Change default value for KeyspaceEventMessageListener keyspace event notifications.

Users must now explicitly call setKeyspaceNotificationsConfigParameter(:String) to a valid redis.config, notify-keyspace-events value to enable Redis keyspace notifications. This aligns with the Redis servers default setting for notify-keyspace-events in redis.conf, which is disabled by default.

Additionally, the default value for KeyExpirationEventMessageListener has been changed to 'Ex', for development-time convenience only.

However, users should be aware that any notify-keyspace-events configuration only applies once on Spring container initialization and any Redis server reboot will not remember dynamic configuration modifications applied at runtime. Therefore, it is recommended that users applly infrastructure-related configuration changes directly to redis.conf.

Closes #2670

Author: jxblum

Diff for: src/main/java/org/springframework/data/redis/listener/KeyExpirationEventMessageListener.java

@@ -25,24 +25,35 @@
 /**
  * {@link MessageListener} publishing {@link RedisKeyExpiredEvent}s via {@link ApplicationEventPublisher} by listening
  * to Redis keyspace notifications for key expirations.
+ * <p>
+ * For development-time convenience the {@link #setKeyspaceNotificationsConfigParameter(String)} is set to
+ * {@literal "Ex"}, by default. However, it is strongly recommended that users specifically set
+ * {@literal notify-keyspace-events} to the appropriate value on the Redis server, in {@literal redis.conf}.
+ * <p>
+ * Any Redis server configuration coming from your Spring (Data Redis) application only occurs during Spring container
+ * initialization, and is not persisted across Redis server restarts.
  *
  * @author Christoph Strobl
+ * @author John Blum
  * @since 1.7
  */
 public class KeyExpirationEventMessageListener extends KeyspaceEventMessageListener implements
 		ApplicationEventPublisherAware {
 
+	private static final String EXPIRED_KEY_EVENTS = "Ex";
+
 	private static final Topic KEYEVENT_EXPIRED_TOPIC = new PatternTopic("__keyevent@*__:expired");
 
 	private @Nullable ApplicationEventPublisher publisher;
 
 	/**
-	 * Creates new {@link MessageListener} for {@code __keyevent@*__:expired} messages.
+	 * Creates new {@link MessageListener} for {@code __keyevent@*__:expired} messages and configures notification on
+	 * expired keys ({@literal Ex}).
 	 *
 	 * @param listenerContainer must not be {@literal null}.
 	 */
 	public KeyExpirationEventMessageListener(RedisMessageListenerContainer listenerContainer) {
-		super(listenerContainer);
+		super(listenerContainer, EXPIRED_KEY_EVENTS);
 	}
 
 	@Override

Diff for: src/main/java/org/springframework/data/redis/listener/KeyspaceEventMessageListener.java

@@ -17,101 +17,199 @@
 
 import java.util.Properties;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.data.redis.connection.Message;
 import org.springframework.data.redis.connection.MessageListener;
 import org.springframework.data.redis.connection.RedisConnection;
+import org.springframework.data.redis.connection.RedisConnectionFactory;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
  * Base {@link MessageListener} implementation for listening to Redis keyspace notifications.
+ * <p>
+ * By default, this {@link MessageListener} does not listen for, or notify on, any keyspace events. You must explicitly
+ * set the {@link #setKeyspaceNotificationsConfigParameter(String)} to a valid {@literal redis.conf},
+ * {@literal notify-keyspace-events} value (for example: {@literal EA}) to enable keyspace event notifications
+ * from your Redis server.
+ * <p>
+ * Any configuration set in the Redis server take precedence. Therefore, if the Redis server already set a value
+ * for {@literal notify-keyspace-events}, then any {@link #setKeyspaceNotificationsConfigParameter(String)}
+ * specified on this listener will be ignored.
+ * <p>
+ * It is recommended that all infrastructure settings, such as {@literal notify-keyspace-events}, be configured on
+ * the Redis server itself. If the Redis server is rebooted, then any keyspace event configuration coming from
+ * the application will be lost when the Redis server is restarted since Redis server configuration is not persistent,
+ * and any configuration coming from your application only occurs during Spring container initialization.
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author John Blum
  * @since 1.7
  */
 public abstract class KeyspaceEventMessageListener implements MessageListener, InitializingBean, DisposableBean {
 
+	protected static final String DISABLED_KEY_EVENTS = "";
+	protected static final String NOTIFY_KEYSPACE_EVENTS = "notify-keyspace-events";
+
 	private static final Topic TOPIC_ALL_KEYEVENTS = new PatternTopic("__keyevent@*");
 
