Load Balancer - Definition + Components + Configuration + Availability

What is Load Balancer ?

 

Load Balancer is component of the WebSphere Application Server Edge Components, formerly called Websphere Edge Server. The Edge Server also includes a Caching Proxy (Web Traffic Express).  

 

Load Balancer is an advanced load balancing server which addresses the limitations of Round Robin DNS servers. Round Robin DNS distributes requests across a group of similar servers. Each request is sent to the next server in the list without taking into account the load on the server, the complexity of the request or even if the server is available.

 

 

Components of Load Balancer :

 

The Load Balancer consists of three subcomponents:

 

1. Dispatcher

Dispatcher provides an advanced IP level load-balancing mechanism, which you install instead of Round Robin DNS. It can provide load balancing for any TCP or UDP protocol. Once installed, Dispatcher remains completely invisible to clients but can deliver superior load balancing, management and availability function. Load Balancer's Dispatcher addresses these limitations by monitoring the status and response time of servers, assigning weights to each server and using an algorithm to return the right server to handle each request.

 

The right server is not always the best server, since it is desirable for all eligible servers to process their share of the load. Even the worst server needs to shoulder some of the burden. If traffic is only forwarded to the best server, it can be guaranteed that it will rapidly cease to be the best, and the load on the servers will swing backwards and forwards. Dispatcher's patented algorithm for choosing the right server and its advanced smoothing techniques achieve and maintain an optimal balance of server load distribution in the shortest possible time.

 

2. Content Based Routing (CBR)

Content Based Routing (CBR) provides full-function load balancing based on information in the HTTP data stream such as URLs, paths, cookies and so forth, or in the POP3 and IMAP data streams. Content Based Routing (CBR) uses information in the request packet to determine the best server to handle the request. For HTTP packets the information could be the URL or cookie contents. CBR also supports POP3 and IMAP servers.

 

3. Interactive Session Support (ISS)

Interactive Session Support (ISS) uses load monitoring of servers to provide an intelligent DNS server that can address the limitations of Round Robin DNS while still providing the standard DNS interface for clients. It provides a least disruptive migration path for applications that are already deployed using Round Robin DNS. ISS also provides an observer module to pass system load information to the Dispatcher. Interactive Session Support (ISS) runs an agent on each server to collect system information such as CPU utilization and number of processes. The agent is monitored by a monitoring daemon on the ISS server which can perform more intelligent load balancing. These three subcomponents can be deployed separately or together in various configurations to suit a wide variety of customer application requirements.

 

 

Load Balancer Configuration

 

Before installing the Load Balancer machine, you should setup a three-tier environment as previously described. The cluster host name should be used in the WebSphere Commerce configuration. Install and configure the additional Web server machines using the same process as the initial machine. Each Web server machine should have the cluster IP address as an alias of its network interface. The Web server configuration file should be edited to ensure that the cluster host name and IP address are used in the ServerName and VirtualHost directives.

 

Load Balancer could also be used in a two-tier configuration. Install Load Balancer (from the Edge Components CD in WebSphere Application Server Network Deployment) and configure the machine with the cluster IP address as an alias of its network interface. The local address of the Load Balancer machine is known as the non-forwarding address. Configure Load Balancer using its graphical user interface (or by editing its configuration file directly). Start the executor and add the cluster. Specify the cluster IP address, subnet mask and the network interface. Add server ports 80 (for HTTP) and 443 (for SSL), and if requests to the administration tools will also go through the Load Balancer, add ports 8000, 8002 or 8004.

 

To provide load monitoring of the Web servers, you could install and configure Interactive Session Support (ISS). ISS is usually only needed is special cases where the load on the different Web servers varies dramatically. This might be the case in a two-tier configuration where the Web server and Websphere Commerce Server run on the same machine and some command requests could take significantly longer than others. It is unlikely that ISS would be needed in a three-tier configuration because the Web servers only serve static content or forward requests to application servers. To set up ISS, the ISS server needs to be installed (either on the Load Balancer machine or a dedicated machine) and configured with the Dispatcher Observer. On each Web server machine the ISS agent is installed to monitor the system load and report it to the ISS server.

