Checking Apache Runtime Status

mod_status provides information on your apache server activity and performance.
This tutorial will show you how to enable this feature in such a way that only requested issued from localhost will be accepted and served.

Setting mod_status up

By default, server status report is commented so you can not access it. To enable it, you need to uncomment from /etc/apache2/apache2.conf or /usr/local/apache/conf/httpd.conf :

SetHandler server-status
Order deny,allow
Deny from all
Allow from .your_domain.com

This is a default setting, and will not work out of the box. What is said here is: server status will be acessible at location http://servername/server-status, access will be denied to everybody but people connecting from domain your_domain.com and any sub-domain from your_domain.com.

We want the server status to be provided only to people connected directly from the host running the apache server. Therefore we are going to deny access to /server-status to everybody except for people connecting from localhost, in the end the setting will look like:

SetHandler server-status
Order deny,allow
Deny from all
Allow from 127.0.0.1

Note: You could be using localhost instead of 127.0.0.1, but keep in mind that if the directive HostnameLookups is turned to Off, apache won't let you access to http://localhost/server-status .

OK, now that everything is set up, check that there is no error in your configuration by using:

$apache2ctl -t or $ /usr/local/apache/bin/apachectl configtest

if everything is fine, reload apache2 configuration with:

$sudo /etc/init.d/apache2 reload or $ /usr/local/apache/bin/apachectl restart

Accessing Apache Status

To access apache status and activity, you need to request the page http://localhost/server-status, you could use text mode navigators such as elinks or links in order to connect through a console using ssh.

Now, you can access information such as server start time, server uptime, number of requests being processed, number of slots available .... The different keys are explained just under the server activity.
A neat feature of server-status is the ability to refresh every X seconds, in order to get up-to-date activity, by calling:

elinks http://localhost/server-status?refresh=2

In the previous example, the status will be updated every 2 seconds.

Getting more from Apache Server-status

If you want to get more information from your server activity, you can add the directive:

ExtendedStatus On

just above the directive. But keep in mind that this cannot be set on a per virtualhost basis and will use more resources.
But in another hand, you will be able to access more informations such as:

• Total accesses
• CPU usage
• number of requests/sec, Bytes/sec and Bytes/request
• See the different clients connected to your server, on which virtual host as well as the page there are requesting, you can even access the time it took to request a specific page as well as the resources required.

References : http://www.debuntu.org/apache-activity-performance-mod_status

Web Developers Link Farm

Recently I found this cool link [ http://www.devlisting.com/ ] which displays all useful links that can be referred during Web Development. Its a resourceful link farm.
Some of the link categories of this farm contains are listed below:

• Ajax
• Firefox Plugins
• Ruby
• Traffic / SEO
• Flash
• Asp.net
• Design

Go here http://www.devlisting.com/

Steps to Improve Front End

1. With reference to my last post that Front End Performance are more important than Back End performance I have finally managed to find a nice descriptive article stating how to exactly achieve it.

The below are some of the common steps taken at Yahoo to improve performance of Yahoo Products.
All the points are covered in this link http://developer.yahoo.com/performance/rules.html

1. The Importance of Front-End Performance

1. Make Fewer HTTP Requests
2. Use a Content Delivery Network
3. Add an Expires Header
4. Gzip Components
5. Put Stylesheets at the Top
6. Put Scripts at the Bottom
7. Avoid CSS Expressions
8. Make JavaScript and CSS External
9. Reduce DNS Lookups
10. Minify JavaScript
11. Avoid Redirects
12. Remove Duplicate Scripts
13. Configure ETags
14. Make Ajax Cacheable

In addition to these Yahoo also provides developers with their custom FireFox extension which finds out what components of your page are slow and what can be done for improvement.
download Page :
http://developer.yahoo.com/yslow/
https://addons.mozilla.org/en-US/firefox/addon/5369

Reduce your page load time

Ever wondered why your page loads slowly even when your database queries execute at lightning speed.
Ever wondered why Super sites like Yahoo, AOL, etc load faster than your site.

If you are still wondering than this small article and the link mentioned at the bottom may help you reduce your page load time.

