Shahzad Bhatti: 2010

Recently, I have been building a stock quote server at work that publishes financial data using using Ejabberd, XMPP, PubSub, Exmpp and Bosh on the server side and Strophe library on the web application front. I will describe a simplified implementation of the quote server using Yahoo Quotes.

Installation

Download Ejabberd and go through the installation wizad. You will be asked your host name, admin account/password and whether ejabberd would be running in a clustered environment. For this tutorial, we will be running ejabberd on a single. Once installed, you can start the ejabbered server using

 /Applications/ejabberd-2.1.3/bin/ejabberdctl start

As, I am using Mac, the actual path on your machine may be different. The ejabbered comes with a web baesd admin tool, that you can access using

 http://<your-host-name>:5280/admin

and you would be able to see available nodes, users, etc.

Registering Users

We will be creating two users: producer and consumer, where the former would be used for publishing stock quotes and latter would be used for subscribing quotes on the web side, i.e.,

 sudo /Applications/ejabberd-2.1.3/bin/ejabberdctl register producer  producer
 sudo /Applications/ejabberd-2.1.3/bin/ejabberdctl register consumer  consumer

Debuging with Psi

You can debug XMPP communications using a jabber client such as Psi, which you can download. After you download, you can install and specify your local hostname as a server, e.g.

You can then login using consumer@<your-host-name> with password consumer. As, we will be using PubSub protocol, you can discover available nodes or topics using General->Service Discovery from the menu, e.g.

Downloading Sample Code

I have stored all code needed for this example on http://github.com/bhatti/FQPubSub, that you can checkout using:

 git clone git@github.com:bhatti/FQPubSub.git

The sample code depends on exmpp, lhttpc, jsonerl, and yaws modules so after downloading the code, checkout dependent modules using

 git submodule init
 git submodule update

Above commands will checkout dependent modules in deps directory.

Building Sample Code

Before building, ensure you have make and autoconf tools installed, then replace <paraclete.local> with your <your-host-name> in docroot/index.html and src/quote_utils.hrl. Then type following command

 make

to build all sample code and dependent libraries

Starting Web Server

Though, the web code including Srophe library and Javascript can be run directly in the browser, but you can start Yaws to serve the application as follows:

 erl -pa ebin deps/exmpp/ebin/ deps/lhttpc/ebin/ deps/yaws/ebin -boot start_sasl -run web_server start

Note, that the web server will be continuously running, so you can open a separate shell before typing above command.

Publishing Quotes

Create two separate shells and type following command in first shell:

   erl -pa ebin deps/exmpp/ebin/ deps/lhttpc/ebin/ deps/yaws/ebin -boot start_sasl -run quote_publisher start AAPL

and following command in second shell

   erl -pa ebin deps/exmpp/ebin/ deps/lhttpc/ebin/ deps/yaws/ebin -boot start_sasl -run quote_publisher start IBM

Above commands will start Erlang processes, that will poll Yahoo Quotes every second and publish the quotes on the node AAPL and IBM respectively.

Next point your browser to http://<your-host-name>:8000/, and add “IBM” and “AAPL” symbols, you would then see quotes for both symbols, e.g.

Code under the hood

Now that you are able to run the example, let’s take a look at the code how it works:

Client library for Yahoo Finance

Though, at work we use our own real time stock quote feed, but for this sample I implemented stock quote feed using Yahoo Finance. The src/yquote_client.hrl and src/yquote_client.erl define client API for accessing Yahoo finance service. Here is the Erlang code for requesting the quote using HTTP request and parsing it:

  1 %%%-------------------------------------------------------------------

  2 %%% File : yquote_client.erl
  3 %%% Author : Shahzad Bhatti

  4 %%% Purpose : Wrapper Library for Yahoo Stock Quotes

  5 %%% Created : May 8, 2010
  6 %%%-------------------------------------------------------------------

  7
  8 -module(yquote_client).

  9
 10 -author('bhatti@plexobject.com').
 11

 12 -export([
 13          quote/1
 14         ]).

