/
rule_roundrobin.go
64 lines (59 loc) · 1.94 KB
/
rule_roundrobin.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 loadbalancer
import (
"github.com/apache/eventmesh/eventmesh-sdk-go/log"
"go.uber.org/atomic"
)
// RoundRobinRule rule with roundrobin algorithm
type RoundRobinRule struct {
BaseRule
cycleCounter *atomic.Int64
}
// Choose return the instance by roundrobin
// the input must be ip
func (r *RoundRobinRule) Choose(interface{}) (interface{}, error) {
count := 0
for {
if count == 64 {
log.Warnf("failed to peek server by roundrobin after try 64 times")
return nil, ErrNoServerFound
}
srvs := r.lb.GetAvailableServer()
if len(srvs) == 0 {
log.Warnf("no available server found, load all server instead")
srvs = r.lb.GetAllStatusServer()
}
serverCount := len(srvs)
nextIndex := r.incrementAndGetModulo(int64(serverCount))
srv := srvs[nextIndex]
if !srv.ReadyForService {
continue
count++
}
log.Debugf("success peek server:%s by roundrobin", srv.Host)
return srv, nil
}
}
// incrementAndGetModulo calculate to get the next modulo
func (r *RoundRobinRule) incrementAndGetModulo(modulo int64) int64 {
for {
current := r.cycleCounter.Load()
next := (current + 1) % modulo
if r.cycleCounter.CAS(current, next) {
return next
}
}
}