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authorSuren A. Chilingaryan <csa@suren.me>2018-03-19 06:21:30 +0100
committerSuren A. Chilingaryan <csa@suren.me>2018-03-19 06:21:30 +0100
commit9d9925ec86bb779c60655bbf487d7921f22a36eb (patch)
treea91c886a7aa65ace740dae91596d99517e1c27d9 /peer-finder/peer-finder.go
parent13c354cf70004f24570b81cc8f291af98ed7380c (diff)
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Include peer-finder and modify to match also IPs in order to support hostNetwork configuration
Diffstat (limited to 'peer-finder/peer-finder.go')
-rw-r--r--peer-finder/peer-finder.go152
1 files changed, 152 insertions, 0 deletions
diff --git a/peer-finder/peer-finder.go b/peer-finder/peer-finder.go
new file mode 100644
index 0000000..5b48c1c
--- /dev/null
+++ b/peer-finder/peer-finder.go
@@ -0,0 +1,152 @@
+/*
+Copyright 2014 The Kubernetes Authors All rights reserved.
+
+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.
+*/
+
+// A small utility program to lookup hostnames of endpoints in a service.
+package main
+
+import (
+ "flag"
+ "fmt"
+ "log"
+ "net"
+ "os"
+ "os/exec"
+ "sort"
+ "strings"
+ "time"
+
+ "./sets"
+// "k8s.io/apimachinery/pkg/util/sets"
+)
+
+const (
+ svcLocalSuffix = "svc.cluster.local"
+ pollPeriod = 1 * time.Second
+)
+
+var (
+ onChange = flag.String("on-change", "", "Script to run on change, must accept a new line separated list of peers via stdin.")
+ onStart = flag.String("on-start", "", "Script to run on start, must accept a new line separated list of peers via stdin.")
+ svc = flag.String("service", "", "Governing service responsible for the DNS records of the domain this pod is in.")
+ namespace = flag.String("ns", "", "The namespace this pod is running in. If unspecified, the POD_NAMESPACE env var is used.")
+)
+
+func lookup(svcName string) (sets.String, error) {
+ endpoints := sets.NewString()
+ _, srvRecords, err := net.LookupSRV("", "", svcName)
+ if err != nil {
+ return endpoints, err
+ }
+ for _, srvRecord := range srvRecords {
+ // The SRV records ends in a "." for the root domain
+ ep := fmt.Sprintf("%v", srvRecord.Target[:len(srvRecord.Target)-1])
+ endpoints.Insert(ep)
+ }
+ return endpoints, nil
+}
+
+func resolve(s *sets.String, dnsName string) (error) {
+ ips, err := net.LookupIP(dnsName)
+ if (err == nil) {
+ for _, ip := range ips {
+ s.Insert(ip.String())
+ }
+ }
+ return err
+}
+
+
+func shellOut(sendStdin, script string) {
+ log.Printf("execing: %v with stdin: %v", script, sendStdin)
+ // TODO: Switch to sending stdin from go
+ out, err := exec.Command("bash", "-c", fmt.Sprintf("echo -e '%v' | %v", sendStdin, script)).CombinedOutput()
+ if err != nil {
+ log.Fatalf("Failed to execute %v: %v, err: %v", script, string(out), err)
+ }
+ log.Print(string(out))
+}
+
+func main() {
+ flag.Parse()
+
+ ns := *namespace
+ if ns == "" {
+ ns = os.Getenv("POD_NAMESPACE")
+ }
+ if *svc == "" || ns == "" || (*onChange == "" && *onStart == "") {
+ log.Fatalf("Incomplete args, require -on-change and/or -on-start, -service and -ns or an env var for POD_NAMESPACE.")
+ }
+
+ hostname, err := os.Hostname()
+ if err != nil {
+ log.Fatalf("Failed to get hostname: %s", err)
+ }
+
+ matchIP := false
+ myName := strings.Join([]string{hostname, *svc, ns, svcLocalSuffix}, ".")
+ myIP := sets.NewString()
+ if (resolve(&myIP, myName) != nil) {
+ if (resolve(&myIP, hostname) != nil) {
+ log.Fatalf("Failed to resolve IP: %s", err)
+ } else {
+ myName = hostname
+ matchIP = true
+ }
+ }
+ log.Printf("MyName is: %v, MyIP is: %v, Match IP: %v.", myName, myIP.List(), matchIP)
+
+ script := *onStart
+ if script == "" {
+ script = *onChange
+ log.Printf("No on-start supplied, on-change %v will be applied on start.", script)
+ }
+ for newPeers, peers := sets.NewString(), sets.NewString(); script != ""; time.Sleep(pollPeriod) {
+ newPeers, err = lookup(*svc)
+ if err != nil {
+ log.Printf("%v", err)
+ continue
+ }
+ log.Printf("Peers is: %v.", newPeers.List())
+ if (newPeers.Equal(peers)) {
+ continue
+ }
+
+ if (!newPeers.Has(myName)) {
+ if (matchIP) {
+ peersIP := sets.NewString()
+ for _, peer := range(newPeers.List()) {
+ _ = resolve(&peersIP, peer)
+ }
+
+ newIP := peersIP.Intersection(myIP)
+ if (newIP.Len() == 0) {
+ continue
+ }
+ } else {
+ continue
+ }
+ }
+ peerList := newPeers.List()
+ sort.Strings(peerList)
+ log.Printf("Peer list updated\nwas %v\nnow %v", peers.List(), newPeers.List())
+ shellOut(strings.Join(peerList, "\n"), script)
+ peers = newPeers
+ script = *onChange
+ }
+ // TODO: Exit if there's no on-change?
+ log.Printf("Peer finder exiting")
+}
+