 15
 16 -record(quote, {
 17         symbol,
 18         price,
 19         change,
 20         volume,

 21         avg_daily_volume,
 22         stock_exchange,
 23         market_cap,
 24         book_value,
 25         ebitda,
 26         dividend_per_share,

 27         dividend_yield,
 28         earnings_per_share,
 29         week_52_high,
 30         week_52_low,
 31         day_50_moving_avg,
 32         day_200_moving_avg,

 33         price_earnings_ratio,
 34         price_earnings_growth_ratio,
 35         price_sales_ratio,
 36         price_book_ratio,
 37         short_ratio}).
 38 

 39

 40
 41 quote(Symbol) ->
 42     inets:start(),
 43     {ok,{_Status, _Headers, Response}} = http:request(get, {url(Symbol), []},

 44         [{timeout, 5000}], [{sync, true}]),
 45

 46     Values = re:split(Response, "[,\r\n]"),
 47     #quote{

 48         symbol = list_to_binary(Symbol),
 49         price = to_float(lists:nth(1, Values)),
 50         change = to_float(lists:nth(2, Values)),
 51         volume = to_integer(lists:nth(3, Values)),

 52         avg_daily_volume = to_integer(lists:nth(4, Values)),
 53         stock_exchange = lists:nth(5, Values), % to_string

 54         market_cap = to_float(lists:nth(6, Values)), % B

 55         book_value = to_float(lists:nth(7, Values)),
 56         ebitda = to_float(lists:nth(8, Values)), % B

 57         dividend_per_share = to_float(lists:nth(9, Values)),

 58         dividend_yield = to_float(lists:nth(10, Values)),
 59         earnings_per_share = to_float(lists:nth(11, Values)),
 60         week_52_high = to_float(lists:nth(12, Values)),
 61         week_52_low = to_float(lists:nth(13, Values)),

 62         day_50_moving_avg = to_float(lists:nth(14, Values)),
 63         day_200_moving_avg = to_float(lists:nth(15, Values)),
 64         price_earnings_ratio = to_float(lists:nth(16, Values)),
 65         price_earnings_growth_ratio = to_float(lists:nth(17, Values)),

 66         price_sales_ratio = to_float(lists:nth(18, Values)),
 67         price_book_ratio = to_float(lists:nth(19, Values)),
 68         short_ratio = to_float(lists:nth(20, Values))}.
 69 

 70 url(Symbol) ->

 71     "http://finance.yahoo.com/d/quotes.csv?s=" ++ Symbol ++ "&f=l1c1va2xj1b4j4dyekjm3m4rr5p5p6s7".
 72 

 73 to_float(<<"N/A">>) ->

 74     -1;
 75 to_float(Bin) ->
 76     {Multiplier, Bin1} = case bin_ends_with(Bin, <<$B>>) of

 77         true ->
 78             {1000000000, bin_replace(Bin, <<$B>>, <<>>)};
 79         false ->

 80             case bin_ends_with(Bin, <<$M>>) of

 81                 true ->

 82                     {1000000, bin_replace(Bin, <<$M>>, <<>>)};
 83                 false ->
 84                     {1,Bin}

 85             end

 86     end,
 87     L = binary_to_list(Bin1),
 88     list_to_float(L) * Multiplier.

 89

 90
 91

Note that I am omitting some code in above listing, as I just wanted to highlight HTTP request and parsing code.

Publishing the Stock Quote

I used exmpp library to communicate with the XMPP server in Erlang. Here is the code for publishing the quotes using Bosh/XMPP protocol:

  1 %%%-------------------------------------------------------------------

  2 %%% File : quote_publisher.erl
  3 %%% Author : Shahzad Bhatti

  4 %%% Purpose : OTP server for publishing quotes

  5 %%% Created : May 8, 2010
  6 %%%-------------------------------------------------------------------

  7 -module(quote_publisher).

  8
  9 -export([
 10     start/1,
 11     start/5,
 12     stop/1]).
 13 

 14 -export([init/5]).
 15

 16 -include_lib("quote_utils.hrl").
 17
 18 -record(state, {session, jid, service=?TEST_XMPP_PUBSUB, symbol}).

