CHAPTER 5 PERFORMANCE THROUGH THE APPLICATION DEVELOPMENT (Web design seattle)
CHAPTER 5 PERFORMANCE THROUGH THE APPLICATION DEVELOPMENT LIFE CYCLE Production Staging Testing Seldom will your applications run in isolation; rather, they typically run in a shared environment with other applications competing for resources. Therefore, testing your applications in a staging environment designed to mirror production is imperative. As the integration test phase is split into two steps, so is the production staging test: Performance production staging general test Performance production staging load test The general test loads the production staging environment with a small user load with the goal of uncovering any egregiously slow functionality or drained resources. Again, this step is interjected before performing the second, full-load test, because a full-load test may completely break the environment and consume all resources, thereby obfuscating the true cause of performance issues. If the application cannot satisfy a minimal amount of load while running in a shared environment, then it is not meaningful to subject it to excessive load. Identifying Performance Issues When running these performance tests, you need to pay particular attention to the following potentially problematic environmental facets: Application code Platform configuration External resources Application code can perform poorly as a result of being subjected to a significant user load. Performance unit tests help identify poorly written algorithms, but code that performs well under low amounts of user load commonly experiences performance issues as the load is significantly increased. The problems occur because subtle programmatic issues manifest themselves as problems only when they become exaggerated. Consider creating an object inside a servlet to satisfy a user request and then destroying it. This is no problem whatsoever for a single user or even a couple dozen users. Now send 5,000 users at that servlet it must create and destroy that object 5,000 times. This behavior results in excessive garbage collection, premature tenuring of objects, CPU spikes, and other performance abnormalities. This example underscores the fact that only after testing under load can you truly have confidence in the quality of your components. Platform configuration includes the entire environment that the application runs in: the application server, JVM, operating system, and hardware. Each piece of this layered execution model must be properly configured for optimal performance. As integration and production staging tests are run, you need to monitor and assess their performance. For example, you need to ensure that you have enough threads in the application server to process incoming requests, that your JVM s heap is properly tuned to minimize major garbage collections, that your operating system s process scheduler is allotting enough CPU to the JVM, and that your hardware is running optimally on a fast network. Ensuring proper configuration requires a depth of knowledge across a breadth of technologies.
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