AWS Application Demo

• Amazon started with S3 (Simple Storage Service) - purely storage service.
• For Computing purposes, Amazon started EC2 
• EC2 allows hosting your application on virtual servers operated by Amazon, widely known as AWS.
• For calculating the availability as a resource, 1 compute unit at Amazon EC2 is roughly equivalent to a 1.2 GHz Xeon server.

• All computing resources are virtualized, none is physical. No physical details are ever published. However, the user has to manage his own file system. Based on need/request, disk space is mounted and is made available to the server. Further, it has to be managed by the application.
• There can be three types of instances, 
• Small
• Medium
• Large instances

Behavior on instances

• like a normal web server
• has a public web address

• Java Software available to convert command line instructions into SOAP wrapped API calls to AWS
• Need to download API tools from AWS
• Key pairs are tied to regions
• The benefit of this is that the servers are replicated across data centers located physically separately

Autoscaling service

• Allows scaling of servers based on need
• Consumes about 60-90 seconds to scale up based on the need (e.g. load on the server). If configured the appropriate way, the system will replicate the application code and launch new server instances within seconds to handle the extra load.
• Handles scaling up as well as down both at the same time. Automaticaly, the extra/unused instances will be shut down and released from the application deployment when there is no load to require their service.
• very useful in cases of spikes, specially high-peaks. New feature launches on sites, or sudden outbreak of news etc, cause spikes in server loads. At such times, AWS works perfectly to scale up the required computing power. The application owners are saved from buying extra servers for that 1 day load... :)
• Its possibel to say how many servers to add
• Such a scaling up/down can be configured. For example, it can be specifiied that request for new instances when current system's load exceeds 85% or scale down, when the usage goes below 20% used

OSs supported

• Linux
• Windows
• openSolaris

Buzzwords

• AMI = Amazon Machine Images
• EBS = Elastic Block Device
• Elastic IP = static ips assigned to instances
• Amazon EC2 = Amazon Elastic Computing Cloud
  

Web Application Debugging Tools

A Talk by Matthew McCullogh


Some tools he talked about and demonstrated

1. tcpdump
      Captures tcp-ip packets during traffic
      Available as an open source project at http://www.tcpdump.org/
      Allows you to save the captured packet information into a file on disk, thereby allowing offline analysis.

tcpdump -i en1 -s0 -n -A

2. WireShark - visual interpretation of tcpdump captured data
       Once you capture packet information using tcpdump, you can get a better view of it, more readable using this tool. Again an open source project, available from http://www.wireshark.org/

3. netstat
      An all time *nix flavors favourite. Every system admin's first choice. Allows port information.
      Available by defautl with almost all port of all OSs. Sometimes differences are found in implementations pertaining to syntaxes, or switch names/usage.

4. curl  - Another all time favorite.
      1. Allows calling/initiating the http request from command line, saves a lot of time since no program or skeleton is needed to be created for testing http calls.

5. jMeter - designed to load test functional behavior and measure performance

6.  soapUI => mocking a server.
       Available from http://www.soapui.org/

7. JavaScript
      FireBug -  for firefox - Javascript functions/elements are easily visible and manageable. Debugging on the fly is allowed too.  Available as an addon for firefox.
      FireBug - Firebug implementation for Safari.

8. FireFinder- find item in DOM. Easily allow an item in the DOM of a given web page.

More details coming on the following -

9.  Visual Event

10. FireFocus

11. JASH - CLI for test javascript


buzzwords
- bpf - berkeley packet filter

workshop day GIDS 2010 - 3 - Functional Programming

Well, for the third session of the day, my choice was clear, cloud computing discussion with Simone, from AWS. I had already had the taste of google cloud solution (app engine), and now I wanted to see the Amazon flavour. Quite horribly unfortunately, the internet link gave way and Simone's presentation plans went awry.

The guy was quite angry and it was so visible, so very visible. He tried to talk people through, plain talk talk talk it never settled in. I see people literally dozing off, and I guess he realized that too, since on more than one occasion, he instructed to keep the hall lights switched on. A bit of bad thing on part of Saltmarch/Airtel...

As a result, midway during the session, I left off, and thought of joining in the Flex-php workshop from adobe guys. However, somehow, I ended up entering the hall where Venkat was talking about functional programming.