 19
 20 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

 21 %% APIs
 22 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

 23 start(Symbol) ->

 24     start(?TEST_XMPP_SERVER, ?TEST_XMPP_PORT, ?PRODUCER_USERNAME,
 25         ?PRODUCER_PASSWORD, Symbol).

 26

 27 start(Host, Port, User, Password, Symbol) ->
 28     spawn(?MODULE, init, [Host, Port, User, Password, Symbol]).

 29

 30 stop(Pid) ->
 31     Pid ! stop.
 32
 33 init(Host, Port, User, Password, Symbol) ->

 34     {ok, {MySession, MyJID}} = quote_utils:connect(Host, Port, User, Password),
 35     State = #state{session=MySession, jid=MyJID, symbol = Symbol},

 36     create_symbol_node(State),
 37     loop(State).
 38

 39 loop(#state{session=MySession, jid=_MyJID, service = _Service,

 40         symbol = _Symbol}=State) ->

 41     receive
 42         stop ->
 43             quote_utils:disconnect(MySession);

 44         Record = #received_packet{packet_type=message, raw_packet=_Packet} ->

 45             loop(State);
 46         Record ->

 47             loop(State)
 48     after 2000 ->

 49         publish_quote(State),
 50         loop(State)

 51     end.
 52

 53 create_symbol_node(#state{session=MySession, jid=MyJID, service = Service,

 54         symbol = Symbol}) ->

 55     IQ = exmpp_client_pubsub:create_node(Service, Symbol),
 56     PacketId = exmpp_session:send_packet(MySession, exmpp_stanza:set_sender(IQ, MyJID)),

 57     PacketId2 = erlang:binary_to_list(PacketId),
 58     receive #received_packet{id=PacketId2, raw_packet=Raw} ->

 59       case exmpp_iq:is_error(Raw) of
 60         true -> {error, Raw};
 61         _ -> ok

 62       end

 63     end.
 64
 65 publish_quote(#state{session=MySession, jid=MyJID, service = Service, symbol = Symbol}) ->

 66     Quote = yquote_client:quote(Symbol),
 67     JsonQuote = ?record_to_json(quote, Quote),
 68     M = exmpp_xml:element(?QUOTE_DATA),

 69     IQ = exmpp_client_pubsub:publish(Service, Symbol, exmpp_xml:append_cdata(M,
 70             JsonQuote)),
 71     Xml = exmpp_stanza:set_id(exmpp_stanza:set_sender(IQ, MyJID), Symbol),

 72     PacketId = exmpp_session:send_packet(MySession, exmpp_stanza:set_sender(IQ, MyJID)),
 73     PacketId2 = erlang:binary_to_list(PacketId),

 74     receive #received_packet{id=PacketId2, raw_packet=Raw} ->

 75       case exmpp_iq:is_error(Raw) of

 76         true -> error;
 77         _ -> ok
 78       end

 79     end.

 80
 81
 82

In above code, a process is created for each symbol, which periodically polls stock quote and publishes it to the XMPP node using pubsub/bosh protocol. Note that a unique node is created for each symbol and node must be created before anyone can publish or subscribe. Also, note that publish/subscribe APIs use request/ack protocol, so after sending the request, the process retrieves the acknowledgement of the request.

Here are some utility functions used by the publisher:

  1 -module(quote_utils).

  2
  3 -include_lib("quote_utils.hrl").
  4

  5 -export([
  6     init_session/2,

  7     connect/4,
  8     disconnect/1]).
  9

 10 bosh_url(Host, Port) ->

 11     "http://" ++ Host ++ ":" ++ integer_to_list(Port) ++ "/http-bind".
 12 

 13

 14 connect(Host, _Port, User, Password) ->
 15     safe_start_apps(),

 16     MySession = exmpp_session:start({1,0}),
 17     exmpp_xml:start_parser(), %% Create XMPP ID (Session Key):

 18     MyJID = exmpp_jid:make(User, Host, random),

 19     %% Create a new session with basic (digest) authentication:
 20     exmpp_session:auth_basic_digest(MySession, MyJID, Password),
 21     