-	private final RedisMessageListenerContainer listenerContainer;
+	private final Logger logger = LoggerFactory.getLogger(getClass());
+
+	private final RedisMessageListenerContainer messageListenerContainer;
+
+	private @Nullable String keyspaceNotificationsConfigParameter;
+
+	/**
+	 * Creates a new {@link KeyspaceEventMessageListener}.
+	 *
+	 * @param messageListenerContainer {@link RedisMessageListenerContainer} in which this listener will be registered;
+	 * must not be {@literal null}.
+	 */
+	public KeyspaceEventMessageListener(RedisMessageListenerContainer messageListenerContainer) {
+		this(messageListenerContainer, DISABLED_KEY_EVENTS);
+	}
+
+	/**
+	 * Creates a new {@link KeyspaceEventMessageListener} along with initialization for
+	 * {@literal notify-keyspace-events}.
+	 *
+	 * @param messageListenerContainer {@link RedisMessageListenerContainer} in which this listener will be registered;
+	 * must not be {@literal null}.
+	 * @param keyspaceNotificationsConfigParameter {@link String default value} for {@literal notify-keyspace-events};
+	 * may be {@literal null}.
+	 */
+	protected KeyspaceEventMessageListener(RedisMessageListenerContainer messageListenerContainer,
+			@Nullable String keyspaceNotificationsConfigParameter) {
+
+		Assert.notNull(messageListenerContainer, "RedisMessageListenerContainer to run in must not be null");
 
-	private String keyspaceNotificationsConfigParameter = "EA";
+		this.messageListenerContainer = messageListenerContainer;
+		this.keyspaceNotificationsConfigParameter = keyspaceNotificationsConfigParameter;
+	}
 
 	/**
-	 * Creates new {@link KeyspaceEventMessageListener}.
+	 * Returns a reference to the configured {@link Logger}.
 	 *
-	 * @param listenerContainer must not be {@literal null}.
+	 * @return a reference to the configured {@link Logger}.
 	 */
-	public KeyspaceEventMessageListener(RedisMessageListenerContainer listenerContainer) {
+	protected Logger getLogger() {
+		return this.logger;
+	}
 
-		Assert.notNull(listenerContainer, "RedisMessageListenerContainer to run in must not be null");
-		this.listenerContainer = listenerContainer;
+	/**
+	 * Returns a configured reference to the {@link RedisMessageListenerContainer} to which this {@link MessageListener}
+	 * is registered.
+	 *
+	 * @return a configured reference to the {@link RedisMessageListenerContainer} to which this {@link MessageListener}
+	 * is registered.
+	 */
+	protected RedisMessageListenerContainer getMessageListenerContainer() {
+		return this.messageListenerContainer;
 	}
 
 	@Override
 	public void onMessage(Message message, @Nullable byte[] pattern) {
 
-		if (ObjectUtils.isEmpty(message.getChannel()) || ObjectUtils.isEmpty(message.getBody())) {
-			return;
+		if (containsChannelContent(message)) {
+			doHandleMessage(message);
 		}
+	}
 
-		doHandleMessage(message);
+	// Message must have a channel and body (contain content)
+	private boolean containsChannelContent(Message message) {
+		return !(ObjectUtils.isEmpty(message.getChannel()) || ObjectUtils.isEmpty(message.getBody()));
 	}
 
 	/**
-	 * Handle the actual message
+	 * Handle the actual {@link Message}.
 	 *
-	 * @param message never {@literal null}.
+	 * @param message {@link Message} to process; never {@literal null}.
 	 */
 	protected abstract void doHandleMessage(Message message);
 
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		init();
+	}
+
 	/**
-	 * Initialize the message listener by writing requried redis config for {@literal notify-keyspace-events} and
-	 * registering the listener within the container.
+	 * Initialize this {@link MessageListener} by writing required Redis server config
+	 * for {@literal notify-keyspace-events} and registering this {@link MessageListener}
+	 * with the {@link RedisMessageListenerContainer}.
 	 */
 	public void init() {
 
-		if (StringUtils.hasText(keyspaceNotificationsConfigParameter)) {
+		String keyspaceNotificationsConfigParameter = getKeyspaceNotificationsConfigParameter();
 
-			RedisConnection connection = listenerContainer.getConnectionFactory().getConnection();
+		if (isSet(keyspaceNotificationsConfigParameter)) {
+			configureKeyspaceEventNotifications(keyspaceNotificationsConfigParameter);
+		}
 
-			try {
+		doRegister(getMessageListenerContainer());
+	}
 
-				Properties config = connection.getConfig("notify-keyspace-events");
+	private boolean isSet(@Nullable String value) {
+		return StringUtils.hasText(value);
+	}
 
