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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 p2c
import (
"errors"
"fmt"
"math/rand"
"sync"
"time"
)
import (
"dubbo.apache.org/dubbo-go/v3/cluster/loadbalance"
"dubbo.apache.org/dubbo-go/v3/cluster/metrics"
"dubbo.apache.org/dubbo-go/v3/common/constant"
"dubbo.apache.org/dubbo-go/v3/common/extension"
"dubbo.apache.org/dubbo-go/v3/common/logger"
"dubbo.apache.org/dubbo-go/v3/protocol"
)
func init() {
extension.SetLoadbalance(constant.LoadBalanceKeyP2C, newLoadBalance)
}
var (
once sync.Once
instance loadbalance.LoadBalance
)
type loadBalance struct{}
func newLoadBalance() loadbalance.LoadBalance {
if instance == nil {
once.Do(func() {
instance = &loadBalance{}
})
}
return instance
}
func (l *loadBalance) Select(invokers []protocol.Invoker, invocation protocol.Invocation) protocol.Invoker {
if len(invokers) == 0 {
return nil
}
if len(invokers) == 1 {
return invokers[0]
}
// m is the Metrics, which saves the metrics of instance, invokers and methods
// The local metrics is available only for the earlier version.
m := metrics.LocalMetrics
// picks two nodes randomly
var i, j int
if len(invokers) == 2 {
i, j = 0, 1
} else {
rand.Seed(time.Now().Unix())
i = rand.Intn(len(invokers))
j = i
for i == j {
j = rand.Intn(len(invokers))
}
}
logger.Debugf("[P2C select] Two invokers were selected, i: %d, j: %d, invoker[i]: %s, invoker[j]: %s.",
i, j, invokers[i], invokers[j])
// TODO(justxuewei): please consider how to get the real method name from $invoke,
// see also [#1511](https://github.com/apache/dubbo-go/issues/1511)
methodName := invocation.MethodName()
// remainingIIface, remainingJIface means remaining capacity of node i and node j.
// If one of the metrics is empty, invoke the invocation to that node directly.
remainingIIface, err := m.GetMethodMetrics(invokers[i].GetURL(), methodName, metrics.HillClimbing)
if err != nil {
if errors.Is(err, metrics.ErrMetricsNotFound) {
logger.Debugf("[P2C select] The invoker[i] was selected, because it hasn't been selected before.")
return invokers[i]
}
logger.Warnf("get method metrics err: %v", err)
return nil
}
remainingJIface, err := m.GetMethodMetrics(invokers[j].GetURL(), methodName, metrics.HillClimbing)
if err != nil {
if errors.Is(err, metrics.ErrMetricsNotFound) {
logger.Debugf("[P2C select] The invoker[j] was selected, because it hasn't been selected before.")
return invokers[j]
}
logger.Warnf("get method metrics err: %v", err)
return nil
}
// Convert interface to int, if the type is unexpected, panic immediately
remainingI, ok := remainingIIface.(uint64)
if !ok {
panic(fmt.Sprintf("[P2C select] the type of %s expects to be uint64, but gets %T",
metrics.HillClimbing, remainingIIface))
}
remainingJ, ok := remainingJIface.(uint64)
if !ok {
panic(fmt.Sprintf("the type of %s expects to be uint64, but gets %T", metrics.HillClimbing, remainingJIface))
}
logger.Debugf("[P2C select] The invoker[i] remaining is %d, and the invoker[j] is %d.", remainingI, remainingJ)
// For the remaining capacity, the bigger, the better.
if remainingI > remainingJ {
logger.Debugf("[P2C select] The invoker[i] was selected.")
return invokers[i]
}
logger.Debugf("[P2C select] The invoker[j] was selected.")
return invokers[j]
}