Monday, November 26, 2007

The Management Kernel

Tools release 8.97 adds two new kernel definitions to the enterprise server: the BI Publisher (XML Publisher) and Server Manager kernels. Like the metadata kernel introduced in 8.96 these new kernels are Java based kernels that start their own JVM instance to run Java code rather than the traditional C based code of kernels past. SM will automatically add and configure these kernels into the JDE.INI when changing the tools release to 8.97. This post will focus on the server manager kernel.

The server manager kernel (number 32 for those keeping count) operates on all platforms and loads a JVM upon startup. This JVM will in turn load the management agent. This is the same codebase as that used by the managed home agent and is used to provide runtime information about the enterprise server to the management console. It uses a couple of INI settings, configured automatically, to provide it with the instance name and managed home location associated with the enterprise server instance. From the managed home location it will read the discussed in previous posts to obtain the connection details for the management console. It also follows the same connection logic used to establish communications as outlined in that post.

The management console uses this kernel to obtain all the runtime information about the server such as the active process list. It also uses this agent to expose and provide the log files that are active for the processes that appear in the process list.

This kernel definition is a singleton; that is there may only be a single process active and must be configured to start automatically, again all configured automatically. In fact the management console will not permit configuring more than one process for this kernel. The underlying network communications used by the management agents is different than the JDENET communications used by other kernels. As such the singleton can properly handle any amount of load and introducing additional processes is not necessary and will cause unexpected results.

The SAW Kernel

The Although SAW has been replaced with 8.97 there are still portions of the SAW infrastructure that are used by server manager. On the enterprise server the SAW kernel is still used. The Management Kernel (Java) exposes the runtime information using the JMX standard. It obtains much of this information by sending JDENET messages to the SAW kernel.

It is advisable to continue to run multiple SAW processes. The information exposed by the management kernel is collected periodically, approximately every 30 seconds. After that elapsed time JDENET messages are sent to the SAW kernels to collect the information. Having multiple SAW kernels will ensure that the information update to the management kernel occurs quickly and reduces the likelihood of any of these messages timing out.


In reality there is very little that needs to be known about this kernel. That said if the runtime information isn't available for a running enterprise server it may be desirable to investigate the log files for the kernel. There are two sets of log files of interest: the jde/jdedebug.log and the java log files.

The first place to check is the server manager jde.log. Since the process list isn't available (that's what we're troubleshooting) we'll have to randomly go through the log files exposed on the management page for the enterprise server until we find the management kernel. A successful startup is shown below. If there are any errors about starting up the JVM, loading the SM classes, or any other content in this log file this is the first place to look.

If there are no problems indicated in the JDE.LOG you may look at the java based logs. Since this is standard E1 Java code, logging is configured in the file contained within the system/classes directory. For each log defined in the you will see a corresponding log file created for each java based kernel process. Since multiple processes can be defined for the other java kernel types (metadata and xml publisher) the process id is added to the filename, as shown below:


The management kernel provides server manager powerful new monitoring capabilities. The operation of the management kernel can generally be ignored and should only be of concern should runtime information not be available for a particular enterprise server in the management console web application.