 

Affect on Overall availability

 

A three-tier configuration with multiple Web servers eliminates the single points of failure in the firewalls, Load Balancer, Web server, WebSphere Commerce server and database server. This is provided using a combination of failover and redundancy.

 

The database machine uses clustering software (such as HACMP on AIX) for failover. If the primary fails, the secondary takes over immediately. The data is stored on external shared disk (such as SSA disk arrays). Distribution over several disks, redundant power supplies and network adapters provide a very high degree of availability. The Websphere Commerce servers and Web servers use redundancy because there is no application data stored in the middle tier. The application will continue to be available if one or more servers fail, although at reduced capacity.

 

The Load Balancer uses a standby server for failover. Only the affinity tables get lost when there is a takeover. They are regenerated within a few seconds so it is transparent for the user of the browser. The firewall machines can also use clustering software for failover.

 

 

Bitter truth about Indian Work Culture

Really a class analogy ……….. Read on.

An Old Story :

The Ant works hard in the withering heat all summer building its house and laying up supplies for the winter.

The Grasshopper thinks the Ant is a fool and laughs & dances & plays the summer away.

Come winter, the Ant is warm and well fed. The Grasshopper has no food or shelter so he dies out in the cold.


Indian Version :


The Ant works hard in the withering heat all summer building its house and laying up supplies for the winter.

The Grasshopper thinks the Ant's a fool and laughs & dances & plays the summer away.

Come winter, the shivering Grasshopper calls a press conference and demands to know why the Ant should be allowed to be warm and well fed while others are cold and starving.

NDTV, BBC, CNN show up to provide pictures of the shivering Grasshopper next to a video of the Ant in his comfortable home with a table filled with food.

The World is stunned by the sharp contrast. How can this be that this poor Grasshopper is allowed to suffer so?

Arundhati Roy stages a demonstration in front of the Ant's house.

Medha Patkar goes on a fast along with other Grasshoppers demanding that Grasshoppers be relocated to warmer climates during winter.

Mayawati states this as `injustice' done on Minorities.

Amnesty International and Koffi Annan criticize the Indian Government for not upholding the fundamental rights of the Grasshopper.

The Internet is flooded with online petitions seeking support to the Grasshopper (many promising Heaven and Everlasting Peace for prompt support as against the wrath of God for non-compliance).

Opposition MPs stage a walkout. Left parties call for 'Bengal Bandh' in West Bengal and Kerala demanding a Judicial Enquiry.

CPM in Kerala immediately passes a law preventing Ants from working hard in the heat so as to bring about equality of poverty among Ants and Grasshoppers.

Lalu Prasad allocates one free coach to Grasshoppers on all Indian Railway Trains, aptly named as the 'Grasshopper Rath'.

Finally, the Judicial Committee drafts the ' Prevention of Terrorism Against Grasshoppers Act' [POTAGA], with effect from the beginning of the winter.

Arjun Singh makes 'Special Reservation ' for Grasshoppers in Educational Institutions & in Government Services.

 

Conclusions Drawn …

The Ant is fined for failing to comply with POTAGA and having nothing left to pay his retroactive taxes, it's home is confiscated by the Government and handed over to the Grasshopper in a ceremony covered by NDTV.


Arundhati Roy calls it ' A Triumph of Justice'.

Lalu calls it 'Socialistic Justice '.

CPM calls it the ' Revolutionary Resurgence of the Downtrodden '

Koffi Annan invites the Grasshopper to address the UN General Assembly.

Many years later ...

The Ant has since migrated to the US and set up a multi- billion dollar company in Silicon Valley,

100s of Grasshoppers still die of starvation despite reservation somewhere in India.



….. AND

As a result of loosing lot of such hard working Ants and feeding the Grasshoppers,

India is still a developing country...!!!

Raise Your Voice …

DO NOT LET THIS HAPPEN to YOU !!

OUR FUTURE IS IN OUR HANDS !! 

BUILD IT WELL !!

 

Jai Hind !!!

