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tracker.go
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/
tracker.go
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// Copyright 2024 Google LLC
//
// 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
//
// https://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.
// Utility for tracking a list of hosts resolved from a service hostname.
// Intended to track IPs in a K8s daemonset, etc.
package servicetracker
import (
"log"
"net"
"net/netip"
"sort"
"time"
)
const (
SecondsBetweenLookups = 10
)
type Tracker struct {
hostname string
hosts map[netip.Addr]*Host
LastUpdate time.Time
}
func MakeTracker(hostname string) *Tracker {
t := &Tracker{
hostname: hostname,
hosts: make(map[netip.Addr]*Host),
LastUpdate: time.Now(),
}
go t.track()
return t
}
func (t *Tracker) track() {
for {
if ips, err := net.LookupIP(t.hostname); err == nil {
// 1. Update active hosts.
active := map[netip.Addr]bool{}
for _, ip := range ips {
addr, ok := netip.AddrFromSlice(ip)
if !ok {
log.Printf("Failed to convert IP: %v", ip)
continue
}
active[addr] = true
if host, ok := t.hosts[addr]; !ok {
t.AddHost(addr)
} else {
t.UpdateHost(host)
}
}
// 2. Mark other hosts as removed.
for _, host := range t.hosts {
if _, ok := active[host.Addr]; ok {
continue
}
if !host.IsRemoved() {
t.RemoveHost(host)
}
}
}
time.Sleep(SecondsBetweenLookups * time.Second)
}
}
func (t *Tracker) AddHost(addr netip.Addr) {
// log.Printf("Tracker: new host: %v", addr)
t.hosts[addr] = MakeHost(addr)
t.LastUpdate = time.Now()
}
func (t *Tracker) UpdateHost(host *Host) {
if updated := host.SetActive(); updated {
t.LastUpdate = time.Now()
}
}
func (t *Tracker) RemoveHost(host *Host) {
// log.Printf("Marking host %v as removed.", host.Addr)
host.SetRemoved()
}
// ActiveHosts returns the list of active hosts in sorted order.
func (t *Tracker) ActiveHosts() []*Host {
result := []*Host{}
for _, host := range t.hosts {
if host.IsActive() {
result = append(result, host)
}
}
sort.SliceStable(result, func(i, j int) bool {
return result[i].Addr.Less(result[j].Addr)
})
return result
}
func (t *Tracker) RemovedHosts() []*Host {
result := []*Host{}
for _, host := range t.hosts {
if host.IsRemoved() {
result = append(result, host)
}
}
return result
}