 22

 23     {ok, _StreamId, _Features} = exmpp_session:connect_BOSH(MySession, bosh_url(Host, 5280), Host, []),

 24     try quote_utils:init_session(MySession, Password)
 25     catch

 26         _:Error -> io:format("got error: ~p~n", [Error]), {error, Error}

 27     end,
 28     {ok, {MySession, MyJID}}.
 29

 30 init_session(MySession, Password) ->

 31     %% Login with defined JID / Authentication:
 32     try exmpp_session:login(MySession, "PLAIN")
 33     catch

 34         throw:{auth_error, 'not-authorized'} ->
 35         %% Try creating a new user:
 36         io:format("Register~n",[]),
 37         %% In a real life client, we should trap error case here

 38         %% and print the correct message.
 39         exmpp_session:register_account(MySession, Password),
 40         %% After registration, retry to login:

 41         exmpp_session:login(MySession)
 42     end,
 43     %% We explicitely send presence:

 44     exmpp_session:send_packet(MySession, exmpp_presence:set_status(exmpp_presence:available(), "Ready to publish!!!")),

 45     ok.
 46
 47 disconnect(MySession) ->

 48     exmpp_session:stop(MySession).
 49 

 50 safe_start_apps() ->
 51     try start_apps()
 52     catch

 53         _:Error -> io:format("apps already started : ~p~n", [Error]), {error, Error}

 54     end.
 55

 56 start_apps() ->
 57     ok = application:start(exmpp),
 58     ok = application:start(crypto),
 59     ok = application:start(ssl),

 60     ok = application:start(lhttpc).
 61

Note that above code auto-registers users, which is not recommended for production use.

Javascript code using Strophe library

The web application depends on jQuery, Strophe and Strophe Pubsub. These libraries are included in docroot directory that are imported by index.html. The Strophe library and ejabbered 2.1.3 version supports cross domain scripting so that bosh service here doesn’t need to be on the same domain/port, but it must have a /crossdomain.xml policy file that allows access from wherever index.html lives. The Javascript initializes the connection parameter as follows (you would have to change Host):

   1 <script type="text/javascript">

   2     // The BOSH_SERVICE here doesn't need to be on the same domain/port, but

   3     // it must have a /crossdomain.xml policy file that allows access from

   4     // wherever crossdomain.html lives.
   5     // TODO: REPLACE <paraclete.local> with your <host-name>

   6     var HOST = 'paraclete.local';
   7     var JID = 'consumer@' + HOST;

   8     var PASSWORD = 'consumer';
   9     var BOSH_SERVICE = 'http://' + HOST + ':5280/http-bind'; //'/xmpp-httpbind'

  10     var PUBSUB = 'pubsub.' + HOST;
  11     var connection = null;

  12     var autoReconnect = true;
  13     var hasQuotes = [];
  14     var subscriptions = [];

  15

  16     function log(msg) {
  17         $('#log').append('<div></div>').append(document.createTextNode(msg));

  18     }
  19

  20     function rawInput(data) {
  21         //log('RECV: ' + data);

  22     }
  23
  24     function rawOutput(data) {
  25         //log('SENT: ' + data);

  26     }
  27     function onQuote(stanza) {
  28         //log('onQuote###### ' + stanza);

  29         try {
  30             $(stanza).find('event items item data').each(function(idx, elem) {
  31                 quote = jQuery.parseJSON($(elem).text());

  32                 //{"price":235.86,"change":-10.39,"volume":59857756,"avg_daily_volume":20775600,"stock_exchange":[78,97,115,100,97,113,78,77],"market_cap":2.146e+11,

  33                 //"book_value":43.257,"ebitda":1.5805e+10,"dividend_per_share":0.0,"dividend_yield":-1,"earnings_per_share":11.796,"week_52_high":272.46,"week_52_low":119.38,

  34                 //"day_50_moving_avg":245.206,"day_200_moving_avg":214.119,"price_earnings_ratio":20.88,"price_earnings_growth_ratio":1.05,"price_sales_ratio":4.38,

