Sentinel three flow control modes

Flow control mode

When adding a current limit rule , Click on advanced options , There are three options Flow control mode ：

Flow control mode	explain
direct	Count the requests for the current resource , When the threshold is triggered, the current resource is directly limited , It's also the default mode
relation	Count another resource related to the current resource , When the threshold is triggered , Limit the current resource
link	Count the requests to access this resource from the specified link , When the threshold is triggered , Limit the current of the specified link

For example, in the figure below, we are Sentinel View the cluster link in the console , Select any requested flow control , Choose advanced options , You can see the flow control mode ：

1. Direct mode

You can refer to the case of quick start test , This is the direct mode ：https://yangyongli.blog.csdn.net/article/details/125948236

2. Association patterns

Association patterns ： Count another resource related to the current resource , When the threshold is triggered , Limit the current resource

Configuration rules ：

Syntax description ： When /write When the resource access triggers the threshold , Would be right. /read Resource limiting , Avoid impact /write resources .

Use scenarios ： For example, the user needs to modify the order status when paying , At the same time, the user needs to query the order . Queries and modifications compete for database locks , Create competition . The business requirement is to give priority to paying and updating orders , Therefore, when modifying the order business trigger threshold , You need to limit the flow of the query order business .

Requirement specification ：

• stay OrderController Create two new endpoints ：/order/query and /order/update, No need to implement business

• Configure flow control rules , When /order/ update Resources are accessed QPS exceed 5 when , Yes /order/query Request current limiting

1） Definition /order/query Endpoint , Simulate order query

@GetMapping("/query")
public String queryOrder() {
    
    return " Order query succeeded ";
}

2） Definition /order/update Endpoint , Simulate order update

@GetMapping("/update")
public String updateOrder() {
    
    return " Update order succeeded ";
}

Restart the service , Access two requests

see sentinel Cluster point link of console ：

3） Configure flow control rules

Which end point is current limited , Just click the button behind which endpoint . We are inquiring about orders /order/query Current limiting , So click the button behind it ：

Fill in flow control rules in the form ：

If there is one more rule in the flow control rules, it will succeed ：

4） stay Jmeter test

Test flow control mode - relation ：

You can see 1000 Users ,100 second , therefore QPS by 10, Exceeded the threshold we set ：5

see http request ：

The goal of the request is /order/update, This breakpoint will trigger the threshold .

But the goal of current limiting is /order/query, We visit... In the browser , It can be found that the current is limited ：

When the update order request ends , We then visit the query request , succeed

5） summary

The association pattern can be used when the following conditions are met ：

• Two competing resources , For example, query and update in the above , Give priority to the update operation
• A higher priority , A lower priority .

3. Link mode

Link mode ： Statistics are only made for requests to access this resource from the specified link , Determine if the threshold is exceeded .

Configuration example ：

For example, there are two request links ：

• /test1 --> /common

• /test2 --> /common

If you only want statistics from /test2 Enter into /common Request , Then you can configure ：

Practical cases

demand ： There are businesses to query orders and create orders , Both need to query products . Statistics on requests from query orders to query goods , And set current limit .

step ：

1. stay OrderService Add a queryGoods Method , No need to implement business

2. stay OrderController in , reform /order/query Endpoint , call OrderService Medium queryGoods Method

3. stay OrderController Add a /order/save The endpoint of , call OrderService Of queryGoods Method

4. to queryGoods Set current limiting rules , from /order/query Get into queryGoods Method limitations QPS Must be less than 2

Realization ：

1） Add a method to query goods

stay order-service In service , to OrderService Class add a queryGoods Method ：

public void queryGoods(){
    
    System.err.println(" Query products ");
}

2） When inquiring about the order , Query products

stay order-service Of OrderController in , modify /order/query The business logic of the endpoint ：

@GetMapping("/query")
public String queryOrder() {
    
    //  Query products 
    orderService.queryGoods();
    //  Query order 
    System.out.println(" Query order ");
    return " Order query succeeded ";
}

3） New order , Query products

stay order-service Of OrderController in , modify /order/save Endpoint , Simulate new orders ：

@GetMapping("/save")
public String saveOrder() {
    
    //  Query products 
    orderService.queryGoods();
    //  Query order 
    System.err.println(" New order ");
    return " New order successfully ";
}

4） Add a resource tag to the query item

By default ,OrderService The method in is not to be Sentinel Monitored , We need our own annotations to mark the methods to be monitored .

to OrderService Of queryGoods Method add @SentinelResource annotation ：

@SentinelResource("goods")
public void queryGoods(){
    
    System.err.println(" Query products ");
}

In link mode , It monitors two links from different sources . however sentinel The default will be to enter SpringMVC Set the same... For all requests root resources , Will cause link mode failure .

We need to close this pair of SpringMVC Resource aggregation , modify order-service Service application.yml file ：

spring:
  cloud:
    sentinel:
      web-context-unify: false #  close context Integrate 

Restart the service , visit /order/query and /order/save, You can see that sentinel Cluster point link rules , New resources have emerged ：

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5） Add flow control rules

Click on goods The flow control button behind the resource , Fill in the following information in the pop-up form ：

Only statistics from /order/query Get into /goods Resources for ,QPS The threshold for 2, If it exceeds, it is limited by current .

6）Jmeter test

You can see here 200 Users ,50 Within seconds ,QPS（ Query rate per second ） by 4, Exceeded the threshold we set 2

One http The request is to access /order/save：

Result of operation , Completely unaffected ：

The other is to visit /order/query：

Running results , Every time only 2 through ：

summary

What are the flow control modes ？

Flow control mode	explain
direct	Count the requests for the current resource , When the threshold is triggered, the current resource is directly limited , It's also the default mode
relation	Count another resource related to the current resource , When the threshold is triggered , Limit the current resource
link	Count the requests to access this resource from the specified link , When the threshold is triggered , Limit the current of the specified link