Master Sentinel Flow Control: Dashboard, RestTemplate & OpenFeign Integration

In a previous article we introduced Sentinel; this article explains how to use Sentinel, configure flow‑control rules via the sentinel‑dashboard, and integrate Sentinel with RestTemplate and OpenFeign.

Install sentinel dashboard

We use sentinel‑dashboard‑1.8.0. Start the console with: java -jar sentinel-dashboard-1.8.0.jar Default port is 8080, default username and password are sentinel. To change the port add -Dserver.port=9999 before the command.

Usage introduction

The most common scenario is adding flow‑control rules for API interfaces. Sentinel also supports RestTemplate and OpenFeign.

Simple example

1. Import dependencies

Add the Maven dependency for the Sentinel client:

<dependency>
  <groupId>com.alibaba.cloud</groupId>
  <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>

Version properties for Spring Boot, Spring Cloud, and Spring Cloud Alibaba:

<properties>
  <spring-boot.version>2.3.10.RELEASE</spring-boot.version>
  <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
  <spring-cloud-alibaba.version>2.2.5.RELEASE</spring-cloud-alibaba.version>
</properties>
<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-dependencies</artifactId>
      <version>${spring-boot.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-dependencies</artifactId>
      <version>${spring-cloud.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    <dependency>
      <groupId>com.alibaba.cloud</groupId>
      <artifactId>spring-cloud-alibaba-dependencies</artifactId>
      <version>${spring-cloud-alibaba.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

2. YML configuration

Register the service with the dashboard in application.yml:

spring:
  cloud:
    sentinel:
      transport:
        port: 8719
        dashboard: localhost:8080

3. Test interface definition

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String hello() {
        return "OK";
    }
}

4. Configure flow rule via console

In the dashboard select the service, go to the "Cluster Link" menu, choose the /hello interface, and click the "Flow Control" button. Set the rule type to QPS and the threshold to 1, meaning the interface can handle only one request per second. When the limit is exceeded Sentinel returns "Blocked by Sentinel (flow limiting)".

Configuration screenshots:

5. Flow rule trigger

Repeatedly calling /hello triggers the rule:

~ curl http://127.0.0.1:8066/hello
OK
~ curl http://127.0.0.1:8066/hello
Blocked by Sentinel (flow limiting)

Integrate RestTemplate

1. YML configuration

resttemplate:
  sentinel:
    enabled: true

2. Create RestTemplate

@Configuration
public class RestTemplateConfig {
    @Bean
    @ConditionalOnMissingBean(RestTemplate.class)
    @LoadBalanced
    @SentinelRestTemplate(blockHandler = "handlerException", blockHandlerClass = SentinelExceptionHandler.class,
                         fallback = "handleFallback", fallbackClass = SentinelExceptionHandler.class)
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

public class SentinelExceptionHandler {
    public static SentinelClientHttpResponse handlerException(HttpRequest request, byte[] body,
        ClientHttpRequestExecution execution, BlockException ex) {
        String message = JSON.toJSONString(CommonResult.error(-100, "系统错误 (限流熔断业务逻辑)"));
        return new SentinelClientHttpResponse(message);
    }
    public static SentinelClientHttpResponse handleFallback(HttpRequest request, byte[] body,
        ClientHttpRequestExecution execution, BlockException ex) {
        String message = JSON.toJSONString(CommonResult.error(-100, "系统错误 (异常降级业务逻辑)"));
        return new SentinelClientHttpResponse(message);
    }
}

3. Interface definition

Example code that calls stock-service via RestTemplate and wraps the result:

@Autowired
private RestTemplate restTemplate;
@GetMapping("/hello2")
public CommonResult<OrderModel> hello2() {
    ParameterizedTypeReference<CommonResult<StockModel>> typeRef = new ParameterizedTypeReference<>() {};
    ResponseEntity<CommonResult<StockModel>> forEntity = restTemplate.exchange(
        "http://stock-service/getStockDetail", HttpMethod.GET, HttpEntity.EMPTY, typeRef);
    OrderModel orderModel = new OrderModel();
    orderModel.setId(100);
    orderModel.setCode("100-100");
    if (Objects.equals(forEntity.getStatusCode(), HttpStatus.OK) && Objects.nonNull(forEntity.getBody())) {
        CommonResult<StockModel> result = forEntity.getBody();
        if (result.getCode() != 1) {
            return CommonResult.error(null, result.getCode(), result.getMessage());
        }
        orderModel.setStockModel(result.getData());
    }
    return CommonResult.success(orderModel);
}

4. Flow trigger

~ curl http://127.0.0.1:8066/hello2
{"code":1,"message":"this is a success message","data":{"id":100,"code":"100-100","stockModel":{"id":1,"code":"STOCK==>1000"}}}
~ curl http://127.0.0.1:8066/hello2
{"code":-100,"message":"系统错误 (限流熔断业务逻辑)","data":null}

Integrate OpenFeign

1. Import OpenFeign dependency

<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

2. YML configuration

feign:
  sentinel:
    enabled: true

Add @EnableFeignClients to the main application class to enable OpenFeign.

3. Feign client definition

@FeignClient(name = "stock-service", fallbackFactory = StockFeignFallbackFactory.class)
public interface StockFeign {
    @GetMapping("/getStockDetail")
    CommonResult<StockModel> getStockDetail();
}

4. Fallback factory

@Component
public class StockFeignFallbackFactory implements FallbackFactory<StockFeign> {
    private Logger log = LoggerFactory.getLogger(StockFeignFallbackFactory.class);
    @Override
    public StockFeign create(Throwable throwable) {
        return new StockFeign() {
            @Override
            public CommonResult<StockModel> getStockDetail() {
                log.error("调用查询库存详情降级", throwable);
                return CommonResult.error(null, -100, "调用查询库存详情降级");
            }
        };
    }
}

5. Controller usage

@Autowired
private StockFeign stockFeign;
@GetMapping("/hello1")
public CommonResult<OrderModel> hello() {
    CommonResult<StockModel> result = stockFeign.getStockDetail();
    if (result.getCode() != 1) {
        return CommonResult.error(null, result.getCode(), result.getMessage());
    }
    StockModel stockDetail = result.getData();
    OrderModel orderModel = new OrderModel();
    orderModel.setStockModel(stockDetail);
    return CommonResult.success(orderModel);
}

6. Business execution

Repeated calls to /hello1 trigger the fallback:

~ curl http://127.0.0.1:8066/hello1
{"code":1,"message":"this is a success message","data":{"id":null,"code":null,"stockModel":{"id":1,"code":"STOCK==>1000"}}}
~ curl http://127.0.0.1:8066/hello1
{"code":-100,"message":"调用查询库存详情降级","data":null}

Source code address

gitee: https://gitee.com/zhengsh/excavator

References

https://spring-cloud-alibaba-group.github.io/github-pages/hoxton/en-us/index.html#_spring_cloud_alibaba_sentinel https://segmentfault.com/a/1190000019070557