Binding visualization and control

Spring Cloud Stream supports visualization and control of the Bindings through Actuator endpoints as well as programmatic way.

Programmatic way

Since version 3.1 we expose org.springframework.cloud.stream.binding.BindingsLifecycleController which is registered as bean and once injected could be used to control the lifecycle of individual bindings

For example, looks at the fragment from one of the test cases. As you can see we retrieve BindingsLifecycleController from spring application context and execute individual methods to control the lifecycle of echo-in-0 binding..

BindingsLifecycleController bindingsController = context.getBean(BindingsLifecycleController.class);
Binding binding = bindingsController.queryState("echo-in-0");
assertThat(binding.isRunning()).isTrue();
bindingsController.changeState("echo-in-0", State.STOPPED);
//Alternative way of changing state. For convenience we expose start/stop and pause/resume operations.
//bindingsController.stop("echo-in-0")
assertThat(binding.isRunning()).isFalse();

Actuator

Since actuator and web are optional, you must first add one of the web dependencies as well as add the actuator dependency manually. The following example shows how to add the dependency for the Web framework:

<dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-web</artifactId>
</dependency>

The following example shows how to add the dependency for the WebFlux framework:

<dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

You can add the Actuator dependency as follows:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

To run Spring Cloud Stream 2.0 apps in Cloud Foundry, you must add spring-boot-starter-web and spring-boot-starter-actuator to the classpath. Otherwise, the application will not start due to health check failures.

You must also enable the bindings actuator endpoints by setting the following property: --management.endpoints.web.exposure.include=bindings.

Once those prerequisites are satisfied. you should see the following in the logs when application start:

: Mapped "{[/actuator/bindings/{name}],methods=[POST]. . .
: Mapped "{[/actuator/bindings],methods=[GET]. . .
: Mapped "{[/actuator/bindings/{name}],methods=[GET]. . .

To visualize the current bindings, access the following URL: <host>:<port>/actuator/bindings

Alternative, to see a single binding, access one of the URLs similar to the following: <host>:<port>/actuator/bindings/<bindingName>;

You can also stop, start, pause, and resume individual bindings by posting to the same URL while providing a state argument as JSON, as shown in the following examples:

curl -d '{"state":"STOPPED"}' -H "Content-Type: application/json" -X POST http://<host>:<port>/actuator/bindings/myBindingName
curl -d '{"state":"STARTED"}' -H "Content-Type: application/json" -X POST http://<host>:<port>/actuator/bindings/myBindingName
curl -d '{"state":"PAUSED"}' -H "Content-Type: application/json" -X POST http://<host>:<port>/actuator/bindings/myBindingName
curl -d '{"state":"RESUMED"}' -H "Content-Type: application/json" -X POST http://<host>:<port>/actuator/bindings/myBindingName

PAUSED and RESUMED work only when the corresponding binder and its underlying technology supports it. Otherwise, you see the warning message in the logs. Currently, only Kafka and [Solace](github.com/SolaceProducts/solace-spring-cloud/tree/master/solace-spring-cloud-starters/solace-spring-cloud-stream-starter#consumer-bindings-pauseresume) binders supports the PAUSED and RESUMED states.