Real Time Scenario 4 Application Having Performance Problem

What is Failure and Load balance?
If a request sent to an application and retrieved an error then it is call failure.
We will get so many requests to our application. In a clustered environment all the requests equally distributed, that is called Load Balancing.

Suppose we have one application having performance problem. I mean it is taking request time more how we will trouble shoot it? What are the log files we need to see?
Generally, poorely written code or data structures will create performance problem in an application. Then the performance will be degraded.
If there are too many firewalls presented from web server to application server will also create performance problem.
If application server is getting lost much of requests then also it will create performance problem.
We need to check the app. server jvm logs and application logs to check the problem and also we need to check the database logs to check the problem.
To troubleshoot this situation, we need to check all the above locations.

Suppose we have 10 applications in our environment? How the request goes to particular application? Could you please clear this?
A request will generally go to an exact application by the context root of that application.