[jira] [Commented] (GROOVY-8113) Groovy script/template engine produce memory leak

["Jochen Kemnade (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-8113?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16004154#comment-16004154 ] 

Jochen Kemnade commented on GROOVY-8113:
----------------------------------------

I tried to check whether this is still an issue with 2.4.11, but the example does not compile:
{code}
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
/tmp/groovy-8113.groovy: 8: Apparent variable 'fullName' was found in a static scope but doesn't refer to a local variable, static field or class. Possible causes:
You attempted to reference a variable in the binding or an instance variable from a static context.
You misspelled a classname or statically imported field. Please check the spelling.
You attempted to use a method 'fullName' but left out brackets in a place not allowed by the grammar.
 @ line 8, column 45.
   atic String TEMPLATE = "Dear ${fullName}
                                 ^

/tmp/groovy-8113.groovy: 8: Apparent variable 'time' was found in a static scope but doesn't refer to a local variable, static field or class. Possible causes:
You attempted to reference a variable in the binding or an instance variable from a static context.
You misspelled a classname or statically imported field. Please check the spelling.
You attempted to use a method 'time' but left out brackets in a place not allowed by the grammar.
 @ line 8, column 75.
   {fullName} please go away at ${time}";
                                 ^

2 errors
{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
>         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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