Monitoring the system using the DMS servlet
The DMS Spy servlet provides access to information from the Oracle Dynamic Monitoring System. It is not strictly a monitoring tool, as it does not display historical metrics or trends, but has a wide range of metrics, so is nevertheless useful.
Getting ready
You will need to have your WebLogic SOA Domain administration server running, and will wneed to know the administration credentials for this recipe.
How to do it...
These steps show us how to use the DMS servlet:
- Open a web browser, and point it at
http://servername:port/dms/Spy. For example,http://localhost:7001/dms/Spy. - A login dialog box will pop up; enter your domain administration credentials.
- The DMS Spy servlet will open, displaying a list of available metrics:
- Select the metric you want from the available categories on the left, and it will be displayed in the main pane.
How it works...
The Oracle Dynamic Monitoring System (DMS) is a library that pulls together metrics from a number of different sources, and exposes them in a common way. This does not only include JMX metrics from the servers, but also other metrics. In fact, you can add your own metrics to the DMS by adding sensors into your Oracle SOA Suite application. We recommend doing this if you wish to track performance metrics from within your application processes.
The DMS Spy servlet provides a simple way to view the metrics made available by the DMS, and is deployed by default on the administration server in a SOA Suite domain. On its own, it is not very powerful, but the simple format of the pages means that you can build simple "screen scraping" tools that will pull the metrics from the DMS servlet and make them available.
There's more...
A majority of the information available via the DMS servlet is also exposed via JMX, which is a much easier way of accessing it, and because you can also expose your own metrics over JMX, we have not seen many organizations that make use of the DMS servlet.
As JMX is a standards-based protocol, with many tools available for retrieving metrics (such as Hyperic, discussed elsewhere in this chapter), we would recommend using this over DMS if you wish to expose your own monitoring information about your application. Having said that, the DMS servlet can be a useful tool in identifying performance problems, and the fact that it is deployed by default in SOA domain environments makes it worth mentioning here.