[GitHub] [dubbo-go] DogBaoBao commented on a change in pull request #659: Ftr: Nearest first for multiple registry

[GitBox <gi...@apache.org>]

DogBaoBao commented on a change in pull request #659:
URL: https://github.com/apache/dubbo-go/pull/659#discussion_r462918881



##########
File path: cluster/cluster_impl/zone_aware_cluster_invoker.go
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cluster_impl
+
+import (
+	"context"
+	"fmt"
+)
+
+import (
+	"github.com/apache/dubbo-go/cluster"
+	"github.com/apache/dubbo-go/common/constant"
+	"github.com/apache/dubbo-go/protocol"
+)
+
+// When there're more than one registry for subscription.
+//
+// This extension provides a strategy to decide how to distribute traffics among them:
+// 1. registry marked as 'preferred=true' has the highest priority.
+// 2. check the zone the current request belongs, pick the registry that has the same zone first.
+// 3. Evenly balance traffic between all registries based on each registry's weight.
+// 4. Pick anyone that's available.
+type zoneAwareClusterInvoker struct {
+	baseClusterInvoker
+}
+
+func newZoneAwareClusterInvoker(directory cluster.Directory) protocol.Invoker {
+	return &zoneAwareClusterInvoker{
+		baseClusterInvoker: newBaseClusterInvoker(directory),
+	}
+}
+
+// nolint
+func (invoker *zoneAwareClusterInvoker) Invoke(ctx context.Context, invocation protocol.Invocation) protocol.Result {
+	invokers := invoker.directory.List(invocation)
+
+	err := invoker.checkInvokers(invokers, invocation)
+	if err != nil {
+		return &protocol.RPCResult{Err: err}
+	}
+
+	// First, pick the invoker (XXXClusterInvoker) that comes from the local registry, distinguish by a 'preferred' key.
+	for _, invoker := range invokers {
+		if invoker.IsAvailable() && "true" == invoker.GetUrl().GetParam(constant.REGISTRY_KEY+"."+constant.PREFERRED_KEY, "false") {

Review comment:
       ok, have some code format?




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