Skip to content

How to Use

Jump to bottom
jialianglinjl edited this page Jul 20, 2018 · 36 revisions

Introduction

There are mainly 2 steps to use Sentinel:

  1. Define resource
  2. Define rules

These two steps don’t have to be synchronized. As long as the resources are defined, you can add rules as necessary. Resources can be applied to multiple rules simultaneously.

Sentinel provides adaptions to popular frameworks as well. After introducing these adapters, services and methods provided by these framework are defined as resources by default.

Define Resource

"try" and "catch" mode

  Entry entry = null;
  try{   
      entry = SphU.entry("hellowrold");
    /**
    * code logic
    */
  } catch (BlockException e1) {
    //resource is rejected
    /**
    * logic to handle exception
    */
  }finally{
    if(entry != null){
      entry.exit();
    }
  }
}

Bool Mode

  if(SphO.entry("helloworld")){
    try {
      /**
      * code logic
      */
    } finally {
      SphO.exit();
    }
  }else{
    //resource is rejected
    /**
    * logic to handle exception
    */
  }
}

Adapters to Popular Frameworks

Details please check: Adapters to popular frameworks

Define Rules

Sentinel provides APIs for users to modify their rules which can be integrated with various kinds of rule repository, such as configuration server, sql, etc.

Definitions of Rule

There are 3 kinds：Flow control rule、Circuit breaking rule　and System protection rule。

Flow control rule (FlowRule)

Definition:

key fields：

field description default value
resource resource name, defined in entry()
count threshold
grade calculated by QPS or concurrent thread count QPS
limitApp refer to specified caller default
strategy by resource itself or other resource (refResource)，or entry (refResource) resource itself
controlBehavior reject directly，queue，slow start up reject directly

one resource can apply more than 1 rules

API

API:FlowRuleManager.loadRules() can be used to configure rules.

private static void initFlowQpsRule() {
        List<FlowRule> rules = new ArrayList<FlowRule>();
        FlowRule rule1 = new FlowRule();
        rule1.setResource(KEY);
        // set limit qps to 20
        rule1.setCount(20);
        rule1.setGrade(RuleConstant.FLOW_GRADE_QPS);
        rule1.setLimitApp("default");
        rules.add(rule1);
        FlowRuleManager.loadRules(rules);
    }

More details please refer to: Flow control

Circuit Break (DegradeRule)

Key fields:

field description default value
resource resource name
count threshold
grade by response time or exception ratio response time
timeWindow degrade time window

one resource can apply more than 1 rules

API

API:DegradeRuleManager.loadRules() can be used to configure rules.

 private static void initDegradeRule() {
        List<DegradeRule> rules = new ArrayList<DegradeRule>();
        DegradeRule rule = new DegradeRule();
        rule.setResource(KEY);
        // set threshold rt, 10 ms
        rule.setCount(10);
        rule.setGrade(RuleConstant.DEGRADE_GRADE_RT);
        rule.setTimeWindow(10);
        rules.add(rule);
        DegradeRuleManager.loadRules(rules);
    }

More details can refer to :Circuit Break

System protection rule (SystemRule)

Key factors

field description default value
highestSystemLoad threshold of Load1 -1(not valid)
avgRt average response time -1(not valid)
maxThread concurrent thread count -1(not valid)

API

API:SystemRuleManager.loadRules()

 private static void initDegradeRule() {
        List<SystemRule> rules = new ArrayList<SystemRule>();
        SystemRule rule = new SystemRule();
        rule.setHighestSystemLoad(10);
        rules.add(rule);
        DegradeRuleManager.loadRules(rules);
    }

More details you can refer to:System Protection

Manage Rules

Sentinel has provided HTTP commands to expose these rules.

To use these commands, make sure that following library has been introduced:

<dependency>
    <groupId>com.alibaba.csp</groupId>
    <artifactId>sentinel-transport-simple-http</artifactId>
    <version>x.y.z</version>
</dependency>

Query command:

curl http://localhost:8719/getRules?type=<XXXX>

type=flow for flow rules;type=degrade for circuit breaking rules;type=system for system protection rules. Rules will be returned in JSON format。

Modification command:

curl http://localhost:8719/setRules?type=<XXXX>&data=<DATA>

其中，type 可以输入 flow、degrade 等方式来制定更改的规则种类，data 则是对应的 JSON 格式的规则。

定制自己的持久化规则

上面的规则配置，都是出于内存状态的。即如果应用发生了重启，这个规则就会失效。我们提供了开放的接口。你可以通过实现 DataSource 的方式，来自定义自己的持久化规则。通常我们的建议有：

  1. 整合 Diamond，动态的实时刷新配置规则
  2. 结合 SQL、GitHub 等来实现该规则
  3. 配合 Dashboard 使用

更多的详情请参见: 动态规则配置

Clone this wiki locally