-				if (!StringUtils.hasText(config.getProperty("notify-keyspace-events"))) {
-					connection.setConfig("notify-keyspace-events", keyspaceNotificationsConfigParameter);
-				}
+	void configureKeyspaceEventNotifications(String keyspaceNotificationsConfigParameter) {
+
+		RedisConnectionFactory connectionFactory = getMessageListenerContainer().getConnectionFactory();
 
-			} finally {
-				connection.close();
+		if (connectionFactory != null) {
+			try (RedisConnection connection = connectionFactory.getConnection()) {
+				if (canChangeNotifyKeyspaceEvents(connection)) {
+					setKeyspaceEventNotifications(connection, keyspaceNotificationsConfigParameter);
+				}
 			}
 		}
+		else {
+			if (getLogger().isWarnEnabled()) {
+				getLogger().warn("Unable to configure notification on keyspace events;"
+					+ " no RedisConnectionFactory was configured in the RedisMessageListenerContainer");
+			}
+		}
+	}
+
+	private boolean canChangeNotifyKeyspaceEvents(@Nullable RedisConnection connection) {
+
+		if (connection != null) {
+
+			Properties config = connection.serverCommands().getConfig(NOTIFY_KEYSPACE_EVENTS);
+
+			return config == null || !isSet(config.getProperty(NOTIFY_KEYSPACE_EVENTS));
+		}
 
-		doRegister(listenerContainer);
+		return false;
+	}
+
+	void setKeyspaceEventNotifications(RedisConnection connection, String keyspaceNotificationsConfigParameter) {
+		connection.serverCommands().setConfig(NOTIFY_KEYSPACE_EVENTS, keyspaceNotificationsConfigParameter);
+	}
+
+	@Override
+	public void destroy() throws Exception {
+		getMessageListenerContainer().removeMessageListener(this);
 	}
 
 	/**
-	 * Register instance within the container.
+	 * Register instance within the {@link RedisMessageListenerContainer}.
 	 *
 	 * @param container never {@literal null}.
 	 */
 	protected void doRegister(RedisMessageListenerContainer container) {
-		listenerContainer.addMessageListener(this, TOPIC_ALL_KEYEVENTS);
-	}
-
-	@Override
-	public void destroy() throws Exception {
-		listenerContainer.removeMessageListener(this);
+		container.addMessageListener(this, TOPIC_ALL_KEYEVENTS);
 	}
 
 	/**
-	 * Set the configuration string to use for {@literal notify-keyspace-events}.
+	 * Set the {@link String configuration setting} (for example: {@literal EA}) to use
+	 * for {@literal notify-keyspace-events}.
 	 *
 	 * @param keyspaceNotificationsConfigParameter can be {@literal null}.
 	 * @since 1.8
@@ -120,8 +218,13 @@ public void setKeyspaceNotificationsConfigParameter(String keyspaceNotifications
 		this.keyspaceNotificationsConfigParameter = keyspaceNotificationsConfigParameter;
 	}
 
-	@Override
-	public void afterPropertiesSet() throws Exception {
-		init();
+	/**
+	 * Get the configured {@link String setting} for {@literal notify-keyspace-events}.
+	 *
+	 * @return the configured {@link String setting} for {@literal notify-keyspace-events}.
+	 */
+	@Nullable
+	protected String getKeyspaceNotificationsConfigParameter() {
+		return this.keyspaceNotificationsConfigParameter;
 	}
 }

Diff for: src/test/java/org/springframework/data/redis/listener/KeyExpirationEventMessageListenerIntegrationTests.java

@@ -27,12 +27,10 @@
 import org.junit.jupiter.api.Test;
 import org.mockito.ArgumentCaptor;
 
-import org.springframework.beans.factory.DisposableBean;
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.data.redis.connection.RedisConnection;
 import org.springframework.data.redis.connection.RedisConnectionFactory;
-import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;
 import org.springframework.data.redis.connection.jedis.extension.JedisConnectionFactoryExtension;
 import org.springframework.data.redis.test.extension.RedisStanalone;
 
@@ -103,7 +101,7 @@ void listenerShouldPublishEventCorrectly() {
 	@Test // DATAREDIS-425
 	void listenerShouldNotReactToDeleteEvents() throws InterruptedException {
 
-		byte[] key = ("to-delete:" + UUID.randomUUID().toString()).getBytes();
+		byte[] key = ("to-delete:" + UUID.randomUUID()).getBytes();
 
 		try (RedisConnection connection = connectionFactory.getConnection()) {