Michigan web site - CHAPTER 10 JAVA EE PERFORMANCE ASSESSMENT it
CHAPTER 10 JAVA EE PERFORMANCE ASSESSMENT it is important to understand what affects performance monitoring overhead, so this section explores some common configuration options that can mitigate performance overhead in two distinct areas: Platform recording Application recording Platform Recording Platform recording includes the entire layered technology stack upon which a Java EE application runs, specifically the following: Application server JVM Operating system Hardware Typically when you record platform metrics, you use a tool to capture periodic snapshots of the current state of the platform, including such metrics as the number of threads in use and the number of database connections in use. The tool then presents summaries of multiple snapshots, sometimes in graphs, from which you can assess the health of the various platform components. For example, knowing that during a one-hour test session the minimum number of threads in use was 7 and the maximum number of threads in use was 48, out of a total of 50, might lead you to increase the thread pool size to provide enough of a buffer to satisfy usage peaks. Statistically speaking, capturing performance metrics in this snapshot fashion provides a representative view into the performance of a platform component. But the accuracy of the representation depends wholly on the length of the recorded session and the interval upon which the metrics are captured. For example, capturing performance metrics every 5 minutes over a 1-week period is sufficient to provide an accurate representation of the platform behavior. But capturing performance metrics every 5 minutes for a 30-minute recorded session hardly yields conclusive results. In a 1-week period, 5-minute samples will converge on the representative behavior, but in a 30-minute period, a finer granularity of sampling is required. Therefore, the sampling interval needs to be appropriately chosen to mitigate performance overhead: you need to balance the granularity of samples between performance overhead and usefulness of the captured data. Ensure that you are capturing information that will help you tune the platform, while not bringing the platform to its knees in the process. The amount of data captured in a snapshot likewise affects the performance overhead of monitoring. For example, if a snapshot includes the entirety of an application server s JMX registry, then capturing this information even every minute adds significant burden to the application server. To mitigate this impact on performance overhead, employ the following strategies: Gather configuration information less frequently than run-time information. Consistently gather cursory or summary information, but gather detailed information only once it has been requested.
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