And did I regret that decision, no chance. I guess, I have never enjoyed a programming language discussion so much, probably because I didnt get a chance to speak to such a learned speaker, and so many of keen and interested students (yeah, blame my college, I know, I do that myself.. all the time :)

It was a packed house, and fantastic atmosphere. For one thing, Venkat knew what he was talking about, and for other, I found that discussion took me back about 15 years to my college days. I had a strong feeling, why didnt I had an educational experience as nice as this. The teacher, the students, the atmosphere, whole place was like a wonderful experience. Though I had no clue what scala is before I entered the place, it never felt like a problem.

The way he talked about issues, the benefits, the arguments he presented, and I think more importantly, the way he engaged the audience in discussions, it was just wonderful. You might think that I am over reacting, but i dont care, I just loved this guy, this session.

He talked about programming paradigms, the way procedural languages were king one day, and the way they are looked at as if ancient history is being talked about today. And similarly, for today's generation OOPS is becoming more of a thing of the past, and new paradigms are coming over.

The way he propounded functional programming, the very idea of not allowing immutability, the way of thinking in terms of having to think of a solution without that.. amazing...

At more than one point in time, the people in the audience tried to contest the idea/need of another language, when we already have so many, and the need of learning another one. There were thoughts on the toughness of a programming language vs the other, and the way he answered.. fantastic... His point in this case was, its as good as a Karnataka person going to Punjab and saying, "These people are crazy, their language is so touch, I cant even read that". And it was a good laugh..

At more than one point in time, he compared different programming languages, their features and pros and cons of each of them. The kind of knowledge that he had, to be able to compare them, was amazing...

I have to say, without any doubt, that this session was my best experience at GIDS 2010. I loved this, probably due to my personal interest in the theory of computer science as such, but also because there probably wasnt any other speaker with that kind of personality and flair for talking.

Hats off to Saltmarch for inviting people like him too...

workshop day gids 2010 - 2 - paypal x

It went even better afterwards, Paypal has opened doors to their Payment methodology to developers. They call it PayPal X. They have published a complete SDK which allows developers to write independent programs that allow integration of paypal as a payment gateway in their e commerce applications.

Their idea is to popularize paypal and use its simplicity and capability in spreading its business reach. The whole team of PayPal was present at the workshop and the atmosphere was pretty nice. Khurram Khan started off by talking a bit on the background of financial transactions, further, Rangarajan took over and talked in detail.

Frankly, the session was interactive, because perhaps people are motivated by money, the chances of earning it, and the basic idea of linking real e-commerce to their websites by such low effort and simplicity. My personal interests in that area are purely out of curiosity, in the sense that I am more keen to know as to whats going on, then get down to the code details and start implementing it.

One thing that stood out for me is that paypal proposes to review the code of the developer before actually allowing to move it to production (live), but has no control thereafter. So, in essence, someone who intends to do something funny (read : wrong/illegal etc...) might pass the initial test by presenting a genuine case, and then once he;s live, he can go back and change the code. I feel that by allowing updations like this, paypal is losing a bit of control on its API usage by the people.

I would probably have built somekind of a dynamic filter or a pair matching kind of mechanism (or a checksum for that matter) which would change the moment the developer changes his code on production site. Every call to the paypal API should check this checksum/authentication token and should go through only if this checks also holds good. Well, its just a thought, and probably paypal has its own reasons not to enforce any such check, but, if I were Khurram, I would probably start like that, perhaps remove it later or something like that.

When I posed this to Khurram, he was saying that, the responsibility of doing anything illegal or wrong lies anyway with the developer or the site owner, so, paypal doenst really want to get in their way. They would be apprehanded sometime anyway, sooner or later. As much as I agree with his argument, I still think that paypal could probably play a role and possibly stop "wrong" things from happening to some extent, after all its happening through their infrastructure, although the ownership lies somewhere else.

Other than, this particular point, I think the SDK is pretty nice and ok. They allow Java, no special downloads etc required to start developing, besides the SDK of course, and that the API supports almost all kinds of operations.

I specially liked their idea of generalizing the paypal kind of services, where it comes to trust building. During one discussion a statement was said, I dont remember which one, but a paypal employee said that, "I am sure that when it comes to trusting someone over internet, you can trust paypal a lot more with your financial information than a relatively unknown website that you are using for the first time." That I agree with, and perhaps the Indian jinx of not using web for payments can be broken with a trusted guy on the net, paypal.

