Tech Scraps

GWT for client side code

2011-06-04T11:12:00.000-07:00

Google Web Toolkit(GWT) is a framework which allows you to write client code using Java and compiles it into JavaScript. It also allows you to write server code but you can choose a server side framework of your choice (like RoR, Spring MVC etc.). If you choose a Java-based framework for the server side, you will have the advantage of using only one language for the entire application (with the exception of CSS of course).

For thin client application, where only minimal code is executed by the browser, there is not much that you can exploit out of the GWT framework as most of the code will be on the server side. But if you are building a thick client, where some JavaScript execution is expected, GWT is a pretty neat choice.

Some features/tools which help manage the client code better than using plain JavaScript are:

1) Gin for Dependency Injection
2) EventBus to manage interaction between various components
3) GWTTestCase to test views (if they have any logic). We should have minimal logic in views but we all know that the views are getting more n more complicated these days ;)
4) Widgets which you can simply plug in
5) Built-in framework for MVP development

There are many more reasons for choosing GWT and depending on your requirement, GWT can be a good contender.

Sharing Internet Connection with Others using Ubuntu

2010-11-09T21:30:00.000-08:00

We were recently at a client's location where the internet access was restricted. We had a single USB Mobile Broadband device which had to be exchanged periodically so that we can go online.

This was a pain and wasted a lot of time. The 'Create New Wireless Connection' feature of Ubuntu came to the rescue. Here's how it works:

1) Enable wireless on your laptop
2) Click on the network icon at the top-right corner
3) Select 'Create New Wireless Connection'
4) Enter the Network Name, Wireless Security (I used None) and a Key
5) Ubuntu will try to immediately connect to this local Wireless network
6) Your friends should now be able to connect to this newly created wireless network like they normally connect to any wireless network
7) Connect to the internet the way you normally do (I connected using the USB device)

That's it, using these simple steps multiple machines can use the same internet connection.

Note: I used Ubuntu 10.10 with the default (Gnome) desktop environment.

Using RSA Software Token with Blackberry

2010-09-20T10:38:00.000-07:00

If you need to use RSA SecurID Software Token on your Blackberry phone, follow these steps:

1) Download bb350.zip from ftp://ftp.rsasecurity.com/pub/agents/bb350.zip
2) After unzipping, open the SecurIDTokenBlackBerry350_quickstart PDF document (under bb350\doc\English).
3) Goto the section 'Use the Application Loader to Perform the Installation'. This method of installation worked for me.
4) Once the installation completes. E-mail the sdtid (Token) provided to you by the administrator. Before mailing, prefix x-RIMDevicetoken to the filename (eg. x-RIMDevicetokenfilename.sdtid).
5) Goto the attachment on your phone (do not open attachment) and select the "Import SecudID Token" option. Enter the password provided for the token.

Thats it. When you start the RSA Application, it will automatically ask for the PIN and then display the OTP.

Adding Volume Conrol Icon to the Panel - Ubuntu 10.04

2010-09-09T22:48:00.000-07:00

After upgrading to Ubuntu 10.04, the Volume control icon disappeared from the Panel (Gnome).

To add it back, do the following:

1) Goto System > Preferences > Startup Applications
2) Click Add Button
3) Enter "/usr/bin/gnome-volume-control-applet" as the Command
4) Enter "Volume Control" (or whatever you like) as the name
5) Click Add

That's it. Next time you start Ubuntu, the Volume Control will start appearing.

Website Performance: Choose Data Center Carefully

2010-08-04T09:41:00.001-07:00

Data center which hosts servers for a website plays a significant role in the performance of the website. There are few things which should be kept in mind before choosing a data center:

1) Measuring distance in terms of hops is not the best approach. Latency is the accurate measure of speed on the internet and should be considered over the physical distance (hops). Thus, a data center closest to your customer might not be the fastest. Check latency of multiple data centers before choosing one. Latency can be tested by simply performing ping/traceroute tests to any server already hosted on the data center.

2) Check latency from regions which represent majority of the website's audience locations. So, if your site will cater to a specific region (like a city or state) then measure latency from only that region. If your site caters to a distributed audience (throughout the country or across continents) then test the latency from regions where you expect the maximum traffic.

3) Choose a ISP neutral data center. Data centers run by an ISP will perform really well with clients using the same ISP but might not be great when connecting with other ISPs.

Website Performance: Reverse Proxy for Spoon Feeding

2010-08-04T09:19:00.000-07:00

When clients with slow internet connection request a page, the server holds on to the thread/process till the complete response is transferred. This results in resources holding up for longer than in cases where clients use fast connections.

To handle this, a reverse proxy (like squid, nginx etc.) can be used in front of the web server. The web server will simply need to transfer content to the reverse proxy (which is super fast as they are on the same network).

The reverse proxy takes the burden of transferring the response slowly and frees the web server immediately.

Website Performance: Web Server for Static Content

2010-08-04T09:04:00.000-07:00

This approach is useful if you are not using a CDN to render static content (like js,css and images).

Servers which are used for the application (like Apache or Tomcat) are great for requests which require execution of some code before rendering the page.

There are a bunch of light weight web servers (like lighttpd, varnish and nginx) which are tuned to render static content really fast.

There are a bunch of benchmarking results out there. You will see clear benefits when a page with multiple static objects is rendered with any of these light weight web servers.

Website Performance: Delay Processing

2010-08-04T08:40:00.000-07:00

When a page is requested from the server, process only what is necessary to generate the required output.

Any additional processing that might be necessary can be delayed or performed asynchronously.

Stuff like sending a an acknowledgement mail or logging are good candidates for delayed processing.

One tool which helps you achieve this is Gearman. Gearmand is a simple server which allows worker threads to register themselves for certain defined processes and clients can send processing requests to the Gearmand server. The Gearmand server queues up thsee requests and dispatches them to worker threads. Client and worker code can be in different languages. For delayed processing, use the asynchronous (do_background) call.

Website Performance: Use CDN Effectively

2010-08-03T10:29:00.000-07:00

In most cases, we consider using a CDN (like Akamai) for static content like images stylesheets and JavaScript whereas ignore it for the HTML content.

Certain HTML might be cacheable. For example, if a certain HTML page changes every hour, for one hour it remains constant. It will be great if this page can be cached by the CDN somehow so that the first request from a region enables the CDN to cache it for the whole region.

The CDN is configurable for your site. Once you access the configuration, there should be options like:
1) Cache content on the edge server basis the cache headers sent by origin OR
2) Cache certain file/folder/url for X minutes/hours

It's imperative to understand and configure the CDN for optimal performance.

Website Performance: Memory as the primary storage

2010-08-03T04:40:00.000-07:00

We normally use databases/filesystems as the primary source of storage and add caching (Memory/RAM) to improve performance of the application.

Consider the opposite approach. Use Memory as the primary storage and file-system as a recovery source. So, perform all read and write operations directly in memory but log inserts/updates in file-system. The writes to file-system can be asynchronous (delayed inserts) and thus never become a bottleneck.

