Merge branch 'master' of https://github.com/codelotus/howtonode.org

articles/redis-pubsub.markdown

@@ -0,0 +1,167 @@
+Title: Node.js and Redis Pub-Sub
+Author: James R. Bracy
+Date: Sat Oct 09 2010 19:30:48 GMT-0400 (EDT)
+Node: v0.2.0
+
+> This is the 7th in a series of posts leading up to [Node.js Knockout](http://nodeknockout.com/) on how to use [node.js](http://nodejs.org/). This post, [cross-posted from GitHub](http://github.com/waratuman/flight-stream), was written by [James Bracy](http://github.com/waratuman), founder of [Redis To Go](http://redistogo.com). [Redis To Go](http://redistogo.com) is a dead simple solution for managed Redis instances.
+
+## Node.js and Redis Pub-Sub
+
+[Node.js](http://nodejs.org/) is a perfect platform for creating event driven
+applications. [Redis](http://code.google.com/p/redis/) and [WebSockets](http://en.wikipedia.org/wiki/WebSockets)
+are great companions to Node.js. The following tutorial will walk through the
+steps to build a web application that streams real time flight information
+using Node.js, Redis, and WebSockets.
+
+## Dependencies
+
+Node.js, Redis, and a WebSocket enabled browser ([Firefox 4](http://www.mozilla.com/en-US/firefox/beta/),
+[Google Chrome 4](http://www.google.com/chrome), or [Safari 5](http://www.apple.com/safari/))
+are required. A tutorial covering the installation of Node.js can be found
+[here](http://nodeknockout.posterous.com/countdown-to-knockout-post-1-how-to-install-n).
+
+The easiest way to get a Redis instance would be to use [Redis To Go](http://redistogo.com/).
+The free plan is all that is needed for this tutorial. If you wish to install
+locally run the following commands:
+
+    $ git clone http://github.com/antirez/redis.git
+    $ cd redis/src
+    $ make
+    $ sudo make install
+    $ cd ../..
+    $ rm -rf redis
+
+Now you can start a Redis instance locally using the `redis-server` command.
+
+## Create the Project
+
+Create a directory for the project. We will name the project "Flight Stream".
+
+    $ mkdir flight-stream
+    $ cd flight-stream
+
+The project will require the Node.js Redis client [`redis-client`](http://github.com/fictorial/redis-node-client),
+the WebSocket library [`node-websocket-server`](http://github.com/miksago/node-websocket-server),
+and the MIME library [node-mime](http://github.com/bentomas/node-mime). Create
+a `lib` directory and copy the libraries to this directory.
+
+    $ mkdir lib
+    $ cd lib
+    $ curl -O http://github.com/fictorial/redis-node-client/raw/master/lib/redis-client.js \
+           -O http://github.com/bentomas/node-mime/raw/master/mime.js \
+           -O http://github.com/miksago/node-websocket-server/raw/master/lib/ws.js
+    $ mkdir ws
+    $ cd ws
+    $ curl -O http://github.com/miksago/node-websocket-server/raw/master/lib/ws/connection.js \
+           -O http://github.com/miksago/node-websocket-server/raw/master/lib/ws/manager.js
+    $ cd ../..
+
+## Create the Server
+
+Initially the Node.js server will simply server the static index.html file that
+will be create. Create the `server.js` file and add the following code:
+
+<redis-pubsub/server.js>
+
+The `httpServer` serves the static files in the `public` directory. The
+`server` is what will be handling the WebSocket connections.
+
+Create the `public` directory:
+
+    $ mkdir public
+
+Now copy the source for the index and stylesheets from [github](http://github.com/waratuman/flight-stream).
+
+    $ cd public
+    $ curl -O http://github.com/waratuman/flight-stream/raw/master/public/application.css \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/reset.css \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/jquery.js \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/text.css \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/index.html
+    $ mkdir images
+    $ cd images
+    $ curl -O http://github.com/waratuman/flight-stream/raw/master/public/images/background.png \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/images/red.png \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/images/orange.png \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/images/green.png \
+           -O http://github.com/waratuman/flight-stream/raw/master/public/images/blue.png
+
+At this point you should be able to run `node server.js` and see the index
+page when you got to `localhost:8000`.
+
+Now lets get `redis-client` working in the server. The following lines
+establish a connection to Redis. The `connected` and `reconnected` listeners
+authenticate the connection after it has been established.
+
+<redis-pubsub/redis-client.js>
+
+<cite style="float: right;">View the full source [here](http://github.com/waratuman/flight-stream/blob/master/server.js)</cite>
+<br /><br />
+
+Now subscribe to the `flight_stream` channel on Redis.
+
+<redis-pubsub/redis-subscribe.js>
+
+<cite style="float: right;">View the full source [here](http://github.com/waratuman/flight-stream/blob/master/server.js)</cite>
+<br /><br />
+
+Whenever a message is published the function passed to the `subscribeTo`
+method will get called. In this case we try to parse the message as JSON then
+publish it to all of the clients if the flight is leaving Boston or arriving
+at Boston.
+
+# Client
+
+Next the client will need to be coded. I previously created the HTML for this
+app, so all that we need to do is set up the WebSockets.
+
+Open `public/application.js` and insert the following code. This code will
+create a WebSocket if the browser supports it and if it does, create a
+connection with the server. When a message is received, another row will be
+inserted on the page displaying the flight.
+
+<redis-pubsub/application.js>
+
+The functions `delay_color` and `delay_name` are helper functions for
+displaying text and selecting the right class for styling.
+
+Now you can start the server, go to [http://localhost:8000/](http://localhost:8000/)
+and you should start seeing updates roll in. If you are using your own Redis,
+you are going to need to publish something to the `flight_stream`. Here is a 
+sample message that you can use:
+
+    {
+        "number": "482",
+        "status": "Scheduled",
+        "origin": {
+            "gate_delay": 0,
+            "icao": "KSFO",
+            "name": "San Francisco International Airport",
+            "iata": "SFO",
+            "gate": "3-88"
+        },
+        "destination": {
+            "gate_delay": 0,
+            "icao": "KBOS",
+            "name": "Denver International Airport",
+            "iata": "BOS",
+            "gate": "-"
+        },
+        "airline": {
+            "icao": "UAL",
+            "name": "United Airlines",
+            "iata": "UA"
+        }
+    }
+
+If you are using the Redis instance used throughout the tutorial, you will
+start seeing flight come up. I will be publishing some data every few seconds
+to the instance for the coming days.
+
+## Basic Operations
+
+Basic operations were not really covered in this tutorial, so here are some
+examples to get you started.
+
+<redis-pubsub/basic-operations.js>
+

