Allow threads to timeout in the thread pool

Author: amanteaux

src/main/java/org/simplejavamail/mailer/internal/mailsender/MailSender.java

@@ -23,8 +23,10 @@
 import java.util.List;
 import java.util.Properties;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
+import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.Phaser;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 
 import static java.lang.String.format;
 import static org.simplejavamail.converter.EmailConverter.mimeMessageToEML;
@@ -192,9 +194,19 @@ the proxy bridge server (or connection pool in async mode) while a non-async ema
         smtpRequestsPhaser.register();
 		if (async) {
 			// start up thread pool if necessary
-			if (executor == null || executor.isShutdown()) {
-				executor = Executors.newFixedThreadPool(operationalConfig.getThreadPoolSize(),
-						new NamedThreadFactory("Simple Java Mail async mail sender"));
+			if (executor == null) {
+				ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(
+					operationalConfig.getThreadPoolSize(),
+					operationalConfig.getThreadPoolSize(),
+					operationalConfig.getThreadPoolTimeout(),
+					TimeUnit.MILLISECONDS,
+					new LinkedBlockingQueue<Runnable>(),
+					new NamedThreadFactory("Simple Java Mail async mail sender")
+				);
+				if(operationalConfig.getThreadPoolTimeout() > 0) {
+					threadPoolExecutor.allowCoreThreadTimeOut(true);
+				}
+				executor = threadPoolExecutor;
 			}
 			configureSessionWithTimeout(session, operationalConfig.getSessionTimeout());
 			executor.execute(new Runnable() {
@@ -300,7 +312,7 @@ private void configureBounceToAddress(final Session session, final Email email)
 	}
 
 	/**
-	 * We need to keep a count of running threads in case a proxyserver is running or a connection pool needs to be shut down.
+	 * We need to keep a count of running threads in case a proxyserver is running
      */
     private synchronized void checkShutDownRunningProcesses() {
         smtpRequestsPhaser.arriveAndDeregister();
@@ -312,11 +324,6 @@ private synchronized void checkShutDownRunningProcesses() {
                 LOGGER.trace("stopping proxy bridge...");
                 proxyServer.stop();
             }
-            // shutdown the threadpool, or else the Mailer will keep any JVM alive forever
-            // executor is only available in async mode
-            if (executor != null) {
-                executor.shutdown();
-            }
         }
     }
 

src/main/java/org/simplejavamail/mailer/internal/mailsender/OperationalConfig.java

@@ -29,6 +29,11 @@ public class OperationalConfig {
 	 */
 	private final int threadPoolSize;
 
+	/**
+	 * @see org.simplejavamail.mailer.MailerBuilder.MailerRegularBuilder#withThreadPoolTimeout(Integer)
+	 */
+	private final int threadPoolTimeout;
+	
 	/**
 	 * @see org.simplejavamail.mailer.MailerBuilder.MailerRegularBuilder#withTransportModeLoggingOnly(Boolean)
 	 */
@@ -56,6 +61,7 @@ public OperationalConfig(@Nonnull Properties properties, int sessionTimeout, int
 		this.properties = properties;
 		this.sessionTimeout = sessionTimeout;
 		this.threadPoolSize = threadPoolSize;
+		this.threadPoolTimeout = 1; // TODO wire it up to all the config files
 		this.transportModeLoggingOnly = transportModeLoggingOnly;
 		this.debugLogging = debugLogging;
 		this.sslHostsToTrust = Collections.unmodifiableList(sslHostsToTrust);
@@ -75,7 +81,14 @@ public int getSessionTimeout() {
 	public int getThreadPoolSize() {
 		return threadPoolSize;
 	}
-	
+
+	/**
+	 * @see org.simplejavamail.mailer.MailerBuilder.MailerRegularBuilder#withThreadPoolSize(Integer)
+	 */
+	public int getThreadPoolTimeout() {
+		return threadPoolTimeout;
+	}
+
 	/**
 	 * @see org.simplejavamail.mailer.MailerBuilder.MailerRegularBuilder#withTransportModeLoggingOnly(Boolean)
 	 */