host`	`LOGUX_HOST`	Host to bind server
`-p`, `--port`	`LOGUX_PORT`	Port to bind server
`-k`, `--key`	`LOGUX_KEY`	Path to SSL key
`-c`, `--cert`	`LOGUX_CERT`	Path to SSL certificate

arhelmus/logux-server