聊聊dubbo-go的registryAwareCluster

type registryAwareCluster struct{}
​
func init() {
    extension.SetCluster("registryAware", NewRegistryAwareCluster)
}
​
// NewRegistryAwareCluster ...
func NewRegistryAwareCluster() cluster.Cluster {
    return &registryAwareCluster{}
}
​
func (cluster *registryAwareCluster) Join(directory cluster.Directory) protocol.Invoker {
    return newRegistryAwareClusterInvoker(directory)
}

type registryAwareClusterInvoker struct {
    baseClusterInvoker
}
​
func newRegistryAwareClusterInvoker(directory cluster.Directory) protocol.Invoker {
    return &registryAwareClusterInvoker{
        baseClusterInvoker: newBaseClusterInvoker(directory),
    }
}

func (invoker *registryAwareClusterInvoker) Invoke(ctx context.Context, invocation protocol.Invocation) protocol.Result {
    invokers := invoker.directory.List(invocation)
    //First, pick the invoker (XXXClusterInvoker) that comes from the local registry, distinguish by a 'default' key.
    for _, invoker := range invokers {
        if invoker.IsAvailable() && invoker.GetUrl().GetParam(constant.REGISTRY_DEFAULT_KEY, "false") == "true" {
            return invoker.Invoke(ctx, invocation)
        }
    }
​
    //If none of the invokers has a local signal, pick the first one available.
    for _, invoker := range invokers {
        if invoker.IsAvailable() {
            return invoker.Invoke(ctx, invocation)
        }
    }
    return nil
}