make cluster interceptor a chain

cluster/cluster_impl/available_cluster.go

@@ -40,5 +40,5 @@ func NewAvailableCluster() cluster.Cluster {
 
 // Join returns a baseClusterInvoker instance
 func (cluster *availableCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return NewAvailableClusterInvoker(directory)
+	return buildInterceptorChain(NewAvailableClusterInvoker(directory))
 }

cluster/cluster_impl/base_cluster_invoker.go

@@ -17,10 +17,6 @@
 
 package cluster_impl
 
-import (
-	"context"
-)
-
 import (
 	perrors "github.com/pkg/errors"
 	"go.uber.org/atomic"
@@ -40,7 +36,6 @@ type baseClusterInvoker struct {
 	availablecheck bool
 	destroyed      *atomic.Bool
 	stickyInvoker  protocol.Invoker
-	interceptor    cluster.ClusterInterceptor
 }
 
 func newBaseClusterInvoker(directory cluster.Directory) baseClusterInvoker {
@@ -165,20 +160,6 @@ func (invoker *baseClusterInvoker) doSelectInvoker(lb cluster.LoadBalance, invoc
 	return nil
 }
 
-func (invoker *baseClusterInvoker) Invoke(ctx context.Context, invocation protocol.Invocation) protocol.Result {
-	if invoker.interceptor != nil {
-		invoker.interceptor.BeforeInvoker(ctx, invocation)
-
-		result := invoker.interceptor.DoInvoke(ctx, invocation)
-
-		invoker.interceptor.AfterInvoker(ctx, invocation)
-
-		return result
-	}
-
-	return nil
-}
-
 func isInvoked(selectedInvoker protocol.Invoker, invoked []protocol.Invoker) bool {
 	for _, i := range invoked {
 		if i == selectedInvoker {

cluster/cluster_impl/broadcast_cluster.go

@@ -41,5 +41,5 @@ func NewBroadcastCluster() cluster.Cluster {
 
 // Join returns a baseClusterInvoker instance
 func (cluster *broadcastCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return newBroadcastClusterInvoker(directory)
+	return buildInterceptorChain(newBroadcastClusterInvoker(directory))
 }

cluster/cluster_impl/failback_cluster.go

@@ -41,5 +41,5 @@ func NewFailbackCluster() cluster.Cluster {
 
 // Join returns a baseClusterInvoker instance
 func (cluster *failbackCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return newFailbackClusterInvoker(directory)
+	return buildInterceptorChain(newFailbackClusterInvoker(directory))
 }

cluster/cluster_impl/failfast_cluster.go

@@ -41,5 +41,5 @@ func NewFailFastCluster() cluster.Cluster {
 
 // Join returns a baseClusterInvoker instance
 func (cluster *failfastCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return newFailFastClusterInvoker(directory)
+	return buildInterceptorChain(newFailFastClusterInvoker(directory))
 }

cluster/cluster_impl/failover_cluster.go

@@ -41,5 +41,5 @@ func NewFailoverCluster() cluster.Cluster {
 
 // Join returns a baseClusterInvoker instance
 func (cluster *failoverCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return newFailoverClusterInvoker(directory)
+	return buildInterceptorChain(newFailoverClusterInvoker(directory))
 }

cluster/cluster_impl/failsafe_cluster.go

@@ -41,5 +41,5 @@ func NewFailsafeCluster() cluster.Cluster {
 
 // Join returns a baseClusterInvoker instance
 func (cluster *failsafeCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return newFailsafeClusterInvoker(directory)
+	return buildInterceptorChain(newFailsafeClusterInvoker(directory))
 }

cluster/cluster_impl/forking_cluster.go

@@ -41,5 +41,5 @@ func NewForkingCluster() cluster.Cluster {
 
 // Join returns a baseClusterInvoker instance
 func (cluster *forkingCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return newForkingClusterInvoker(directory)
+	return buildInterceptorChain(newForkingClusterInvoker(directory))
 }

