GH-9112: Workaround for Paho stopReconnectCycle

Fixes: #9112

`Mqttv5ClientManager` hangs in `stop()` if never was connected.
The scheduled reconnect timer in the client is never cancelled.

* Call `stopReconnectCycle()` on the client via reflection when we disconnect
from the client in Spring Integration MQTT components

**Auto-cherry-pick to `6.2.x` & `6.1.x`**

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/aot/MqttRuntimeHints.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.mqtt.aot;
+
+import java.util.stream.Stream;
+
+import org.springframework.aot.hint.ExecutableMode;
+import org.springframework.aot.hint.ReflectionHints;
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * {@link RuntimeHintsRegistrar} for Spring Integration MQTT module.
+ *
+ * @author Artem Bilan
+ *
+ * @since 6.1.9
+ */
+class MqttRuntimeHints implements RuntimeHintsRegistrar {
+
+	@Override
+	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+		ReflectionHints reflectionHints = hints.reflection();
+		// TODO until the real fix in Paho library.
+		Stream.of("org.eclipse.paho.client.mqttv3.MqttAsyncClient", "org.eclipse.paho.mqttv5.client.MqttAsyncClient")
+				.filter((typeName) -> ClassUtils.isPresent(typeName, classLoader))
+				.map((typeName) -> loadClassByName(typeName, classLoader))
+				.flatMap((type) -> Stream.ofNullable(ReflectionUtils.findMethod(type, "stopReconnectCycle")))
+				.forEach(method -> reflectionHints.registerMethod(method, ExecutableMode.INVOKE));
+	}
+
+	private static Class<?> loadClassByName(String typeName, ClassLoader classLoader) {
+		try {
+			return ClassUtils.forName(typeName, classLoader);
+		}
+		catch (ClassNotFoundException ex) {
+			throw new IllegalArgumentException(ex);
+		}
+	}
+
+}

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/aot/package-info.java

@@ -0,0 +1,6 @@
+/**
+ * Provides classes to support Spring AOT.
+ */
+@org.springframework.lang.NonNullApi
+@org.springframework.lang.NonNullFields
+package org.springframework.integration.mqtt.aot;

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/core/Mqttv3ClientManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2023 the original author or authors.
+ * Copyright 2022-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@
 import org.eclipse.paho.client.mqttv3.MqttMessage;
 
 import org.springframework.integration.mqtt.event.MqttConnectionFailedEvent;
+import org.springframework.integration.mqtt.support.MqttUtils;
 import org.springframework.util.Assert;
 
 /**
@@ -149,6 +150,9 @@ public void stop() {
 			}
 			try {
 				client.disconnectForcibly(getDisconnectCompletionTimeout());
+				if (getConnectionInfo().isAutomaticReconnect()) {
+					MqttUtils.stopClientReconnectCycle(client);
+				}
 			}
 			catch (MqttException e) {
 				logger.error("Could not disconnect from the client", e);

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/core/Mqttv5ClientManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2023 the original author or authors.
+ * Copyright 2022-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,6 +28,7 @@
 import org.eclipse.paho.mqttv5.common.packet.MqttProperties;
 
 import org.springframework.integration.mqtt.event.MqttConnectionFailedEvent;
+import org.springframework.integration.mqtt.support.MqttUtils;
 import org.springframework.util.Assert;
 
 /**
@@ -151,6 +152,9 @@ public void stop() {
 
 			try {
 				client.disconnectForcibly(getDisconnectCompletionTimeout());
+				if (getConnectionInfo().isAutomaticReconnect()) {
+					MqttUtils.stopClientReconnectCycle(client);
+				}
 			}
 			catch (MqttException e) {
 				logger.error("Could not disconnect from the client", e);

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/inbound/MqttPahoMessageDrivenChannelAdapter.java

@@ -228,6 +228,9 @@ protected void doStop() {
 
 			try {
 				this.client.disconnectForcibly(getDisconnectCompletionTimeout());
+				if (getConnectionInfo().isAutomaticReconnect()) {
+					MqttUtils.stopClientReconnectCycle(this.client);
+				}
 			}
 			catch (MqttException ex) {
 				logger.error(ex, "Exception while disconnecting");

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/inbound/Mqttv5PahoMessageDrivenChannelAdapter.java

@@ -53,6 +53,7 @@
 import org.springframework.integration.mqtt.support.MqttHeaderMapper;
 import org.springframework.integration.mqtt.support.MqttHeaders;
 import org.springframework.integration.mqtt.support.MqttMessageConverter;
+import org.springframework.integration.mqtt.support.MqttUtils;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
@@ -299,6 +300,9 @@ protected void doStop() {
 				}
 				if (getClientManager() == null) {
 					this.mqttClient.disconnectForcibly(getDisconnectCompletionTimeout());
+					if (getConnectionInfo().isAutomaticReconnect()) {
+						MqttUtils.stopClientReconnectCycle(this.mqttClient);
+					}
 				}
 			}
 		}

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/outbound/MqttPahoMessageHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -176,6 +176,9 @@ protected void doStop() {
 			IMqttAsyncClient theClient = this.client;
 			if (theClient != null) {
 				theClient.disconnect().waitForCompletion(getDisconnectCompletionTimeout());
+				if (getConnectionInfo().isAutomaticReconnect()) {
+					MqttUtils.stopClientReconnectCycle(theClient);
+				}
 				theClient.close();
 				this.client = null;
 			}