This is a risky proposition and should be considered only if:
1) The database operations are becoming a bottleneck and you have tried all possible optimizations. Only the problematic data sets should be considered for this approach.
2) The data is non-critical i.e. it is acceptable even if the data is not available for certain time period. The time duration that this data will be unavailable will at least equal the recovery time from file-system.
3) Typical database constraints (unique, foreign key etc.) do not apply to the data.

Website Performance: Cache Database Query Results

2010-08-02T09:50:00.000-07:00

Querying the database is an expensive operation and should be kept to a minimal.

Certain databases provide query caching capabilities. MySQL's query cache is great for tables which are used primarily for read operations Any insert/update query clears the complete query cache for the table. Thus, query caching cannot be leveraged for tables requiring regular insert/update operations.

Adding caching capabilities above the database layer can help boost performance. Before passing a read request to the database, an additional layer can check for appropriate content in the cache. If content is not available in the cache, request can be forwarded to the database and the cache populated before returning the result to application.

The caching layer can also trap any insert/update operation so that the cache is up-to-date.

If you are using Hibernate to persist your objects, the second level cache (and query cache) should be considered. They help achieve the same performance benefits using application level caching.

Website Performance: Cache HTML when possible

2010-08-02T09:19:00.001-07:00

HTML content for a dynamic page is generated for each request made to the server. Though the page is dynamic (as it changes from time to time) there are 2 things which should be looked at:

1) What is the frequency of change. Does the content change with each request or does it remain constant for some duration (15,30 mins?).
2) If it remains constant for certain time-period, how much requests are made for the same content within that duration.

Using a combination of this, caching the content (on server side) might be feasible.

Example:
1) If the content is constant for 15 mins and only 2-3 requests are made for the same content within 15 mins, then caching is not of much benefit.
2) If content is constant for even 5 mins, and 10 requests will be made for the same content in that time, caching will certainly be beneficial.

Caching complete HTML can be expensive and if you do not have sufficient memory (RAM) to hold this data, it might be feasible to keep this data cached on the disk as well. If disk is chosen, then caching is beneficial only if the read operation from the disk is cheaper than actually generating the content dynamically :)

When caching HTML, an appropriate cache clearing mechanism will have to be built so that stale content is never shown.

Website Performance: Choose Appropriate Cache

2010-08-02T08:44:00.000-07:00

Caching plays a key role in speeding up a web application. Before looking at what and when to cache, some consideration should be given to the appropriate cache which is suitable for your environment.

In case your application is deployed on a single server, then caching content on that server itself will suffice.

For distributed architecture (application deployed on multiple servers), distributed cache should be used.

Usually, the argument against a distributed cache is that it will involve accessing a remote machine which is expensive.

Let's look at how expensive this operation is.

Following are few interesting numbers picked from a presentation by Jedd Dean (from Google):

Time taken to read 1 MB sequentially from memory - 250,000 ns (thats nano seconds)
Time taken for round trip within the same data center - 500,000 ns

So, reading 1 MB from a remote server's memory should take roughly 750,000 ns (0.75 ms).

Considering that 1 second page load time is good enough, this is less than 1/1000th of the time. Thus, when we talk about web applications, reading from a remote server's memory will not degrade performance by any noticeable amount.

When using a distributed cache, it's advisable to use a bit more than what is required. This ensures that failure of a single server does not overload the application.

Example: If you need 4 GB of memory and you are using 4 servers (with 1 GB cache on each), add another (5th) server with 1 GB of memory for caching. This way, when 1 server goes down, the application performance will not get impacted much.

One of the most popular distributed cache implementation is Memcached. It's used by companies like Wikipedia, Flickr, YouTube and Twitter.

Website Performance: Don’t Let Third Parties Slow You Down

2010-08-01T03:38:00.000-07:00

Recently a presentation was made by 2 Googlers (Arvind Jain and Michael Kleber) @ Velocity 2010 where they talked abnout how third party code can slow a website.

Third party code (like Google ads, Digg widget etc.) usually includes an external script. Since browsers block rendering while fetching JavaScript, this third party code also blocks rendering of your page.

Analyse your page with and without this third party component to understand the impact that it has on your site.

If you have an option to choose from multiple vendors, then choose the one which has least impact on your page.

Example: The new Google Analytics code loads JavaScript asynchronously to ensure minimal impact on page loading.

Website Performance: Separate Static from Dynamic

2010-08-01T01:22:00.001-07:00

A dynamic page is one which can potentially change with each request to the server. But in most cases, there is also some content within these pages which does not change. This content remains static even when the dynamic elements change.

Such static content within a dynamic page varies from application to application but mostly it's stuff like the header, footer, drop-down values (like city, state and country) etc.

Analyse the dynamic page from this angle and come up with a list of static elements on it. If the static elements are considerable (like 30% of the content on a page) then consider separation. There are various techniques which can be used to cache the static elements on the browser.

This approach is useful only when rendering similar layout repeatedly. So, if the same static content (header footer etc.) will be shown for multiple page requests, then separation of static from dynamic is feasible. Whereas, if the static portion changes for each request, there is not much to gain by separation, rather you will end up slowing the existing pages.

Some of the techniques which can be used once the static and dynamic elements are separated:
1) Ajax: A popular and commonly used technique for search result pages. The ajax request is made and only the results are updated whereas the layout remains constant.
2) XSLT (XML+XSL): While requesting for a page, the static elements are embedded in the xsl file and the dynamic elements are fetched using a xml. The xsl can have cache headers defined so that the browser caches it. This is beneficial to the Ajax approach in cases where a new page request is to be made and the user leaves the current page to get content of a new dynamic page. Google for "Browser side XSLT" to get more details on this.
3) HTML in JavaScript as string: This is a simple approach to add html snippets within JavaScript as string so that they can be rendered (inner html) wherever necessary. Not a particularly good design as you will need to add html (view) within the code (javascript).

Website Performance: Utilize Browser's Idle Time

2010-08-01T00:47:00.000-07:00

Once the page loads completely, the user spends few seconds on the page before moving to the next one. The browser is idle during this time and can be used to speed performance of subsequent pages on the website.

For example, in case of search results, it's highly likely that the user will move the the next page once he completes viewing results on the current page. Thus, developers can use intelligent javascript to pre-fetch content of the next page when the browser is idle. This will help the next page load much faster.

Another condition for pre-fetching could be before launching a new version of the site.

New version of a website usually has new static content (javascript, style sheets and images). When a regular user of the site opens this new version for the first time, he will find the site extremely slow. Thus, initially many customers complain about performance.

If we start fetching the static content in the background couple of days before the launch of the new version, customers will not face the slowness and find the performance to be much better. Of course, care has to taken so that there is no clash in names of classes (CSS) and functions (JS).

Website Performance: Hosted JavaScript Libraries

2010-08-01T00:15:00.000-07:00

Most web applications these days make use of Libraries like jQuery.

