multithreading MessagePack usage without java PermGen memory error

If you use new MessagePack() too many time, perm gem memory error occurs soon.

MessagePack msgpack = new MessagePack();
byte[] bytes = msgpack.write(object);

You can test this with
-XX:+TraceClassLoading -XX:+TraceClassUnloading
VM parameters or JConsole.

[Loaded learningtest.msgpack.MessagePackTest$MyMessage_$$_Template_1527741453_0 from __JVM_DefineClass__]
MyMessage [name=msgpack, version=0.6]
[Loaded learningtest.msgpack.MessagePackTest$MyMessage_$$_Template_831556519_0 from __JVM_DefineClass__]
MyMessage [name=msgpack, version=0.6]
[Loaded learningtest.msgpack.MessagePackTest$MyMessage_$$_Template_1872305359_0 from __JVM_DefineClass__]
MyMessage [name=msgpack, version=0.6]

MessagePack.write()
TemplateRegistry.lookup()
TemplateRegistry.lookupAfterBuilding()
TemplateRegistry.buildAndRegister()
AbstractTemplateBuilder.buildTemplate()
DefaultBuildContext.buildTemplate()
BuildContext.build()
BuildContext.createClass()
CtClass.toClass()

But, writing with the MessagePack instance is not thread-safe.
msgpack.setOutputStream(outputStream);
msgpack.write(object);

Insteads, you can should the packer and the unpacker from a singleton MessagePack instance

MessagePack msgpack = new MessagePack(); // singleton
Packer packer = msgpack.createPacker(outputStream); // createPacker every time
packer.write(object);

for (int i = 0; i < 100; i++) {

final int iTask = i;

tasks.add(new Thread() {

@Override

public void run() {

try {

System.out.println(iTask + " start ");

File file = new File("eraseme" + iTask);

FileOutputStream outputStream = null;

outputStream = new FileOutputStream(file);

SomeClass info = new SomeClass();

try {

packer.write(info);

} catch (IOException e) {

System.out.println(iTask + " write failed " + e.getMessage());

assertTrue(false);

}

outputStream.close();

FileInputStream inputStream = new FileInputStream(file);

Unpacker unpacker = msgpack.createUnpacker(inputStream);

// Deserialize directly using a template

SomeClass reply = null;

try {

reply = (ReplyMessage.ImageInfoMessage) unpacker.read(SomeClass.class);

} catch (IOException e) {

System.out.println(iTask + " read failed " + e.getMessage());

assertTrue(false);

}

System.out.println(iTask + " finished " + reply + " " + file.getAbsolutePath());

} catch (Exception exc) {

System.out.println("exc " + exc.getMessage());

assertTrue(false);

}

};

});

}

for (Thread task : tasks) {

task.start();

}

for (Thread task : tasks) {

task.join();

}

assertTrue(true);

Or, we should use pool of MessagePack instances.
I suggest the apache commons pool.
http://commons.apache.org/proper/commons-pool/