=== Redis backend

The service discovery has a plug-able backend using the `link:../../apidocs/io/vertx/servicediscovery/spi/ServiceDiscoveryBackend.html[ServiceDiscoveryBackend]` SPI. This is an implementation of the SPI based
on Redis.

==== Using the Redis backend

To use the Redis backend, add the following dependency to the _dependencies_ section of your build
descriptor:

* Maven (in your `pom.xml`):

[source,xml,subs="+attributes"]
----
<dependency>
 <groupId>io.vertx</groupId>
 <artifactId>vertx-service-discovery-backend-redis</artifactId>
 <version>4.1.8</version>
</dependency>
----

* Gradle (in your `build.gradle` file):

[source,groovy,subs="+attributes"]
----
compile 'io.vertx:vertx-service-discovery-backend-redis:4.1.8'
----

Be aware that you can have only a single implementation of the SPI in your _classpath_. If none,
the default backend is used.

==== Configuration

The backend is based on the http://vertx.io/docs/vertx-redis-client/java[vertx-redis-client].
The configuration is the client configuration as well as `key` indicating in which _key_ on Redis
the records are stored.

Here is an example:

[source,java]
----
ServiceDiscovery.create(vertx, new ServiceDiscoveryOptions()
    .setBackendConfiguration(
        new JsonObject()
            .put("connectionString", "redis://localhost:6379")
            .put("key", "records")
    ));
----

It's important to note that the backend configuration is passed in the `setBackendConfiguration` method (or
`backendConfiguration` entry if you use JSON):

[source,java]
----
ServiceDiscovery.create(vertx,
  new ServiceDiscoveryOptions(new JsonObject()
    .put("backendConfiguration",
      new JsonObject().put("connectionString", "redis://localhost:6379").put("key", "my-records")
)));
----