  35                 //"price_book_ratio":5.69,"short_ratio":0.7}
  36                 if (hasQuotes[quote.symbol] != undefined) {

  37                     $('price_' + quote.symbol).innerHTML = quote.price;
  38                     $('change_' + quote.symbol).innerHTML = quote.change;
  39                     $('volume_' + quote.symbol).innerHTML = quote.volume;

  40                 } else {
  41                     hasQuotes[quote.symbol] = true;
  42                     $('#quotesTable > tbody:last').append('<tr id="quote_' +

  43                         quote.symbol + '"><td>' + quote.symbol +
  44                         '</td><td id="price_' + quote.symbol + '">' + quote.price +

  45                         '</td><td id="change_' + quote.symbol + '" class="class_change_' + quote.symbol + '">' +
  46                         quote.change + '</td><td id="volume_' +

  47                         quote.symbol + '">' +
  48                         quote.volume + '</td></tr>');
  49                 }

  50

  51                 if(quote.change < 0) {
  52                     $('.class_change_' + quote.symbol).css('color', 'red');

  53                 } else {
  54                     $('.class_change_' + quote.symbol).css('color', 'green');

  55                 }
  56             });
  57         } catch (e) {
  58             log(e)

  59         }
  60         return true;
  61     }
  62 

  63     function handleSubscriptionChange (stanza) {
  64         //log("***handleSubscriptionChange Received: " + stanza);

  65     }
  66
  67     function onConnect(status) {
  68         if (status == Strophe.Status.CONNECTING) {

  69             log('Strophe is connecting.');
  70         } else if (status == Strophe.Status.CONNFAIL) {
  71             log('Strophe failed to connect.');

  72             $('#connect').get(0).value = 'connect';
  73         } else if (status == Strophe.Status.DISCONNECTING) {

  74             log('Strophe is disconnecting.');
  75         } else if (status == Strophe.Status.DISCONNECTED) {
  76             if (autoReconnect) {

  77                 log( "Streaming disconnected. Trying to reconnect...", METHODNAME );
  78                 connection.connect($('#jid').get(0).value, $('#pass').get(0).value, onConnect);
  79                 log( "Streaming reconnected.", METHODNAME );

  80             } else {
  81                 log('Strophe is disconnected.');
  82                 $('#connect').get(0).value = 'connect';

  83                 //publishEvent( "streamingDisconnected" );

  84             }
  85         } else if (status == Strophe.Status.CONNECTED) {

  86             log('Strophe is connected.');
  87             //log('QUOTE_BOT: Send a message to ' + connection.jid + ' to talk to me.');

  88             connection.addHandler(onMessage, null, 'message', null, null, null);
  89             connection.send($pres().tree());

  90             publishEvent( "streamingConnected" );
  91         }
  92     }
  93 

  94     function subscribe(symbol) {
  95         if (subscriptions[symbol]) return;
  96         try {

  97             connection.pubsub.subscribe(JID, PUBSUB, symbol, [], onQuote, handleSubscriptionChange);
  98             subscriptions[symbol] = true;
  99             log("Subscribed to " + symbol);

 100         } catch (e) {
 101             alert(e)
 102         }
 103     }
 104     function unsubscribe(symbol) {

 105         if (!subscriptions[symbol]) return;
 106         try {
 107             connection.pubsub.unsubscribe(JID, PUBSUB, symbol, handleSubscriptionChange);
 108             subscriptions[symbol] = false;

 109             log("Unsubscribed from " + symbol);
 110         } catch (e) {
 111             alert(e)
 112         }

 113     }
 114

 115     function onMessage(msg) {
 116         var to = msg.getAttribute('to');

 117         var from = msg.getAttribute('from');
 118         var type = msg.getAttribute('type');
 119         var elems = msg.getElementsByTagName('body');

 120

 121         if (type == "chat" && elems.length > 0) {
 122             var body = elems[0];

 123             log('QUOTE_BOT: I got a message from ' + from + ': ' + Strophe.getText(body));
 124             var reply = $msg({to: from, from: to, type: 'chat'}).cnode(Strophe.copyElement(body));
 125             connection.send(reply.tree());

 126             log('QUOTE_BOT: I sent ' + from + ': ' + Strophe.getText(body));
 127         }
 128         // we must return true to keep the handler alive.

