Document ReactiveHealthIndicator support

Closes gh-10881

spring-boot-project/spring-boot-docs/src/main/asciidoc/production-ready-features.adoc

@@ -476,7 +476,31 @@ The following table shows the default status mappings for the built-in statuses:
 |No mapping by default, so http status is 200
 |===
 
+[[reactive-health-indicators]]
+==== ReactiveHealthIndicators
+For reactive applications, such as those using Spring WebFlux, ReactiveHealthIndicators provide a
+non-blocking contract for getting application health. Similar to traditional HealthIndicators,
+health information is collected from all {sc-spring-boot-actuator}/health/ReactiveHealthIndicator.{sc-ext}[`ReactiveHealthIndicator`]
+beans defined in your `ApplicationContext`. Spring Boot adds autoconfiguration for `RedisReactiveHealthIndicator`.
+Regular HealthIndicators that do not check against a reactive API are executed on the elastic scheduler.
+
+To provide custom health information from a reactive API, you can register Spring beans that implement the
+{sc-spring-boot-actuator}/health/ReactiveHealthIndicator.{sc-ext}[`ReactiveHealthIndicator`] interface.
+The following code shows a sample `ReactiveHealthIndicator` implementation:
 
+[source,java,indent=0]
+----
+	@Component
+	public class MyReactiveHealthIndicator implements ReactiveHealthIndicator {
+
+		@Override
+		public Mono<Health> health() {
+			return doHealthCheck() //perform some specific health check that returns a Mono<Health>
+				.onErrorResume(ex -> Mono.just(new Health.Builder().down(ex).build())));
+		}
+
+	}
+----
 
 [[production-ready-application-info]]
 === Application Information