mirror of https://github.com/k3s-io/k3s
129 lines
3.6 KiB
Go
129 lines
3.6 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// A small utility program to lookup hostnames of endpoints in a service.
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package main
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import (
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"flag"
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"fmt"
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"io/ioutil"
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"log"
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"net"
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"os"
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"os/exec"
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"sort"
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"strings"
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"time"
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"k8s.io/apimachinery/pkg/util/sets"
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)
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const (
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pollPeriod = 1 * time.Second
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)
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var (
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onChange = flag.String("on-change", "", "Script to run on change, must accept a new line separated list of peers via stdin.")
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onStart = flag.String("on-start", "", "Script to run on start, must accept a new line separated list of peers via stdin.")
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svc = flag.String("service", "", "Governing service responsible for the DNS records of the domain this pod is in.")
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namespace = flag.String("ns", "", "The namespace this pod is running in. If unspecified, the POD_NAMESPACE env var is used.")
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domain = flag.String("domain", "cluster.local", "The Cluster Domain which is used by the Cluster.")
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)
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func lookup(svcName string) (sets.String, error) {
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endpoints := sets.NewString()
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_, srvRecords, err := net.LookupSRV("", "", svcName)
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if err != nil {
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return endpoints, err
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}
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for _, srvRecord := range srvRecords {
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// The SRV records ends in a "." for the root domain
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ep := fmt.Sprintf("%v", srvRecord.Target[:len(srvRecord.Target)-1])
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endpoints.Insert(ep)
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}
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return endpoints, nil
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}
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func shellOut(sendStdin, script string) {
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log.Printf("execing: %v with stdin: %v", script, sendStdin)
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cmd := exec.Command(script)
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stdin, err := cmd.StdinPipe()
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if err != nil {
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log.Fatalf("Failed to get stdin pipe: %v", err)
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}
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stdout, err := cmd.StdoutPipe()
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if err != nil {
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log.Fatalf("Failed to get stdout pipe: %v", err)
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}
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cmd.Start()
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stdin.Write([]byte(sendStdin))
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stdin.Close()
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out, err := ioutil.ReadAll(stdout)
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if err != nil {
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log.Fatalf("Failed to execute %v: %v, err: %v", script, string(out), err)
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}
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log.Print(string(out))
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}
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func main() {
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flag.Parse()
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ns := *namespace
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if ns == "" {
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ns = os.Getenv("POD_NAMESPACE")
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}
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if *svc == "" || ns == "" || (*onChange == "" && *onStart == "") {
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log.Fatalf("Incomplete args, require -on-change and/or -on-start, -service and -ns or an env var for POD_NAMESPACE.")
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}
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hostname, err := os.Hostname()
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if err != nil {
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log.Fatalf("Failed to get hostname: %s", err)
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}
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svcLocalSuffix := strings.Join([]string{"svc", *domain}, ".")
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myName := strings.Join([]string{hostname, *svc, ns, svcLocalSuffix}, ".")
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script := *onStart
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if script == "" {
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script = *onChange
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log.Printf("No on-start supplied, on-change %v will be applied on start.", script)
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}
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for newPeers, peers := sets.NewString(), sets.NewString(); script != ""; time.Sleep(pollPeriod) {
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newPeers, err = lookup(*svc)
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if err != nil {
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log.Printf("%v", err)
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continue
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}
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if newPeers.Equal(peers) || !newPeers.Has(myName) {
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continue
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}
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peerList := newPeers.List()
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sort.Strings(peerList)
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log.Printf("Peer list updated\nwas %v\nnow %v", peers.List(), newPeers.List())
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shellOut(strings.Join(peerList, "\n"), script)
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peers = newPeers
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script = *onChange
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}
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// TODO: Exit if there's no on-change?
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log.Printf("Peer finder exiting")
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}
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