聊聊dubbo-go的gracefulShutdownFilter

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

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
    })
}

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)
}

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
}

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

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)
}