Merge pull request #1358 from philips/etcdserver-cleanup-cluster-id-msg

etcdserver: cleanup the cluster ID error message

Documentation/0.5/clustering.md

@@ -70,6 +70,18 @@ etcd: infra0 has different advertised URLs in the cluster and advertised peer UR
 exit 1
 ```
 
+If you configure a peer with a different set of configuration and attempt to
+join this cluster you will get a cluster ID mismatch and etcd will exit.
+
+```
+$ etcd -name infra3 -advertise-peer-urls http://10.0.1.13:2379 \
+	-initial-cluster infra0=http://10.0.1.10:2379,infra1=http://10.0.1.11:2379,infra3=http://10.0.1.13:2379 \
+	-initial-cluster-state=new
+etcd: conflicting cluster ID to the target cluster (c6ab534d07e8fcc4 != bc25ea2a74fb18b0). Exiting.
+exit 1
+```
+
+
 ## Discovery
 
 In a number of cases you might not know the IPs of your cluster peers ahead of

etcdserver/cluster_store.go

@@ -221,11 +221,11 @@ func httpPost(c *http.Client, url string, cid uint64, data []byte) bool {
 	switch resp.StatusCode {
 	case http.StatusPreconditionFailed:
 		// TODO: shutdown the etcdserver gracefully?
-		log.Panicf("clusterID mismatch")
+		log.Fatalf("etcd: conflicting cluster ID with the target cluster (%s != %s). Exiting.", resp.Header.Get("X-Etcd-Cluster-ID"), strconv.FormatUint(cid, 16))
 		return false
 	case http.StatusForbidden:
 		// TODO: stop the server
-		log.Panicf("the member has been removed")
+		log.Fatalf("etcd: this member has been permanently removed from the cluster. Exiting.")
 		return false
 	case http.StatusNoContent:
 		return true

etcdserver/etcdhttp/http.go

@@ -222,8 +222,10 @@ func (h serverHandler) serveRaft(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	gcid := r.Header.Get("X-Etcd-Cluster-ID")
 	wcid := strconv.FormatUint(h.clusterStore.Get().ID(), 16)
+	w.Header().Set("X-Etcd-Cluster-ID", wcid)
+
+	gcid := r.Header.Get("X-Etcd-Cluster-ID")
 	if gcid != wcid {
 		log.Printf("etcdhttp: request ignored: clusterID mismatch got %s want %x", gcid, wcid)
 		http.Error(w, "clusterID mismatch", http.StatusPreconditionFailed)