聊聊dubbo-go的gracefulShutdownFilter

序

本文主要研究一下dubbo-go的gracefulShutdownFilter

gracefulShutdownFilter

dubbo-go-v1.4.2/filter/filter_impl/graceful_shutdown_filter.go

type gracefulShutdownFilter struct {
    activeCount    int32
    shutdownConfig *config.ShutdownConfig
}

• gracefulShutdownFilter定义了activeCount、shutdownConfig属性

init

dubbo-go-v1.4.2/filter/filter_impl/graceful_shutdown_filter.go

func init() {
    var consumerFiler = &gracefulShutdownFilter{
        shutdownConfig: config.GetConsumerConfig().ShutdownConfig,
    }
    var providerFilter = &gracefulShutdownFilter{
        shutdownConfig: config.GetProviderConfig().ShutdownConfig,
    }

    extension.SetFilter(constant.CONSUMER_SHUTDOWN_FILTER, func() filter.Filter {
        return consumerFiler
    })

    extension.SetFilter(constant.PROVIDER_SHUTDOWN_FILTER, func() filter.Filter {
        return providerFilter
    })
}

• init方法分别创建并设置了CONSUMER_SHUTDOWN_FILTER、PROVIDER_SHUTDOWN_FILTER

Invoke

dubbo-go-v1.4.2/filter/filter_impl/graceful_shutdown_filter.go

func (gf *gracefulShutdownFilter) Invoke(ctx context.Context, invoker protocol.Invoker, invocation protocol.Invocation) protocol.Result {
    if gf.rejectNewRequest() {
        logger.Info("The application is closing, new request will be rejected.")
        return gf.getRejectHandler().RejectedExecution(invoker.GetUrl(), invocation)
    }
    atomic.AddInt32(&gf.activeCount, 1)
    return invoker.Invoke(ctx, invocation)
}

• Invoke方法先判断gracefulShutdownFilter的rejectNewRequest是否为true，若为true则执行getRejectHandler().RejectedExecution，否则执行atomic.AddInt32及invoker.Invoke(ctx, invocation)

OnResponse

dubbo-go-v1.4.2/filter/filter_impl/graceful_shutdown_filter.go

func (gf *gracefulShutdownFilter) OnResponse(ctx context.Context, result protocol.Result, invoker protocol.Invoker, invocation protocol.Invocation) protocol.Result {
    atomic.AddInt32(&gf.activeCount, -1)
    // although this isn't thread safe, it won't be a problem if the gf.rejectNewRequest() is true.
    if gf.shutdownConfig != nil && gf.activeCount <= 0 {
        gf.shutdownConfig.RequestsFinished = true
    }
    return result
}

• OnResponse方法先执行atomic.AddInt32(&gf.activeCount, -1)，之后判断gf.activeCount是否小于等于0，是的话则标记gf.shutdownConfig.RequestsFinished为true

rejectNewRequest

dubbo-go-v1.4.2/filter/filter_impl/graceful_shutdown_filter.go

func (gf *gracefulShutdownFilter) rejectNewRequest() bool {
    if gf.shutdownConfig == nil {
        return false
    }
    return gf.shutdownConfig.RejectRequest
}

• rejectNewRequest方法在shutdownConfig为nil是返回false，否则返回gf.shutdownConfig.RejectRequest的值

getRejectHandler

dubbo-go-v1.4.2/filter/filter_impl/graceful_shutdown_filter.go

func (gf *gracefulShutdownFilter) getRejectHandler() filter.RejectedExecutionHandler {
    handler := constant.DEFAULT_KEY
    if gf.shutdownConfig != nil && len(gf.shutdownConfig.RejectRequestHandler) > 0 {
        handler = gf.shutdownConfig.RejectRequestHandler
    }
    return extension.GetRejectedExecutionHandler(handler)
}

• getRejectHandler方法在gf.shutdownConfig不为nil且gf.shutdownConfig.RejectRequestHandler长度大于0时设置handler值为gf.shutdownConfig.RejectRequestHandler，之后根据该值执行extension.GetRejectedExecutionHandler

小结

gracefulShutdownFilter定义了activeCount、shutdownConfig属性；其Invoke方法先判断gracefulShutdownFilter的rejectNewRequest是否为true，若为true则执行getRejectHandler().RejectedExecution，否则执行atomic.AddInt32及invoker.Invoke(ctx, invocation)；其OnResponse方法先执行atomic.AddInt32(&gf.activeCount, -1)，之后判断gf.activeCount是否小于等于0，是的话则标记gf.shutdownConfig.RequestsFinished为true

doc

• graceful_shutdown_filter