You trust one person, paypal, and the rest is handled by paypal. As far as this statement goes, there actually is a greater risk, what if paypal goes rogue ? It would then have all my information, all of it... well then you would have to trust someone.. right ?? or not ???

The workshop day @GIDS 2010 - I - cloud computing using Google App engine

Well, A developer day cant get better than that... And, whatever issues I mentioned regarding scheduling of the summit were gone up in air.

I had the choice to go attend the Cloud Computing/hosting workshop with Mathhew McCullogh. It was based on java, which I dont care about anyway. Not that I have any kind of disrespect for the language, but I strongly think that we ought to think beyond languages.

He perfectly showcased how easy it is to build and host you own web application on the google app engine cloud platform. Its hard to imagine how easy it has become with eclipse plugin for google app engine and web toolkit, to develop an application for the cloud and deploy it. With those tools installed and configured (its surprisingly easy task to do it anyway), its a button click to deploy your application to the cloud.

I am not a big fan of java, or of huge complex configuration files for that matter, but the way this app engine thing is coming pre-configured, it reminds me of ruby on rails. At least to start with. Its surprisingly easy to start developing with GWT (Google Web Toolkit) and Google App Engine.

I tried to replicate what he was doing/showing, and, remember I am no big shots in java, that last professional java work I did was about 8 years back, It was surprisingly easy. Just a few clicks and it was done. I have to say, it was infectious, as if I felt like delving more into java and go back to experimenting with it...

Is that a workable idea ?

Actually, we are waiting for a new server to be installed and any new physical server installation takes some time, we all know that. The project would request it, there would be financials and then the order would be approved internally.
It would be placed with the vendor by purchasing, the vendor will ship it, and then a few days/weeks after, technicians will come over to install the stuff.

Then the local admins will get to work and configure it to be used by the respective teams. Another few days/weeks...

Just wondering, any given enterprise has hundreds ir not thousands computers, all classes, laptops, desktop development PCs, server class PCs and others...

How about taking off 10% of all these PCs' computing power to create a cloud computing environment (of course within the company environment only). An application can be installed which will make sure that a given percentage of computing power will go to only a particular resource.

A lot like how BOINC works. You install a client/manager app on ur PC and then u receive a piece of computation for your part of computing power.

That kind of computing environment can easily replace an average server's computing power.
The storage can easily be hooked up to a SAN.

I'd encourage a discussion on this... see what others think around the idea...

in reference to: Distributed computing - Wikipedia, the free encyclopedia (view on Google Sidewiki)

Fantastic Effort by SaltMarch

Well, i have to say it like that, The one day that I attended at the GIDS - 2010 was amazing. Probably I am reacting like that since its my first such summit, nonetheless the quality of speakers and the content they delivered was top of the ladder.

Amazing truely.

To get people of such caliber at one platform is a job in itself which saltmarch have done to perfection. I chose to be there for .Web day, and the kind of knowledge that was flowing around, technologies being talked about and the manner in which they were addressed, simply great.

We know some things as simple buzzwords, but we ought to realize that the buzzwords actually have lot more behind them. The way Simone (from AWS) put it, "Everybody in the confrerence hall would know what is Cloud computing, but I am sure that when I ask you what is it, you'd all come back with different definitions, and perhaps they are all correct as well". That statement sort of sums up the whole experience, we all know to some extent, or varying degree of perception what something is about, but unless we know it from the source, as they say, from the horse's mouth, its always a bit farther from the real reality.

I like that way the speaker and sessions were compiled, though a few of my favorite sessions were canceled (blame that volcano in Iceland for canceling all the flights), I still enjoyed a lot of it.

Personally me, interested in Ajax, came a lot closure to experimenting with it, and perhaps using it in professional environment as well. Thanks to people at Adobe booth there, I have a chance to try out the Adobe Flex Builder IDE, and check out the potential first hand.

Tomorrow, there is a workshop on php and Flex delivering RIA, and I cant wait to be there :)


However, as is the custom for people like me, to comment and find fault with something or other, after all we are humans, we are bound to make mistakes and other humans are bound to find them and report them publicly, like on this blog... :)

I believe the scheduling of some of the sessions could have been better. For example, I missed out on the PayPal X presentation, because I wanted to attend Marty Hall's session on evaluation of Ajax/JavaScript Libraries too. Now, I'd have to contend only with the video of that presentation, hoping that it would be made available. :)

I like the scheduling of the workshop day a lot better. It gives people like me options to attend sessions diff technologies ...