These libraries offer significant advantages, but increase the initial page load time to a certain extent.

Most popular libraries are widely hosted by companies like Google and Microsoft. Instead of hosting these libraries yourself, it is feasible to include these libraries from such common locations.

When using the common location, chances are that the Browser has already cached the same URL and need not re-fetch the library for your site.

All in all, it's a win-win situation for you:
1) Saves bandwidth as you need not refer to your hosted library. In some cases this may save you some money.
2) Page loads faster as browsers might already have the libraries cached.

Google Libraries API provides a wrapper around the well known and widely used libraries (jQuery, Dojo, prototype, YUI etc.). Once included, you can directly load any popular library with a simple function call (example: google.load("jquery", "1.4.2"))

Setting up Go/Cruise 2 with github

2010-07-27T07:55:00.000-07:00

I recently installed Cruise(now known as Go) Server to setup Continuation Integration for a project.

I ran into some minor problems while configuring git as the VCS. Following are few tips to ensure that you don't face the same issues:

1) Assuming that Git is installed under the default folder (C:\Program Files\Git), add C:\Program Files\Git\bin to System PATH (C:\Program Files\Git\cmd was already added but bin was not).
2) Restart Cruise Server
3) Use Git Read-Only URL (git://github.com/bagheera/getin.git). Initially I tried with SSH (git@github.com:bagheera/getin.git) which failed.

ext4 with Ubuntu 9.10

2010-01-06T08:12:00.001-08:00

I was using Ubuntu 8.10 with ext3 as the file system type. The system performance was somewhat not up to the mark so I decided to install Ubuntu 9.10 with ext4 as the fs type. The overall system performance improved significantly after the installation.

For example: The HUGE folders in thunderbird are now opening much faster than with Ubunti 8.10 + ext3.

Till now i'm impressed with ext4 :)

Syncing Thunderbird 2.0 mailbox with Blackberry for an Exchange account

2009-09-14T22:07:00.000-07:00

My organization uses Microsoft Exchange as the Mail Server and a BES server to sync mails on my blackberry.

The mailbox on server is allowed only 50 MB of space and thus I need to continuously delete mails on the server. Previously I used POP to fetch mails from Exchange to Thunderbird mail client but this had sync issues (mails were downloaded multiple times, the read/unread information was different on mobile and desktop) once I configured my Blackberry using BES.

I recently shifted from POP to IMAP (had to get IMAP enabled from the administrator) and this has solved a number of problems.

I've created filters which automatically shift few mails to the local folders and I manually move emails to local folders whenever required. The move operation does not automatically compact (delete emails on mailbox which were moved/deleted locally) folders but the following will make that happen:

Goto Edit -> Preferences -> Advanced -> General -> Config Editor and then make the mail.imap.expunge_after_delete option as 'true'. Restart Thunderbird to use this config.

Secondly, I wanted the sent mails to be saved on the 'Sent Items' folder on the Exchange Server's mailbox. This can be achieved by subscribing to the 'Sent Items' folder and placing a copy of send messages in the 'Sent Items' folder. To achieve this:

1) Right click on the 'Inbox' for the IMAP account and click 'Subscribe'. Select the 'Sent Items' folder. You should now see the folder next to Inbox on the left panel.

2) Goto Edit -> Account Settings -> Copies & Folders and select 'Sent Items' as the Other folder under 'when sending messages, automatically' -> 'Place a copy in'.

Setting up your mail using BIS (Blackberry Internet Service)

2009-09-05T20:08:00.000-07:00

Once you've opted for blackberry services, the provider will setup an account on blackberry.com for you. For example, I'm using an Airtel connection and I access my account on http://www.airtel.blackberry.com/.

Once you log in, you'd probably want to add your official and personal e-mail. Setting up the email account is simple if you have a gmail account. Just enter your email address and password, it'll start delivering mails in minutes.

For your official id (for non Blackberry Enterprise Server users), blackberry will first try to automatically get the settings after you enter the e-mail/password and if it succeeds, you won't have to enter any more detail. But this could be troublesome for some, as in my case I wanted to setup using OWA (Outlook Web Access) and it picked the POP settings. A workaround is to enter the right e-mail id and a wrong password, this will throw up the settings page where you can manually select which protocol you want to use.

Lastly, I've noticed that mails sent to my gmail address are delivered instantly (using Push I guess) but mails sent to a POP or OWA account takes a few minutes to reach my phone. I guess if you are using Google for your official mails (http://www.google.com/apps/intl/en/business/index.html) then the delivery would be instant.

PHP Error after updating to 5.2.6 (Ubuntu 9.04)

2009-08-26T05:47:00.000-07:00

After updating to PHP 5.2.6 using the update manager, I got the following error:

php: symbol lookup error: /usr/lib/php5/20060613+lfs/pdo_mysql.so: undefined symbol: php_pdo_declare_long_constant

To fix, I simply installed the php5-mysql package using Synaptic Package Manager.

Reference: https://lists.ubuntu.com/archives/ubuntu-server-bugs/2009-February/009968.html

Migrating from Outlook 2007 to Thunderbird on Linux

2009-07-19T00:25:00.000-07:00

I recently migrated to Thunderbird on Linux from Microsoft Outlook 2007 (on Windows XP).

Following are the steps (should work for Outlook Express and older Outlook versions as well):

1) Install Thunderbird on Windows (Yes! On Windows first).
2) After installation go to 'Tools->Import'. Select Mails and then Outlook. This process might take some time and you should ensure that there is sufficient disk space available. Refer to http://kb.mozillazine.org/Moving_your_mail_storage_location_(Thunderbird) , if you want to change the location of Local Folders on Thunderbird.
3) Note the location where Thunderbird keeps it's folders (Tools->Account Settings->Local Folders will show the location). Copy Local Folders to a USB/External Drive (if the current location is not accessible from Linux).
4) On Linux, Install Thunderbird. Start Thunderbird. Configure your E-mail Account. Note the location where your local folders are located.
5) Create a 'New Folder' under 'Local Folders'(say 'Import'). Create another sub-folder inside 'Import'.
6) Go to the location where you can find the local folders. You should be able to locate the Import.sbd folder inside it.
7) From the original location where you imported the Outlook mails using Windows Thunderbird, copy contents of the Outlook.sbd folder to the Import.sbd on linux.
8) Ensure that the owner and permissions of all content under Import.sbd is appropriate (refer to the Inbox/Import folder/file permissions).
9) Start Thunderburd.

You should be able to see all your Outlook 2007 mails under the Import Folder. Initially they will all appear as un-read.

Memory leak in xcache extension of PHP

2009-06-18T21:28:00.000-07:00

I recently encountered memory leak while using the xcache extension (version 1.2) with PHP 5.2.6.