cluster/cluster_impl/interceptor_invoker.go

@@ -0,0 +1,76 @@
+/*
+ * 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"
+)
+
+import (
+	"dubbo.apache.org/dubbo-go/v3/cluster"
+	"dubbo.apache.org/dubbo-go/v3/common"
+	"dubbo.apache.org/dubbo-go/v3/common/extension"
+	"dubbo.apache.org/dubbo-go/v3/protocol"
+)
+
+// InterceptorInvoker mocks cluster interceptor as an invoker
+type InterceptorInvoker struct {
+	next        protocol.Invoker
+	interceptor cluster.Interceptor
+}
+
+// GetURL is used to get url from InterceptorInvoker
+func (i *InterceptorInvoker) GetURL() *common.URL {
+	return i.next.GetURL()
+}
+
+// IsAvailable is used to get available status
+func (i *InterceptorInvoker) IsAvailable() bool {
+	return i.next.IsAvailable()
+}
+
+// Invoke is used to call service method by invocation
+func (i *InterceptorInvoker) Invoke(ctx context.Context, invocation protocol.Invocation) protocol.Result {
+	return i.interceptor.Invoke(ctx, i.next, invocation)
+}
+
+// Destroy will destroy invoker
+func (i *InterceptorInvoker) Destroy() {
+	i.next.Destroy()
+}
+
+func buildInterceptorChain(invoker protocol.Invoker, builtins ...cluster.Interceptor) protocol.Invoker {
+	// The order of interceptors is from left to right, so loading from right to left
+	next := invoker
+	interceptors := extension.GetClusterInterceptors()
+	if len(interceptors) != 0 {
+		for i := len(interceptors) - 1; i >= 0; i-- {
+			v := &InterceptorInvoker{next: next, interceptor: interceptors[i]}
+			next = v
+		}
+	}
+
+	if builtins != nil && len(builtins) > 0 {
+		for i := len(builtins) - 1; i >= 0; i-- {
+			v := &InterceptorInvoker{next: next, interceptor: builtins[i]}
+			next = v
+		}
+	}
+
+	return next
+}

cluster/cluster_impl/mock_cluster.go

@@ -35,5 +35,5 @@ func NewMockCluster() cluster.Cluster {
 
 // nolint
 func (cluster *mockCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return protocol.NewBaseInvoker(directory.GetURL())
+	return buildInterceptorChain(protocol.NewBaseInvoker(directory.GetURL()))
 }

cluster/cluster_impl/zone_aware_cluster.go

@@ -40,5 +40,5 @@ func NewZoneAwareCluster() cluster.Cluster {
 
 // Join returns a zoneAwareClusterInvoker instance
 func (cluster *zoneAwareCluster) Join(directory cluster.Directory) protocol.Invoker {
-	return newZoneAwareClusterInvoker(directory)
+	return buildInterceptorChain(newZoneAwareClusterInvoker(directory), getZoneAwareInterceptor())
 }

cluster/cluster_impl/zone_aware_cluster_interceptor.go

@@ -0,0 +1,57 @@
+/*
+ * 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"
+)
+
+import (
+	"dubbo.apache.org/dubbo-go/v3/cluster"
+	"dubbo.apache.org/dubbo-go/v3/common/constant"
+	"dubbo.apache.org/dubbo-go/v3/protocol"
+)
+
+type zoneAwareInterceptor struct {
+}
+
+func (z *zoneAwareInterceptor) Invoke(ctx context.Context, invoker protocol.Invoker, invocation protocol.Invocation) protocol.Result {
+	key := constant.REGISTRY_KEY + "." + constant.ZONE_FORCE_KEY
+	force := ctx.Value(key)
+
+	if force != nil {
+		switch value := force.(type) {
+		case bool:
+			if value {
+				invocation.SetAttachments(key, "true")
+			}
+		case string:
+			if "true" == value {
+				invocation.SetAttachments(key, "true")
+			}
+		default:
+			// ignore
+		}
+	}
+
+	return invoker.Invoke(ctx, invocation)
+}
+
+func getZoneAwareInterceptor() cluster.Interceptor {
+	return &zoneAwareInterceptor{}
+}

cluster/cluster_impl/zone_aware_cluster_invoker.go

@@ -40,16 +40,14 @@ type zoneAwareClusterInvoker struct {
 }
 
 func newZoneAwareClusterInvoker(directory cluster.Directory) protocol.Invoker {
-	invoke := &zoneAwareClusterInvoker{
+	invoker := &zoneAwareClusterInvoker{
 		baseClusterInvoker: newBaseClusterInvoker(directory),
 	}
-	// add local to interceptor
-	invoke.interceptor = invoke
-	return invoke
+	return invoker
 }
 
