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load_balancer.go
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load_balancer.go
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// Copyright (c) 2023 Paweł Gaczyński
//
// Licensed 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 gain
import (
"hash/crc32"
"net"
"github.com/pawelgaczynski/gain/pkg/errors"
)
type LoadBalancing int
const (
// RoundRobin forwards accepted connections to dedicated workers sequentially.
RoundRobin LoadBalancing = iota
// LeastConnections forwards the next accepted connection to the worker with the least number of active connections.
LeastConnections
// SourceAddrHash forwards the next accepted connection to the worker by hashing the remote peer address.
SourceIPHash
)
type loadBalancer interface {
register(consumer)
next(net.Addr) consumer
forEach(func(consumer) error) error
}
type genericLoadBalancer struct {
workers []consumer
size int
}
func (b *genericLoadBalancer) register(worker consumer) {
worker.setIndex(b.size)
b.workers = append(b.workers, worker)
b.size++
}
type roundRobinLoadBalancer struct {
*genericLoadBalancer
nextWorkerIndex int
}
func (b *roundRobinLoadBalancer) next(_ net.Addr) consumer {
worker := b.workers[b.nextWorkerIndex]
if b.nextWorkerIndex++; b.nextWorkerIndex >= b.size {
b.nextWorkerIndex = 0
}
return worker
}
func (b *roundRobinLoadBalancer) forEach(callback func(consumer) error) error {
for _, c := range b.workers {
err := callback(c)
if err != nil {
return err
}
}
return nil
}
func newRoundRobinLoadBalancer() loadBalancer {
return &roundRobinLoadBalancer{
genericLoadBalancer: &genericLoadBalancer{},
}
}
type leastConnectionsLoadBalancer struct {
*genericLoadBalancer
}
func (b *leastConnectionsLoadBalancer) next(_ net.Addr) consumer {
worker := b.workers[0]
minN := worker.activeConnections()
for _, v := range b.workers[1:] {
if n := v.activeConnections(); n < minN {
minN = n
worker = v
}
}
return worker
}
func (b *leastConnectionsLoadBalancer) forEach(callback func(consumer) error) error {
for _, c := range b.workers {
err := callback(c)
if err != nil {
return err
}
}
return nil
}
func newLeastConnectionsLoadBalancer() loadBalancer {
return &leastConnectionsLoadBalancer{
genericLoadBalancer: &genericLoadBalancer{},
}
}
type sourceIPHashLoadBalancer struct {
*genericLoadBalancer
}
func (b *sourceIPHashLoadBalancer) hash(s string) int {
hash := int(crc32.ChecksumIEEE([]byte(s)))
if hash < 0 {
return -hash
}
return hash
}
func (b *sourceIPHashLoadBalancer) next(addr net.Addr) consumer {
return b.workers[b.hash(addr.String())%b.size]
}
func (b *sourceIPHashLoadBalancer) forEach(callback func(consumer) error) error {
for _, c := range b.workers {
err := callback(c)
if err != nil {
return err
}
}
return nil
}
func newSourceIPHashLoadBalancer() loadBalancer {
return &sourceIPHashLoadBalancer{
genericLoadBalancer: &genericLoadBalancer{},
}
}
func createLoadBalancer(loadBalancing LoadBalancing) (loadBalancer, error) {
switch loadBalancing {
case RoundRobin:
return newRoundRobinLoadBalancer(), nil
case LeastConnections:
return newLeastConnectionsLoadBalancer(), nil
case SourceIPHash:
return newSourceIPHashLoadBalancer(), nil
default:
return nil, errors.ErrNotSupported
}
}