The following code confirms the memory leak:

$data = "data";
xcache_set("key",$data);
while(1) {
$a = xcache_get("key");
echo "Memory Usage :".memory_get_usage()."\n";
}

This seems like a known issue and a worksround is suggested by oli at http://xcache.lighttpd.net/ticket/95 . Simply type-cast the data to a string while using xcache_set. The following works without any memory leak:

$data = "data";
xcache_set("key",(string)$data);
while(1) {
$a = xcache_get("key");
echo "Memory Usage :".memory_get_usage()."\n";
}

Don't know the root cause of this issue but the workaround helped.

Browsers are getting faster!!

2009-06-09T10:42:00.001-07:00

Google Chrome has raised the bar for browser speeds as far as rendering/javascript is concerned. Ever since it's launch, all other browsers are releasing newer and faster versions one by one.

I recently tried the following browsers:

1) Opera 9.64
2) Chrome 1.0
3) IE 8
4) Firefox 3.5
5) Safari 4

Apart from IE 8 (whose javascript processing is awful) all the browsers are amazingly fast compared to their predecessors. I use to think that browsing was slow mainly because of the internet speed but it seems that the browser rendering speed has a major role to play.

Firefox 3.5 version is beta as of now but the final release should be out soon. I kind of like Firefox because of the add-ons available with it. There's just about any kind of extension that you'd like.

If given an option where all these browsers perform almost at par in terms of speed (5% here or there does not really matter) i'd use Firefox.

Tagging pattern in an element of XML using PHP

2009-06-03T09:48:00.001-07:00

Recently I had a requirement to tag a pattern within an element of the provided XML.

Following code worked:
<?php

function replaceElementWithTaggedElement($doc, $element, $pattern, $tagNameForPattern)
{
$newElement = $doc->appendChild(new domelement($element->nodeName));

$content = $element->nodeValue;
while(preg_match($pattern, $content, $matches, PREG_OFFSET_CAPTURE))
{
$match = $matches[0][0];
$offset = $matches[0][1];
$firstPart = substr($content,0,$offset);
$secondPart = substr($content,$offset+strlen($match));
$newElement->appendChild($doc->createTextNode($firstPart));

$taggedElement = $doc->createElement($tagNameForPattern);
$taggedElement->appendChild($doc->createTextNode($match));
$newElement->appendChild($taggedElement);

$content = $secondPart;
}
$newElement->appendChild($doc->createTextNode($content));

$element->parentNode->replaceChild($newElement, $element);
}

$doc = new DOMDocument();
$doc->loadXML("<root><one>This is the first text node</one><two>This is the second text node and the word to be highlighted is second</two></root>");
$oldElement = $doc->getElementsByTagName("two")->item(0);

replaceElementWithTaggedElement($doc, $oldElement, "/second/", "tagged");

echo $doc->saveXML();
?>

OUTPUT

<?xml version="1.0"?>
<root><one>This is the first text node</one><two>This is the <tagged>second</tagged> text node and the word to be highlighted is <tagged>second</tagged></two></root>

Gearman Client and Worker with PHP

2009-04-18T03:09:00.000-07:00

To write the Gearman client or worker in PHP there are 2 options available:

1) Net_Gearman pear package: http://pear.php.net/package/Net_Gearman/download/0.1.1
2) Gearman PHP Extension: http://www.gearman.org/doku.php?id=download

As per my experiments, Net_Gearman does not processes all requests when multiple (more than 5) simultaneous clients are sending requests.

The PHP extension available on gearman.org is better and initial tests are encouraging.

I encourage using the Gearman server and library available on gearman.org as well.

Keyword Suggestor in PHP 5

2009-03-27T19:17:00.000-07:00

To add a feature like Google's Did You Mean in your PHP application a reasonable solution is to use PHP's pspell library.

This comes bundled with PHP (http://php.net/pspell). Compile PHP with the '--with-pspell' option but before this ensure that you have aspell (version 0.6 or above) already installed.

Custom dictionary can also be created for aspell but this will require the aspell-lang package. You can download the same from here.

Details on how to create your custom dictionary are available here under the 'Creating a Custom Language Dictionary' section.

Using multiple field separators with gawk

2009-02-21T07:37:00.000-08:00

To define multiple field separators with gawk, set the FS variable with the appropriate regex.

For example, to use comma(,), colon(:) and equal-to (=) as field separators, following can be used

cat file.txt | gawk '{FS = "[:,=]+"} {print $3" "$5}'

The above example also prints the 3rd and 5th field elements.

Altering a HUGE MyISAM table in MySQL

2009-02-10T00:21:00.000-08:00

I recently tried to alter a MyISAM table with appx. 300 million records (15 GB MYD size) having unique indexes and it took forever to execute (more than 20 days).

Then, I came across this . The following suggestion simply rocks:

- You can create table of the same structure without keys,
- load data into it to get correct .MYD,
- Create table with all keys defined and copy over .frm and .MYI files from it,
- followed by FLUSH TABLES.
- Now you can use REPAIR TABLE to rebuild all keys by sort, including UNIQUE keys.

The alter completed within 5 hours flat. Just incredible!!

Google Calendar - Mobile Setup

2009-02-01T21:04:00.001-08:00

I recently tried the Mobile Setup provided by Google Calendar and thought of sharing it.

After you login to Google Calendar (http://calendar.google.com/) click on the Settings->Mobile Setup Tab. Enter your mobile number and validate your number.

Once done, you can now ask Google Calendar to send Event Reminders through SMS (For free):

This is a fantastic feature and will remind you of calendar events even if you are away from your Desktop and do not have a PDA/Smartphone to sync your calendar.

For MS Outlook users, Google also provides a Calendar Sync feature (http://www.google.com/support/calendar/bin/answer.py?answer=98563) which will keep your Google and Outlook calendar in sync.

Thus, you can now get SMS before any personal or official event :)

Which Blackberry is the best?

2009-02-01T00:21:00.000-08:00

There are a bunch off new Blackberries in the market these days. I'll take a look at each and give my views:

* Blackberry Bold (Powerful)
This is a power-packed Blackberry. It supports almost all the wireless protocols out there including WiFi and 3G. The screen resolution is equivalent to an iPhone even though the screen size is smaller and thus gives a very clear view. The processor and memory of this phone is better than any other blackberry (it will respond faster to your commands compared to other blackberries). The only negative aspect I can think of is the size. It's bigger than the 8900 or the pearl and will need a bigger pocket to go into.

* Blackberry Storm (Touch Screen)
After viewing the commercials, I was really exited about this phone. It was suppose to give serious competition to the iPhone as it is a blackberry with the touch screen. But sadly after going through few videos in YouTube it seems that the Storm lacks in power and has a slow response time. Moving through pictures/videos can be a pain. I would not like a smartphone which is slow.

* Blackberry Pearl Flip
When the original pearl was launched it was clearly a winner. The blackberry which is not FAT and fits in your hand comfortably. With the Flip, RIM has taken Pearl to the next level. So, if you want a sleek/small blackberry, then this is THE one for you. But you will have to compromise on the performance and screen quality if you settle for this one.

