Merge remote-tracking branch 'origin/#246-fix-lingering-threads-bug' into develop

Author: bbottema

README.md

@@ -1,6 +1,6 @@
 [![APACHE v2 License](https://img.shields.io/badge/license-apachev2-blue.svg?style=flat)](modules/simple-java-mail/LICENSE-2.0.txt) 
-[![Latest Release](https://img.shields.io/maven-central/v/org.simplejavamail/simple-java-mail.svg?style=flat)](https://search.maven.org/#search%7Cgav%7C1%7Cg%3A%22org.simplejavamail%22%20AND%20v%3A%226.0.1%22) 
-[![Javadocs](https://img.shields.io/badge/javadoc-6.0.1-brightgreen.svg?color=brightgreen)](https://www.javadoc.io/doc/org.simplejavamail/maven-master-project) 
+[![Latest Release](https://img.shields.io/maven-central/v/org.simplejavamail/simple-java-mail.svg?style=flat)](https://search.maven.org/#search%7Cgav%7C1%7Cg%3A%22org.simplejavamail%22%20AND%20v%3A%226.0.2%22) 
+[![Javadocs](https://img.shields.io/badge/javadoc-6.0.2-brightgreen.svg?color=brightgreen)](https://www.javadoc.io/doc/org.simplejavamail/maven-master-project) 
 [![Codacy](https://img.shields.io/codacy/grade/c7506663a4ab41e49b9675d87cd900b7.svg?style=flat)](https://www.codacy.com/app/b-bottema/simple-java-mail)
 ![Java 1.7+](https://img.shields.io/badge/java-1.7+-lightgray.svg)
 
