RE: Groovy and JRuby: Enterprise-Ready?

There is a report that is being pushed around comments on blog posts with the aim of spreading FUD. The report can be found here:

http://www.huxili.com/index.php?cat=reports&id=ID000188

It is entitled "Groovy and JRuby: Enterprise Ready?" and its conclusion is that Groovy is not due to "memory leaks". The report is complete nonsense of course, and it put together by someone who doesn't understand the different language idioms.

The report provides no code examples, further bringing to question its validity, however it states that Groovy runs out of memory when running these steps:

1. Call shell.evaluate("x = 100")

2. Call System.gc()

3. Thread.sleep(1000)

4. Record used memory

5. Repeating (1-4)

I'm going to have a go at guessing the Groovy code they used. I can bet it goes something like this:

shell = new GroovyShell()
while(true) {
shell.evaluate("x = 100")
sleep(2000)
System.gc()
}

So what is the problem with this code? And why would it result in a memory leak? The answer is that each GroovyShell instance has an internal class loader. Groovy is a compiled language. Even little scripts like this are compiled into classes so over time the class loader just gets bigger and bigger. The solution? Here we go:

while(true) {
new GroovyShell().evaluate("x = 100")
sleep(2000)
}

So what this does is allow the GroovyShell (and its class loader) to be garbage collected by the JVM. When the class loader is garbage collected so are the classes loaded within it. JRuby of course doesn't have this problem as its interpreted.

Judging whether a language is "enterprise-ready" without knowing the language idioms and basing it on a 4 line script is to be honest quite ridiculous, so remember beware of silly "official" looking reports without verifying the facts for yourself.