Sentinel flow control quick start

flow control

Although there are four solutions to the avalanche problem , However, current limiting is to avoid service failure due to sudden traffic , It is the prevention of the avalanche of microservices .

Can prevent the best , So let's first introduce flow control ：

1. Cluster link

When requesting access to the microservice , First of all, I will visit DispatcherServlet（ Front controller ）, Then enter Controller、Service、Mapper, Such a call chain is called cluster [cù] Point link .

Each monitored interface in the cluster link is a resources .

By default sentinel Will monitor SpringMVC Every endpoint of （Endpoint, That is to say controller The method in ）, therefore SpringMVC Every endpoint of （Endpoint） Is to call a resource in the link .

Small expansion ：DispatcherServlet It's the front controller , Configure in web.xml In the document . Block matching requests ,Servlet The interception matching rules should be defined by themselves , Put the intercepted request , Distribute to the target... According to the corresponding rules Controller To deal with it , It's configuration spring MVC The first step .

DispatcherServlet It is the implementation of the design pattern of the front-end controller , Provide Spring Web MVC The central access point of , And responsible for the assignment of responsibilities , And with the Spring IoC Seamless integration of containers , So that you can get Spring All the benefits of .

for example , We visited order-service Medium OrderController Endpoint in ：/order/{orderId}

stay Sentinel There will be a display in the console （ No first visit , The request will not be displayed here ）

Flow control 、 Fusing, etc. are set for the resources in the cluster link , Therefore, we can click the button behind the corresponding resource to set the rules ：

The rules	explain
Flow control	flow control
Downgrade	Degraded fuse
hotspot	Hot spot parameter current limiting , It is a kind of current limiting
to grant authorization	Request permission control

Let's start with a quick start , Then explain the configuration of each rule in detail

2. Quick start

2.1. Example

Click resources /order/{orderId} The flow control button at the back , You can pop up a form .

Flow restriction rules can be filled in the form , as follows ：

It means to limit /order/{orderId} The stand-alone of this resource QPS by 1, That is, only 1 Requests , The exceeded request will be intercepted and an error will be reported .

If we ask too soon , He will control the flow , Show the access , For example, visit the browser with your life , It will return an error message

2.2. practice ：

demand ： to /order/{orderId} This resource sets flow control rules ,QPS No more than 5, Then test .

1） First, in the sentinel Add current limit rule to console

2） utilize jmeter test

Turn on 20 Thread access 20 Time

Set request information

20 Users ,2 Run... In seconds ,QPS yes 10, More than the 5.

Run the test

Be careful , Do not click the execute button in the menu to run .

result ：

You can see , Successful requests only... At a time 5 individual