@@ -18,12 +18,17 @@ Simple Java Mail is also available in [Maven Central](https://search.maven.org/#
 <dependency>
     <groupId>org.simplejavamail</groupId>
     <artifactId>simple-java-mail</artifactId>
-    <version>6.0.1</version>
+    <version>6.0.2</version>
 </dependency>
 ```
 
 ### Latest Progress ###
 
+[v6.0.2](https://search.maven.org/#artifactdetails%7Corg.simplejavamail%7Csimple-java-mail%7C6.0.2%7Cjar) (21-Januari-2020)
+
+- [#246](https://github.com/bbottema/simple-java-mail/issues/246) Bug: Sending async emails with and without the Batch module cause lingering threads
+
+
 v6.0.0-rc1 - [v6.0.1](https://search.maven.org/#artifactdetails%7Corg.simplejavamail%7Csimple-java-mail%7C6.0.1%7Cjar) (18-December-2019 - 24-January-2020)
 
 After almost two years of development the next major release 6.0.0 is finally here! And what a doozy it is, with the following major new features:

RELEASE.txt

@@ -3,9 +3,14 @@ http://www.simplejavamail.org
 <dependency>
     <groupId>org.simplejavamail</groupId>
     <artifactId>simple-java-mail</artifactId>
-    <version>6.0.1</version>
+    <version>6.0.2</version>
 </dependency>
 
+v6.0.2 (21-Januari-2020)
+
+- #246: Bug: Sending async emails with and without the Batch module cause lingering threads
+
+
 v6.0.0-rc1 - v6.0.1 (18-December-2019 - 24-January-2020)
 
 After almost two years of development the next major release 6.0.0 is finally here! And what a doozy it is, with the following major new features:

modules/batch-module/pom.xml

@@ -30,7 +30,7 @@
         <dependency>
             <groupId>org.simplejavamail</groupId>
             <artifactId>smtp-connection-pool</artifactId>
-            <version>1.0.7</version>
+            <version>1.0.10</version>
         </dependency>
     </dependencies>
 </project>

modules/batch-module/src/main/java/org/simplejavamail/internal/batchsupport/AsyncOperationHelper.java

@@ -1,15 +1,16 @@
 package org.simplejavamail.internal.batchsupport;
 
+import org.jetbrains.annotations.NotNull;
 import org.simplejavamail.api.mailer.AsyncResponse;
 import org.simplejavamail.internal.batchsupport.concurrent.NamedRunnable;
 import org.slf4j.Logger;
 
-import org.jetbrains.annotations.NotNull;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicReference;
 
 import static java.util.concurrent.Executors.newSingleThreadExecutor;
+import static org.simplejavamail.internal.util.Preconditions.assumeTrue;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
@@ -51,6 +52,7 @@ private static AsyncResponse executeAsync(final @NotNull ExecutorService executo
 		// atomic reference is needed to be able to smuggle the asyncResponse
 		// into the Runnable which is passed itself to the asyncResponse.
 		final AtomicReference<AsyncResponseImpl> asyncResponseRef = new AtomicReference<>();
+		assumeTrue(!executorService.isShutdown(), "cannot send async email, executor service is already shut down!");
 		asyncResponseRef.set(new AsyncResponseImpl(executorService.submit(new NamedRunnable(processName) {
 			@Override
 			public void run() {

modules/cli-module/src/main/java/org/simplejavamail/internal/clisupport/CliCommandLineProducer.java

@@ -38,7 +38,7 @@ static CommandLine configurePicoCli(List<CliDeclaredOptionSpec> declaredOptions,
                         "%n" +
                         "Note: All the regular functionality regarding properties and config files work with the CLI so you can provide defaults in a " +
                         "property file as long as it is visible (on class path) or as system environment variables.")
-                .version("Simple Java Mail 6.0.1");
+                .version("Simple Java Mail 6.0.2");
 
         rootCommandsHolder.usageMessage()
                 .customSynopsis("",

modules/core-module/src/main/java/org/simplejavamail/api/mailer/Mailer.java

@@ -112,7 +112,9 @@ public interface Mailer {
 	 * Shuts down the connection pool associated with this {@link Mailer} instance and closes remaining open connections. Waits until all connections still in use become available again
 	 * to deallocate them as well.
 	 * <p>
-	 * In order to shut down the whole connection pool (in case of clustering), each individual {@link Mailer} instance should be shutdown.
+	 * <strong>Note:</strong> In order to shut down the whole connection pool (in case of clustering), each individual {@link Mailer} instance should be shutdown.
+	 * <p>
+	 * <strong>Note:</strong> This does *not* shut down the executor service if it was provided by the user.
 	 * <p>
 	 * <strong>Note:</strong> this is only works in combination with the {@value org.simplejavamail.internal.modules.BatchModule#NAME}.
 	 */

modules/core-module/src/main/java/org/simplejavamail/api/mailer/MailerGenericBuilder.java

@@ -243,6 +243,10 @@ public interface MailerGenericBuilder<T extends MailerGenericBuilder<?>> {
 	 * <strong>Note:</strong> What makes it NonJvm is that the default keepAliveTime is set to the lowest non-zero value (so 1), so that
 	 * any threads will die off as soon as possible, as not to block the JVM from shutting down.
 	 * <p>
+	 * <p>
+	 * <strong>Note:</strong> Simple Java Mail will <strong>not</strong> shut down the provided executor service, even if the connection pool is being shut down.
+	 * <em>This will block the JVM from shutting down</em>. The user is responsible for managing the provided executor's life cycle.
+	 * <p>
 	 * <strong>Note:</strong> this only works in combination with the {@value org.simplejavamail.internal.modules.BatchModule#NAME}.
 	 *
 	 * @param executorService A custom executor service (ThreadPoolExecutor), replacing the {@code NonJvmBlockingThreadPoolExecutor}.

modules/core-module/src/main/java/org/simplejavamail/api/mailer/config/OperationalConfig.java

@@ -109,6 +109,12 @@ public interface OperationalConfig {
 	@NotNull
 	ExecutorService getExecutorService();
 
+	/**
+	 * Indicates whether the executor service was provided by the user or internally. Used to known if Simple Java Mail should shut down the executor
+	 * when the connection pool is shut down.
+	 */
+	boolean executorServiceIsUserProvided();
+
 	/**
 	 * @see MailerGenericBuilder#withCustomMailer(CustomMailer)
 	 */

modules/simple-java-mail/src/main/java/org/simplejavamail/mailer/internal/InternalMailerBuilder.java

@@ -0,0 +1,11 @@
+package org.simplejavamail.mailer.internal;
+
+import org.simplejavamail.api.mailer.MailerGenericBuilder;
+
+/**
+ * This interface is only there to improve readability there where internal builder API is used.
+ */
+@SuppressWarnings("UnusedReturnValue")
+public interface InternalMailerBuilder<T extends MailerGenericBuilder<?>> extends MailerGenericBuilder<T> {
+	boolean isExecutorServiceUserProvided();
+}

modules/simple-java-mail/src/main/java/org/simplejavamail/mailer/internal/MailerGenericBuilderImpl.java

@@ -39,7 +39,7 @@
  * @see MailerGenericBuilder
  */
 @SuppressWarnings({"UnusedReturnValue", "unchecked"})
-abstract class MailerGenericBuilderImpl<T extends MailerGenericBuilderImpl<?>> implements MailerGenericBuilder<T> {
+abstract class MailerGenericBuilderImpl<T extends MailerGenericBuilderImpl<?>> implements InternalMailerBuilder<T> {
 
 	/**
 	 * @see MailerGenericBuilder#async()
@@ -95,6 +95,11 @@ abstract class MailerGenericBuilderImpl<T extends MailerGenericBuilderImpl<?>> i
 	@NotNull
 	private ExecutorService executorService;
 
+	/**
+	 * @see InternalMailerBuilder#isExecutorServiceUserProvided()
+	 */
+	private boolean executorServiceIsUserProvided = false;
+
 	/**
 	 * @see MailerGenericBuilder#withThreadPoolSize(Integer)
 	 */
@@ -266,6 +271,7 @@ OperationalConfig buildOperationalConfig() {
 				isTrustAllSSLHost(),
 				isVerifyingServerIdentity(),
 				getExecutorService(),
+				isExecutorServiceUserProvided(),
 				getCustomMailer());
 	}
 
@@ -376,6 +382,7 @@ public T withEmailAddressCriteria(@NotNull final EnumSet<EmailAddressCriteria> e
 	@Override
 	public T withExecutorService(@NotNull final ExecutorService executorService) {
 		this.executorService = executorService;
+		this.executorServiceIsUserProvided = true;
 		return (T) this;
 	}
 
@@ -569,6 +576,7 @@ public T resetEmailAddressCriteria() {
 	@Override
 	public T resetExecutorService() {
 		this.executorService = determineDefaultExecutorService();
+		this.executorServiceIsUserProvided = false;
 		return (T) this;
 	}
 
@@ -773,6 +781,14 @@ public ExecutorService getExecutorService() {
 		return executorService;
 	}
 
+	/**
+	 * @see InternalMailerBuilder#isExecutorServiceUserProvided()
+	 */
+	@Override
+	public boolean isExecutorServiceUserProvided() {
+		return executorServiceIsUserProvided;
+	}
+
 	/**
 	 * @see MailerGenericBuilder#getThreadPoolSize()
 	 */