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Creating Well Performing Custom Code

Balance trade-offs and maximize performance

This article provides general guidance for creating well performing custom code for IBM WebSphere Portal. Custom code does not only refer to portlets (although they are the most common programming model for portals), but also includes code for WebSphere Portal themes and skins. Since these are implemented using the same basic technologies used for portlets, many performance considerations are applicable in the same way.

Regarding portlets, this article focuses on standardized portlets following the Java Portlet Specification, JSR 168, and the corresponding implementation in WebSphere Portal. The basis for this article is WebSphere Portal V5.1 or higher, although most guidelines and recommendations presented here will apply regardless of the version of WebSphere Portal you are running.

This series of articles explains how to set up and exploit the deployment parameters of a portlet application to optimize portal and portlet performance, since this is the last step in creating custom portal code. In contrast, general tuning of WebSphere Portal (that is, administrative actions that are performed after custom code has already been created and deployed) will not be covered here. (Look for another series of articles, beginning in the October issue of WebSphere Journal, that covers WebSphere Portal performance tuning. Those articles, combined with this series, will provide an excellent resource on portals and performance.)

This article is intended for programmers, designers, and architects involved in building custom portal applications and want to improve their understanding of potential performance issues with regard to custom code.

WebSphere Portal Environment Overview
IBM WebSphere Portal is built upon the IBM WebSphere Application Server product. As a result, the programming environment for custom portal code is threefold, with important corresponding implications:

  • WebSphere Portal and all its components are Java-based programs. Thus, in general, best practices with regard to programming high-performance Java code should be followed.
  • WebSphere Portal is a J2EE application running on top of an application server platform. J2EE embraces multi-threading; J2EE containers typically take a thread-per-request approach to handle the request burden. Any implementation or performance considerations inherent with using this mechanism should likewise be taken into account.
  • WebSphere Portal provides APIs to expand portal functionality. Many tasks can be programmed in many different ways. Differences that affect performance should be addressed as a priority.
The next sections introduce some general performance considerations for different parts of the portal programming environment.

Java
Clearly, this section is not intended as a complete treatment of Java performance. Instead, we present here the items we have found most useful when dealing with WebSphere Portal development, and suggest some resources that can help provide an indepth understanding of Java performance.

Basic Java Performance
In this section, we will cover some general performance items that will apply to most Java programs. Although these recommendations may not yield order of magnitude performance improvements, they can make you aware of the importance of low-level program execution performance while in the development phase.

  • Use java.lang.StringBuffers instead of java.lang.String instances when the modification of strings is required. String objects in Java are immutable, whereas StringBuffer objects are mutable. Whenever text is to be appended to or deleted from a String, a new object is created under the covers and the old object is discarded. Hence we prefer this:

    StringBuffer sb = new StringBuffer("Hello ");
    sb.append(var).append(" World");

    over this string concatenation:

    String s = "Hello" + var + " World";

    You can sometimes further improve performance by setting the initial capacity of a StringBuffer; the class is designed to automatically grow when it can no longer hold all its data. However, there is a performance penalty here, since a StringBuffer must work to transparently increase its size and shift the data around. For example, if a StringBuffer is used as a collecting parameter (meaning that more and more data is added to it), you should compute the appropriate buffer size before instantiating it so that it never needs to grow in size.

  • Avoid costly I/O operations in server-side programs. Execution of at least this thread is blocked during the I/O operation; if other threads also must wait for the disk, then system response times will easily and rapidly increase. Unless logging is being performed (for example, of exceptions or site access information), WebSphere Portal does not cause any disk access on its own. We will discuss I/O more later.
  • Minimize the number and length of synchronized code blocks. The synchronized keyword lets only one thread enter a code block at a time. The longer a synchronized code block requires for execution, the longer other threads wait to enter that block. We will discuss synchronization more later.
  • Avoid expensive calculations and method calls. For example, retrieving the current time information using System.currentTimeMillis() is rather expensive. If you need time information in your code, verify whether you need the exact time in every case, or (for example) if accuracy to the nearest second would be sufficient. If you have many get-time calls in your code path, but millisecond-accuracy is not mandatory, an alternative could be to determine the time at the beginning of a request and simply reuse this information throughout the request.
  • Restrict your use of exceptions. In general, exceptions in Java should be used to indicate a faulty situation. Do not use exceptions to indicate the success of an operation, especially because creating the exception stack traces is a time-consuming effort for the JVM, and because the traces can be very deep in a WebSphere Portal system.
  • Take care when using the Java Reflection API. This API adds powerful options to dynamic code execution, but also imposes severe performance penalties in terms of method execution times in exchange for this flexibility. In general, try to avoid the use of the Java Reflection API in portal code. However, if it is necessary to have reflection calls, try to have them in init methods so that they are not executed during every request.
Memory Consumption and Garbage Creation
While memory often is not a predominant performance issue for Java client software, it is a major concern for J2EE applications, mainly because enterprise applications are typically accessed by many users at the same time. For an application server to be efficient, the available resources, including memory, CPU and bandwidth, are shared among the clients' requests. There are three major memory issues we want to mention:

More Stories By Rainer Dzierzon

Rainer Dzierzon is team lead of the WebSphere Portal performance team located in the IBM Development Laboratory in Boeblingen, Germany. Since 1990, he has worked on numerous software projects for several companies in the area of database performance tools, text search, SyncML, online banking, and financial services architecture and standards. He and his team work as part of the WebSphere Portal development community to provide developers with the necessary insights of performance behaviour, and to consult customers and solve their performance issues. He holds a diploma in Computer Engineering from the University of Cooperative Education, Stuttgart.

More Stories By Klaus Nossek

Klaus Nossek is a performance analyst on the WebSphere Portal team at the IBM Development Laboratory in Boeblingen, Germany. He received a diploma in Computer Science from the University of Stuttgart in 1996. After working for several years on various software projects, he joined the IBM WebSphere Portal division in 2003. Currently, he belongs to the WebSphere Portal performance team. His main working areas are developing of performance scenarios for WebSphere Portal, and Java code profiling for detailed performance analysis.

More Stories By Michael Menze

Michael Menze joined IBM development in 2002 after studying with IBM for three years. He works in the Boeblingen development team for WebSphere Portal and is responsible for WebSphere Portal performance analysis, and the introduction of performance improvements.

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