[ https://issues.apache.org/jira/browse/OPENJPA-219?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12491104 ]
Patrick Linskey commented on OPENJPA-219: ----------------------------------------- I agree about the mem leak problem in the patch that I created; hence my comments in the original post about using weak references. There are a number of ways that you could solve this caching problem, such as making all / part of Reflection non-static and setting up per-Configuration caches, or using weak references in the cache, or even (and probably least attractively) creating undeploy APIs. Abe said: > If we're going to cache, I don't see why we wouldn't cache the declared > fields/methods rather than the nonexistent ones. It would be a simple > matter of keeping a Class->Set cache, where the Set is the names of > the fields/methods returned by Class.getDeclaredFields/Methods(). > Then we'd have both a positive (set.contains(x)) and negative > (!set.contains(x)) cache. As I mentioned in the original description, the bug here is that negative lookups are slow because of the exception creation. I see no reason to add extra caching if we don't know if we need it, although Bret's numbers potentially indicate that there is a benefit to positive caching. I have no problem with having a positive cache, but I think that we should only include it if it's going to help, since otherwise it'll just be one more thing contributing to memory consumption. > Reflection: negative caching would be beneficial in redeployment scenarios > -------------------------------------------------------------------------- > > Key: OPENJPA-219 > URL: https://issues.apache.org/jira/browse/OPENJPA-219 > Project: OpenJPA > Issue Type: Bug > Components: kernel > Affects Versions: 0.9.0, 0.9.6, 0.9.7 > Reporter: Patrick Linskey > Fix For: 0.9.8 > > Attachments: OPENJPA-219.patch > > > In a variety of situations, OpenJPA searches class hierarchies for fields. > These searches invoke Class.getDeclaredField() in order to find non-public > fields. This method throws an exception when it fails to find the specified > field, and the exception creation is, as ever, slow. > It would be useful to create a static (and thus per-classloader) > Map<WeakReference<Class>,Collection<String>> of fields known not to be > available in a given class. > It may also be beneficial to maintain a cache of which fields *are* present > in a given class, but this issue is being filed as a result of a demonstrated > performance hit during deployment due to the lack of a negative cache. If we > obtain quantitative data indicating that a positive cache would be useful, we > might want to implement such a thing at that time. > Trace 3 (2115 occurances): [excepti][00090] java/lang/NoSuchFieldException: > domainName > at > java/lang/Class.getDeclaredField(Ljava/lang/String;I)Ljava/lang/reflect/Field;(Unknown > Source) > at > org/apache/openjpa/enhance/Reflection.findField(Ljava/lang/Class;Ljava/lang/String;Z)Ljava/lang/reflect/Field;(Reflection.java:101) > at > org/apache/openjpa/util/ApplicationIds.toPKValues(Ljava/lang/Object;Lorg/apache/openjpa/meta/ClassMetaData;)[Ljava/lang/Object; > (ApplicationIds.java:89) -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.