[GROOVY-9068] GroovyScriptEngine causes Metaspace OOM

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.4.9
• Component/s: GroovyScriptEngine
• Labels: GroovyScriptEngineImpl Metaspace OOM
• Environment: macOS Mojave, MacBook Pro (Retina, 15-inch, Mid 2015)
• Assignee: Unassigned
• Reporter: Jingfei Hu
• Created: 05/Apr/19 13:05
• Updated: 29/Jul/19 13:34

Description

Hello team,

We've encountered this troublesome Metaspace OOM in our application recently as the number of groovy scripts increases. The groovy usage pattern in our application is evaluating scripts adhoc and directly. There are no any kinds of caches. And we use below code to do the evaluation. 

 

engine.eval(scriptText, bindings);

We thought the cache of GroovyScriptEngineImpl which is below field would take effect, but actually not in the multi-threading context

// script-string-to-generated Class map
private ManagedConcurrentValueMap<String, Class> classMap = new ManagedConcurrentValueMap<String, Class>(ReferenceBundle.getSoftBundle());

So without proper cache, our application continuously leverages the groovy class loader of GroovyScriptEngineImpl to parse scripts to generate Class objects and fill up Metaspace eventually. 

 

And below code snippets can easily reproduce this.  

 

package com.jingfei;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class Main {

    static final GroovyScriptExecutor groovyScriptExecutor = new GroovyScriptExecutor();

    public static void main(String[] args) throws InterruptedException {

        ExecutorService executor = Executors.newFixedThreadPool(10000);

        while (true)  {
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        groovyScriptExecutor.executeScript("(1..10).sum()");
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            });
        }
    }
}

package com.jingfei;

import java.util.HashMap;
import java.util.Map;

import javax.script.CompiledScript;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

import groovy.lang.GroovyClassLoader;
import org.codehaus.groovy.jsr223.GroovyCompiledScript;
import org.codehaus.groovy.jsr223.GroovyScriptEngineImpl;
/**
 * @author jingfei
 * @version $Id: GroovyScriptExecutor.java, v 0.1 2019-04-02 20:07 jingfei Exp $$
 */
public class GroovyScriptExecutor {

    /**  Script Engine Manager */
    private static final ScriptEngineManager factory = new ScriptEngineManager();
    /**  Script engine */
    private static final ScriptEngine engine  = factory.getEngineByName("groovy");

    public void executeScript(final String scriptText) throws ScriptException {
        System.out.println(engine.eval(scriptText));
    }
}

Looking into the Metaspace dump, we find out within the Metaspace there are hundreds of class loader objects named groovy/lang/GroovyClassLoader$InnerLoader and all of Class meta info loaded by them with the naming pattern ScriptXXXX.

 

Since the script is all the same, i.e. 

(1..10).sum()

, this behavior seems totally odd to me, because I thought due to the existence of the cache, there would be only one class loader created necessary to parse the script. 

 

Any help is appreciated to work out this problem! Thanks!