articles/redis-pubsub/application.js

@@ -0,0 +1,46 @@
+
+function delay_color(mins) {
+    var min = parseInt(mins);
+    if (min <= -15) return 'green';
+    else if (min <= 0) return 'green';
+    else if (min <= 15) return 'orange';
+    else return 'red';
+}
+
+function delay_name(mins) {
+    var min = parseInt(mins);
+    if (min <= 0) return 'On-Time';
+    else return 'Delayed';
+}
+
+var ws;
+var connect = function() {
+    if (!window['WebSocket']) {
+        alert("No WebSocket support.");
+        return;
+    }
+
+    ws = new WebSocket('ws://' + window.location.host);
+    ws.onmessage = function(evt) {
+        try { var flight = JSON.parse(evt.data); }
+        catch (SyntaxError) { return false; }
+
+        $('table.flight-updates > tbody').prepend(
+            '<tr>' +
+                '<td>' + flight.airline.icao + ' ' + flight.number + '</td>' +
+                '<td>' + flight.origin.iata + '</td>' +
+                '<td>' + flight.destination.iata + '</td>' +
+                '<td>' +
+                    '<div class="tag ' + delay_color(flight.destination.gate_delay) + '">' +
+                        delay_name(flight.destination.gate_delay) +
+                        '<span>' + flight.destination.gate_delay + ' min</span>' +
+                    '</div>'+
+                '</td>'+
+                '<td>' + flight.destination.gate + '</td>' +
+            '</tr>');
+    };
+};
+
+$(document).ready( function() {
+    connect();
+});

articles/redis-pubsub/basic-operations.js

@@ -0,0 +1,6 @@
+db.set("foo", 1)
+db.get("foo", function(err, value) { sys.puts(value); });
+db.randomkey(function(err, key) { sys.puts(key); });
+db.hset("bar", "hi", "world");
+db.hget("bar", "hi", function(err, value) { sys.puts(value); });
+db.hgetall("bar", function(err, data) { sys.puts(data["hi"]); });

articles/redis-pubsub/redis-client.js

@@ -0,0 +1,5 @@
+var db = redis.createClient(9281, 'goosefish.redistogo.com');
+var dbAuth = function() { db.auth('dc64f7b818f4e3ec2e3d3d033e3e5ff4'); }
+db.addListener('connected', dbAuth);
+db.addListener('reconnected', dbAuth);
+dbAuth();

articles/redis-pubsub/redis-subscribe.js

@@ -0,0 +1,8 @@
+db.subscribeTo("flight_stream", function(channel, message, pattern) {
+    try { var flight = JSON.parse(message); }
+    catch (SyntaxError) { return false; }
+
+    if ( flight.origin.iata == "BOS" || flight.destination.iata == "BOS") {
+        server.broadcast(message);
+    }
+});

articles/redis-pubsub/server.js

@@ -0,0 +1,42 @@
+require.paths.unshift(__dirname + '/lib');
+
+var fs = require('fs'),
+    ws = require('ws'),
+    sys = require('sys'),
+    url = require('url'),
+    http = require('http'),
+    path = require('path'),
+    mime = require('mime'),
+    redis = require('redis-client');
+
+var httpServer = http.createServer( function(request, response) {
+    var pathname = url.parse(request.url).pathname;
+    if (pathname == "/") pathname = "index.html";
+    var filename = path.join(process.cwd(), 'public', pathname);
+
+    path.exists(filename, function(exists) {
+        if (!exists) {
+            response.writeHead(404, {"Content-Type": "text/plain"});
+            response.write("404 Not Found");
+            response.end();
+            return;
+        }
+
+        response.writeHead(200, {'Content-Type': mime.lookup(filename)});
+        fs.createReadStream(filename, {
+            'flags': 'r',
+            'encoding': 'binary',
+            'mode': 0666,
+            'bufferSize': 4 * 1024
+        }).addListener("data", function(chunk) {
+            response.write(chunk, 'binary');
+        }).addListener("close",function() {
+            response.end();
+        });
+    });
+});
+
+
+var server = ws.createServer({server: httpServer});
+
+server.listen(8000);

authors/James R. Bracy.markdown

@@ -0,0 +1,5 @@
+Email: waratuman@gmail.com
+Github:   waratuman
+Homepage: http://www.waratuman.com
+Twitter: waratuman
+Location: San Francisco, CA