In any optimization effort it's critical to profile current performance to identify where the greatest improvement can be made. It's clear that the place to focus for fast web pages is the front end:

1. There is more potential for improvement by focusing on the front end. Making the back-end twice as fast reduces response times by 5-10%, whereas making the front end twice as fast saves 40-45%.
2. Front end improvements typically require less time and resources than back-end performance projects.
3. Focusing on front end improvements has proven to work. Over fifty teams at Yahoo! have reduced their end-user response times by following the best practices described here.

As web applications evolve to contain more functionality and content, these best practices are expected to have an even bigger impact.

Results Php Benchmark tests:
http://www.php.lt/benchmark/phpbench.php

The above link serves only the programming aspect of PHP.
There is still lot of improvement you can do in JavaScript and DOM.
So keep googling you might end up with what you exactly want.

Send Header without error

One of the common errors a web developer often gets is "Headers already sent" error.This happens when we render some text/characters /space in the browser and then try to redirect the page using header function of php.
For long I always thought that header function will only work when there is nothing rendered before the header call.
But recently I discovered(ofcorse with help of google) that we can render anything before the header call and still redirect the page.

Normal Usage with error is


echo "This will give error"
header("location:http://www.yahoo.com");


echo "This will NOT give error";
header("refresh:0; url:http://www.yahoo.com");


Here refresh:0 means the page will load after 0 seconds(which is instantly).
Basically this can be used when we want to have delay the page loading say we want to load yahoo after 2 seconds.
In this case the code will be


header("refresh:2; url:http://www.yahoo.com");



So start using this header call and redirect the page anytime during page execution.

Store procedure usage in PHP

Stored routines (procedures and functions) are supported in MySQL 5.1. A stored procedure is a set of SQL statements that can be stored in the server. Once this has been done, clients don't need to keep reissuing the individual statements but can refer to the stored procedure instead.

A stored routine is either a procedure . Stored routines are created with CREATE PROCEDURE statements. A procedure is invoked using a CALL statement, and can only pass back values using output variables. Stored routines may call other stored routines.
A stored procedure or function is associated with a particular database.

Procedures can be created using CREATE PROCEDURE command of mysql.
To know the exact syntax visit Online MySql documentation.

Once the procedure is created we have to use it in php code for this PHP's mysqli extension allows you to access the functionality provided by MySQL 4.1 and above

In order to have these functions available, you must compile PHP with support for the mysqli extension(MySQL Improved Extension).

To install the mysqli extension for PHP, use the --with-mysqli=mysql_config_path/mysql_config configuration option where mysql_config_path represents the location of the mysql_config program that comes with MySQL versions greater than 4.1.

mysqli functions are similar to mysql functions, there is substitute for each mysql functions in mysqli.
For e.g.

mysqli_query() has to be used instead of mysql_query()

using mysqli_query() the stored procedure query can be called and its result can be fetched.

Note: if you have to use any of mysqli functions then you will have to use mysqli functions throughout the current mysql connection
i.e. from mysqli_connect() to mysqli_close() all intermediate functions used must be of mysqli and not mysql.

references:

http://in.php.net/
http://dev.mysql.com/doc/refman/5.1/en/

Control Flow Functions of MySQL

While doing web programming many times you fetch data from database and depending on the value fetched, the user is shown something or other.
In case of optional fields in table it is quite likely that the value may be NULL or something default that you have set.
Take for example and option field called product awards which lists all awards bagged by that product.

When you write query
SELECT pro_id, pro_awards FROM products

This will give info regarding all the awards bagged by products.
However since pro_awards is optional many records will contain value NULL.

To tackle this NULL value you check in php whether the fetched value is NULL, if yes you display "No awards bagged by this product".

You can also do this checking at database level to reduce some load on webserver.
And as Databases are configured at their optimum level the processing time is much faster than your php / any script.

This can be done this way:
SELECT pro_id, IF(pro_awards IS NULL,'No awards bagged by this product', pro_awards) as pro_awards
FROM products
Above was use of if-else construct in MySQL

You can also make use of Switch-case construct effectively.
SELECT pro_id, CASE WHEN pro_awards IS NULL THEN No awards bagged by this product' ELSE pro_awards END FROM products

Above examples are very simple to understand, I am sure you can come out with difficult situations and use these Control flow functions of MySQL effectively to reduce script execution time.

references: http://dev.mysql.com/doc/refman/4.1/en/control-flow-functions.html