1. Overview

1.1 Plugin Name

• Sentinel Plugin

1.2 Appropriate Scenario

• Sentinel is one of the options that supports flow control and circuit breaking.
• Sentinel supports flow control and circuit breaking functions for gateway.

1.3 Plugin functionality

• flow control
• request circuit breaker and service degrade

1.4 Plugin code

• Core Module shenyu-plugin-sentinel.

• Core Class org.apache.shenyu.plugin.sentinel.SentinelPlugin

1.5 Added Since Which shenyu version

• Since 2.4.0

2. How to use plugin

2.1 Plugin-use procedure chart

2.2 Import pom

• Add sentinel dependency in the pom.xml file of the gateway(shenyu-bootstrap).

<!-- apache shenyu sentinel plugin start--><dependency>  <groupId>org.apache.shenyu</groupId>  <artifactId>shenyu-spring-boot-starter-plugin-sentinel</artifactId>  <version>${project.version}</version></dependency><!-- apache shenyu sentinel plugin end-->

2.3 Enable plugin

• In shenyu-admin--> BasicConfig --> Plugin --> sentinel set to enable.

2.4 Config plugin

2.4.1 Plugin configuration

2.4.2 Selector configuration

It is used to filter traffic for the first time and does not require handle fields.

2.4.3 Rule configuration

For the final filtering of traffic, there is a rule handler logic.

field	default value	field type	desc
degradeRuleCount		Doule	degrade threshold
degradeRuleEnable	1(enabled)	Integer	whether enable circuit breaking function of sentinel
degradeRuleGrade	0(slow call ratio)	Integer	circuit breaker strategy, support RT of seconds level/ Error Ratio of seconds level/ Error Count of minutes level strategy
degradeRuleMinRequestAmount	5	Integer	circuit breaker min request amount
degradeRuleSlowRatioThreshold	1.0d	Double	slow ratio threshold of degrading
degradeRuleStatIntervals	1	Integer	status intervals of degrade
degradeRuleTimeWindow		Integer	time of degrading(unit: second)
flowRuleControlBehavior	0(direact reject)	Integer	effect(reject directly/ queue/ slow start up), it do not support flow control by invocation relation.
flowRuleControlBehavior-direct rejection by default
flowRuleControlBehavior-warm up
flowRuleControlBehavior-constant speed queuing
flowRuleControlBehavior-preheating uniformly queued
flowRuleMaxQueueingTimeMs	500ms	Integer	Maximum queuing time (valid in "preheating uniformly queued", "constant speed queuing" mode)
flowRuleWarmUpPeriodSec	10	Integer	Cold start warm-up time (seconds) (valid in "preheating uniformly queued" "warm up" mode)
flowRuleCount		Integer	sentinel flow control count
flowRuleEnable	1(enabled)	Integer	whether enable sentinel flow control function.
flowRuleGrade	1(QPS)	Integer	type of current limit threshold(QPS or Thread Count)。
fallbackUri		String	degraded uri after circuit breaking.

2.5 Examples

2.5.1 Using sentinel for flow control

2.5.1.1 Plugin configuration

For more information on selectors and rules configuration, see Selector And Rule Config , only some of the fields are covered here.

• In shenyu-admin--> BasicConfig --> Plugin --> sentinel set to enable.

2.5.1.2 Selector configuration

2.5.1.3 Rule configuration

just use qps flow control strategy, and qps is 10, reject strategy is directly reject.

the code is as follows:

@RestController@RequestMapping("/order")@ShenyuSpringMvcClient("/order")public class OrderController {
    /**     * Save order dto.     *     * @param orderDTO the order dto     * @return the order dto     */    @PostMapping("/save")    @ShenyuSpringMvcClient("/save")    public OrderDTO save(@RequestBody final OrderDTO orderDTO) {        orderDTO.setName("hello world save order");        return orderDTO;    }}

2.5.1.4 request by Apache Jmeter

• Jmeter thead group config

• Jmeter http request config

2.5.1.5 Check result

2.5.2 Using sentinel for request circuit breaker

2.5.2.1 Plugin configuration

• In shenyu-admin--> BasicConfig --> Plugin --> sentinel set to enable.

2.5.2.2 Selector configuration

2.5.2.3 Rule configuration

when degrade strategy is exception number, degradeRuleSlowRatioThreshold is not effective. When the minimum number of requests per unit of time is 5, and the request happens exception great than 3, it will trigger the circuit breaker.

when degrade strategy is slow call ratio, degradeRuleSlowRatioThreshold is effective, degradeRuleCount means RT(e.g. 200).

the code is as follows:

@RestController@RequestMapping("/order")@ShenyuSpringMvcClient("/order")public class OrderController {
    /**     * Save order dto.     *     * @param orderDTO the order dto     * @return the order dto     */    @PostMapping("/save")    @ShenyuSpringMvcClient("/save")    public OrderDTO save(@RequestBody final OrderDTO orderDTO) {
        Random random = new Random();        int num = random.nextInt(100);        if (num > 40) {            throw new RuntimeException("num great than 20");        }        orderDTO.setName("hello world save order");        return orderDTO;    }
}

2.5.2.4 request by Apache Jmeter

• Jmeter thead group config

• Jmeter http request config

2.5.2.5 Check result

3. How to disable plugin

• In shenyu-admin --> BasicConfig --> Plugin --> sentinel set Status disable.