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https://issues.apache.org/jira/browse/GROOVY-8113?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17279013#comment-17279013
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João Paulo commented on GROOVY-8113:
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I have found a workaround for this.
It's not so simple to do and quite ugly to see what was needed to solve this
issue.
Basically, I clean myself all metaclasses after run the script.
The code below use GroovyShell instead of SimpleTemplateEngine, but wok's for
both cases.
In all cases that I was using SimpleTemplateEngine, I have created a cache of
Template and only reuse it instead of always create a new template.
{code:java}
Field fieldParallelLockMap = ClassLoader.getDeclaredField('parallelLockMap')
fieldParallelLockMap.setAccessible(true)
final Script groovyScript = new GroovyShell().parse('scriptAsString')
groovyScript.run()
final Class theClass = groovyScript.metaClass.theClass
final String name = theClass.name
ClassLoader classLoader = theClass.classLoader
final ClassLoader parent = classLoader.parent
if (parent != null) {
((GroovyClassLoader) parent).removeClassCacheEntry(theClass.name)
final List<String> classNamesToRemove =
["groovy.runtime.metaclass.${name}MetaClass".toString(),
"${name}BeanInfo".toString(), "${name}Customizer".toString()]
ClassLoader classLoaderToRemoveClasses = classLoader
while (classLoaderToRemoveClasses != null) {
final Map<String, Object> parallelLockMap = (Map<String, Object>)
fieldParallelLockMap.get(classLoaderToRemoveClasses)
if (parallelLockMap != null) {
parallelLockMap.entrySet().removeIf { classNamesToRemove.contains(it.key) }
}
classLoaderToRemoveClasses = classLoaderToRemoveClasses.parent
}
}
InvokerHelper.removeClass(theClass){code}
> Groovy script/template engine produce memory leak
> --------------------------------------------------
>
> Key: GROOVY-8113
> URL: https://issues.apache.org/jira/browse/GROOVY-8113
> Project: Groovy
> Issue Type: Bug
> Components: GroovyScriptEngine, Templating
> Affects Versions: 2.4.8
> Environment: Groovy 2.4.8, Oracle Java JDK 8u121
> Reporter: Artyom Kravchenko
> Priority: Critical
> Attachments: merged_path.png, object_explorer.png
>
>
> There is a simple way to produce OutOfMemoryException if run infinite
> numbers of groovy scripts or evaluate groovy templates.
> Simple test to reproduce a memory leak(run groovy script and make template
> inside the script):
> set max heap size: -Xmx7m
> {code:java}
> import javax.script.*;
> import java.util.HashMap;
> import java.util.Map;
> public class OutOfMemoryTest {
> private static String TEMPLATE = "Dear ${fullName} please go away at
> ${time}";
> private static String SCRIPT = "def run(args) {\n" +
> "def bindings = ['fullName' : 'Ali Baba', 'time' : new Date()]\n"
> +
> "println
> args.templateEngine.createTemplate(args.template).make(bindings).toString()\n"
> +
> "}";
> public static void main(String... args) {
> //
> GroovySystem.getMetaClassRegistry().getMetaClassCreationHandler().setDisableCustomMetaClassLookup(true);
> while(true) {
> ScriptEngineManager engineManager = new ScriptEngineManager();
> ScriptEngine engine = engineManager.getEngineByName("groovy");
> try {
> engine.eval(SCRIPT);
> } catch (ScriptException e) {
> throw new RuntimeException(e);
> }
> groovy.text.SimpleTemplateEngine templateEngine = new
> groovy.text.SimpleTemplateEngine();
> Invocable inv = (Invocable) engine;
> Map<String, Object> params = new HashMap<>();
> params.put("template", TEMPLATE);
> params.put("templateEngine", templateEngine);
> Object[] runArgs = { params };
> try {
> inv.invokeFunction("run", runArgs);
> } catch (ScriptException | NoSuchMethodException e) {
> e.printStackTrace();
> }
> }
> }
> }
> {code}
> The main cause of issue is Java class loader. Two instances:
> sun.misc.Launcher.AppClassLoader and sun.misc.Launcher.ExtClassLoader
> (parent for first one), each of them has a strong reference:
> {code:java}
> ConcurrentHashMap<String, Object> parallelLockMap
> {code}
> It collects all loaded classes (and never releases their) for application
> including newly created script/template classes.
> The main reason of introduction of this reference described here:
> https://blogs.oracle.com/dholmes/entry/parallel_classloading_revisited_fully_concurrent
> For each iteration of my test I see that parallelLockMap grows with 6 new
> entries:
> {code:java}
> groovy.runtime.metaclass.Script94MetaClass
> Script94BeanInfo
> Script94Customizer
> groovy.runtime.metaclass.SimpleTemplateScript94MetaClass
> SimpleTemplateScript94BeanInfo
> SimpleTemplateScript94Customizer
> {code}
> See memory snapshots(attached): objects_explorer, merged_path.
> I have found a partial solution of the issue, if I add this code line to my
> test:
> {code:java}
>
> GroovySystem.getMetaClassRegistry().getMetaClassCreationHandler().setDisableCustomMetaClassLookup(true);
> {code}
> I see that classes like:
> {code:java}
> groovy.runtime.metaclass.Script94MetaClass
> groovy.runtime.metaclass.SimpleTemplateScript94MetaClass
> {code}
> goes away (groovy engine don't ask ClassLoader to find this classes on class
> path therefore such classes are not collected by ClassLoader) but classes
> like
> {code:java}
> Script94BeanInfo
> Script94Customizer
> SimpleTemplateScript94BeanInfo
> SimpleTemplateScript94Customizer
> {code}
> still has affect on memory.
> Dear developers, could you please point me any advice/workarounds for this
> issue. It will be fine to get rig this issue in future releases.
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