123 lines
2.5 KiB
Go
123 lines
2.5 KiB
Go
package udp
|
|
|
|
import (
|
|
"errors"
|
|
"sync"
|
|
|
|
"github.com/traefik/traefik/v2/pkg/log"
|
|
)
|
|
|
|
type server struct {
|
|
Handler
|
|
weight int
|
|
}
|
|
|
|
// WRRLoadBalancer is a naive RoundRobin load balancer for UDP services.
|
|
type WRRLoadBalancer struct {
|
|
servers []server
|
|
lock sync.Mutex
|
|
currentWeight int
|
|
index int
|
|
}
|
|
|
|
// NewWRRLoadBalancer creates a new WRRLoadBalancer.
|
|
func NewWRRLoadBalancer() *WRRLoadBalancer {
|
|
return &WRRLoadBalancer{
|
|
index: -1,
|
|
}
|
|
}
|
|
|
|
// ServeUDP forwards the connection to the right service.
|
|
func (b *WRRLoadBalancer) ServeUDP(conn *Conn) {
|
|
b.lock.Lock()
|
|
next, err := b.next()
|
|
b.lock.Unlock()
|
|
|
|
if err != nil {
|
|
log.WithoutContext().Errorf("Error during load balancing: %v", err)
|
|
conn.Close()
|
|
return
|
|
}
|
|
|
|
next.ServeUDP(conn)
|
|
}
|
|
|
|
// AddServer appends a handler to the existing list.
|
|
func (b *WRRLoadBalancer) AddServer(serverHandler Handler) {
|
|
w := 1
|
|
b.AddWeightedServer(serverHandler, &w)
|
|
}
|
|
|
|
// AddWeightedServer appends a handler to the existing list with a weight.
|
|
func (b *WRRLoadBalancer) AddWeightedServer(serverHandler Handler, weight *int) {
|
|
b.lock.Lock()
|
|
defer b.lock.Unlock()
|
|
|
|
w := 1
|
|
if weight != nil {
|
|
w = *weight
|
|
}
|
|
b.servers = append(b.servers, server{Handler: serverHandler, weight: w})
|
|
}
|
|
|
|
func (b *WRRLoadBalancer) maxWeight() int {
|
|
maximum := -1
|
|
for _, s := range b.servers {
|
|
if s.weight > maximum {
|
|
maximum = s.weight
|
|
}
|
|
}
|
|
return maximum
|
|
}
|
|
|
|
func (b *WRRLoadBalancer) weightGcd() int {
|
|
divisor := -1
|
|
for _, s := range b.servers {
|
|
if divisor == -1 {
|
|
divisor = s.weight
|
|
} else {
|
|
divisor = gcd(divisor, s.weight)
|
|
}
|
|
}
|
|
return divisor
|
|
}
|
|
|
|
func gcd(a, b int) int {
|
|
for b != 0 {
|
|
a, b = b, a%b
|
|
}
|
|
return a
|
|
}
|
|
|
|
func (b *WRRLoadBalancer) next() (Handler, error) {
|
|
if len(b.servers) == 0 {
|
|
return nil, errors.New("no servers in the pool")
|
|
}
|
|
|
|
// The algorithm below may look messy,
|
|
// but is actually very simple it calculates the GCD and subtracts it on every iteration,
|
|
// what interleaves servers and allows us not to build an iterator every time we readjust weights.
|
|
|
|
// Maximum weight across all enabled servers
|
|
maximum := b.maxWeight()
|
|
if maximum == 0 {
|
|
return nil, errors.New("all servers have 0 weight")
|
|
}
|
|
|
|
// GCD across all enabled servers
|
|
gcd := b.weightGcd()
|
|
|
|
for {
|
|
b.index = (b.index + 1) % len(b.servers)
|
|
if b.index == 0 {
|
|
b.currentWeight -= gcd
|
|
if b.currentWeight <= 0 {
|
|
b.currentWeight = maximum
|
|
}
|
|
}
|
|
srv := b.servers[b.index]
|
|
if srv.weight >= b.currentWeight {
|
|
return srv, nil
|
|
}
|
|
}
|
|
}
|