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/outbound/Mqttv5PahoMessageHandler.java

@@ -41,6 +41,7 @@
 import org.springframework.integration.mqtt.event.MqttProtocolErrorEvent;
 import org.springframework.integration.mqtt.support.MqttHeaderMapper;
 import org.springframework.integration.mqtt.support.MqttMessageConverter;
+import org.springframework.integration.mqtt.support.MqttUtils;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandlingException;
@@ -184,6 +185,9 @@ protected void doStop() {
 		try {
 			if (getClientManager() == null) {
 				this.mqttClient.disconnect().waitForCompletion(getDisconnectCompletionTimeout());
+				if (getConnectionInfo().isAutomaticReconnect()) {
+					MqttUtils.stopClientReconnectCycle(this.mqttClient);
+				}
 			}
 		}
 		catch (MqttException ex) {

spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/support/MqttUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2021 the original author or authors.
+ * Copyright 2020-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,13 @@
 
 package org.springframework.integration.mqtt.support;
 
+import java.lang.reflect.Method;
+
 import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
 
 import org.springframework.beans.BeanUtils;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
 
 /**
  * MQTT Utilities.
@@ -30,6 +34,38 @@
  */
 public final class MqttUtils {
 
+	private static final boolean PAHO_MQTTV3_PRESENT =
+			ClassUtils.isPresent("org.eclipse.paho.client.mqttv3.MqttAsyncClient", null);
+
+	private static final boolean PAHO_MQTTV5_PRESENT =
+			ClassUtils.isPresent("org.eclipse.paho.mqttv5.client.MqttAsyncClient", null);
+
+	private static final Method V3_STOP_RECONNECT_CYCLE_METHOD;
+
+	private static final Method V5_STOP_RECONNECT_CYCLE_METHOD;
+
+	static {
+		if (PAHO_MQTTV3_PRESENT) {
+			V3_STOP_RECONNECT_CYCLE_METHOD =
+					ReflectionUtils.findMethod(org.eclipse.paho.client.mqttv3.MqttAsyncClient.class,
+							"stopReconnectCycle");
+			ReflectionUtils.makeAccessible(V3_STOP_RECONNECT_CYCLE_METHOD);
+		}
+		else {
+			V3_STOP_RECONNECT_CYCLE_METHOD = null;
+		}
+
+		if (PAHO_MQTTV5_PRESENT) {
+			V5_STOP_RECONNECT_CYCLE_METHOD =
+					ReflectionUtils.findMethod(org.eclipse.paho.mqttv5.client.MqttAsyncClient.class,
+							"stopReconnectCycle");
+			ReflectionUtils.makeAccessible(V5_STOP_RECONNECT_CYCLE_METHOD);
+		}
+		else {
+			V5_STOP_RECONNECT_CYCLE_METHOD = null;
+		}
+	}
+
 	private MqttUtils() {
 	}
 
@@ -47,4 +83,26 @@ public static MqttConnectOptions cloneConnectOptions(MqttConnectOptions options)
 		return options2;
 	}
 
+	/**
+	 * Perform a {@code stopReconnectCycle()} (via reflection) method on the provided client
+	 * to clean up resources on client stop.
+	 * TODO until the real fix in Paho library.
+	 * @param client the MQTTv3 Paho client instance.
+	 * @since 6.1.9
+	 */
+	public static void stopClientReconnectCycle(org.eclipse.paho.client.mqttv3.IMqttAsyncClient client) {
+		ReflectionUtils.invokeMethod(V3_STOP_RECONNECT_CYCLE_METHOD, client);
+	}
+
+	/**
+	 * Perform a {@code stopReconnectCycle()} (via reflection) method on the provided client
+	 * to clean up resources on client stop.
+	 * TODO until the real fix in Paho library.
+	 * @param client the MQTTv5 Paho client instance.
+	 * @since 6.1.9
+	 */
+	public static void stopClientReconnectCycle(org.eclipse.paho.mqttv5.client.IMqttAsyncClient client) {
+		ReflectionUtils.invokeMethod(V5_STOP_RECONNECT_CYCLE_METHOD, client);
+	}
+
 }

spring-integration-mqtt/src/main/resources/META-INF/spring/aot.factories

@@ -0,0 +1 @@
+org.springframework.aot.hint.RuntimeHintsRegistrar=org.springframework.integration.mqtt.aot.MqttRuntimeHints

spring-integration-mqtt/src/test/java/org/springframework/integration/mqtt/MqttAdapterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -488,8 +488,8 @@ public void testDifferentQos() throws Exception {
 		given(token.getGrantedQos()).willReturn(new int[] {2, 0});
 		willReturn(token).given(client).subscribe(any(String[].class), any(int[].class), any());
 
-		MqttPahoMessageDrivenChannelAdapter adapter = new MqttPahoMessageDrivenChannelAdapter("foo", "bar", factory,
-				"baz", "fix");
+		MqttPahoMessageDrivenChannelAdapter adapter =
+				new MqttPahoMessageDrivenChannelAdapter("tcp://mqtt.host", "bar", factory, "baz", "fix");
 		AtomicReference<Method> method = new AtomicReference<>();
 		ReflectionUtils.doWithMethods(MqttPahoMessageDrivenChannelAdapter.class, m -> {
 			m.setAccessible(true);