* Blackberry 8900 (Javelin)
This one comes really close to the Bold and will probably win if you consider the size. It's smaller than the Bold and has those curves which you will love. It has Wifi but no 3G. If you can compromise a bit on power and are not particular about having a 3G smartphone, then this is the one for you.

Sample C Server which handles zombie processes

2009-01-06T20:48:00.000-08:00

After a bit of googling I managed to create a simple Server (written in C) which accepts connection on port 5000 and spawns a new thread to handle each request:



#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>
#include <signal.h>

#define MAX_CLIENT    10

void zombie_handler(int iSignal)
{
        signal(SIGCHLD,zombie_handler); //reset handler to catch SIGCHLD for next time;
        int status;
        pid_t pid;

        pid = wait(&status); //After wait, child is definitely freed.
        printf("pid = %d , status = %d\n", pid, status);
}

int main(int argc, char *argv[])
{
        int tcp_sockfd, k, portno=0, tcp_newsockfd, n;
        struct sockaddr_in myServer, myClient;
        char bufferin[256],bufferout[256],ipaddress[20],hostname[50];
        char s[INET6_ADDRSTRLEN];
        struct hostent *host;
        pid_t pid=-1;

        signal(SIGCHLD,zombie_handler);

        //////////////////// Create a TCP Socket and get the port number dynamically

        tcp_sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (tcp_sockfd < 0)
                error("ERROR opening TCP socket");

        bzero((char *) &myServer, sizeof(myServer));
        myServer.sin_family = AF_INET;
        myServer.sin_addr.s_addr = htonl(INADDR_ANY);
        myServer.sin_port = htons(5000);
        if (bind(tcp_sockfd, (struct sockaddr *) &myServer, sizeof(myServer)) < 0)
                error("ERROR on binding");

        portno = ntohs(myServer.sin_port);

        if(gethostname(hostname,50) == -1)                                              // get hostname of the chat server machine
                error("ERROR on gethostname");
        host = gethostbyname(hostname);                                                 // get host information
        strcpy(ipaddress,(char *)inet_ntoa(*(long*)host->h_addr_list[0]));              //get IP Address string format

        printf("Chat Server IP Address : %s\n",ipaddress);
        printf("Chat Server Port Number : %d\n",portno);

//////////////////////////////////////// Now wait for connection from Client
        if(listen(tcp_sockfd,MAX_CLIENT) == -1)
                error("ERROR on listen");

        while(1)
        {
                printf("Waiting for connection...\n");
                k=sizeof(myClient);
                tcp_newsockfd = accept(tcp_sockfd,(struct sockaddr *)&myClient,&k);
                if (tcp_newsockfd == -1) {
                        printf("error in accept\n");
                        continue;
                }

                if (!fork()) { // this is the child process
                        close(tcp_sockfd); // child doesn't need the listener
                        if (send(tcp_newsockfd, "Hello, world!", 13, 0) == -1)
                                perror("send");
                        close(tcp_newsockfd);
                        exit(0);
                }
                close(tcp_newsockfd);  // parent doesn't need this


        }
        close(tcp_sockfd);

        return 0;
}

Here I simply write a string (Hello World!) to the client. You may perform multiple reads/writes.

The zombie_handler function ensures that no zombie processes are created once the child exists.

Getting Lightning to work with Ubuntu 8.10

2008-12-05T01:40:00.000-08:00

The Lightning extension(0.9) of Thunderbird(2.0.0.18) does not work appropriately on Ubuntu 8.10 .

The primary reason is that Lightning works best with libstdc++5 whereas Ubuntu 8.10 comes with libstdc++6.

Following steps will help fix this:

1) sudo apt-get install libstdc++5
2) Un-install the Lightning Extension of Thunderbird
3) Re-install Lightning

Update: The first step fails with Ubuntu 9.10. Install libstdc++5 using the instructions here.

Resize ntfs partition to install Ubuntu 8.10

2008-11-04T07:43:00.000-08:00

I recently tried to upgrade Ubuntu 8.04 to 8.10 on my PC but the installation failed due to insufficient disk space under the /boot partition. 8.10 needs about 120 MB free space but I had only 60 MB free under /boot.

To expand the /boot (second) partition, I had to shrink the first partition which was (unfortunately) ntfs. The gparted (disk partition tool for linux/ubuntu) installed on 8.04 wasn't of much help as it only supports deletion or formating of ntfs partitions.

I got a Ubuntu 8.10 installation CD and booted my PC using the same. The gparted utility on 8.10 supports resize of ntfs partitions :) . I successfully shrunk the ntfs partition and expanded the second (/boot) partition.

After restarting the system with the installed Ubuntu 8.04 version, the upgrade started successfully.

Note: Before attempting resize of any partition, do backup your critical data.

"Fan Error" - ThinkPad

2008-11-04T07:27:00.000-08:00

My laptop is about 2 years old and it was working perfectly fine till today morning. While booting (after the bios loaded) it displayed "Fan Error" and the system automatically shut down. I started the system a number of times but the same error kept occurring.

There was some weird sound coming from the Fan. I guess the Fan must've got stuck due to dust or something. I tapped (quite hard) the laptop from the side a couple of times and surprisingly it started working :)

If you get a similar problem then try this at your OWN risk coz the situation might worsen. Eventually, I guess the fan will have to be replaced but if at all you get it working for once, do take backup of critical data immediately (I did).

Configuring app.yaml for static websites

2008-11-02T20:18:00.000-08:00

In case you want to publish a static website on Google App Engine (http://appengine.google.com/) then the following configuration can be used (app.yaml):

application: appname
version: 1
api_version: 1
runtime: python

handlers:
- url: /(.*)
  static_files: static/\1
  upload: static/(.*)

This assumes the following:

1) The application name is appname (change it to your registered application name on appengine.google.com)
2) All static pages are under the static directory (appname/static)

This works fine, but any request to http://appname.appspot.com/ (or another domain in case you are using Google Apps) will not automatically be redirected to http://appname.appspot.com/index.htm (or index.html). In case you want such a behavior, create a python script (like main.py) under the application directory (appname/) with the following content:


import cgi

from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app

class MainPage(webapp.RequestHandler):
  def get(self):
    self.redirect('/index.htm')

application = webapp.WSGIApplication(
                                     [('/', MainPage)],
                                     debug=True)

def main():
  run_wsgi_app(application)

if __name__ == "__main__":
  main()

and change the app.yaml to:


application: appname
version: 1
api_version: 1
runtime: python

handlers:
- url: /
  script: main.py

- url: /(.*)
  static_files: static/\1
  upload: static/(.*)

Pre-populate cache for faster performance

2008-07-12T08:47:00.000-07:00

Recently I came across a scenario where load had to be shifted from an existing database server to a newer (faster) machine. This is usually not a problem but the challenge this time was to do this during peak-load.

I tried to shift queries to the new server a number of times, but found the load shooting up each time. Thus, the queries had to be shifted back to the old machine.

