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")
+}
+