59 lines
2.2 KiB
Markdown
59 lines
2.2 KiB
Markdown
# Sentinel Parameter Flow Control
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This component provides functionality of flow control by frequent ("hot spot") parameters.
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## Usage
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To use Sentinel Parameter Flow Control, you need to add the following dependency to `pom.xml`:
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```xml
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<dependency>
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<groupId>com.alibaba.csp</groupId>
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<artifactId>sentinel-parameter-flow-control</artifactId>
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<version>x.y.z</version>
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</dependency>
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```
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First you need to pass parameters with the following `SphU.entry` overloaded methods:
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```java
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public static Entry entry(String name, EntryType type, int count, Object... args) throws BlockException
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public static Entry entry(Method method, EntryType type, int count, Object... args) throws BlockException
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```
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For example, if there are two parameters to provide, you can:
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```java
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// paramA in index 0, paramB in index 1.
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SphU.entry(resourceName, EntryType.IN, 1, paramA, paramB);
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```
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Then you can configure parameter flow control rules via `loadRules` method in `ParamFlowRuleManager`:
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```java
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// QPS mode, threshold is 5 for every frequent "hot spot" parameter in index 0 (the first arg).
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ParamFlowRule rule = new ParamFlowRule(RESOURCE_KEY)
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.setParamIdx(0)
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.setCount(5);
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// We can set threshold count for specific parameter value individually.
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// Here we add an exception item. That means: QPS threshold of entries with parameter `PARAM_B` (type: int)
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// in index 0 will be 10, rather than the global threshold (5).
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ParamFlowItem item = new ParamFlowItem().setObject(String.valueOf(PARAM_B))
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.setClassType(int.class.getName())
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.setCount(10);
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rule.setParamFlowItemList(Collections.singletonList(item));
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ParamFlowRuleManager.loadRules(Collections.singletonList(rule));
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```
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The description for fields of `ParamFlowRule`:
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| Field | Description | Default |
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| :----: | :----| :----|
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| resource| resource name (**required**) ||
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| count | flow control threshold (**required**) ||
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| grade | metric type (QPS or thread count) | QPS mode |
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| paramIdx | the index of provided parameter in `SphU.entry(xxx, args)` (**required**) ||
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| paramFlowItemList | the exception items of parameter; you can set threshold to a specific parameter value ||
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Now the parameter flow control rules will take effect. |