After a bit of investigation it was found that since the new server had not cached the database contents, it lead to high load and thus the server response time dropped drastically. To overcome this, I used a small trick. I cached the database contents (at least the indexes) before sending the queries back to the new server. To pre-populate the cache (RAM), use the following:

cat TABLE_FILES > /dev/null

(Considering that TABLE_FILES are the file names which contain the data/index)

This will make the OS read complete contents of the desired files and dump the output to /dev/null. Certainly this is useful only if your data/index size is less than RAM.

After this, the new machine worked like a breeze and there was no significant i/o.

More memory does not necessarily mean more speed

2008-05-26T10:02:00.001-07:00

If the processor waits for i/o most of the time then adding more Primary Memory (RAM) usually helps. But before that decision is made, there are a few important things to look at:

1) What is the total data size that can be accessed?
2) How much data is accessed multiple times (at least more than once)? And how much Memory does this data require?

If the total data size is only a couple of gigs then you can probably think of having equivalent amount of Memory. But if the data size is tens or hundreds of gigabytes then adding that much Memory will certainly be very expensive.

Lets consider a case where the a database instance stores 200 GB of data. Out of this, only 4 GB is accessed multiple times in day and the rest might be accessed only once. In such a scenario, anything above 6 GB (the extra memory for kernel and other processes, if any) should be of no help because every time that extra data (other than the 4 GB) is accessed, the CPU has to wait for the disk i/o to complete.

Parsing apache logs to identify IP with max requests

2008-05-24T03:11:00.000-07:00

To find out the IP Addresses which generated the maximum number of requests, following Linux command can be used:

gawk {'print $1'} access_log | sort -n | uniq -d -c | sort -n

Note: This assumes that you're logging the IP Address in the first column

Scaling Up Vs Scaling Out

2008-04-12T06:45:00.000-07:00

You've got the website up and running, your clients love it, more and more people want to use it. Everything seems to be going great. One fine day you realize that your systems are getting chocked and clients have started complaining. You keep adding new machines to your environment (doing quick-fixes in the application to support this distributed architecture) and believe that this scaling-out approach is the right way to move forward (after all, the big guys like google n yahoo have thousands of machines). After a couple of years, there are 10s (or probably 100s) of machines serving your website traffic and the infrastructure, administration etc. costs have gone up considerably. And due to the quick-fixes, its really difficult to work on a new clean architecture and add more features to your application.

Lets consider what Googles got and how the scaling-out approach works great for them:

1) Possibly the best Engineers in the world
2) Google File System (GFS)
3) Map-Reduce
4) An infrastructure where you can treat a server class machine like a plug-n-play device
5) Applications which are designed keeping GFS and MapReduce in mind
... and god knows what else

If you've got anything close to this, then scaling-out is the obvious answer. Otherwise, read on...

There are 3 major components to consider while choosing a Server:

1) CPUs
2) Primary Memory (RAM)
3) RAID configuration (RAID 0, RAID 1, RAID 5 etc.)

A server has certain limitations in terms of the amount of Memory and number of CPUs it can hold. (mid-level, server class systems come with support of up to 32 GB memory and 4 CPUs). Adding more CPU or Memory becomes very expensive after this. So, there is linear cost of adding more memory and CPU to a certain extent and after that it becomes exponential.

Example: Lets say you've got a 100 GB database. It works comfortably with a 16 GB(expandable upto 32GB) RAM, 2-CPU Server. Once the database size goes up and the users increase, this single server might not be able to handle the load. The option is either to increase RAM (most database servers need more memory and not CPU power) or add another machine. The economical solution will probably be to add more RAM (addition of another 16 GB memory will cost significantly less than what a new server would). After a certain point addition of RAM might be more costly than adding a new server and thus the better option is to scale-out at this point.

The key is to scale-up till the cost is linear and side-by-side start work on the Application architecture such that you can run your application smoothly on multiple servers and scale-out thereafter.

Choosing the right RAID configuration is also important, it depends on what operation you perform the most (read, write or read+write). I'm not an expert in RAID configurations so do a bit of googling and you'll get a number of articles on this.

Profiling PHP code with xdebug

2008-02-29T02:38:00.001-08:00

Using xdebug to profile php code is very simple.

Following are the steps to get started:

1) Install the xdebug extension (http://xdebug.org/docs/install) for PHP.
2) Enable profiling for any PHP which gets executed by setting xdebug.profiler_enable=1 in php.ini
3) Restart the Apache Server

From now on, whenever you execute a PHP, files with name starting from cachegrind.out will be created under the /tmp directory.

4) Install kcachegrind (http://kcachegrind.sourceforge.net/)
5) start kcachegrind with the cachegrind.out file as the parameter (eg. kcachegrind cachegrind.out.12345)
6) Set xdebug.profiler_enable=0 in php.ini to disable profiling.

Average file size within a directory

2008-02-20T21:05:00.000-08:00

To calculate the average file size within a directory on a Linux system, following command can be used:

ls -l | gawk '{sum += $5; n++;} END {print sum/n;}'

If you'd like to know the average size of some particular kind of files (like jpg files) then use the following:

ls -l *.jpg | gawk '{sum += $5; n++;} END {print sum/n;}'

Gmail Spam Filter

2008-02-11T09:43:00.000-08:00

I've been using Yahoo Mail, Hotmail and Gmail for few years now. Out of these, Gmail certainly has the most effective spam filter and keeps junk out of your Inbox.

The sad part is that at times it even marks some of the important mails as spam and thus you have to keep checking the spam filter regularly.

Few points to keep in mind if you use gmail:

* One way to reduce the chances of important mails being marked as spam is to add to your contact list the addresses from where you expect to receive mails.

* When you send out a mail to some address, then Gmail automatically adds that id to your contact list and thus Gmail should never mark any mail from that id as spam.

* If you download mails using POP, the Spam mails will never get downloaded (which is great in a way). Thus, you will always have to login using the web interface to check mails marked as Spam.

Apache ReWrite Module

2008-02-06T21:00:00.000-08:00

Apache has a very powerful tool (mod_rewrite) which can be used to redirect/rewrite requested URLs on the fly.

To use this module, you can configure apache with the '--enable-rewrite' option before compilation. Then, set 'RewriteEngine on' in the httpd.conf to start using it.

For complete details, please go to http://httpd.apache.org/docs/1.3/mod/mod_rewrite.html.

I will give a brief example which redirects all requests on http://www.localhost.com/ to http://localhost.com/ (I needed to do something like this for a site) and any request starting with '/redir/xyz' will execute '/test.php/redir/xyz'.

Following is copied from the httpd.conf.

