Adding back bulkhead document

docs/src/main/asciidoc/spring-cloud-circuitbreaker-resilience4j.adoc

@@ -94,6 +94,105 @@ public Customizer<ReactiveResilience4JCircuitBreakerFactory> slowCusomtizer() {
 ----
 ====
 
+==== Bulkhead pattern supporting
+If `resilience4j-bulkhead` is on the classpath, Spring Cloud CircuitBreaker will wrap all methods with a Resilience4j Bulkhead.
+You can disable the Resilience4j Bulkhead by setting `spring.cloud.circuitbreaker.bulkhead.resilience4j.enabled` to `false`.
+
+Spring Cloud CircuitBreaker Resilience4j provides two implementation of bulkhead pattern:
+
+* a `SemaphoreBulkhead` which uses Semaphores
+* a `FixedThreadPoolBulkhead` which uses a bounded queue and a fixed thread pool.
+
+By default, Spring Cloud CircuitBreaker Resilience4j uses `FixedThreadPoolBulkhead`. For more information on implementation
+of Bulkhead patterns see the https://resilience4j.readme.io/docs/bulkhead[Resilience4j Bulkhead].
+
+The `Customizer<Resilience4jBulkheadProvider>` can be used to provide a default `Bulkhead` and `ThreadPoolBulkhead` configuration.
+
+====
+[source,java]
+----
+@Bean
+public Customizer<Resilience4jBulkheadProvider> defaultBulkheadCustomizer() {
+    return provider -> provider.configureDefault(id -> new Resilience4jBulkheadConfigurationBuilder()
+        .bulkheadConfig(BulkheadConfig.custom().maxConcurrentCalls(4).build())
+        .threadPoolBulkheadConfig(ThreadPoolBulkheadConfig.custom().coreThreadPoolSize(1).maxThreadPoolSize(1).build())
+        .build()
+);
+}
+----
+====
+
+==== Specific Bulkhead Configuration
+
+Similarly to proving a default 'Bulkhead' or 'ThreadPoolBulkhead' configuration, you can create a `Customize` bean this
+is passed a `Resilience4jBulkheadProvider`.
+
+====
+[source,java]
+----
+@Bean
+public Customizer<Resilience4jBulkheadProvider> slowBulkheadProviderCustomizer() {
+    return provider -> provider.configure(builder -> builder
+        .bulkheadConfig(BulkheadConfig.custom().maxConcurrentCalls(1).build())
+        .threadPoolBulkheadConfig(ThreadPoolBulkheadConfig.ofDefaults()), "slowBulkhead");
+}
+----
+====
+
+In addition to configuring the Bulkhead that is created you can also customize the bulkhead and thread pool bulkhead after they
+have been created but before they are returned to caller. To do this you can use the `addBulkheadCustomizer` and `addThreadPoolBulkheadCustomizer`
+methods.
+
+===== Bulkhead Example
+
+====
+[source,java]
+----
+@Bean
+public Customizer<Resilience4jBulkheadProvider> customizer() {
+    return provider -> provider.addBulkheadCustomizer(bulkhead -> bulkhead.getEventPublisher()
+        .onCallRejected(slowRejectedConsumer)
+        .onCallFinished(slowFinishedConsumer), "slowBulkhead");
+}
+----
+====
+
+===== Thread Pool Bulkhead Example
+
+====
+[source,java]
+----
+@Bean
+public Customizer<Resilience4jBulkheadProvider> slowThreadPoolBulkheadCustomizer() {
+    return provider -> provider.addThreadPoolBulkheadCustomizer(threadPoolBulkhead -> threadPoolBulkhead.getEventPublisher()
+        .onCallRejected(slowThreadPoolRejectedConsumer)
+        .onCallFinished(slowThreadPoolFinishedConsumer), "slowThreadPoolBulkhead");
+}
+----
+====
+
+==== Bulkhead Properties Configuration
+
+You can configure ThreadPoolBulkhead and SemaphoreBulkhead instances in your application's configuration properties file.
+Property configuration has higher priority than Java `Customizer` configuration.
+
+====
+[source]
+----
+resilience4j.thread-pool-bulkhead:
+    instances:
+        backendA:
+            maxThreadPoolSize: 1
+            coreThreadPoolSize: 1
+resilience4j.bulkhead:
+    instances:
+        backendB:
+            maxConcurrentCalls: 10
+----
+====
+
+For more inforamtion on the Resilience4j property configuration, see https://resilience4j.readme.io/docs/getting-started-3#configuration[Resilience4J Spring Boot 2 Configuration].
+
 ==== Collecting Metrics
 
 Spring Cloud Circuit Breaker Resilience4j includes auto-configuration to setup metrics collection as long as the right