Looking forward to another exciting day of fun filled experiments that enhance know how...

in reference to: Great Indian Developer Summit :: Conference, Expo, and Awards on Java, .NET, Rich Web :: Saltmarch Media Summits (view on Google Sidewiki)

Web Changing the face of the world : Ramesh

Ramesh, a senior technologist/scientist from Adobe, talked about how and what has web 2.0 done to change the world, especially the way the information is treated/used/processed etc...

Here are some of his points -

Real Time Web

• kind of content that is coming around
• no more old docs
• social networking
• live collaboration

experiencing the web - how the web is experienced, the way its accessed, used etc.

• Some tools are coming up in the VR world, which allows
  
• augmented reality -> web apps capturing reality and using the inputs
  

proliferating devices

• Already more web access from non PC devices
• More devices are coming through which access web differently

democratization of data

• Some govts have already started putting their data in public domain.
• Lots of application development opportunities based on that data.
• Cloud computing also coming around to provide processing power and applications for the data.

Buzzwords

• ActionScript
• ECMAScript
• Flex

Quite interesting talk :) Learned person, Ramesh.

Marty Hall : Why Ajax : Using Ajax in ur web apps

Why WebApps - Ajax

• Asynchronous JavaScript and XML => doesnt hold good anymore
  
• allow the browser to utilize the time when the main page is gone tofetch the result of your initial app
• Add/modify content on the webpage at runtime
  
• trends -> more jobs on Ajax than any other technology - php, vb, asp etc...

Ajaxifying an Application

• libraries - jQuery, ext-ja, dojo, yui, prototype, google closure, mootols
• Browser allow calls to only the server from where the original code came in, due to firewall issues.

• Situation 2 - Hybrid
  
• Libraries to use for new apps - JSF 2.0, Struts 2.0, Spring MVC 3.
• JSF is better because
• integrated in main code - jquery needs u to write javascript
  
• no javascript to write - a simple tag

• Situation 3 - Hardcore Ajax
• Google web toolkit
• Use java everywhere
• Write java code at front end -> compiles to javascript at run time
  
• Write java code at back end-> provides facility of communication in terms of java objects

Buzzwords

• Jboss Seam <-> JSF 2.0
  
• 
  

@GIDS 2010 Bangalore

I am going to be there at the "Great Indian Developer Summit" in Bangalore April 20th to 23rd 2010.

Its hosted at the lush green IISc campus, in the J N Tata Auditorium. Various pieces of info are available from the organizer website -

www.saltmarch.com

http://www.developermarch.com/developersummit/


It looks like an amazing place to be, full of tech discussions, and hopefully knowledge too...

Apple and India...

Well, this is sad, particularly for someone in India, who avoids getting cracked iPhones...

Only yesterday Apple and Airtel announced availability of iPhone 3GS in India and today I get to read this, that Apple is releasing a new/better hardware for iPhone coming summer.

So, basically, India as an iPhone market is going to lag behind the rest of world by at least one model this time around as well.

Sometimes, I dont understand Apple's marketing strategy, specially in Indian context. As an Economy, India is probably the largest in the emerging market economies closely behind China. That statement should alone prove to be a "lucrative market" for any company which aims for growth.

This is specially interesting when we look at the number of iPhones already used in India with cracked OS's.

This doenst help a company's revenues if the product is consumed in a market where the company doesn't officially sell the product.

Also, the number of iPhones used in India, should give Apple an indication about the marketability of their product in this market. Personally, I think as a product from Apple's stable, iPhone has a lot of glamour linked to it.
And therefore, huge possibilities in India for Apple.

The new iPhone's rumoured specs look stunning, 5 MP camera, better display resolution, more processing power, possible multi tasking, video calling camera and few other things. After reading that, my plans to order an iPhone 3GS have taken a back seat. I want to see this product coming to market, further to see, when does it come to India.

Apple seems to listening to customers.. the kind of improvements rumoured is possibly the exact list of things someone might say are downsides of iPhone...

