Performance Testing

Problem : You are observing high CPU usage on the application servers and are beyond your SLA.

Symptom(s) : APP Server CPU utilization, measured from the application servers via monitoring tools or Server Stats.

Solution: We will have to find root cause by carefully analyzing the server stats and correlating it with the test conditions. Following are the possible pointers to the root cause of the bottleneck.

A: Verify that the application server(s) are tuned as suggested by manufacturer specifications.

B: Check the application code of the transaction being executed, and verify that it is optimized. Use profiling tools or tools that can help spot locks or inefficiencies in the code. The key is to spot the slow transaction using Reporting tool, and to work with the developers or database engineers/DBA’s to identify what that transaction is doing, and fix problems where applicable.

C: If you are unable to find any issues with above two, there may be requirement of the addtional hardware to support Application Servers to handle the load. A sepearate Capacity Modeling excercise can be done to prove this in additional to the test results and server logs. In this case, we may have to scale the existing servers (either a Vertical or Horizontal Scaling, depending on the circumstances). Just do an etilogy in detail, I am sure problem will be identified with a proper solution.

The goal of performance testing is to identify how well your application performs in relation to your Performance Objectives/Performance Requirements/Performance SLA/Non-Functional Requirements.

Some of the other goals of performance testing includes the following:

• Identify bottlenecks and their causes.
• Optimize and tune the platform configuration (both the hardware and software) for maximum performance.
• Verify the reliability of your application under stress.
• You may not be able to identify all the characteristics by running a single type of performance test. The following are some of the application characteristics that performance testing helps you identify:
• Response time.
• Throughput or Maximum throughput which can be obtained from the Application
• Maximum concurrent users supported.
• Resource utilization in terms of the amount of CPU, RAM, network I/O, and disk I/O resources your application consumes during the test.
• Behavior under various workload patterns including normal load conditions, excessive load conditions, and conditions in between.
• Application breaking point. The application breaking point means a condition where the application stops responding to requests. Some of the symptoms of breaking point include 5xx errors with a “Server Unavailable” or “Service Unavailable” messages, and errors in the application servers, etc.
• Symptoms and causes of application failure under stress conditions.
• Weak points in your application.

What is required to support a projected increase in load. For example, an increase in the number of users, amount of data, application activity or even new usage pattern might cause an increase in load.

Performance testing is used to verify that an application is able to perform under expected and peak load conditions, and that it can scale sufficiently to handle increased capacity. There are three types of performance tests that share similarities yet accomplish different goals:

Load testing: Use load testing to verify application behavior under normal and peak load conditions. This allows you to verify that your application can meet your desired performance objectives; these performance objectives are often specified in a service level agreement. It enables you to measure response times, throughput rates, resource utilization levels, and to identify your application’s breaking point, assuming that breaking point occurs below the peak load condition.