 // nolint
-func (invoker *zoneAwareClusterInvoker) DoInvoke(ctx context.Context, invocation protocol.Invocation) protocol.Result {
+func (invoker *zoneAwareClusterInvoker) Invoke(ctx context.Context, invocation protocol.Invocation) protocol.Result {
 	invokers := invoker.directory.List(invocation)
 
 	err := invoker.checkInvokers(invokers, invocation)
@@ -104,29 +102,6 @@ func (invoker *zoneAwareClusterInvoker) DoInvoke(ctx context.Context, invocation
 	}
 }
 
-func (invoker *zoneAwareClusterInvoker) BeforeInvoker(ctx context.Context, invocation protocol.Invocation) {
-	key := constant.REGISTRY_KEY + "." + constant.ZONE_FORCE_KEY
-	force := ctx.Value(key)
-
-	if force != nil {
-		switch value := force.(type) {
-		case bool:
-			if value {
-				invocation.SetAttachments(key, "true")
-			}
-		case string:
-			if "true" == value {
-				invocation.SetAttachments(key, "true")
-			}
-		default:
-			// ignore
-		}
-	}
-}
-
-func (invoker *zoneAwareClusterInvoker) AfterInvoker(ctx context.Context, invocation protocol.Invocation) {
-}
-
 func matchParam(target, key, def string, invoker protocol.Invoker) bool {
 	return target == invoker.GetURL().GetParam(key, def)
 }

cluster/cluster_interceptor.go

@@ -25,15 +25,9 @@ import (
 	"dubbo.apache.org/dubbo-go/v3/protocol"
 )
 
-// ClusterInterceptor
-// Extension - ClusterInterceptor
-type ClusterInterceptor interface {
-	// Before DoInvoke method
-	BeforeInvoker(ctx context.Context, invocation protocol.Invocation)
-
-	// After DoInvoke method
-	AfterInvoker(ctx context.Context, invocation protocol.Invocation)
-
-	// Corresponding cluster invoke
-	DoInvoke(ctx context.Context, invocation protocol.Invocation) protocol.Result
+// Interceptor
+// Extension - Interceptor
+type Interceptor interface {
+	// Invoke is the core function of a cluster interceptor, it determines the process of the interceptor
+	Invoke(context.Context, protocol.Invoker, protocol.Invocation) protocol.Result
 }

common/extension/cluster_interceptor.go

@@ -0,0 +1,60 @@
+/*
+ * 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 extension
+
+import (
+	"sync"
+)
+
+import (
+	"dubbo.apache.org/dubbo-go/v3/cluster"
+)
+
+var (
+	lock         sync.RWMutex
+	interceptors = make(map[string]func() cluster.Interceptor)
+)
+
+// SetClusterInterceptor sets cluster interceptor so that user has chance to inject extra logics before and after
+// cluster invoker
+func SetClusterInterceptor(name string, fun func() cluster.Interceptor) {
+	lock.Lock()
+	defer lock.Unlock()
+	interceptors[name] = fun
+}
+
+// GetClusterInterceptor returns the cluster interceptor instance with the given name
+func GetClusterInterceptor(name string) cluster.Interceptor {
+	lock.RLock()
+	defer lock.RUnlock()
+	if interceptors[name] == nil {
+		panic("cluster_interceptor for " + name + " doesn't exist, make sure the corresponding package is imported")
+	}
+	return interceptors[name]()
+}
+
+// GetClusterInterceptors returns all instances of registered cluster interceptors
+func GetClusterInterceptors() []cluster.Interceptor {
+	lock.RLock()
+	defer lock.RUnlock()
+	ret := make([]cluster.Interceptor, 0, len(interceptors))
+	for _, f := range interceptors {
+		ret = append(ret, f())
+	}
+	return ret
+}