 129         // returning false would remove it after it finishes.

 130         return true;
 131     }
 132
 133     $(document).ready(function () {

 134         connection = new Strophe.Connection(BOSH_SERVICE);
 135         connection.rawInput = rawInput;
 136         connection.rawOutput = rawOutput;
 137         connection.connect(JID, PASSWORD, onConnect);
 138         //connection.disconnect();

 139         $('#add_symbol').bind('click', function () {
 140             var symbol = $('#symbol').get(0).value;

 141             subscribe(symbol);
 142         });
 143     });
 144

 145 </script>
 146

When the document is loaded, the connection to the ejabberd server is established. Here is the form and table that is used to add subscription and display current quote information for the symbols:

  1 <form name='symbols'>

  2     <label for='symbol'>Symbol:</label>
  3     <input type='text' id='symbol'/>

  4     <input type='button' id='add_symbol' value='add' />

  5 </form>
  6 <hr />
  7 <div id='log'></div>

  8 <table id="quotesTable" width="600" border="2" bordercolor="#333333">

  9     <thead>
 10         <tr>
 11             <th>Symbol</th>

 12             <th>Price</th>
 13             <th>Change</th>

 14             <th>Volume</th>

 15         </tr>
 16     </thead>

 17     <tbody>
 18     </tbody>

 19 </table>

 20

When the form is submitted, it calls subscribe method, which in turn sends request to the ejabbered server for subscription. When a new quote is received, it calls onQuote function, which inserts a row in the table when a new symbol is added or updates the quote information if it already exists.

Conclusion

The ejabberd, XMPP, exmpp, Bosh and Strophe provides a robust and mature solution for messaging and are especially suitable for web applications that want to build highly scalable and interactive applications. Though, above code is fairly simple, but same design principles can be used to support large number of stock quotes updates. As, we need to send stock quotes from tens of thousands symbols for every tick within a fraction of a second, the Erlang provides very scalable solution, where each symbol is simply served by an Erlang process. Finally, I am still learning more about Ejabberd’s clustering, security, and other features so that it can truly survive the production load, so I would love to hear any feedback you might have with similar solution.

Saturday, April 24, 2010

Favorite fifteen tips from “Rework” book by Jason Fried and DHH

I have been a long admirer of Jason Fried of 37Signals and read his first book Getting Real. Jason along with DHH have put forth many of the ideas from that book along with other ideas from their blog Signal vs. Noise into a new book Rework. I just finished reading it and though it reiterates many ideas from the earlier book “Getting Real” and their blogs, it’s worth re-reading those ideas as many of business companies today still runs on old fallacies. The book consists of thirteen sections and over eighty ideas, here are my favorite ideas from the book:

Failure is not a rite of passage

I have heared the advice from startup folks about “Fail early and fail often.” On the contrary, this book shows people who learn from mistakes will make new mistakes, instead success shows what actually works. Another related avice in the book is “Reason to quit”, which shows when you can quit and choose something else. When I read Founders at Work: Stories of Startups’ Early Days, it also showed that most startups don’t stick to their original ideas and move to other ideas based on early feedback.

Planning is Guessing

This is related to another advice from the book “Your estimates suck” as Planning and Estimation is hard especially in software business. I have written about Software Estimation in my earlier blogs, however most places still equate estimates with commitments. Jason and DHH reminds us again that estimates are just guesses that were made based on the best information available at the time.

Workaholism

This is another unorthodox advice that is contradictory to how most software projects are run. Most companies measure workers’ dedication on how many hours he/she put even when they are not actually producing. This is also common when managers treat estimates as commitments and refuse to admit reality when things change. We are all familiar with iron triangle of schedule/cost/functionality or sometime referred to as cost/quality/schedule or cost/resourcs/schedule. Often business folks are unwilling to change schedule and functionality, which often requires working late hours. This is also related to Heroism, which I have blogged before and go to sleep, as workholism can result in sleep deprivation, which reduces creativity and productivity.

