Version: 2021.0.4.0

Advanced Guide

Sentinel Console

Sentinel provides out-of-the-box consoles: Sentinel Dashboard

There are 3 steps to enable this feature:

Get console

You can download the latest version of the console jar package from the Release page.

You can also build Sentinel Console yourself from the latest version of the source code:

Download Dashboard project.
Package the code into a fat jar with the following command:
```
$ mvn clean package
```

Start the console

The Sentinel console is a standard Spring Boot application, just run the jar package in the Spring Boot way.

$ java -Dserver.port=8080 -Dcsp.sentinel.dashboard.server=localhost:8080 -Dproject.name=sentinel-dashboard -jar sentinel-dashboard.jar

If port 8080 conflicts, use -Dserver.port=new port to set it.

In the application configuration file, add the following console configuration information:

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

The spring.cloud.sentinel.transport.port port configuration here will start an Http Server on the machine corresponding to the application, which will interact with the Sentinel console. For example, if a current limiting rule is added to the Sentinel console, the rule data will be pushed to the Http Server for reception, and the Http Server will then register the rule in Sentinel.

For more usage and problems of Sentinel console, please refer to Sentinel Console.

Client support

The Sentinel-related Starter provided by Spring Cloud Alibaba provides adaptation support for mainstream client components such as OpenFeign and RestTemplate in the Spring Cloud ecosystem.

OpenFeign

spring-cloud-starter-alibaba-sentinel is adapted to the OpenFeign component. If you want to use it, in addition to introducing the necessary Starter dependencies, you also need to enable sentinel's support for feign in the configuration file: feign.sentinel.enabled=true.

Here is a simple usage example of FeignClient:

@FeignClient(name = "service-provider", fallback = EchoServiceFallback.class, configuration = FeignConfiguration.class)
public interface EchoService {
     @GetMapping(value = "/echo/{str}")
     String echo(@PathVariable("str") String str);
}

class FeignConfiguration {
     @Bean
     public EchoServiceFallback echoServiceFallback() {
         return new EchoServiceFallback();
     }
}

class EchoServiceFallback implements EchoService {
     @Override
     public String echo(@PathVariable("str") String str) {
         return "echo fallback";
     }
}

NOTE: The resource name policy definition in the interface corresponding to Feign: httpmethod:protocol://requesturl. All attributes in the @FeignClient annotation are compatible with Sentinel.

The name of the resource corresponding to the method echo in the EchoService interface is GET:http://service-provider/echo/{str}.

RestTemplate

spring-cloud-starter-alibaba-sentinel supports using Sentinel to protect RestTemplate service calls. When constructing a RestTemplate bean, you need to add the @SentinelRestTemplate annotation.

@Bean
@SentinelRestTemplate(blockHandler = "handleException", blockHandlerClass = ExceptionUtil.class)
public RestTemplate restTemplate() {
     return new RestTemplate();
}

The properties of the @SentinelRestTemplate annotation support the processing of current limiting (blockHandler, blockHandlerClass) and degradation (fallback, fallbackClass).

The method corresponding to the blockHandler or fallback attribute must be a static method in the corresponding blockHandlerClass or fallbackClass attribute.

The parameters and return value of this method are consistent with the org.springframework.http.client.ClientHttpRequestInterceptor#interceptor method, and the parameter has an additional BlockException parameter to obtain the exception caught by Sentinel.

For example, the method declaration corresponding to the handleException attribute of ExceptionUtil in the above @SentinelRestTemplate annotation is as follows:

public class ExceptionUtil {
     public static ClientHttpResponse handleException(HttpRequest request, byte[] body, ClientHttpRequestExecution execution, BlockException exception) {
         ...
     }
}

NOTE: When the application starts, it will check whether the current limiting or downgrading method corresponding to the @SentinelRestTemplate annotation exists, and an exception will be thrown if it does not exist

The current limiting (blockHandler, blockHandlerClass) and downgrading (fallback, fallbackClass) attributes of the @SentinelRestTemplate annotation are not mandatory.

When the RestTemplate call is broken by Sentinel, it will return the RestTemplate request block by sentinel information, or you can write the corresponding method to process the returned information by yourself. SentinelClientHttpResponse is provided here for constructing return information.

The resource rules of Sentinel RestTemplate current limiting provide two granularities:

httpmethod:schema://host:port/path: protocol, host, port and path
httpmethod:schema://host:port: protocol, host and port

NOTE: Take the url https://www.taobao.com/test and use the GET method as an example. The corresponding resource names have two granularities, namely GET:https://www.taobao.com and GET:https://www.taobao.com/test.

Dynamic data source support

SentinelProperties internally provides the datasource property of TreeMap type for configuring data source information.

