istio.io/istio@v0.0.0-20240520182934-d79c90f27776/pkg/test/loadbalancersim/loadbalancer/roundrobin.go (about)

     1  //  Copyright Istio Authors
     2  //
     3  //  Licensed under the Apache License, Version 2.0 (the "License");
     4  //  you may not use this file except in compliance with the License.
     5  //  You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  //  Unless required by applicable law or agreed to in writing, software
    10  //  distributed under the License is distributed on an "AS IS" BASIS,
    11  //  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  //  See the License for the specific language governing permissions and
    13  //  limitations under the License.
    14  
    15  package loadbalancer
    16  
    17  import (
    18  	"math/rand"
    19  	"sync"
    20  
    21  	"istio.io/istio/pkg/test/loadbalancersim/network"
    22  )
    23  
    24  func NewRoundRobin(conns []*WeightedConnection) network.Connection {
    25  	// Add instances for each connection based on the weight.
    26  	var lbConns []*WeightedConnection
    27  	for _, conn := range conns {
    28  		for i := uint32(0); i < conn.Weight; i++ {
    29  			lbConns = append(lbConns, conn)
    30  		}
    31  	}
    32  
    33  	// Shuffle the connections.
    34  	rand.Shuffle(len(lbConns), func(i, j int) {
    35  		lbConns[i], lbConns[j] = lbConns[j], lbConns[i]
    36  	})
    37  
    38  	return &roundRobin{
    39  		weightedConnections: newLBConnection("RoundRobinLB", lbConns),
    40  	}
    41  }
    42  
    43  type roundRobin struct {
    44  	*weightedConnections
    45  
    46  	next      int
    47  	nextMutex sync.Mutex
    48  }
    49  
    50  func (lb *roundRobin) Request(onDone func()) {
    51  	// Select the connection to use for this request.
    52  	lb.nextMutex.Lock()
    53  	selected := lb.get(lb.next)
    54  	lb.next = (lb.next + 1) % len(lb.conns)
    55  	lb.nextMutex.Unlock()
    56  
    57  	lb.doRequest(selected, onDone)
    58  }