Solved Overriding Entities (ADVANCED)

Hey guys,

I've been screwing with custom entity classes with custom pathfinders and whatnot but I've found that it has the tendency to create PermGenSpace errors. I'm assuming this is caused due to a memory leak as I use reflection to register the entity (and replace the default Minecraft entity with it) using a method by the brilliant Jacek (tutorial here)

I haven't been able to correct this memory leak. On disable, I've tried calling System.gc() to invoke a garbage collection, unregistering the entities on disable and despawning all my overriding entities, etc. etc.

So my question is this:
*How can I spawn in custom entities without having to use reflection to get Minecraft to allow it?
* Alternatively, how can I use the method I'm using but do garbage collection on the overriding class and its pathfinders to prevent memory leaks?

Bonus points to anyone that can answer:
* How can I make the overriding entity spawn only in specified worlds?

I don't know if this is permitted (and pardon my ignorance if it isn't) but I'm going to tag all the brilliant minds I can think of that have dabbled in entity customization in the past and might be able to help.
bergerkiller Keyle CorrieKay RingOfStorms

Link to GitHub where all my fancy CustomMobs reside: here

 

Hmm, how exactly are you spawning your NMS entities? I've never had a memory leak issue when extending/overriding mobs. Maybe you should give RemoteEntitys a go?

 

TeeePeee
Found this:
http://lasithh.wordpress.com/2012/0...n-space-exception-when-using-java-reflection/

 

You should not be calling System.gc(). The jvm will call garbage collector when it needs to, and by forcibly invoking the method, you could be causing a bunch more issues.

 

Notice that when you register a custom entity to minecraft, you also need to unregister it, else ALL plugins will get affected by a memory leak that YOU created.

 

I've noticed in your code you have this in the constructor of your custom entity.

Code:java

                try {
                        Field field = PathfinderGoalSelector.class.getDeclaredField("a");
                        field.setAccessible(true);
 
                        field.set(goalSelector, new UnsafeList<PathfinderGoalSelector>());
                        field.set(targetSelector, new UnsafeList<PathfinderGoalSelector>());
                } catch (Exception exc) {
                        exc.printStackTrace();
                }

I'm not sure if this will exactly solve this problem, but this code is inefficient. A new field object is created every time you create a new instance of your entity. Instead, you can have an external class create the field object once (as static), and then access the field method from your entity class.

 

That being said, I don't believe that would cause an issue with PermGenSpace

TeeePeee

Are you registering static entity instances?

 

You get permgen errors because you still have (some) of your own Class instances used in your plugin being used as variables on the server. When your plugin enables again later on, your classes are re-loaded, causing a duplicate of that class to be stored. If you want to fix these errors, be sure to unhook all your plugin-added classes. Also, avoid static variables in these classes, as they add up to the permgen space. Even better, set them to null so no memory is lost there. Preferably you would unhook all you possibly can.

 

bob7
They spawn naturally after using the CustomEntityType in the link I provided.
ferrybig
I realize this and onDisable, I unregister them (see https://github.com/JordanSicherman/MyZ-3.0/blob/master/src/myz/MyZ.java#L268).
Scyntrus
Fair enough, thanks! As you said, I don't know if that can be attributed to the PermGenSpace but if the entities aren't being disposed of, it will certainly add to the memory leak.
1Rogue
I am, as you can see in my GitHub source, registering the entity class, not an instance of the entity.
bergerkiller
I don't believe I store any references to a custom entity anywhere, but I'll take a fine toothed comb to it again. By unhook I assume you mean essentially nullify? Correct me if I'm wrong but shouldn't the ClassLoader dispose of the main class when the plugin is disabled and unhook all static variables, etc. by default?

 

Can you link this github source?

 

1Rogue look at the end of his first post, because the source is linked there

 

As an update, nowhere is it storing any references to a Custom Entity. I also made the change suggested by Scyntrus to not create a field for each entity pathfinder. Still, I get the PermGenSpace error after a few reloads. I also ensured there are no static variables in any Custom Entity Class as suggested by bergerkiller.

From the articlelinked to by xTrollxDudex:

This sounds like what is happening. I wish there was a way other than to modify the startup batch file to fix it though. Any more ideas, anyone?

Thanks for all the replies thus far! You guys have been tremendously helpful.

[EDIT] Even with the arguments (-XX:+CMSPermGenSweepingEnabled -XX:+CMSClassUnloadingEnabled) from the article quoted above, I still get the same error after the same amount of time.

 

TeeePeee
Did you modify the batch file? I think there may be a method in System to modify garbage collecting parameters, may.

