programming

Let us take a this hypothetical situation. You have to serve a web page. You want the whole page to be sent back in 500 ms (milliseconds). If your user has a good network and he is not too far from your webserver, you can further assume that around 50 ms will be spent on the network. This means that you have 450 ms to collect all the data about this web request, do the fancy manipulations (sorting/filtering/updating files etc.) and serve it to the user. You need to make four external calls to get this data - 2 of them to an external web service and 2 of them to your own database.

Now assume that one of your external webservice calls take one second to send back the result 50% of the time and one of your database queries can take upto a second to give back the result 25% of the time. What will you do to make sure none of your users ever have to wait for more than 500 ms to get back the page? (500 ms excludes the time taken to download the images/css/do fancy javascript magic).

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I am in love with the book Higher-Order Perl, especially the technique in the Chapter 2: Dispatch Tables.

Today morning I came across this piece of writing - Does GPL still matter?. The whole article is based on a few anecdotes from CEOs and marketing droids. They have gotten quite a few points wrong in the article.

GPL is a developer friendly license. The basic premise of the GPL is that the user should not subtract from the freedom he gets when redistributing software. GPL is not restrictive. It merely insists that whoever takes from the common pool must contribute back to the pool.

I would like to point to these 2 articles in support of GPL -

• GPL-Virus Or Vaccine
• Why I (A/L)GPL

I attended the Hackers and Founders meetup yesterday. It was a high energy meetup and I liked it. When I walked in, I was already 2 hours late but there were still quite a few people around. I walked in, took a name tag and tried to "merge in". Merging was easy - the folks were friendly and did not mind if you joined the discussion.

Some observations

• I did not have a good answer for "what are you working on right now" . This made me realize that from a technology perspective, I have not worked on anything interesting for some time now. I have tinkered with a few things in the past 6 months (man!), but have not really done a deep dive on any of them.
• There was a focus on programming language in the group. I am not sure if the choice of a programming language is really a big deal when creating a webapp. Rails, PHP, Python, Perl, Java - all have a good web framework. One of the arguments was that it would be difficult to organize PHP code in a coherent manner. In my opinion, that is a matter of discipline instead of language.
• I did not find people thinking of totally different ideas. Or maybe, the folks were not telling those ideas . The ideas floated around ads, community, social networking, websites etc.
• I am not a unique case when it comes to the case of creating a startup. A few folks there had a regular job and were planning on side projects.

I am using a Mac now, and this blog post is brought to you by the same php and lisp scripts that I was using on my linux box. Cheers!

Have you read the man malloc page recently? Did you notice this section there

Recent versions of Linux libc (later than 5.4.23) and GNU libc (2.x) include a malloc implementation which is tunable via environment variables. When MALLOC_CHECK_ is set, a special (less efficient) implementation is used which is designed to be tolerant against simple errors, such as double calls of free() with the same argument, or overruns of a single byte (off-by-one bugs). Not all such errors can be protected against, however, and memory leaks can result. If MALLOC_CHECK_ is set to 0, any detected heap corruption is silently ignored; if set to 1, a diagnostic is printed on stderr; if set to 2, abort() is called immediately. This can be useful because otherwise a crash may happen much later, and the true cause for the problem is then very hard to track down.

So, you can do export MALLOC_CHECK_=1 and malloc will print debugging messages to the stderr.

I have created a emacs major mode, called lunatech-journal, that I use for blogging. It is a derived mode from muse-mode, an excellent mode for writing and publishing.

Currently, it has following functions defined

• lunatech-journal-skeleton - loads a skeleton for blogging
• lunatech-journal-show-hints - shows a buffer with questions to help me blog about my day
• lunatech-journal-make-html - creates a html file from the muse-mode
• lunatech-journal-preview - allows me to preview my journal in the browser

I use a php script to post the blog entry to the website. To use it, I have the following in my .emacs file

(defun journal ()
  (interactive)
  (find-file "~/blog/journal.muse")
  )
(require 'lunatech-journal)
(add-to-list 'auto-mode-alist '("journal\\.muse\\'" . lunatech-journal-mode))

When I feel the need to blog, I do M-x journal, I get dropped into my journal file and I can blog.

Links:

• lunatech-journal.el - the blogging mode
• Playing with your blog's xml-rpc interface shows the php script that I use to post entries to my blog
• MuseMode