...
...
NameVirtualHost 127.0.0.1:80

<VirtualHost 127.0.0.1:80>
ServerAdmin your@email.com
DocumentRoot /usr/local/apache/htdocs
ServerName localhost.com
ServerAlias localhost.com
RewriteEngine on
RewriteRule ^/redir/(.*) /test.php/redir/$1 [QSA,PT,L]
RewriteLog logs/rewrite_log
RewriteLogLevel 3
ErrorLog logs/local_error_log
CustomLog logs/local_access_log common
</VirtualHost>

<VirtualHost 127.0.0.1:80>
ServerAdmin your@email.com
DocumentRoot /usr/local/apache/htdocs
ServerName www.localhost.com
ServerAlias www.localhost.com
RewriteEngine on
RewriteRule ^/(.*) http://localhost.com/$1 [QSA,R,L]
RewriteLog logs/rewrite1_log
RewriteLogLevel 3
ErrorLog logs/local1_error_log
CustomLog logs/local1_access_log common
</VirtualHost>

Compiling PHP with PDO-mysql

2008-02-01T20:18:00.000-08:00

To install pdo-mysql with PHP, following are the steps:

1) configure PHP with '--enable-pdo=shared --with-pdo-mysql=shared' options.
2) compile and install PHP (make, make install)
3) Add 'extension = pdo.so' and 'extension = pdo_mysql.so' in the php.ini after pointing the extension_dir variable to the appropriate location where these 'so' reside. (eg. extension_dir = /usr/local/php/lib/php/extensions/no-debug-non-zts-20060613)

Buying the WRT54G Wireless Router in India

2008-01-25T11:10:00.000-08:00

To make my home wi-fi enabled, I decided to buy a Wireless Router. Loads of such routers are available these days and after doing a bit of research online I decided to go for the Linksys WRT54G router.

WRT54G routers allow you to install certain open-source (linux) firmware. If you are the kind who likes to play around with hardware, then this is the one for you. It allows you to do all sorts of things like increase the range (using the Xmit power), port-forwarding etc. etc. For details please goto http://www.dd-wrt.com/.

A friend of mine suggested to go for WRT54G Version-5 or 6 since he already had one and it was working fine with Linux firmware. So... I went to Nehru Place (supposedly THE place to buy computer hardware in New Delhi) and asked for Linksys WRT54G router. Surprisingly the version information wasn't mentioned on the router's box.. I tried a few more shops.... but again, no version information. Hoping that the router will work with linux firmware I decided to purchase the router for Rs. 2150/-. Once I got home and opened the box 'version 7' was mentioned at the back of the router. After a bit of googling it was clear that this version of WRT54G CANNOT be upgraded to Linux firmware. Even if I try to install the firmware, the router will get 'bricked' (basically of no use and will have to be thrown).

If you are planning to buy the WRT54G router and install Linux firmware on it, please ensure that it's NOT 'version 7'. All versions (v5,6,8) can be upgraded to Linux firmware but not v7. The serial number of all WRT54G v7 routers starts with 'CDFE'. The serial number is mentioned on the router's box (wish I knew this early on).

Luckily I found someone who already had a 2 year old v5 WRT54G and was happy to exchange his router with my new v7 router :)

I have now successfully upgraded the v5 router to Linux firmware(dd-wrt) and its working fine.

Hosting multiple sites on a single server using the same IP

2008-01-24T20:17:00.000-08:00

Apache has a great feature which allows hosting multiple sites using the same apache instance and even the same IP address. To know more click here

Following example shows how this can be done.

Open the httpd.conf configuration file which is being used by apache.

Add following at the end:

NameVirtualHost 127.0.0.1:80

<VirtualHost 127.0.0.1:80>
ServerAdmin your@email.com
DocumentRoot /doc/root/for/first/domain/
ServerName www.firstdomain.com
ServerAlias www.firstdomain.com
ErrorLog logs/firstdomain_error_log
CustomLog logs/firstdomain_access_log common
</VirtualHost>

<VirtualHost 127.0.0.1:80>
ServerAdmin your@email.com
DocumentRoot /doc/root/for/second/domain/
ServerName www.seconddomain.com
ServerAlias www.seconddomain.com
ErrorLog logs/seconddomain_error_log
CustomLog logs/seconddomain_access_log common
</VirtualHost>

Replace 127.0.0.1 with the appropriate IP address, firstdomain and seconddomain as per the requirement.

Restart apache.

I tried this with apache 2.0.59 and it works fine.

Finding Intersections between two sets in C++

2008-01-17T17:38:00.000-08:00

Following C++ code (intersection.cpp) creates 2 sets ( a and b), creates a vector out of those (av and bv) and then finds the intersection between the two vectors.



#include <iostream>
#include <vector>
#include <set>
#include<sys/time.h>

using namespace std;

#define MAX_SIZE 1000000

int main()
{
        set<int> a,b,un,in,di;
        timeval tim;

        srand ( time(NULL) );

        cout << "Adding to a : " << endl;

        for( int i = 0; i < MAX_SIZE; i++ ) {
                int r = rand() % MAX_SIZE;
                a.insert( r );
        }  

        cout << "Creating vector av" << endl;
        vector<int> av(a.begin(),a.end());
        cout << "There are " << av.size() << " elements in av" << endl;

        cout << "Adding to b : " << endl;

        for( int i = 0; i < MAX_SIZE; i++ ) {
                int r = rand() % MAX_SIZE;
                b.insert( r );
        }  

        cout << "Creating vector bv" << endl;

        vector<int> bv(b.begin(),b.end());
        cout << "There are " << bv.size() << " elements in bv" << endl;

        gettimeofday(&tim, NULL);
        double t1=tim.tv_sec+(tim.tv_usec/1000000.0);

        set_intersection(a.begin(),a.end(),b.begin(),b.end(),insert_iterator<set<int> >(in,in.begin()));

        gettimeofday(&tim, NULL);
        double t2=tim.tv_sec+(tim.tv_usec/1000000.0);

        vector<int> inv(in.begin(),in.end());

        cout << "Elements in intersection " << inv.size() << endl;
        cout << "Intersection time " << (t2-t1) << " seconds" << endl;
        return 0;
}

compile: c++ intersection.cpp -o intersection
Sample Output


./intersection
Adding to a :
Creating vector av
There are 632163 elements in av
Adding to b :
Creating vector bv
There are 631924 elements in bv
Elements in intersection 399250
Intersection time 0.65199 seconds

Technologies to look out for in 2008

2008-01-14T07:54:00.000-08:00

Here are a bunch of exciting technologies to look out for this year:

1) Wireless USB: Tired of carrying all those wires with your USB devices. Well... there is hope of getting rid of them. Wireless USB is capable of high speed data transfer (much faster than Bluetooth). http://en.wikipedia.org/wiki/Wireless_USB

2) Solid State Drive (SSD): These are the next generation of Disk Drives. They should be hugely successful with mobile devices (like laptops n phones) coz they are mechanically very reliable. They have the ability to endure extreme shock, high altitude, vibration and temperatures. http://en.wikipedia.org/wiki/Solid_state_disk.

3) Organic Light-Emitting Diode (OLED): Much more efficient than the traditional LED and plasma due to their low power consumption and ability to provide more color depth without any backlight. Extremely thin TVs with amazing colors will be possible with this technology. http://en.wikipedia.org/wiki/Organic_light-emitting_diode.

