Radar

http://radar.zendesk.com/
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Radar is a real-time service layer that provides high-availability, scalable Node.js infrastructure...
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### Install Radar Client

Source: http://radar.zendesk.com

Add the radar_client package to your project's dependencies using npm.

```bash
npm install --save radar_client
```

--------------------------------

### Initialize Radar Client in HTML

Source: http://radar.zendesk.com

Include the bundled radar_client.js in your HTML and configure the client with necessary parameters like host, port, userId, userType, and accountName.

```html
<!doctype html>
<html>
  <head>
    <title>Test</title>
    <script src="/radar_client.js"></script>
<script>
Minilog.enable();
RadarClient.configure({
  host: window.location.hostname,
  port: 8000,

  userId: Math.floor(Math.random()*100),
  userType: 0,
  accountName: 'dev'
});
</script>
  </head>
  <body>
    <p>Open the developer console...</p>
  </body>
</html>
```

--------------------------------

### Connect to Radar Server using alloc()

Source: http://radar.zendesk.com

Use alloc() to establish a connection to the Radar server. The scope name identifies the functionality, and a callback is executed once the connection is established. Subsequent calls with the same scope name reuse the existing connection.

```javascript
RadarClient.alloc('example', function() {  console.log('Radar is ready'); });
```

--------------------------------

### Initialize Radar Server

Source: http://radar.zendesk.com

Attaches the Radar server to a standard Node.js HTTP server instance using a configuration object.

```javascript
var http = require('http'),
    Radar = require('radar'),
    config = Radar.configurator.load({persistence: true});

// create an HttpServer instance
var server = http.createServer(function(req, res) {
  console.log('404', req.url);
  res.statusCode = 404;
  res.end();
});

// attach Radar server to the HttpServer
var radar = new Radar.server();

radar.attach(server, config);
console.log(config)
server.listen(config.port, function () {
  console.log('Server listening on localhost:' + config.port);  
});
```

--------------------------------

### Initialize Second Client Session and Subscribe

Source: http://radar.zendesk.com

Initializes a second client session and subscribes to the same message resource. This allows for multi-tab or multi-client communication.

```javascript
RadarClient.alloc('example', function() {
      RadarClient.message('chat/1').on(function(message) {
        console.log('Chat:', message.value);
      }).sync();
    });
```

--------------------------------

### Create Combined Client File

Source: http://radar.zendesk.com

Use a Makefile to concatenate the Radar client, engine.io-client, and minilog distribution files into a single JavaScript file for easier distribution.

```makefile
build:
  @echo 'Building public/radar_client.js'
  @mkdir -p public
  @cat ./node_modules/radar_client/node_modules/minilog/dist/minilog.js > public/radar_client.js
  @cat ./node_modules/radar_client/node_modules/engine.io-client/dist/engine.io.js >> public/radar_client.js
  @cat ./node_modules/radar_client/dist/radar_client.js >> public/radar_client.js
  # uncomment if you want to use uglifyJS to further minify the file @uglifyjs --overwrite public/radar_client.js
  @echo 'Wrote public/radar_client.js'

.PHONY: build
```

--------------------------------

### Configure HTTP Server for Client Files

Source: http://radar.zendesk.com

Modify the server's HTTP request handler to serve the bundled radar_client.js and the index.html file. Handles requests for the client script and the root path.

```javascript
var server = http.createServer(function(req, res) {
  var pathname = url.parse(req.url).pathname;

  if (/^\/radar_client.js$/.test(pathname)) {
    res.setHeader('content-type', 'text/javascript');
    res.end(fs.readFileSync('./public/radar_client.js'));
  } else if (pathname == '/') {
    res.setHeader('content-type', 'text/html');
    res.end(fs.readFileSync('./public/index.html'));
  } else {
    console.log('404', req.url);
    res.statusCode = 404;
    res.end();
  }
});
```

--------------------------------

### Subscribe to a MessageList Resource

Source: http://radar.zendesk.com

Subscribe to a MessageList resource to receive messages and historical data. The .on() handler processes incoming messages, while .sync() fetches existing messages and sets up the subscription.

```javascript
RadarClient.message('chat/1').on(function(message) {
      console.log('Chat:', message.value);
    }).sync();
```

--------------------------------

### Subscribe to Presence Events

Source: http://radar.zendesk.com

Subscribe to presence events for a chat channel and log user online/offline status. This code should be run in each client tab.

```javascript
RadarClient.alloc('example', function() {
  RadarClient.presence('chat/1').on(function(message) {
    if (!message.op || !message.value) { return; }
    for (var userId in message.value) {
      if (!message.value.hasOwnProperty(userId)) { continue; }
      if (message.op == 'online' || message.op == 'offline') {
        console.log('User ' + userId+' is now '+message.op);
      }
    }
  }).sync();
});
```

--------------------------------

### Publish a Message to a Resource

Source: http://radar.zendesk.com

Publish a message to a specific resource. Messages published will be received by all clients subscribed to that resource, including the publishing client.

```javascript
RadarClient.message('chat/1').publish('Hello world');
```

--------------------------------

### Set User Presence to Online

Source: http://radar.zendesk.com

Explicitly set the user's presence status to 'online' for a given chat channel. This code should be run in each client tab.

```javascript
RadarClient.presence('chat/1').set('online');
```

--------------------------------

### Register Chat Message Type with Caching Policy

Source: http://radar.zendesk.com

Register a new channel type for chat messages to enable message caching. Configure the maximum number of messages to store per connection using the 'maxCount' option.

```javascript
    var Type = require('radar').core.Type;

    Type.register('chatMessage', {
        expr: new RegExp('^message:/.+/chat/(.+)$'),
        type: 'MessageList',
        policy: { cache: true, maxCount: 300 }
    });
```

--------------------------------

### Set User Presence to Offline

Source: http://radar.zendesk.com

Explicitly set the user's presence status to 'offline' for a given chat channel. This is useful when closing a tab gracefully.

```javascript
RadarClient.presence('chat/1').set('offline');
```
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