Category Archives: Technology

What is node.js?

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The logo of the Node.js Project from the offic...
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If you follow the world of Javascript and/or high-performance networking, you have probably heard of node.js. If you already grok Node, then this post is not for you; move along. If, however, you are a bit confused as to exactly what Node.js is and how it works, then you should read on.

The node.js website doesn’t mince words in describing the software: “Evented I/O for V8 JavaScript.” While that statement is precise and captures the essence of node.js succinctly, at first glance it did not tell me much about node.js. I did what anyone interested in node.js should do: downloaded the source and started playing around with it.

So what exactly is node.js? Well, first and foremost it is a Javascript runtime. Think of your web browser; how does it run Javascript? It implements a Javascript runtime and supports APIs that make sense in the browser such as DOM manipulation etc. Javascript as a language itself is fairly browser agnostic. So node.js is yet another runtime for Javascript, implemented primarily in C++.

Because node.js focuses on networking, it does not support the standard APIs available in a browser. Instead, it provides a different set of APIs (with fantastic documentation). Thus, for instance, HTTP support is built into node.js — it is not an external library.

The other salient feature of node.js is that it is event driven. If you are familiar with event driven programming (ala Python Twisted, Ruby’s Event Machine, the event loop in Qt etc), you know what I’m talking about. The key difference though is that unlike all these systems, you never explicitly invoke a blocking call to start the event loop — node.js automatically enters the event loop as soon as it has finished loaded the program. A corollary is that you can only write event driven programs in node.js, no other programming models are supported. Another consequence of this design choice is that node.js is single-threaded. To exploit CPU parallelism, you need to run multiple node.js instances. Of course, there are several node.js modules and projects already available to address this very issue.

To implement a runtime for Javascript, node.js first needs to parse the input Javascript. node.js leverages Google’s V8 Javascript engine to do this. V8 takes care of interpreting the Javascript so node.js need not worry about syntactical issues; it only need to implement the appropriate hooks and callbacks for V8.

node.js claims to be extremely memory efficient and scalable. This is possible because node.js does not expose any blocking APIs. As a result, the program is completely callback driven. Of course, any kind of I/O (disk or network) will eventually block. node.js does all blocking I/O in an internal thread pool — thus even though the application executes in a single thread, internally there are multiple threads that node.js manages.

Overall, node.js is very refreshing. The community seems great and there is a lot of buzz around the project right now, with some big companies like Yahoo starting to use experiment with node.js. node.js is also driving the “server side Javascript” movement. For instance, Joyent’s Smart platform allows you to write your server code in Javascript, which they can then execute on their hosted platforms.

Finally, no blog post about node.js is complete without an example of node.js code. Here is a simple web server:

Rupee symbol finalists

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The ToI reported a few days ago that there are five finalists for the Indian Rupee symbol:

Rupee symbol finalists

I had previously written about the Rupee symbol here. The ToI seems to suggest that #4 is the likely candidate. According to the article, the symbol should have been decided by now, but I haven’t found any information to that effect. Does anyone know the final outcome? I can’t say I like any of the finalists that much, but I guess out of the five #4 is probably one of the better ones.

How the mouse moves

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Random interesting find of the day: IOGraphica. Here’s mine for about 7 hours at work:

Such a simple app, but such a fascinating output. An easy way to create computer generated art! Couple of observations:

  • I have a dual-monitor setup at work. I use the left monitor for email for browsing and the right monitor for code. The mouse patterns clearly reflect this usage pattern. I tend to rest the mouse roughly equally on the both the monitors.
  • I was very intrigued by the fact that most of the mouse motions are very smooth. Most curves almost look parabolic. There are very few jerks and jittery lines. Once again, nature seems poetic even in the most chaotic and random actions.

Throw away mailing lists

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Have you ever found yourself in a situation where you are on a mailing list and you want to send an email to all but 2 members on that list? A common case here is planning a surprise for someone on that list.

Photo by http://www.anna-om-line.com/

In general, I find myself on (long) email threads containing a different subset of people for different occasions (birthdays, anniversaries etc) several times a year. The email threads quickly become long and unwieldy. People keep adding other people as the thread progresses, and the only way the new adds can figure out whats going on is looking at the content of future emails. There is no way for anyone to go back and read all the discussion so far.

