Logging and Debugging deployed Flex applications

I want to share my experience with troubleshooting Flex problem in deployed environment. I am working on a application that uses web service as back end. I do development and basic testing in Flex Builder so I can run debugger and see trace outputs.

But lately I decided to try run my app from web container (tomcat). The first problem I encountered was my login screen doesn't work. I pressed login and nothing happened. I have code that uses Application.application.url parameter to figure out host site and based on url decide where to locate web services. In local debug environment I use hardcoded url (and it works fine), in deployed one I have code that construct url dynamically (and obviously it wasn't working well).

What should I do?

Luckily Flex Builder provides an easy way to run remote application (loaded from web container) in debug mode. First you need to make sure that you used -debug=true flag when you compiled your application. Once you done it, you can create a new debug run configuration in Flex Builder and specify url of deployed application and related project:



Now you just need to set breakpoints, press debug and see why something doesn't work.

Remote debug mode is quite convenient if you have full control over environment. But eventually your application would be deployed in customer site and most likely you would not be able to use debugger to trace down your problem.

To address this problem you need to make sure you have enough log statements in your code that would help to pinpoint the problem so make sure you are aware about mx.logging.* package.

It's very similar to java logging api and should not take long to figure out. The main caveat is that to use default trace facility(mx.logging.targets.TraceTarget) you need to run debug version of flash player. TraceTarget allows you to output message to system.out (eclipse console) or flashlog.txt. To make sure that flashlog.txt is created, you need to check that you have mm.cfg in your user home directory (in my case I didn't have mm.cfg created by installer). If you don't have mm.cfg - create it in C:\Documents and Settings\{username}\( obviously this window specific, check manual for linux path) and populate with parameter you want to use for ex.:

ErrorReportingEnable=1
TraceOutputFileEnable=1
MaxWarnings=100

Now you would be able to see flashlog.txt in c:\Documents and Settings\{username}\Application Data\Macromedia\Flash Player\Logs\.


Most likely you would not be able to use debug flash player in customer environment. You can write your own extension of flex logging classes to make sure you can capture trace event somehow. But the easier way to start with already existing flex logging extension "trace panel" from Adobe Flex Exchange (or directly from author's site http://www.faratasystems.com/?page_id=45) . It provide log capturer win32 application and source code for AbstractTarget that communicates with the win32 app and shows log statement when using none-debug version of flash player.



Hope this was helpful. If know some other techniques that can be used in Flex to simplify problem troubleshooting let me know.