Java and Spring development

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Monitoring a web application with tcServer developer edition

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The tcServer developer edition is a Tomcat server with monitor support. The monitor support is provided through a tcServer template called Spring insight. The template is a web application. The monitor data from your application are gathered with AspectJ load-time weaving, stored in memory and presented on the Spring insight web site deployed on the tcServer developer edition server. For local monitoring, you can find the insight application here: http://localhost:8080/insight.

The screenshot shows all the recent traffic to the demo application’s servlets. A click on one of the bars gives you access to detailed information about the requests processed in that time period.

The other view is application health. The screenshot below shows the application health for the “findBalance” web service.

The service monitored above behave quite well and Spring insight claims its health is excellent.

If you click on one of the bars, you can drill down to each response and see details for that response:

The example is from a web service and shows which parameters and return types my monitored beans are invoked with. Almost all the execution time for this request was used in the repository and you can see that the repository throwed an exception back. You can even read the exception message. If you’re using the WEB browser inside Spring Tool Suite (STS), you can also jump directly into the source code through the “Go to STS” link.

For a full introduction into monitoring with tcServer and Spring insight, you should see this presentation. It shows that you can see all the SQLs sent to the database and all the HTTP request and response messages handled by your application’s servlets.

How it works

The Spring insight application uses load-time weaving to monitor your application. Out of the box, Spring insight monitors the SQLs and HTTP request/response messages. To monitor your own classes, you have to add an @Component annotation above your class or preferably a specification like @Controller, @Service or @Repository. For Spring insight, these annotations are just marker annotations that tells AspectJ which classes to weave.

These annotations can also be used to define your Spring beans with component scanning. But it’s not related to the way Spring insight uses them since Spring insight uses them at load-time, which is before the Spring container is started (runtime).

A class that will be monitored because of the @Service annotation:

@Service
public class AccountServiceImpl implements AccountService {

Some examples

The screenshot below shows a server that increases the load with ten clients every fifth second. In the beginning, the throughput increases with a low increase in response time. With more clients the throughput still improves, but the average response time increases much more.

The last image shows the same application with the number of clients doubled every fifth second. After a while it results in bad and unstable response time. The graph isn’t 100% correct since I run the clients on the same machine as the server. But the tests indicates quite clear that this application shouldn’t have unlimited number of server threads.

You can see the response time is very unstable and Spring insight claims the application has bad health. With less server threads the application health improves.

Summary

The tcServer developer edition is an excellent choice for monitoring web applications that can run on Tomcat. With an annotation over all the classes you’re interested in monitoring, you get access to detailed information like execution time, parameters, exceptions and return types. And you’re only a click away from inspecting the code you find something interesting.

The code used in this article was developed in my work time at Redpill Linpro.


Redpill Linpro is the leading provider of Professional Open Source services and products in the Nordic region.

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Written by Espen

March 9, 2010 at 19:52