Recent Posts by Laurent Goldsztejn

The following thread was extracted from a thread dump taken on a JVM instance running WebLogic Server. In this post I will deconstruct this thread and describe the data it contains and the potential issues it may illuminate. [STUCK] ExecuteThread: '2' for queue: 'weblogic.kernel.Default (self-tuning)' id=73 idx=0x128 nid=13410 prio=1 alive, in native, daemon   java.net.SocketInputStream.socketRead0(Native Method) java.net.SocketInputStream.read(SocketInputStream.java:129) oracle.ne...

In this new post I will talk about diagnostic data and more importantly what data and source of data are needed to troubleshoot and resolve some specific common problems. WebLogic Server along with the JVM offers various ways to collect logs, debug traces, diagnostic images, thread dumps, and much more. However, useful data can easily get buried with lots of noise, unneeded data that won't help resolving a particular problem. Performance Issues We will start with performance...

A Heap Dump is a snapshot of the Java process heap memory at a given time.  It's a useful tool to troubleshoot memory leaks and other memory related issues.  Heap dumps are to memory what thread dumps are to java threads. There are different ways to dump the java heap used by a Java application such as WebLogic Server.  Heap dumps can be triggered automatically by JVMs such as HotSpot or JRockit when an OutOfMemory event occurs. Example: java...

Certain configuration files's access sometime need to be restricted in order to only allow one Weblogic Server instance or user to access them at any specific time.  Files with .lok extension are created for this purpose.  While browsing your domain directory structure, you might find config.lok under the domain config directory.  This file exists to ensure that config.xml is being updated serially.  Edit.lok's purpose is to ensure that only one user at a timecan edit the...

After migrating Hibernate applications to a more recent version of WebLogic Server from WLS 9.2.x, you might encounter query exceptions such as: EXCEPTION STACK TRACE: org.hibernate.QueryException: aggregate function expected before ( in SELECT [select distinct c, (select count(*) from ... The same query working properly under the old environment.  At first it might look like an invalid syntax in the query but the issue is really coming from a conflict between parsers clients. ...

In my latest blog post I talked about VisualVM, a very effective monitoring and troubleshooting tool.  Many other easy-to-use and free tools can be used while working with Java SE.  First of all, and since there is no need to re-invent the wheel, you can access documentation of such tools for Windows at Quick Troubleshooting Tips on Windows for Java SE 6 and for Solaris and Linux at Troubleshooting Tools on Solaris OS and Linux for Java SE 6 These tools include jstack, jinfo,...

A variety of free troubleshooting and debugging tools exist but which ones are really useful when analyzing issues with WebLogic Server?  In this new blog post series, I will talk about some of the best tools that are available, easy to use, free, and very effective in identifying a bunch of issues.  In this first post I will cover VisualVM. VisualVMmost recent version, or 1.3.5, was released on 11/13/2012.  This tool consists of an user-friendly visual interface...

On October 17th I delivered a webcast on WebLogic Clustering that included a demo with Apache as the proxy server.  I realized that many steps are needed to set up the configuration I used during the demo.  The purpose of this article is to go through these steps to show how quickly and easily one can define a new cluster and then proxy requests via an Oracle Http Server (OHS). The domain configuration wizard offers the option to create a cluster.  The administration console...