[GROOVY-3557] Remove synchronization of isModified method in ExpandoMetaClass to improve performance

• Type: Improvement
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.6, 1.6.1, 1.5.8, 1.6.2, 1.6.3
• Fix Version/s: 1.9-beta-4, 1.8.4
• Environment: Linux, Java 1.6, Tomcat
• Assignee: Jochen Theodorou
• Reporter: Mark Smithson
• Created: 21/May/09 08:09
• Updated: 13/Jan/12 04:05
• Resolved: 12/Oct/11 07:39

Description

Sscalability seems to suffer as a result of TagLibs being implemented as singletons and locking occurring on ExpandoMetaClass.isModified() when the server is processing multiple requests concurrently.

Performance is fine when there is a small number of concurrent requests, but as the number of concurrent requests increases response times increase dramatically.

Locking was noticed by profiling a running application using Your Kit Java Profiler and JMeter to simulate load.

More details are available here:
http://digitalmorphosis.blogspot.com/2009/05/grails-scalability.html

Obvious fix would be to create new instances of taglibs for each request/thread, but not sure what side effects this would have?