72 lines
3.9 KiB
Markdown
72 lines
3.9 KiB
Markdown
# Sentinel Dubbo Adapter
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> Note: 中文文档请见[此处](https://github.com/alibaba/Sentinel/wiki/主流框架的适配#dubbo)。
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Sentinel Dubbo Adapter provides service consumer filter and provider filter
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for [Dubbo](https://dubbo.apache.org/en-us/) services.
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**Note: This adapter only supports legacy Dubbo 2.6.x version and below.**
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For new Apache Dubbo 2.7.x or above version, please use `sentinel-apache-dubbo-adapter` module instead.
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To use Sentinel Dubbo Adapter, you can simply add the following dependency to your `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-dubbo-adapter</artifactId>
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<version>x.y.z</version>
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</dependency>
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```
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The Sentinel filters are **enabled by default**. Once you add the dependency,
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the Dubbo services and methods will become protected resources in Sentinel,
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which can leverage Sentinel's flow control and guard ability when rules are configured.
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Demos can be found in [sentinel-demo-dubbo](https://github.com/alibaba/Sentinel/tree/master/sentinel-demo/sentinel-demo-dubbo).
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If you don't want the filters enabled, you can manually disable them. For example:
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```xml
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<dubbo:consumer filter="-sentinel.dubbo.consumer.filter"/>
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<dubbo:provider filter="-sentinel.dubbo.provider.filter"/>
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```
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For more details of Dubbo filter, see [here](http://dubbo.apache.org/en-us/docs/dev/impls/filter.html).
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## Dubbo resources
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The resource for Dubbo services has two granularities: service interface and service method.
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- Service interface：resourceName format is `interfaceName`，e.g. `com.alibaba.csp.sentinel.demo.dubbo.FooService`
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- Service method：resourceName format is `interfaceName:methodSignature`，e.g. `com.alibaba.csp.sentinel.demo.dubbo.FooService:sayHello(java.lang.String)`
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## Flow control based on caller
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In many circumstances, it's also significant to control traffic flow based on the **caller**.
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For example, assuming that there are two services A and B, both of them initiate remote call requests to the service provider.
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If we want to limit the calls from service B only, we can set the `limitApp` of flow rule as the identifier of service B (e.g. service name).
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Sentinel Dubbo Adapter will automatically resolve the Dubbo consumer's *application name* as the caller's name (`origin`),
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and will bring the caller's name when doing resource protection.
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If `limitApp` of flow rules is not configured (`default`), flow control will take effects on all callers.
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If `limitApp` of a flow rule is configured with a caller, then the corresponding flow rule will only take effect on the specific caller.
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> Note: Dubbo consumer does not provide its Dubbo application name when doing RPC,
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> so developers should manually put the application name into *attachment* at consumer side,
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> then extract it at provider side. Sentinel Dubbo Adapter has implemented a filter (`DubboAppContextFilter`)
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> where consumer can carry application name information to provider automatically.
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> If the consumer does not use Sentinel Dubbo Adapter but requires flow control based on caller,
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> developers can manually put the application name into attachment with the key `dubboApplication`.
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>
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> Since 1.8.0, the adapter provides support for customizing origin parsing logic. You may register your own `DubboOriginParser`
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> implementation to `DubboAdapterGlobalConfig`.
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## Global fallback
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Sentinel Dubbo Adapter supports global fallback configuration.
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The global fallback will handle exceptions and give replacement result when blocked by
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flow control, degrade or system load protection. You can implement your own `DubboFallback` interface
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and then register to `DubboAdapterGlobalConfig`.
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If no fallback is configured, Sentinel will wrap the `BlockException` as the fallback result.
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Besides, we can also leverage [Dubbo mock mechanism](http://dubbo.apache.org/en-us/docs/user/demos/local-mock.html) to provide fallback implementation of degraded Dubbo services. |