 

Protect your password in cyber cafe and on public computers

Protect your password in cyber cafe and on public computers

source : online website (try google)

Some time or the other, you must have used cyber dafe or public
computers to access internet or mail.
Public computers are most prone to password hacking. Anyone can simply
install a keylogger software to hack your password. Keylogging is one
of the most insidious threats to a user's personal information.
Passwords, credit card numbers etc. It is now very easy for the
keylogger to harvest passwords. Each and every keystroke (whatever you
type on the keyboard) gets recorded in the keylogger software and the
person installing it can easily view what you have typd in. For
example, if you go to hotmail.com and check your mails. Say your ID is
sarahj7@hotmail.com and password is snoopy2. the keylogger software
records your usename and password in its log file as
Microsoft Internet Explorer :
www.hotmail.comsarahj7@hotmail.comsnoopy2
Or
Firefox:
www.hotmail.comsarahj7@hotmail.comsnoopy2

Risky isnt it???!!!
There's solution to this problem and you can easily fool the hacker.
The keylogger software sees and records everything,but it doesn't
understand what it sees. I t does not know what to do with keys that
are typed anywhere other than the password or user name fields.

So,between successive keys of the password if you enter random keys,
the keylogger software wont ever come to konw where you typed in what..
In the process of recording the keys, the string that the keylogger
receives will contain the password, but embedded in so much random
junk that discovering it is infeasible.
So...

1.Go to hotmail.com or yahoo.com or any of the site where you need to
insert a password or PIN.
2.Type in your user ID.
3. Type in the first characterof the password.
4. Click on the address bar in the internet explorer or Firefox. Type
in some 3/4 random charachters.
5. Again go to password field and type in the second character of the
password.And probably third too.
6. Again go to the addressbar and type in a few mroe random character.
7. Back to the password field and the next characters of the password.
Keep on repeatin the process till you type in the full password in the
password field.

Instead of the password
snoopy2 the keylogger now gets:
hotmail.comspqmlainsdgsosdgfsodgfdpuouuyhdg2
Here a total of 26 random characters have been inserted among the 7
characters of the actual password!!!

No doubt it takes a little bit of more time than the usual process,
but you're safe and secure that way!!!

Income Tax Return Filing (Electronically)

The Central Board of Direct Taxes (CBDT) has initiated a program where you can file your annual tax claims electronically. This initiative by the CBDT is to streamline and assist taxpayers to file their taxes in a fast and efficient manner. You can follow the link below for further information and to file your taxes for the year.

http://incometaxindiaefiling.gov.in/portal/index.jsp

Write Song Lyrics - wikiHow

Write Song Lyrics - wikiHow

Calculate Hourly & Daily wages

Quick formulae to Calculate Hourly & Daily wages :

 

  daily_income  = annual_income / 360

&

  hourly_income = daily_income / 8

 

 [here 360 = 12 months * 30 days] and [8 denotes 8 working hours in a day]

 

pls add on top of daily_income in case you have any additional benefits, like daily overtime, daily incentives, etc.

 

Note :
 Currency Conversions should be done either at beginning or end of calculations.

 

 for example :
    1.00  USD = 40.00 INR
   60000 USD = 24,00,000 INR

 

 therefore :

 

   Daily wages  (INR)  = 2400000 / 360 = 6666.67  (USD 166.67)

 &

   Hourly wages (INR) =   833.33 /     8 =  833.33   (USD   20.83)

 

Outlook Hotmail account server address

http://services.msn.com/svcs/hotmail/httpmail.asp

Learn how to Manage Data Effectively

See here how to Manage Data Effectively:
http://www.buddyschool.com/manage_data_effectively/tutor.html?pa=7058

Get a Free Professional Resume Critique

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Complimentary Online Career Assessment Test

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LiveCareer is easy to use. There's a series of questions that asks you to select what you like the most and least amongst 3 things. When you're done you'll be instantly provided a great deal of insight on yourself and the environments you thrive in, as well as the kind of jobs, careers and activities you're suited for. You might be surprised. It's fun, incredibly accurate and no-cost-to you! Change your life by going to Live Career today!