 

xTrollxDudex
As stated above, I did modify the batch file to include the parameters that allegedly 'solve' PermGenSpace errors. The other arguments can create more PermGenSpace, but this will only postpone the inevitable. This memory leak will be the death of me and I am sure it is because of the custom entities as I commented the registering and spawning out and everything ran smoothly (reloaded 40+ times without PermGenSpace error).

 

TeeePeee
Try running a few commands using Runtime#execute(...)

 

xTrollxDudex
Never really used Runtime#exec calls. Care to provide an example for this context? Thanks!

 

TeeePeee
I'm not really sure what it does

 

TeeePeee
Actually, you not unregistering you custom entities,
At https://github.com/JordanSicherman/MyZ-3.0/blob/master/src/myz/mobs/CustomEntityType.java#L71
you putting your custom entity inside a hasmap of minecraft:
https://github.com/Bukkit/mc-dev/blob/master/net/minecraft/server/EntityTypes.java#L16
And you never used anny code to hook into that class and remove your entities onunload (most tutorials dont tell you how to do it because they dont know it creates memory leaks

 

ferrybig
Sorry, I didn't update my git recently. This is the code I use to unregister the entities I previously register:
[EDIT] *snip*
And do so on disable of the plugin. This is effectively the reverse of what registerEntities() does, so I figure it should work, but correct me if I'm wrong.

[EDIT] Went through the EntityTypes class and realized that calling the method 'a' in reverse (NMS instead of custom) won't cut it. About to write the reflection to remove my custom class from each HashMap.

[EDIT 2] Found the source of the leak, thanks to ferrybig Went through EntityTypes in net.minecraft.server and realized that I never removed the custom class reference in the HashMaps 'c' and 'e' (the others were already overwritten due to my previous method. Here's the before and after unregister (the after one works, before one doesn't):

Before:

Code:java

public static void unregisterEntities() {
        for (CustomEntityType entity : values())
            try {
                if (method == null) {
                    method = EntityTypes.class.getDeclaredMethod("a", new Class<?>[] { Class.class, String.class, int.class });
                    method.setAccessible(true);
                }
                method.invoke(null, entity.getNMSClass(), entity.getName(), entity.getID());
            } catch (Exception e) {
                e.printStackTrace();
            }
 
        for (BiomeBase biomeBase : BiomeBase.biomes) {
            if (biomeBase == null)
                break;
 
            for (String field : new String[] { "K", "J", "L", "M" })
                try {
                    Field list = BiomeBase.class.getDeclaredField(field);
                    list.setAccessible(true);
                    @SuppressWarnings("unchecked")
                    List<BiomeMeta> mobList = (List<BiomeMeta>) list.get(biomeBase);
 
                    for (BiomeMeta meta : mobList)
                        for (CustomEntityType entity : values())
                            if (entity.getCustomClass().equals(meta.b))
                                meta.b = entity.getNMSClass();
                } catch (Exception e) {
                    e.printStackTrace();
                }
        }
    }

After:

Code:java

public static void unregisterEntities() {
        // Remove the custom class from the maps where it is the key, not the value.
        for (CustomEntityType entity : values()) {
            try {
                Field c = EntityTypes.class.getDeclaredField("c");
                c.setAccessible(true);
                ((Map) c.get(null)).remove(entity.getCustomClass());
            } catch (Exception e) {
                e.printStackTrace();
            }
 
            try {
                Field e = EntityTypes.class.getDeclaredField("e");
                e.setAccessible(true);
                ((Map) e.get(null)).remove(entity.getCustomClass());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
 
        for (CustomEntityType entity : values())
            try {
                if (method == null) {
                    method = EntityTypes.class.getDeclaredMethod("a", new Class<?>[] { Class.class, String.class, int.class });
                    method.setAccessible(true);
                }
                method.invoke(null, entity.getNMSClass(), entity.getName(), entity.getID());
            } catch (Exception e) {
                e.printStackTrace();
            }
 
        for (BiomeBase biomeBase : BiomeBase.biomes) {
            if (biomeBase == null)
                break;
 
            for (String field : new String[] { "K", "J", "L", "M" })
                try {
                    Field list = BiomeBase.class.getDeclaredField(field);
                    list.setAccessible(true);
                    @SuppressWarnings("unchecked")
                    List<BiomeMeta> mobList = (List<BiomeMeta>) list.get(biomeBase);
 
                    for (BiomeMeta meta : mobList)
                        for (CustomEntityType entity : values())
                            if (entity.getCustomClass().equals(meta.b))
                                meta.b = entity.getNMSClass();
                } catch (Exception e) {
                    e.printStackTrace();
                }
        }
    }