聊聊dubbo-go的gracefulShutdownFilter

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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
}

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
	})
}

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)
}

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
}

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
}

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)
}

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

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