Scratch your own itch

Most successful businesses started with hobbies or personal interests or problems and there are tons of examples of this. This advice is also related to eat your own dog food, though not mentioned in this book.

Start making something

Jason and DHH reminds us another great point that ideas are cheap and the real question is how well you execute them.

Draw a line in the sand

One of the key characteristics of Ruby on Rails software that DHH produced is having strong opinions that limits variations. Similarly, 37Signals is known for their simple design and limited features. You can differentiate yourself from others by standing for something.

Outside money is Plan Z

Both DHH and Jason often talked about downside of getting money from venture capitalists and I agree that these days you can start most software startups with minimal money and raising money can be very distracting. Another related tip that “building a flip is building to flop”, which is often what startup founders hope to get out.

Start at the epicenter

This book advices you to focus on your core product. Though, this book briefly mentiosn this topic but there is a great presentation of Video of Geoffrey Moore at Business of Software 2009 that talks about similar topic. This advice is also reated to other tips from the book such as “don’t copy”, “decommoditize your product”, “focus on you instead of they”, i.e., focus on your core strengths and not your competitors.

Focus on what won’t change

This is great advice for building business that will last. I remember when I started working at Amazon, we were told the core values of Amazon that included having a large selection, cheap prices, customer service and everything we built started from outside-in focus, i.e., it started with customers.

Get it out here

This is similar to common advice from the startup and agile community, i.e. release early and release often.

Interruption is the enemy of productivity

More and more research is showing that our brain can’t focus on onething at a time, and constant interruption and multi-tasking hampers your productivity. This is also somewhat related to office space is setup as many agile practices encourage more open space with pair programming and I have found that it prevents concentration. I found that private office offered from Organizational Patterns of Agile Software Development provides less interruption.

Meetings are toxic

This is another hallmark idea of 37Signals and the book contains a number of tips on making your productive such as fixed time, fewer people, clear agenda, beginning with a specific problem and ending with action items and making someone responsible for them.

Good enough is fine

37Signals is known for their simple design and fewer features. This is related other advice in the book such as “embrace the constraints”, “throw less at the problem”, “underdo your competitor”, “say no” and “be a curator”. When you have limited resources, you can become more creative. Also, you are better off building half a product, not a half assed product.

Make tiny decisions

The authors encourage to make tiny decisions as big decisions are hard to make and hard to change. This advice is related to other tips such as “decisions are progress”, which encourages you to always make progress and “quick wins”, which encourages you to build momentum by accomplishing small tasks.

Build an audience

The authors encourage to build audience that come back to you by writing blogs, tweets and speaking. This is also reated to “sell your by-products”, “emulate chefs”, “emulate drug dealers” and “out-teach your competitors”.

Conclusion

Though, I skipped many gems of advice on hiring, culture and marketing but I suggest you read the book to build long lasting and successful business.

Thursday, March 18, 2010

Smarter Email appender for Log4j with support of duplicate-removal, summary-report and JMX

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Shahzad Bhatti

Friday, August 13, 2010

Monday, May 10, 2010

Building a stock quote server in Erlang using Ejabberd, XMPP, Bosh, Exmpp, Strophe and Yaws

Installation

Registering Users

Debuging with Psi

Downloading Sample Code

Building Sample Code

Starting Web Server

Publishing Quotes

Code under the hood

Client library for Yahoo Finance

Publishing the Stock Quote

Javascript code using Strophe library

Conclusion

Saturday, April 24, 2010

Favorite fifteen tips from “Rework” book by Jason Fried and DHH

Failure is not a rite of passage

Planning is Guessing

Workaholism

Scratch your own itch

Start making something

Draw a line in the sand

Outside money is Plan Z

Start at the epicenter

Focus on what won’t change

Get it out here

Interruption is the enemy of productivity

Meetings are toxic

Good enough is fine

Make tiny decisions

Build an audience

Conclusion

Thursday, March 18, 2010

Smarter Email appender for Log4j with support of duplicate-removal, summary-report and JMX

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