DATAREDIS-1093 - Document that Master/Replica connections do not support Pub/Sub.

src/main/asciidoc/reference/redis.adoc

@@ -133,7 +133,7 @@ class WriteToMasterReadFromReplicaConfiguration {
 }
 ----
 
-TIP: For environments reporting non-public addresses through the `INFO` command (for example, when using AWS), use `RedisStaticMasterReplicaConfiguration` instead of `RedisStandaloneConfiguration`.
+TIP: For environments reporting non-public addresses through the `INFO` command (for example, when using AWS), use `RedisStaticMasterReplicaConfiguration` instead of `RedisStandaloneConfiguration`. Please note that `RedisStaticMasterReplicaConfiguration` does not support Pub/Sub because of missing Pub/Sub message propagation across individual servers.
 
 [[redis:sentinel]]
 == Redis Sentinel Support

src/main/java/org/springframework/data/redis/connection/RedisStaticMasterReplicaConfiguration.java

@@ -27,6 +27,7 @@ import org.springframework.util.Assert;
  * Master / Replica configuration to nodes know to not change address. Eg. when connecting to
  * <a href="https://aws.amazon.com/documentation/elasticache/">AWS ElastiCache with Read Replicas</a>. <br/>
  * Note: Redis is undergoing a nomenclature change where the term replica is used synonymously to slave.
+ * Please also note that a Master/Replica connection cannot be used for Pub/Sub operations.
  *
  * @author Mark Paluch
  * @author Christoph Strobl

src/main/java/org/springframework/data/redis/connection/lettuce/StaticMasterReplicaConnectionProvider.java

@@ -22,6 +22,7 @@ import io.lettuce.core.api.StatefulConnection;
 import io.lettuce.core.codec.RedisCodec;
 import io.lettuce.core.masterslave.MasterSlave;
 import io.lettuce.core.masterslave.StatefulRedisMasterSlaveConnection;
+import io.lettuce.core.pubsub.StatefulRedisPubSubConnection;
 
 import java.util.Collection;
 import java.util.Optional;
@@ -68,6 +69,10 @@ class StaticMasterReplicaConnectionProvider implements LettuceConnectionProvider
 	@Override
 	public <T extends StatefulConnection<?, ?>> T getConnection(Class<T> connectionType) {
 
+		if (connectionType.equals(StatefulRedisPubSubConnection.class)) {
+			throw new UnsupportedOperationException("Pub/Sub connections not supported with Master/Replica configurations");
+		}
+
 		if (StatefulConnection.class.isAssignableFrom(connectionType)) {
 
 			// See https://github.com/lettuce-io/lettuce-core/issues/845 for MasterSlave -> MasterReplica change.

src/test/java/org/springframework/data/redis/connection/lettuce/LettuceConnectionFactoryTests.java

@@ -475,6 +475,28 @@ public class LettuceConnectionFactoryTests {
 		factory.destroy();
 	}
 
+	@Test // DATAREDIS-1093
+	public void pubSubDoesNotSupportMasterReplicaConnections() {
+
+		assumeTrue(String.format("No replicas connected to %s:%s.", SettingsUtils.getHost(), SettingsUtils.getPort()),
+				connection.info("replication").getProperty("connected_slaves", "0").compareTo("0") > 0);
+
+		RedisStaticMasterReplicaConfiguration elastiCache = new RedisStaticMasterReplicaConfiguration(
+				SettingsUtils.getHost()).node(SettingsUtils.getHost(), SettingsUtils.getPort() + 1);
+
+		LettuceConnectionFactory factory = new LettuceConnectionFactory(elastiCache);
+		factory.setClientResources(LettuceTestClientResources.getSharedClientResources());
+		factory.afterPropertiesSet();
+
+		RedisConnection connection = factory.getConnection();
+
+		assertThatThrownBy(() -> connection.pSubscribe((message, pattern) -> {
+		}, "foo".getBytes())).isInstanceOf(RedisSystemException.class).hasCauseInstanceOf(UnsupportedOperationException.class);
+
+		connection.close();
+		factory.destroy();
+	}
+
 	@Test // DATAREDIS-762, DATAREDIS-869
 	public void factoryUsesElastiCacheMasterWithoutMaster() {