[jboss-jira] [JBoss JIRA] (WFLY-7037) Memory leak when doing deploy/undeploy app using REST and JPA

[Manuel Blechschmidt (JIRA)]

    [ https://issues.jboss.org/browse/WFLY-7037?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13412218#comment-13412218 ] 

Manuel Blechschmidt commented on WFLY-7037:
-------------------------------------------

Hi guys,
I used a quite dirty workaround to resolve this. Maybe this is interesting for others as well:

{code}
package de.blechschmidt.memory;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.annotation.PreDestroy;
import javax.ejb.Singleton;
import javax.ejb.Startup;

@Singleton
@Startup
public class MemoryLeakFixer {

	private static final Logger log = Logger
			.getLogger(MemoryLeakFixer.class.getName());

	@PreDestroy
	public void clean() {
		try {
			log.info("Fixing Memory Leak from: WFLY-7037");
			Class<?> classUtil = Class
					.forName("com.fasterxml.jackson.databind.util.ClassUtil");
			// https://stackoverflow.com/questions/3301635/change-private-static-final-field-using-java-reflection
			Field sCachedField = classUtil.getDeclaredField("sCached");
			sCachedField.setAccessible(true);
			Field modifiersField = Field.class.getDeclaredField("modifiers");
			modifiersField.setAccessible(true);
			modifiersField.setInt(sCachedField,
					sCachedField.getModifiers() & ~Modifier.FINAL);

			Class<?> lruMapClass = Class
					.forName("com.fasterxml.jackson.databind.util.LRUMap");

			// Get a fresh new lruMap cache
			Object lruMap = lruMapClass
					.getConstructor(int.class, int.class)
					.newInstance(48, 48);

			// Reset the cache
			sCachedField.set(null, lruMap);
		} catch (ClassNotFoundException | NoSuchFieldException
				| SecurityException | IllegalArgumentException
				| IllegalAccessException | InstantiationException
				| InvocationTargetException | NoSuchMethodException e) {
			log.log(Level.WARNING, "Could not clean Jackson", e);
		}
	}
}
{code}

> Memory leak when doing deploy/undeploy app using REST and JPA
> -------------------------------------------------------------
>
>                 Key: WFLY-7037
>                 URL: https://issues.jboss.org/browse/WFLY-7037
>             Project: WildFly
>          Issue Type: Bug
>          Components: REST, XML Frameworks
>    Affects Versions: 10.1.0.Final
>            Reporter: Tomas Remes
>            Assignee: Stuart Douglas
>            Priority: Critical
>             Fix For: 11.0.0.Alpha1
>
>         Attachments: gc_path.png, mem-leak.zip
>
>
> It seems that exposing some type (ApplicationUser in attached app) which has enum type as attribute via REST api could cause memory leak (See steps to reproduce). You can observe that person.joey.test.UserType instances are kept in memory when GC happens (metaspace exceeds) and the path to GC root looks:
> !gc_path.png|thumbnail!
> Note that this map https://github.com/FasterXML/jackson-databind/blob/jackson-databind-2.7.4/src/main/java/com/fasterxml/jackson/databind/util/ClassUtil.java#L366 was not available in 2.5.4 version used in WF 10.0.0.Final



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