ColdFusion 7 Memory Leak

In working on Financial Peace University Online last year, I became aware of a really ugly memory leak that had developed in the app (thankfully it was still in development, not in production). It took a few days to track down, but when I found it, it proved to have some implications that applied to all our ColdFusion web apps.

First I’ll describe the environment:

• ColdFusion 7 running in JRun 4
• Mach-II 1.1 framework
• ColdSpring object factories

I discovered that for each singleton instance of a cfc that the ColdSpring factories provided, a little memory was leaked and never garbage collected. I simplified things to remove Mach-II, ColdSpring, and eventually everything except the simplest form I could think of. A cfm would create an instance of a cfc that had a method in it that would return a reference to itself. Then the cfm would go through 100 iterations of calling that method and place the result in an array. So I would have an array with 100 references to the same object, and still, the memory leak was present.

Finally I noticed that on my cfc method, I hadn’t specified output=”false”, though I had specified it on the cfcomponent tag. Adding output=”false” to the method that returned a reference to the cfc cured the memory leak. It seems bizarre, but if a memory leak was obvious, it wouldn’t have made it into the release version of ColdFusion.

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Tags: ColdFusion