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50 lines
1.6 KiB
50 lines
1.6 KiB
5 years ago
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## 熔断器/Breaker
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熔断器是为了当依赖的服务已经出现故障时，主动阻止对依赖服务的请求。保证自身服务的正常运行不受依赖服务影响，防止雪崩效应。
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## kratos内置breaker的组件
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一般情况下直接使用kratos的组件时都自带了熔断逻辑，并且在提供了对应的breaker配置项。
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目前在kratos内集成熔断器的组件有:
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- RPC client: pkg/net/rpc/warden/client
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- Mysql client：pkg/database/sql
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- Tidb client：pkg/database/tidb
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- Http client：pkg/net/http/blademaster
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## 使用说明
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```go
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//初始化熔断器组
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//一组熔断器公用同一个配置项，可从分组内取出单个熔断器使用。可用在比如mysql主从分离等场景。
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brkGroup := breaker.NewGroup(&breaker.Config{})
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//为每一个连接指定一个breaker
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//此处假设一个客户端连接对象实例为conn
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//breakName定义熔断器名称 一般可以使用连接地址
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breakName = conn.Addr
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conn.breaker = brkGroup.Get(breakName)
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//在连接发出请求前判断熔断器状态
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if err = conn.breaker.Allow(); err != nil {
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return
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}
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//连接执行成功或失败将结果告知breaker
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if(respErr != nil){
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conn.breaker.MarkFailed()
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}else{
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conn.breaker.MarkSuccess()
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}
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```
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## 配置说明
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```go
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type Config struct {
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SwitchOff bool // 熔断器开关,默认关 false.
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K float64 //触发熔断的错误率（K = 1 - 1/错误率）
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Window xtime.Duration //统计桶窗口时间
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Bucket int //统计桶大小
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Request int64 //触发熔断的最少请求数量（请求少于该值时不会触发熔断）
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}
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```
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