4) Near Field Communication (NFC): This is a short range, high-frequency wireless communication technology aimed primarily at usage in the mobiles. This makes things like Mobile ticketing and payment possible. http://en.wikipedia.org/wiki/Near_Field_Communication.

Removing all non-ASCII characters from a string using php

2008-01-11T04:11:00.000-08:00

ASCII characters have hex code from 00 to 7F (http://www.asciitable.com/).

Following php function removes all non-ASCII characters from a string:

function removeNonAscii($string) {
return preg_replace('/[^\x00-\x7f]/','',$string);
}

Reliance Broadnet (Broadband internet connection)

2008-01-06T01:52:00.000-08:00

I recently got a pamphlet of Reliance Broadnet (Broadband service provided by Reliance in India) which mentions that the service provides download speeds ranging from 150 Kbps to 2 Mbps.

Following are the plans mentioned:

1. Rs. 750/month for 150 Kbps (unlimited upload and download)
2. Rs. 999/month for 300 Kbps (unlimited upload and download)
3. Rs. 1799/month for 600 Kbps (unlimited upload and download)
4. Rs. 750/month for speed upto 2 Mbps with free usage of 4 GB (upload+download) and 90 paise/MB for additional usage

Installation charge is Rs. 500 + Service Tax.

Call 1-800-227773 or 3033 7777 for details.

Set Clipboard contents from command line using java

2008-01-04T21:49:00.000-08:00

Following code(setClipboardContents.java) sets the Clipboard contents for 10 seconds:

import java.awt.datatransfer.StringSelection;
import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;

public class setClipboardContents{
public static void main(String[] args) throws Exception {
StringSelection stringSelection = new StringSelection( args[0] );
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
clipboard.setContents( stringSelection, null);
try{
Thread.sleep(10000);
} catch(InterruptedException e){
System.out.println("Sleep Interrupted");
}
}
}

Compile: javac setClipboardContents.java
Run: java -cp . setClipboardContents "add this content to the Clipboard"

Capturing string input without echo in java

2008-01-04T21:26:00.000-08:00

Following code will demonstrate capturing a string without any echo using java:

Create a java file (noEcho.java) with the following code:

import java.lang.System;
import java.io.Console;

public class noEcho {
public static void main(String[] args) throws Exception {
char[] passwd;
Console cons;
if ((cons = System.console()) != null && (passwd = cons.readPassword("[%s]", "Enter Text:")) != null) {
String text = new String(passwd);
System.out.println("You Entered :"+text);
}
}
}

Compile: javac noEcho.java
Run: java -cp . noEcho
Sample output:

[Enter Text:]
You Entered :this is a test string

Hibernate instead of Shutdown for faster performance

2008-01-02T04:25:00.000-08:00

When you boot your computer, certain critical modules (like kernel) are loaded into the Primary Memory (RAM) which allow the operating system to start. After this whenever you start an application (like Microsoft Word or Outlook) it first gets loaded into the Primary Memory from where the OS loads the Application. Thus, the first time you start an application there might be a delay of a few seconds and the next time it'll be much faster.

Hibernate saves the contents of the RAM into Secondary Memory (Hard Disk) and when you boot the OS next time, it simply loads the RAM image back from the Hard Disk.

Thus, even though time taken for a normal boot vs time for a boot after hibernate may be similar, you save a lot of time while working on the same set of applications.

MTNL Broadband in Delhi

2007-12-29T02:27:00.000-08:00

I was using an Airtel Broadband connection in Hyderabad last year and was pretty satisfied with their service. After shifting to Delhi, I wanted to get an Airtel connection again but unfortunately they do not provide telephone/broadband services in my area. Tried Tata Indicom also, but no luck there too.

So finally I decided to go with MTNL Triband and requested a connection on 25th August 2007. Its been 4 months and after a number of calls and mails I have still not been given a connection. I went to the MTNL office last week and they told me that the 'ports' are not available in my area and I will get a connection only if someone else releases their connection. This is really funny and I suggest anyone who wants to go for an MTNL Broadband connection to first ask their Local MTNL telephone exchange whether there is a possibility of getting a connection anytime soon.

Gmail App using Airtel Live on Sony Ericsson K750i

2007-12-27T20:07:00.000-08:00

Activating Airtel Live (skip if you already have Airtel Live)

1) Call the customer care and ask for Airtel Live activation (or send "PLIVE" to 170). It takes about 24 hours for the activation.
2) Once activated. Get the settings by sending "LIVE" to 52567.

Once you have the settings enabled you can start using your phone's browser to access your gmail account (http://mail.google.com/mail/x/). This works but you might find this slow to access your mails again and again (as I did). If your Phone is capable of running Java Applications (which most phones are these days) then using the Java Application for Gmail is a much better option.

Setting up Gmail App (On Sony Ericsson K750i)
1) Goto http://gmail.com/app/ from the phone's browser and download the java application (about 160 KB). This is required only one time.
2) Once download is successful. The phone asks for confirmations. Allow the phone to install the application.
3) Goto Menu->Settings->Connectivity->Settings for Java and select the appropriate Internet profile ("AIRTEL LIVE" in case you are using Airtel Live).
4) Goto Menu->Organizer->Applications and select "Gmail".
5) Enter the gmail username and password and sign in.

Note: Accessing mails using the Gmail App are charged as per the standard download rates.

Enable External Display on Thinkpad R60 with Linux (Ubuntu 7.10)

2007-12-24T22:10:00.000-08:00

Followings steps got my external CRT Display working on ThinkPad R60 with Linux Ubuntu 7.10 installed:

1) cd /opt
2) sudo wget http://www16.plala.or.jp/mano-a-mano/i810switch/i810switch-0.6.5.tar.gz
3) sudo tar -xzvf i810switch-0.6.5.tar.gz
4) cd i810switch-0.6.5/
5) sudo vi i810switch.c
Insert the lines marked in BOLD below:

//#define I865STR "8086:2572"
#define I915STR "8086:2592"
#define I945STR "8086:27a2" //line 63
#define MEMSTR "Memory at"
...
...

i = (p = strstr(*buff_ptr, I830STR)) != NULL ||
(p = strstr(*buff_ptr, I945STR)) != NULL || //line 266
#if defined (I865STR)
(p = strstr(*buff_ptr, I865STR)) != NULL ||
#endif /*defined (I865STR)*/
(p = strstr(*buff_ptr, I845STR)) != NULL;
if (i)
...
...

6) sudo make
7) sudo make install
8) sudo i810switch crt on (turns on the external display)
9) sudo i810switch crt off (turns off the extrenal display)

To allow any user to perform this switch:

chmod u+s /usr/bin/i810switch

I use a simple script to toggle my external display:

STATUS=`i810switch | grep CRT | awk '{print $2}'`
if [ "$STATUS" = "off" ]
then
i810switch crt on >> /dev/null
elif [ "$STATUS" = "on" ]
then
i810switch crt off >> /dev/null
fi