[jboss-cvs] JBoss Messaging SVN: r3227 - trunk/src/main/org/jboss/messaging/util.

[jboss-cvs-commits at lists.jboss.org]

Author: timfox
Date: 2007-10-20 13:36:08 -0400 (Sat, 20 Oct 2007)
New Revision: 3227

Added:
   trunk/src/main/org/jboss/messaging/util/ClearableSemaphore.java
Log:
Missing file


Added: trunk/src/main/org/jboss/messaging/util/ClearableSemaphore.java
===================================================================
--- trunk/src/main/org/jboss/messaging/util/ClearableSemaphore.java	                        (rev 0)
+++ trunk/src/main/org/jboss/messaging/util/ClearableSemaphore.java	2007-10-20 17:36:08 UTC (rev 3227)
@@ -0,0 +1,77 @@
+package org.jboss.messaging.util;
+
+import java.util.concurrent.Semaphore;
+
+import org.jboss.logging.Logger;
+
+/**
+ * 
+ * @author <a href="mailto:tim.fox at jboss.com">Tim Fox</a>
+ * @version <tt>$Revision: $</tt>20 Oct 2007
+ *
+ * $Id: $
+ *
+ */
+public class ClearableSemaphore
+{
+   protected Logger log = Logger.getLogger(ClearableSemaphore.class);
+	
+	private Semaphore semaphore;
+	
+	private boolean enabled;
+	
+	private int permits;
+	
+	private void createSemaphore()
+	{
+		semaphore = new Semaphore(permits, true);
+		
+		enabled = true;
+	}
+	
+	public ClearableSemaphore(int permits)
+	{				
+		this.permits = permits;
+		
+		createSemaphore();
+	}
+	
+	public synchronized void acquire() throws InterruptedException
+	{
+		if (enabled)
+		{
+			semaphore.acquire();
+		}
+	}
+	
+	public synchronized void release()
+	{
+		if (enabled)
+		{
+			semaphore.release();
+		}
+	}
+	
+	public synchronized void enable()
+	{
+		if (!enabled)
+		{
+			createSemaphore();
+		}
+	}
+	
+	// We need to be able to disable the semaphore since during failover requests may be sent but responses
+	// may not come back (node is dead or hasn't loaded it's queues yet)
+	// In which case we don't want to acquire a token since we might end up locking and using up all permits	
+	public synchronized void disable()
+	{
+		if (enabled)
+		{
+			semaphore.release(permits);
+			
+			semaphore = null;
+			
+			enabled = false;
+		}
+	}
+}