[JEXL-344] Don't fill stack trace for JexlExpression#Return (to improve performance)

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.1
• Fix Version/s: 3.2
• Assignee: Henri Biestro
• Reporter: David Costanzo
• Created: 02/Feb/21 15:06
• Updated: 07/Jun/21 13:14
• Resolved: 03/Feb/21 06:03

Description

In profiling my JEXL-enabled application, I observed that nearly 10% of the execution time is spend filling in the JexlExpression#Return class's stack.  As far as I can tell, the Return object's stack is not used by JEXL and so does not need to be present.

I read about an optimization technique where you override fillInStackTrace() to be a no-op when using exceptions for control flow.  As I understand it, this practice was codified into Java 7 with the "writableStackTrace" parameter to Throwable's ctor that lets you disable filling in the stack trace.

For Java 6 and below, this is as easy as adding this to the body of Return.

@Override
public Throwable fillInStackTrace()
{
    // Don't fill in the stack.  It's not needed for return values.
    return this;
}

In private testing, this has the expected effect: my application finishes in ~10% less time and all unit tests continue to pass.

 

There's a discussion of this on stack overflow:

https://stackoverflow.com/questions/1836164/override-fillinstacktrace-for-control-flow-performance

 

There's a better discussion in the answer given to:

https://stackoverflow.com/questions/11434431/exception-without-stack-trace-in-java