CollectingOrphanedCoroutines.java

import org.luaj.vm2.Globals;
import org.luaj.vm2.LuaThread;
import org.luaj.vm2.LuaValue;
import org.luaj.vm2.lib.jse.JsePlatform;

/** Example that continually launches coroutines, and illustrates how to make 
* sure the orphaned coroutines are cleaned up properly.
* 
* Main points:
* <ul><li>Each coroutine consumes one Java Thread while active or reference anywhere</li>
* <li>All references to a coroutine must be dropped for the coroutine to be collected</li>
* <li>Garbage collection must be run regularly to remove weak references to lua threads</li>
* <li>LuaThread.thread_orphan_check_interval must be short enough to find orphaned references quickly</li>
* </ul>
*/
public class CollectingOrphanedCoroutines {

	// Script that launches coroutines over and over in a loop. 
	// Garbage collection is done periodically to find and remove orphaned threads.
	// Coroutines yield out when they are done.
	static String script = 
			"i,n = 0,0\n print(i)\n"
			+ "f = function() n=n+1; coroutine.yield(false) end\n"
			+ "while true do\n"
			+ "  local cor = coroutine.wrap(f)\n"
			+ "  cor()\n"
			+ "  i = i + 1\n"
			+ "  if i % 1000 == 0 then\n"
			+ "    collectgarbage()\n" 
			+ "    print('threads:', i, 'executions:', n, collectgarbage('count'))\n"
			+ "  end\n"
			+ "end\n";

	public static void main(String[] args) throws InterruptedException {
		// This timer controls how often each Java thread wakes up and checks if
		// it has been orhaned or not. A large number here will produce a long
		// delay between orphaning and colleciton, and a small number here will
		// consumer resources polling for orphaned status if there are many threads.
		LuaThread.thread_orphan_check_interval = 500;

		// Should work with standard or debug globals.
		Globals globals = JsePlatform.standardGlobals();
		// Globals globals = JsePlatform.debugGlobals();
		
		// Should work with plain compiler or lua-to-Java compiler.
		// org.luaj.vm2.luajc.LuaJC.install(globals);;

		// Load and run the script, which launches coroutines over and over forever.
		LuaValue chunk = globals.load(script, "main");
		chunk.call();
	}

}