JAVA Related Performance Tuning Tips - Part 2

Servlet performance Tips:

• Use the servlet init() method to cache static data, and release them in the destroy() method.
• Use StringBuffer rather than using + operator when you concatenate multiple strings.
• Use the print() method rather than the println() method.
• Use a ServletOutputStream rather than a PrintWriter to send binary data.
• Initialize the PrintWriter with the optimal size for pages you write.
• Flush the data in sections so that the user can see partial pages more quickly.
• Minimize the synchronized block in the service method.
• Implement the getLastModified() method to use the browser cache and the server cache.
• Use the application server's caching facility.
• Session mechanisms from fastest to slowest are: HttpSession, Hidden fields, Cookies, URL rewriting, the persistency mechanism.
• Remove HttpSession objects explicitly in your program whenever you finish the session.
• Set the session time-out value as low as possible.
• Use transient variables to reduce serialization overheads.
• Disable the servlet auto reloading feature.
• Tune the thread pool size.

JSP performance Tips:

• Use the jspInit() method to cache static data, and release them in the jspDestroy() method.
• Use the jspInit() method to cache static data.
• Use StringBuffer rather than using + operator when you concatenate multiple strings.
• Use the print() method rather than the println() method.
• Use a ServletOutputStream rather than a PrintWriter to send binary data.
• Initialize the PrintWriter with the optimal size for pages you write.
• Flush the data in sections so that the user can see partial pages more quickly.
• Minimize the synchronized block in the service method.
• Avoid creating a session object with the directive <%@ page session="false" %>
• Increase the buffer size of System.out with the directive <%@ page buffer="12kb" %>
• Use the include directive instead of the include action when you want to include another page.
• Minimize the scope of the 'useBean' action.
• Custom tags incur a performance overhead. Use as few as possible.
• Use the application server's caching facility, and the session and application objects (using getAttribute()/setAttribute()). There are also third-party caching tags available.
• Session mechanisms from fastest to slowest are: session, Hidden fields, Cookies, URL rewriting, the persistency mechanism.
• Remove 'session' objects explicitly in your program whenever you finish the session.
• Reduce the session time-out as low as possible.
• Use 'transient' variables to reduce serialization overheads.
• Disable the JSP auto reloading feature.
• Tune the thread pool size.

Web application scalability Tips:

• Web application scalability is the ability to sustain the required number of simultaneous users and/or transactions, while maintaining adequate response times to end users.
• The first solution built with new skills and new technologies will always have room for improvement.
• Avoid deploying an application server that will cause embarrassment, or that could weaken customer confidence and business reputation [because of bad response times or lack of calability].
• Consider application performance throughout each phase of development and into production.
• Performance testing must be an integral part of designing, building, and maintaining Web applications.
• There appears to be a strong correlation between the use of performance testing tools and the likelihood that a site would scale as required.
• Automated performance tests must be planned for and iteratively implemented to identify and remove bottlenecks.
• Validate the architecture: decide on the maximum scaling requirements and then performance test to validate the necessary performance is achievable. This testing should be done on the prototype, before the application is built.
• Have a clear understanding of how easily your configurations of Web, application, and/or database servers can be expanded.
• Factor in load-balancing software and/or hardware in order to efficiently route requests to the least busy resource.
• Consider the effects security will have on performance: adding a security layer to transactions will impact response times. Dedicate specific server(s) to handle secure transactions.
• Select performance benchmarks and use them to quantify the scalability and determine performance targets and future performance improvements or degradations. Include all user types such as "information-gathering" visitors or "transaction" visitors in your benchmarks.
• Perform "Performance Regression Testing": continuously re-test and measure against the established benchmark tests to ensure that application performance hasn?t been degraded because of the changes you?ve made.
• Performance testing must continue even after the application is deployed. For applications expected to perform 24/7 inconsequential issues like database logging can degrade performance. Continuous monitoring is key to spotting even the slightest abnormality: set performance capacity thresholds and monitor them.
• When application transaction volumes reach 40% of maximum expected volumes, it is time to start executing plans to expand the system