gistfile1.txt

== NGINX HTTP PUSH ==

Steps to reproduce:

Install passenger gem:
  sudo gem install passenger

Download nginx:
  wget http://sysoev.ru/nginx/nginx-0.7.62.tar.gz
  tar -zxvf nginx-0.7.62.tar.gz

##HACK##
Edit nginx-0.7.62/auto/cc/gcc and search for -Werror and change it to -Wno-error
Otherwise the nginx compile will fail because of warnings in the http push module.
I expect this will be fixed very soon, possibly by the time you read this.

Clone the nginx http push module:
  git clone git://github.com/slact/nginx_http_push_module.git

Use the passenger script to install nginx with support for passenger and long polling:
  sudo passenger-install-nginx-module --nginx-source-dir=/path/to/src/nginx-0.7.62 \
       --extra-configure-flags="--add-module='/path/to/src/nginx_http_push_module'"

Be sure to specify absolute paths.

Edit /opt/nginx/conf/nginx.conf and make it look something like this:
(make sure to change /path/to to point to the correct directories)

############################## SAMPLE NGINX ################################

worker_processes  1;

events {
    worker_connections  1024;
}

http {
    passenger_root /path/to/passenger-2.2.5;
    passenger_ruby /path/to/bin/ruby;

    include       mime.types;
    default_type  application/octet-stream;

    #maximum amount of memory the push module is allowed to use 
    #for buffering and stuff
    push_max_reserved_memory      12M; 
    push_queue_messages           off;

    sendfile        on;
    keepalive_timeout  65;

    server {
        listen       80;
        server_name  localhost;

        location / {
            root   /path/to/your/rails/application/public;
            index  index.html index.htm;
            passenger_enabled on;
            rack_env development;
        }

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        #sender
        location /send {
          allow 127.0.0.1;
          deny all;

          default_type text/plain;
          set $push_channel_id $arg_id; #/?id=239aff3 or somesuch
          push_publisher;
          push_message_timeout 2h; #buffered messages expire after 2 hours\
        }
     
        #receiver
        location /listen {
          push_subscriber;
          push_subscriber_concurrency broadcast;
          set $push_channel_id $arg_id; #/?id=239aff3 or somesuch
          default_type  text/plain;
        }

    }

}

########################### END SAMPLE NGINX #############################

The ruby/rails app just needs to do a post to localhost/listen.  I'm doing
it in-process for now since nginx is on the same box and very responsive,
but there could be reliability implications.

########################## START RUBY EXAMPLE ############################

class MessagesController < ApplicationController
  def create
    @msg = Message.new(:content => params[:content], :user => current_user)
    if @msg.save
      http = Net::HTTP.new("localhost", 80)
      http.post "/send/?id=messages", @msg.to_json
      render :json => {:response => 200}
    else
      render :json => {:response => 500, :errors => @msg.errors }
    end
  end

  def index
    render :json => Message.all.to_json
  end
end

########################## END RUBY EXAMPLE ##############################

To fetch new messages in javascript you need to hold an ajax connection open.
This example uses jQuery:

########################## START JS EXAMPLE ##############################

var newMessage = function(data) {
  console.log(data);
};

// From http://stackoverflow.com/questions/333664/simple-long-polling-example-code
// (by dbr)
function waitForMsg(){
  /* This requests the url "msgsrv.php"
     When it complete (or errors)*/
  $.ajax({
    type: "GET",
    url: "/listen?id=messages",

    async: true, /* If set to non-async, browser shows page as "Loading.."*/
    cache: false,
    timeout:50000, /* Timeout in ms */
    dataType: 'json',

    success: function(data){ /* called when request to barge.php completes */
      newMessage(data); /* Add response to a .msg div (with the "new" class)*/
      setTimeout(
         'waitForMsg()', /* Request next message */
         1000 /* ..after 1 seconds */
      );
    },
    error: function(XMLHttpRequest, textStatus, errorThrown){
      console.log("error " + textStatus + " (" + errorThrown + ")");
      setTimeout(
        'waitForMsg()', /* Try again after.. */
        "4000"); /* milliseconds (15seconds) */
    },
 });
};

$(function() { waitForMsg(); } );

########################## END JS EXAMPLE ##############################