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director.go
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director.go
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/*
* VC5 load balancer. Copyright (C) 2021-present David Coles
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
package cue
import (
"errors"
"net/netip"
"sort"
"sync"
"time"
"github.com/davidcoles/cue/mon"
)
const (
TCP = 0x06
UDP = 0x11
)
type Check = mon.Check
type Scheduler = string
type Service struct {
Address netip.Addr
Port uint16
Protocol uint8
Scheduler string
Persist uint32
Sticky bool
Reset bool
Required uint8
Destinations []Destination
available uint8
Up bool
When time.Time
}
type Destination struct {
Address netip.Addr `json:"address"`
Port uint16 `json:"port"`
Disabled bool `json:"disabled"`
Weight uint8 `json:"weight"`
Status mon.Status `json:"status"`
Checks []mon.Check `json:"checks"`
}
type protocol uint8
type tuple = mon.Service
// If the destination is healthy then this function returns its weight. If unhealthy or disabled, zero is returned
func (d *Destination) HealthyWeight() uint8 {
if !d.Disabled && d.Status.OK && d.Weight > 0 {
return 1
}
return 0
}
func (p protocol) MarshalText() ([]byte, error) {
switch p {
case TCP:
return []byte("TCP"), nil
case UDP:
return []byte("UDP"), nil
}
return []byte("Unknown"), nil
}
func (s *Service) Available() uint8 {
return s.available
}
func (s *Service) Healthy() bool {
return s.available >= s.Required
}
func (i Service) less(j Service) bool {
if r := i.Address.Compare(j.Address); r != 0 {
return r < 0
}
if i.Port != j.Port {
return i.Port < j.Port
}
if i.Protocol != j.Protocol {
return i.Protocol < j.Protocol
}
return false
}
type Director struct {
// A channel which may be used to receive notifications of changes in status of backend servers.
C chan bool
// The Balancer which will implement the services managed by this Director.
//Balancer Balancer
Notifier mon.Notifier
Prober mon.Prober
SNI bool
// Default IP address to use for network probes (needed for SYN, should be optional).
Address netip.Addr
mutex sync.Mutex
cfg map[tuple]Service
mon *mon.Mon
die chan bool
svc map[tuple]status
}
type status struct {
up bool
time time.Time
}
func (d *Director) Start(cfg []Service) error {
d.C = make(chan bool, 1)
// start monitoring with an empty set of services (nil)
//d.mon, err = mon.New(d.Address, nil, d.Balancer)
//d.mon, err = mon.New(d.Address, nil, d.Notifier, d.Prober)
d.mon = &mon.Mon{
Notifier: d.Notifier,
Prober: d.Prober,
SNI: d.SNI,
}
err := d.mon.Start(d.Address, nil)
if err != nil {
return err
}
err = d.Configure(cfg)
if err != nil {
d.mon.Update(nil)
return err
}
d.die = make(chan bool)
go d.background()
return nil
}
func (d *Director) Stop() {
close(d.die)
}
func (d *Director) Configure(config []Service) error {
d.mutex.Lock()
defer d.mutex.Unlock()
cfg := map[tuple]Service{}
for _, s := range config {
t := tuple{Address: s.Address, Port: s.Port, Protocol: s.Protocol}
cfg[t] = s
}
vips := map[netip.Addr]bool{}
svcs := map[mon.Service]bool{}
// scan previous config for checks to see if vip/service existed ...
for s, _ := range d.cfg {
vips[s.Address] = true
svcs[mon.Service{Address: s.Address, Port: s.Port, Protocol: s.Protocol}] = true
}
services := map[mon.Instance]mon.Target{}
for _, s := range cfg {
if s.Port == 0 {
return errors.New("Service port cannot be 0")
}
if s.Protocol != TCP && s.Protocol != UDP {
return errors.New("Only TCP and UDP protocols supported")
}
for _, d := range s.Destinations {
if d.Port == 0 {
return errors.New("Destination port cannot be 0")
}
}
}
for _, s := range cfg {
service := mon.Service{Address: s.Address, Port: s.Port, Protocol: s.Protocol}
// When:
// 1) adding a new vip, all checks should start as down(false) to prevent routing flaps
// 2) adding a new service to an existing vip, start up(true) to prevent vip being withdrawn
// 3) adding a new real to an existing service, start as down(false) state to prevent rehash
init := vips[s.Address] && !svcs[service]
// 1: false && ?????? => false
// 2: true && !false => true
// 3: true && !true => false
for _, d := range s.Destinations {
i := mon.Instance{Service: service, Destination: mon.Destination{Address: d.Address, Port: d.Port}}
services[i] = mon.Target{Init: init, Checks: d.Checks}
}
}
d.cfg = cfg
d.mon.Update(services)
d.inform()
return nil
}
func clone(in []Service) (out []Service) {
for _, s := range in {
c := s
c.Destinations = nil
for _, d := range s.Destinations {
c.Destinations = append(c.Destinations, d)
}
out = append(out, c)
}
return out
}
func (d *Director) services() (r []Service) {
m := d.mon
svc := map[tuple]status{}
for _, s := range d.cfg {
var available uint8
var destinations []Destination
t := tuple{Address: s.Address, Port: s.Port, Protocol: s.Protocol}
for _, d := range s.Destinations {
status, _ := m.Status(t, mon.Destination{Address: d.Address, Port: d.Port})
d.Status = status
if d.HealthyWeight() > 0 {
available++
}
destinations = append(destinations, d)
}
s.Destinations = destinations
s.available = available
state, ok := d.svc[t]
up := s.Healthy()
if !ok || state.up != up {
state.time = time.Now()
}
state.up = up
svc[t] = state
s.Up = state.up
s.When = state.time
r = append(r, s)
}
d.svc = svc
return
}
func (d *Director) status() (services []Service) {
services = d.services()
sort.SliceStable(services, func(i, j int) bool { return services[i].less(services[j]) })
return services
}
func (d *Director) Status() (services []Service) {
d.mutex.Lock()
defer d.mutex.Unlock()
return d.status()
}
func (d *Director) inform() {
select {
case d.C <- true:
default:
}
}
func (d *Director) background() {
for {
select {
case <-d.mon.C:
d.mutex.Lock()
d.inform()
d.mutex.Unlock()
case <-d.die:
d.Configure(nil)
d.mon.Update(nil)
d.inform()
return
}
}
}
func AllVIPs(services []Service) (r []netip.Addr) {
vips := map[netip.Addr]bool{}
for _, s := range services {
vips[s.Address] = true
}
for v, _ := range vips {
r = append(r, v)
}
return
}
func HealthyVIPs(services []Service) (r []netip.Addr) {
vips := map[netip.Addr]bool{}
for _, s := range services {
vip := s.Address
if s.Up {
if _, ok := vips[vip]; !ok {
vips[vip] = true
}
} else {
vips[vip] = false
}
}
for ip, ok := range vips {
if ok {
r = append(r, ip)
}
}
return
}