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what is distributed enviroment?

 
Hai Lin
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Hi All,
Any good explanation for Distributed enviroment? The best way is giving an example in the real life, since the term "Distributed enviroment" is too abstract!
And what is the servlet runing int he distributed enviroment?

Thanks a lot.

Hai
 
Jacques Bosch
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Hi Hai.

It means that the web app is distributed over more than one VM / server.
Say you have 5 servers running together as a distributed environment, and something goes wrong with 1 or two of them, there are still the others to carry the load until the problems can be sorted out. I.e. the clients don't even know there was a problem.

Plus other benefits like faster processing of requests etc.
 
Hai Lin
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Jacques,
Based on your reply, for example, I have a very simple application Hello World ( just use it as example), runing this "hello world" application in distributed enviroment means I install this application (e.x helloworld.war) three times (or whichever times) in server1.com, server2.com, server3.com?
Is it true?
How about I install helloworld.war three times in different port of one server, for exampel, server1.com:10124, server1.com:10125, server1.com:10126, if this is also fine, since they are all running on one server, how come one server has serverl JVMs? (by the way, if one server can install several JVMs, how to install serverl JVMs on my local PC?)

Thanks a lot and greatly appreciate your reply.

Hai
 
Sivasundaram Umapathy
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JVM is a just program which runs on a machine.So you can run multiple copies of the same program. It's just as you open multiple command prompts. Although you execute the same physical file for the command prompt, they are different instances with different processes

You may multiple JVM's without noticing it. For example, you could run weblogic, have SmartCvs running for your source control and IntelliJ Idea as your IDE. In this case, you have 3 instances of the JVM.
 
subri
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Distributed Environment from the web perspective is done to address 2 issues (a) High Availability and (b) Load Balancing.

If there are many users and if we need more horsepower we add more elements to the cluster to address (b) above. However if want to make sure that failure of one server does not bring the application to its knees we use many cluster elements to address (a) above.
 
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