For example, configure 4 data sources:

spring.cloud.sentinel.datasource.ds1.file.file=classpath: degraderule.json
spring.cloud.sentinel.datasource.ds1.file.rule-type=flow

#spring.cloud.sentinel.datasource.ds1.file.file=classpath: flowrule.json
#spring.cloud.sentinel.datasource.ds1.file.data-type=custom
#spring.cloud.sentinel.datasource.ds1.file.converter-class=org.springframework.cloud.alibaba.cloud.examples.JsonFlowRuleListConverter
#spring.cloud.sentinel.datasource.ds1.file.rule-type=flow

spring.cloud.sentinel.datasource.ds2.nacos.server-addr=127.0.0.1:8848
spring.cloud.sentinel.datasource.ds2.nacos.data-id=sentinel
spring.cloud.sentinel.datasource.ds2.nacos.group-id=DEFAULT_GROUP
spring.cloud.sentinel.datasource.ds2.nacos.data-type=json
spring.cloud.sentinel.datasource.ds2.nacos.rule-type=degrade

spring.cloud.sentinel.datasource.ds3.zk.path=/Sentinel-Demo/SYSTEM-CODE-DEMO-FLOW
spring.cloud.sentinel.datasource.ds3.zk.server-addr=localhost:2181
spring.cloud.sentinel.datasource.ds3.zk.rule-type=authority

spring.cloud.sentinel.datasource.ds4.apollo.namespace-name=application
spring.cloud.sentinel.datasource.ds4.apollo.flow-rules-key=sentinel
spring.cloud.sentinel.datasource.ds4.apollo.default-flow-rule-value=test
spring.cloud.sentinel.datasource.ds4.apollo.rule-type=param-flow

This configuration method refers to the configuration of Spring Cloud Stream Binder, which uses TreeMap for storage internally, and the comparator is String.CASE_INSENSITIVE_ORDER.

NOTE: d1, ds2, ds3, ds4 are the names of ReadableDataSource and can be freely written. The following file, zk, nacos, and apollo correspond to specific data sources. The configuration behind them is the respective configuration of these specific data sources.

Each data source has two common configuration items: data-type, converter-class and rule-type.

The data-type configuration item indicates the Converter type. Spring Cloud Alibaba Sentinel provides two built-in values by default, namely json and xml (if not filled, the default is json). If you don't want to use the built-in json or xml Converter, you can fill in custom to represent the custom Converter, and then configure the converter-class configuration item, which needs to write the full path name of the class (such as spring.cloud.sentinel.datasource. ds1.file.converter-class=org.springframework.cloud.alibaba.cloud.examples.JsonFlowRuleListConverter).

The rule-type configuration indicates which type of rules the rules in the data source belong to (flow, degrade, authority, system, param-flow, gw-flow, gw-api-group).

NOTE: When a data source rule information fails to load, it will not affect the startup of the application, and an error message will be printed in the log.

NOTE: By default, xml format is not supported. It will take effect automatically after adding jackson-dataformat-xml dependency.

For the implementation principle of Sentinel dynamic data source, refer to: [Dynamic rule extension](https://github.com/alibaba/Sentinel/wiki/%E5%8A%A8%E6%80%81%E8%A7%84% E5%88%99%E6%89%A9%E5%B1%95).

Spring Cloud Gateway support

Refer to Sentinel Gateway Current Limiting.

If you want to use it with Sentinel Starter, you need to add the spring-cloud-alibaba-sentinel-gateway dependency, and you need to add the spring-cloud-starter-gateway dependency to make the Spring Cloud Gateway in the spring-cloud-alibaba-sentinel-gateway module The automatic configuration class takes effect:

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

Externally exposed Endpoint

Sentinel provides an Endpoint internally, and the corresponding endpoint id is sentinel.

The json exposed by Endpoint contains various properties:

appName: application name
logDir: the directory where the log is located
logUsePid: whether to carry the process id in the log file name
blockPage: The page to be redirected after the current limiting block
metricsFileSize: The size of the metrics file
metricsFileCharset: the character set corresponding to the metrics file
totalMetricsFileCount: the maximum number of files retained by metrics
consoleServer: sentinel dashboard address
clientIp: client ip
heartbeatIntervalMs: heartbeat interval between client and dashboard
clientPort: The port that the client needs to expose to interact with the dashboard
coldFactor: cold start factor
filter: CommonFilter related attributes, such as order, urlPatterns and enable
datasource: the data source information configured by the client
rules: rules that take effect on the client side, including flowRules, degradeRules, systemRules, authorityRule, paramFlowRule

Here is an example of json exposed by Endpoint:

{
  "blockPage": null,
  "appName": "sentinel-example",
  "consoleServer": "localhost:8080",
  "coldFactor": "3",
  "rules": {
    "flowRules": [
      {
        "resource": "GET:http://www.taobao.com",
        "limitApp": "default",
        "grade": 1,
        "count": 0.0,
        "strategy": 0,
        "refResource": null,
        "controlBehavior": 0,
        "warmUpPeriodSec": 10,
        "maxQueueingTimeMs": 500,
        "clusterMode": false,
        "clusterConfig": null
      },
      {
        "resource": "/test",
        "limitApp": "default",
        "grade": 1,
        "count": 0.0,
        "strategy": 0,
        "refResource": null,
        "controlBehavior": 0,
        "warmUpPeriodSec": 10,
        "maxQueueingTimeMs": 500,
        "clusterMode": false,
        "clusterConfig": null
      },
      {
        "resource": "/hello",
        "limitApp": "default",
        "grade": 1,
        "count": 1.0,
        "strategy": 0,
        "refResource": null,
        "controlBehavior": 0,
        "warmUpPeriodSec": 10,
        "maxQueueingTimeMs": 500,
        "clusterMode": false,
        "clusterConfig": null
      }
    ]
  },
  "metricsFileCharset": "UTF-8",
  "filter": {
    "order": -2147483648,
    "urlPatterns": ["/*"],
    "enabled": true
  },
  "totalMetricsFileCount": 6,
  "datasource": {
    "ds1": {
      "file": {
        "dataType": "json",
        "ruleType": "FLOW",
        "converterClass": null,
        "file": "...",
        "charset": "utf-8",
        "recommendRefreshMs": 3000,
        "bufSize": 1048576
      },
      "nacos": null,
      "zk": null,
      "apollo": null,
      "redis": null
    }
  },
  "clientIp": "30.5.121.91",
  "clientPort": "8719",
  "logUsePid": false,
  "metricsFileSize": 52428800,
  "logDir": "...",
  "heartbeatIntervalMs": 10000
}

More configuration items

The following table shows that when there is a corresponding bean type in the ApplicationContext of the application, automatic settings will be performed:

Type of Bean	Operation	Function
UrlCleaner	WebCallbackManager.setUrlCleaner(urlCleaner)	Resource cleaning (resources (for example, all URLs satisfying /foo/:id are grouped under /foo/* resources))
UrlBlockHandler	WebCallbackManager.setUrlBlockHandler(urlBlockHandler)	Custom flow limit processing logic
RequestOriginParser	WebCallbackManager.setRequestOriginParser(requestOriginParser)	Set source information

Spring Cloud Alibaba Sentinel provides these configuration options:

Configuration Item	key	Default Value	Description
project name	spring.application.name or project.name	application	Sentinel project name
Automatic configuration	spring.cloud.sentinel.enabled	true	Whether Sentinel is effective
Sentinel initialization	spring.cloud.sentinel.eager	false	Whether to trigger Sentinel initialization in advance
Sentinel Console Interaction Port	spring.cloud.sentinel.transport.port	8719	The port used by the application to interact with the Sentinel console, the application will locally start a HttpServer occupied by this port
Console address	spring.cloud.sentinel.transport.dashboard	8719	Sentinel console address
Heartbeat interval	spring.cloud.sentinel.transport.heartbeat-interval-ms		Heartbeat interval between application and Sentinel console
Registration IP	spring.cloud.sentinel.transport.client-ip		The client IP of this configuration will be registered to the Sentinel Server
Filter Loading Order	spring.cloud.sentinel.filter.order		The loading order of Servlet Filter. The filter will be constructed inside the Starter
url pattern collection	spring.cloud.sentinel.filter.url-patterns		The data type is an array. Represents the url pattern collection of Servlet Filter
Whether to enable CommonFilter	spring.cloud.sentinel.filter.enabled	true	Enable to instance CommonFilter
metric file character set	spring.cloud.sentinel.metric.charset		metric file character set
metric single file size	spring.cloud.sentinel.metric.file-single-size		Sentinel metric single file size
metric total file count	spring.cloud.sentinel.metric.file-total-count		metric total file count
Log file path	spring.cloud.sentinel.log.dir		Directory where Sentinel log files are located
Whether to append the log PID	spring.cloud.sentinel.log.switch-pid	false	Whether the Sentinel log file name needs to carry the pid
Redirect URL	spring.cloud.sentinel.servlet.block-page		Customized redirect URL, when the request is limited, it will automatically redirect to the set URL
Cold start factor	spring.cloud.sentinel.flow.cold-factor		[Cold start factor](https://github.com/alibaba/Sentinel/wiki/%E9%99%90%E6%B5%81 ---%E5%86%B7%E5%90%AF%E5%8A%A8)
Response mode after fuse	spring.cloud.sentinel.scg.fallback.mode		Response mode after Spring Cloud Gateway fuse (choose redirect or response)
Redirect URL when it is redirect	spring.cloud.sentinel.scg.fallback.redirect		Spring Cloud Gateway response mode is the redirect URL corresponding to redirect mode
Response content redirected when it is response	spring.cloud.sentinel.scg.fallback.response-body		The response mode of Spring Cloud Gateway is the response content corresponding to the response mode
Response code for redirection when it is response	spring.cloud.sentinel.scg.fallback.response-status	429	The response mode of Spring Cloud Gateway is the response code corresponding to response mode
Content-Type redirected when it is response	spring.cloud.sentinel.scg.fallback.content-type	application/json	Spring Cloud Gateway response mode is the content-type corresponding to response mode

NOTE: Please note. These configurations will only take effect in the Servlet environment, and neither RestTemplate nor OpenFeign will take effect for these configurations.

Sentinel Console​

Get console​

Start the console​

Client support​

OpenFeign​

RestTemplate​

Dynamic data source support​

Spring Cloud Gateway support​

Externally exposed Endpoint​

More configuration items​