Sentinel's quick start takes you through flow control in three minutes

What is flow control

Flow control is a common concept in network transmission , It is used to adjust the sending data of network packets . However , From the perspective of system stability , In terms of the speed of processing requests , There is also a lot of stress . Requests coming at any time are often random and uncontrollable , And the processing power of the system is limited . We need to control the flow according to the processing capacity of the system .Sentinel
As a tuner , You can adjust random requests to the right shape as needed , As shown in the figure below ：

Flow control design concept

Flow control has the following angles :

Resource call relationship , For example, the call link of resources , The relationship between resources ;

Operation index , for example QPS、 Thread pool 、 System load, etc ;

The effect of control , For example, direct current limiting 、 Cold start 、 Line up, etc .

Sentinel The design concept is to let you freely choose the angle of control , And flexible combination , So as to achieve the desired effect .

That's all , Let's take you to a quick experience sentinel, Check his effect .

First step , Create a springboot engineering

The second step , introduce sentinel rely on

 		<dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-core</artifactId>
            <version>1.7.2</version>
        </dependency>

The third step , To write TestController class

Step four , To write sentinel Related methods

 @PostConstruct
    public void initFlowRules() {
    

        List<FlowRule> rules = new ArrayList<>();

        FlowRule flowRule = new FlowRule();

        flowRule.setResource("testSentinel");

        flowRule.setGrade(RuleConstant.FLOW_GRADE_QPS);

        // Limit the current more than twice a second 
        flowRule.setCount(2);

        rules.add(flowRule);

        FlowRuleManager.loadRules(rules);
    }

@PostConstruct The purpose of this annotation is to TestController This method is called when the class is instantiated ,

flowRule.setCount(2);

This means that a request can only be called twice in a second

Step five , Write test methods

  @GetMapping("/hello")
    public String hello() {
    

        try(Entry entry =  SphU.entry("testSentinel")) {
    
            return "hello sentinel";
        } catch (BlockException e) {
    
            e.printStackTrace();
            return " The system is busy ";
        }


    }

Step six , Test our method

If we call normally ：

If we click more than twice in a second ：

Warehouse address ：

https://gitee.com/WangFuGui-Ma/sentinel-quickstart