Wait for weaveDNS HTTP to be running before sending it names

This adds a no-op endpoint to the HTTP API at `/status`. The script
simply tries this until it succeeds or gets bored.

nameserver/http.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"github.com/miekg/dns"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -26,6 +27,15 @@ func httpErrorAndLog(level *log.Logger, w http.ResponseWriter, msg string,
 }
 
 func ListenHttp(domain string, db Zone, port int) {
+
+	http.HandleFunc("/status", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != "GET" {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		} else {
+			io.WriteString(w, "ok")
+		}
+	})
+
 	http.HandleFunc("/name/", func(w http.ResponseWriter, r *http.Request) {
 
 		reqError := func(msg string, logmsg string, logargs ...interface{}) {

weave

@@ -317,6 +317,17 @@ tell_dns() {
 # Tell the newly-started weaveDNS about existing weave IPs
 populate_dns() {
     DNS_IP=$(docker inspect --format '{{ .NetworkSettings.IPAddress }}' $DNS_CONTAINER_NAME)
+    WAIT_TIME=1
+    while ! http_call_ip $DNS_IP $DNS_HTTP_PORT GET /status >/dev/null && [ $WAIT_TIME -lt 4 ]; do
+        echo "Waiting for weaveDNS container to start" >&2
+        sleep $WAIT_TIME
+        WAIT_TIME=$((WAIT_TIME+1))
+    done
+    if [ $WAIT_TIME = 4 ]; then
+        echo "Timed out waiting for weaveDNS container to start." >&2
+        echo "If running, it will not be pre-populated." >&2
+    fi
+
     for CONTAINER in $(docker ps -q); do
         MORE_ARGS=$(docker inspect --format '--data-urlencode local_ip={{ .NetworkSettings.IPAddress }} --data-urlencode fqdn={{ .Config.Hostname }}.{{ .Config.Domainname }}.' $CONTAINER 2>/dev/null) && true
         if CONTAINER_ADDRS=$(with_container_netns $CONTAINER container_weave_addrs 2>&1) ; then