Wicket, Ajax panels and hung threads

The system administrators: 
– Why is your application using much CPU and much memory? And what’s up with these hung thread alerts in the server log? 
The test team: 
– Why is the application so slow? 
The programmers: 
– we don’t know! 
After a while we found out. The application its main page contains several Ajax panels, most of them can be typed as containers of ‘nice to have information’. In some test cases one of the Ajax panels kept showing: 


. It is something you do not mind if it doesn’t block the flow you’re in. It turned out that this little animated gif hid an infinite loop that was caused by unexpected output from a web service. 
Lesson learned: keep an eye on those friendly looking animated waiting gifs! They might just be hiding a monster!

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