Redis Client: improve documentation for sentinel and cluster

docs/src/main/asciidoc/redis-reference.adoc

@@ -173,10 +173,16 @@ quarkus.redis.hosts=redis://localhost:5000,redis://localhost:5001,redis://localh
 quarkus.redis.client-type=sentinel
 
 # Optional
-quarkus.redis.master-name=my-sentinel # Default is my-master
+quarkus.redis.master-name=my-sentinel # Default is mymaster
 quarkus.redis.role=master # master is the default
 ----
 
+The host URLs here must be the sentinel servers.
+The client will obtain the URLs of actual Redis servers (master or replicas, depending on `role`) from one of the sentinels, using the `master-name` as an identifier of the "master set".
+
+Note that you practically never want to configure `quarkus.redis.role=sentinel`.
+This setting means that the Redis client will execute commands directly on one of the sentinel servers, instead of an actual Redis server guarded by the sentinels.
+
 === Use the Cluster Mode
 
 When using Redis in cluster mode, you need to pass multiple _host urls_, configure the client type to `cluster` and configure the `replicas` mode:
@@ -188,6 +194,10 @@ quarkus.redis.client-type=cluster
 quarkus.redis.replicas=share
 ----
 
+The host URLs here must be some of the cluster members.
+Not all cluster members need to be configured, as the client will obtain a full cluster topology from one of the known servers.
+However, it is advisable to configure at least 2 or 3 nodes, not just 1.
+
 === Use the replication Mode
 
 When using the replication mode, you need to pass a single host url and configure the type to be `replication`:

extensions/redis-client/runtime/src/main/java/io/quarkus/redis/runtime/client/config/RedisClientConfig.java

@@ -56,7 +56,7 @@ public interface RedisClientConfig {
     /**
      * The master name (only considered in HA mode).
      */
-    @ConfigDocDefault("my-master")
+    @ConfigDocDefault("mymaster")
     Optional<String> masterName();
 
     /**