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loadbalance.go
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loadbalance.go
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/*
* 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 consistenthashing
import (
"encoding/json"
"hash/crc32"
"regexp"
)
import (
"dubbo.apache.org/dubbo-go/v3/cluster/loadbalance"
"dubbo.apache.org/dubbo-go/v3/common/constant"
"dubbo.apache.org/dubbo-go/v3/common/extension"
"dubbo.apache.org/dubbo-go/v3/protocol"
)
const (
// HashNodes hash nodes
HashNodes = "hash.nodes"
// HashArguments key of hash arguments in url
HashArguments = "hash.arguments"
)
var (
selectors = make(map[string]*selector)
re = regexp.MustCompile(constant.CommaSplitPattern)
)
func init() {
extension.SetLoadbalance(constant.LoadBalanceKeyConsistentHashing, newConshashLoadBalance)
}
// conshashLoadBalance implementation of load balancing: using consistent hashing
type conshashLoadBalance struct{}
// newConshashLoadBalance creates NewConsistentHashLoadBalance
//
// The same parameters of the request is always sent to the same provider.
func newConshashLoadBalance() loadbalance.LoadBalance {
return &conshashLoadBalance{}
}
// Select gets invoker based on load balancing strategy
func (lb *conshashLoadBalance) Select(invokers []protocol.Invoker, invocation protocol.Invocation) protocol.Invoker {
methodName := invocation.MethodName()
key := invokers[0].GetURL().ServiceKey() + "." + methodName
// hash the invokers
var bs []byte
for _, invoker := range invokers {
b, err := json.Marshal(invoker)
if err != nil {
return nil
}
bs = append(bs, b...)
}
hashCode := crc32.ChecksumIEEE(bs)
selector, ok := selectors[key]
if !ok || selector.hashCode != hashCode {
selectors[key] = newSelector(invokers, methodName, hashCode)
selector = selectors[key]
}
return selector.Select(invocation)
}