That got me thinking, wouldn’t it be great to have a service that provide throw away mailing lists? Hear me out. Here’s how the service would work:

  • To start a new mailing list, I simply send an email to newlist@mycoolservice.com. In the email, I also include a list of email addresses I want to seed the list with.
  • The service sends me back the address of a newly created throw away list. This could be of the form some-random-number@googlegroups.com.
  • For all practical purposes, this is exactly like any other mailing list (or Google Group). We can add more members, search the messages etc.
  • Start your discussion and let the thoughts flow.
  • …
  • At some point, the purpose behind the list will cease to exist (successful surprise, for instance). Needless to add, further discussions on the topic will also cease.
  • You forget you even created this mailing list. After the mailing list has been idle for some time (say two weeks), the service automatically deletes the mailing list. Any future messages to that address will bounce back saying that the list has been deleted, please contact the administrator.

Does anyone else think this could be useful?

India Census 2011

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Amidst all the chatter, billboards, news coverage and ads about the 2010 census here in the US, I heard a stories on the radio about the upcoming census in India next year. Since I didn’t know much about the census process in India and since this particular census seemed particularly newsworthy, I decided to learn more about it. Here’s what I found.

First, I was a bit surprised and disappointed that the top hit for a Google search for “india census 2011″ does not point to an Indian government website for the census. Instead, most of the top hits are from various news stories. An interesting aside here — check out the same search carried on google.co.in; the results are quite different. In fact, I found it quite interesting that the censusindia.gov website is the top hit for the US search, but not in the India search.

Second, the census website is pretty shabby. Forget about SEO, typography, accessibility — the folks who are building these websites are still living in 1999. Someone needs to tell them about good web design. Design and usability issues apart, the content itself is lacking in many places; even incorrect in some places. Consider this page:

  • the breadcrumb style navigation is only for appearances — the links don’t really work
  • It says “Census 2001″!!!!
  • the <title> anchor says “Evolution of Data Processing”. There’s no indication of the title on the page itself. Instead, it says “Preparation for the 2011 census.”
  • Best viewed in 1024×768? Wow.
  • None of the foreign language links at the bottom of the page work. It would be trivial to link to a Google-translated page.
  • The header image or text don’t link to the Census home page. This is really basic stuff. I wonder if any of the developers building the website have actually used it.
  • Most of the links on the Census home page are “under construction.”

Anyways, I don’t want to waste this post on nitpicking. After all, the issues at stake here are considerably more serious than web design. Without further ado, here are the key facts:

  • This is the 15th census. The first one took place in 1872.
  • I couldn’t get any information about how the previous censuses were conducted, but this time around the Indian Government is aiming to record each and every one of the 1.2 billion individuals. Thats a really lofty goal.
  • This Census is also being used to piggy back another significant project: the construction of a National Public Registry (NPR). The NPR will contain some key stats about everyone in India. The NPR will also be used to generate biometric IDs for all Indians at some point.
  • For the first time in Census history, some NGOs will be involved in the training phase.
  • A lot of geo-spatialization technologies are in play. The only article I could find was this.
  • Another first: this Census will be collecting some data on basic sanitation, drinking water etc.
  • The 2001 census employed roughly 2 million “enumerators” (data collection personnel). This census will undoubtedly require more.

The FAQ has several interesting nuggets:

The information collected about individuals is kept absolutely confidential. In fact this information is not accessible even to Courts of law.

Once this database has been created, biometrics such as photograph, 10 fingerprints and probably Iris information will be added for all persons aged 15 years and above.

The issue of Cards will be done in Coastal Villages to start with. After this the coastal Towns will be covered and so on till the entire country is covered.

35 questions relating to Building material, Use of Houses, Drinking water, Availability and type of latrines, Electricity, possession of assets etc. will be canvassed.

Like I said earlier, these are lofty goals and this is a massive effort. But there’s so little information out there. I have a lot of questions and concerns. For one, the construction of the NPR poses a huge privacy risk. How is the Government going to ensure that corrupt officials don’t sell out the data to whoever pays the right price? What kind of audit policies and procedures are in place such that a neutral third-party can attest to the integrity of the entire process? Who all within the government will be able to look up my data? If the Government is going to store the biometric data as well, aren’t they constructing a gold-mine of identity-theft ammunition?

Digging around for more information, I found this fascination presentation (linked off of the United Nations Statistics Division). The PPT claims that it was prepared by someone from within the Census organization, but I can’t vouch for its authenticity.

India Census Data Processing

View more presentations from diwakergupta.

I really hope that a lot more information on the technology behind the Census comes out in the coming months. The news channels in India should take some time out from reporting on tabloid/gossip issues and focus some energy on something that will impact every single Indian.