Good luck Apple, and India, hoping for a better collaboration this time around...

in reference to: More on next-gen iPhone and Verizon iPhone dreams (view on Google Sidewiki)

Explain plan of Infobright

We all knw that Infobright is based on MySql. However, when I started with Infobright, I was equally unaware of both.

Today I got to know about Infobright's explain plan collection technique, and realized how different it is from Oracle's.

A typical explain plan from oracle talks about the path it follows to retrieve the data, and somehow makes common sense to read a plan.

On the other hand, an explain plan from Infobright looks nothing like the Oracle's plan. Its a set of cryptic rows put together. An example of such a plan -

2010-03-18 01:31:01 [4] T:-1 = TABLE_ALIAS(T:0,"myTableName")
T:-2 = TMP_TABLE(T:-1)
VC:-2.0 = CREATE_VC(T:-2,PHYS_COL(T:-1,A:20))
A:-1 = T:-2.ADD_COLUMN(VC:-2.0,AVG,"avg(col1)","ALL")
A:-2 = T:-2.ADD_COLUMN(VC:-2.0,MAX,"max(col1)","ALL")
A:-3 = T:-2.ADD_COLUMN(VC:-2.0,MIN,"min(col1)","ALL")
A:-4 = T:-2.ADD_COLUMN(,COUNT,"count(1)","ALL")
VC:-2.1 = CREATE_VC(T:-2,PHYS_COL(T:-1,A:2))
A:-5 = T:-2.ADD_COLUMN(VC:-2.1,GROUP_BY,"col2","ALL")
VC:-2.2 = CREATE_VC(T:-2,PHYS_COL(T:-1,A:5))
A:-6 = T:-2.ADD_COLUMN(VC:-2.2,GROUP_BY,"col3","ALL")
VC:-2.3 = CREATE_VC(T:-2,PHYS_COL(T:-1,A:7))
A:-7 = T:-2.ADD_COLUMN(VC:-2.3,GROUP_BY,"col4","ALL")
VC:-2.4 = CREATE_VC(T:-2,PHYS_COL(T:-1,A:11))
A:-8 = T:-2.ADD_COLUMN(VC:-2.4,GROUP_BY,"col5","ALL")
VC:-2.5 = CREATE_VC(T:-2,PHYS_COL(T:-1,A:12))
A:-9 = T:-2.ADD_COLUMN(VC:-2.5,GROUP_BY,"col6","ALL")
VC:-2.6 = CREATE_VC(T:-2,PHYS_COL(T:-1,A:13))
A:-10 = T:-2.ADD_COLUMN(VC:-2.6,GROUP_BY,"col7","ALL")
VC:-2.7 = CREATE_VC(T:-2,PHYS_COL(T:-2,A:-1))
T:-2.ADD_ORDER(VC:-2.7,DESC)
RESULT(T:-2)

And, guess what, to generate a plan, you have to change a setting in the initialization parameters file, and then bounce the db. I wonder if there have been any instances when someone had to look into production database's performance and therefore needed to look at some plan.

Being as new a system as it is, I cant really complain, since such things of maturity will slowly creep in. The focus right now is probably elsewhere, building the functionality, and probably performance.

in reference to: Infobright.org Forums | Enable MySQL Logging (view on Google Sidewiki)

Discovered BOINC 5 years ago, joined today :)

It was George, a colleague at Axa Tech in Switzerland who first introduced me to this idea. I was thrilled alright, but didnt join right away.

Today I did.

Its a nice feeling, and a feeling of giving back something to science.

http://en.wikipedia.org/wiki/Berkeley_Open_Infrastructure_for_Network_Computing

http://boinc.berkeley.edu/

I would not go into details how it works and all that. However, I would have to say, for whatever time your laptop/workstation remains idle, you can donate the processing power to a better cause. Absolutely fantastic idea, genuinely noble.

And then, look a the stats, people like me are contributing to the processing power generated to the extent of 4 pFLOPS, as against the fastest supercomputer system at mere 1.79 pFLOPS.

As I said, feels great. :)

I hope to inspire others to join in...

in reference to: BOINC (view on Google Sidewiki)

Connecting to an Oracle Server...which way is faster...

I've never came across this question as such, because its sort of given that you connect to a server any-which way the administrators define the policy. The tuning perspectives came in only afterwards.

