cluster/cluster/interceptor_invoker.go

/*
 * 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

import (
	"context"
	"sync"
)

import (
	"dubbo.apache.org/dubbo-go/v3/common"
	"dubbo.apache.org/dubbo-go/v3/protocol"
)

var (
	lock         sync.RWMutex
	interceptors = make(map[string]func() 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() Interceptor) {
	lock.Lock()
	defer lock.Unlock()
	interceptors[name] = fun
}

// GetClusterInterceptor returns the cluster interceptor instance with the given name
func GetClusterInterceptor(name string) 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() []Interceptor {
	lock.RLock()
	defer lock.RUnlock()
	ret := make([]Interceptor, 0, len(interceptors))
	for _, f := range interceptors {
		ret = append(ret, f())
	}
	return ret
}

// InterceptorInvoker mocks cluster interceptor as an invoker
type InterceptorInvoker struct {
	next        protocol.Invoker
	interceptor 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 ...Interceptor) protocol.Invoker {
	// The order of interceptors is from left to right, so loading from right to left
	next := invoker
	interceptors := 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
}