However, in a recent situation, I had to connect to a remote server from my client system and was wondering whether I should connect using tnsnames.ora or should I use the basic authentication mechanism, using the complete connect string.

I thought that the tnsnames.ora would incur some latency in connections. On the other hand, connecting directly without using any such files is like doing a telnet to the server on a given port.

Also, I have seen that if you attempt to connect using the complete connect string from the tnsnames.ora file, it also works.

Since I was not clear myself, I did post this question on oracle forums. And a gentleman, Billy Verreynne took out some time to help explain the concept. Many thanks to him.

As it stands, the basic methodology of connection is same in both cases. However, if you happen to have a huge tnsnames.ora file, it would be an overhead to parse the file and get the connect string for the service name you attempted to connect to. But it would only make a difference, if your client connection process go into hundreds then it might make any noticeable degradation. Basically, client would have to parse the huge tnsnames file few hundred times per second.. then it might make a difference.

Billy also suggested that if you switch the server mode from dedicated to shared, it would help.

So, for my conclusions, its the same if you connect through tnsnames or through a native connect string.

availability of native drivers !!!

As I mentioned earlier, I was busy experimenting with a columnar database, InfoBright.

The experience till now is mixed, in some scenarios, the data loading is very good, as much as 40k rows per second, whereas through other channels its a poorer 500 rows per second. When I go with their built in loader, its lightening fast, but when I try from Pentaho or Informatica, its measly.

Apparantly, the drivers and the compatibility of the third party tools do play a role in attaining the performance.

The fact that they dont have any native driver published, is a huge bottleneck. Informatica dont even have a native connector for MySql, the more known cousin of InfoBright (being open source, the core engine of InfoBright is based on MySql only).

One thing came out of this experience for sure, the liking for open source got better and better. During the hunt to see the reason for slow performance from Pentaho, I even tried and managed to get the source code of the plugin (transformation) that pentaho uses for Infobright. Its pure java and it was a very powerful and awakening feeling to see the code of the item. I felt as if I have the power, the choice to make a difference, make it better. :)


I am currently exploring other options, one of them includes creating a dump file (read : csv) of the data, and then launching the command line tool to load the data into target db. I dont like it, but lets see if there is any better (read:faster) way around...

Its been a while...

Its been quite some time since I wrote anything to this blog, let alone anything valuable.

However, last few months have been quite eventful in my personal and professional life. I have landed a job with a company in Bangalore now, which works a lot more with open source systems/applications than my previous employer. I can easily say that this was one of the points in my decision making.

Currently, I am opening up to working on Ubuntu and probably virtualization, mysql, postgresql and most importantly, Informatica Powercenter and Pentaho. The suite of tools is just too exciting for me to find right words to express my feelings.

Recently I have picked up a project to do a Proof of Concept for using an open source columnar database and compare its behavior with oracle for a given application. Of course it involves data loading, and analytical queries, so there would be some interesting stats collection and comparison. Attempts to break a system are always more interesting than to make it J

Lets see how it goes…

Also, I would try to be more regular on the blog now onwards…

Compile all packages in a schema

BEGIN
FOR cur IN
(
SELECT OBJECT_NAME,
OBJECT_TYPE ,
owner
FROM all_objects
WHERE object_type IN('PACKAGE', 'PACKAGE BODY')
AND owner = ':OWNER
AND status = 'INVALID'
)
LOOP
BEGIN
IF cur.OBJECT_TYPE = 'PACKAGE BODY' THEN
EXECUTE IMMEDIATE 'alter package "' || cur.owner || '"."' || cur.OBJECT_NAME ||
'" compile body';
ELSE
EXECUTE IMMEDIATE 'alter ' || cur.OBJECT_TYPE || ' "' || cur.owner || '"."' ||
cur.OBJECT_NAME || '" compile';
END IF;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('Errors compiling - ' || cur.owner ||'.'||cur.object_name);
END;
END LOOP;
END;

MDX Tutorial

MDX Tutorial

Blogged with the Flock Browser

Interesting Demos from Informatica

Pretty Basic Demo by Infa guys on their DW offering...
Informatica Enterprise Data Warehousing Demo

Another interesting one on Data Migration...
Informatica Data Migration

Top 12 Ruby on Rails Tutorials

Looks like an interesting set of tutorials...

Top 12 Ruby on Rails Tutorials

Blogged with the Flock Browser