[proxy] use a container-local unix socket to get the address, instead of logs

prog/weaveproxy/main.go

@@ -64,5 +64,6 @@ func main() {
 	listeners := p.Listen()
 	p.AttachExistingContainers()
 	go p.Serve(listeners)
+	go p.ListenAndServeStatus("/home/weave/status.sock")
 	SignalHandlerLoop()
 }

proxy/proxy.go

@@ -69,6 +69,7 @@ type Proxy struct {
 	dockerBridgeIP      string
 	hostnameMatchRegexp *regexp.Regexp
 	weaveWaitVolume     string
+	normalisedAddrs     []string
 	waiters             map[*http.Request]*wait
 }
 
@@ -168,17 +169,17 @@ func (proxy *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 func (proxy *Proxy) Listen() []net.Listener {
 	listeners := []net.Listener{}
-	addrs := []string{}
+	proxy.normalisedAddrs = []string{}
 	for _, addr := range proxy.ListenAddrs {
 		listener, normalisedAddr, err := proxy.listen(addr)
 		if err != nil {
 			Log.Fatalf("Cannot listen on %s: %s", addr, err)
 		}
 		listeners = append(listeners, listener)
-		addrs = append(addrs, normalisedAddr)
+		proxy.normalisedAddrs = append(proxy.normalisedAddrs, normalisedAddr)
 	}
 
-	for _, addr := range addrs {
+	for _, addr := range proxy.normalisedAddrs {
 		Log.Infoln("proxy listening on", addr)
 	}
 	return listeners
@@ -199,6 +200,23 @@ func (proxy *Proxy) Serve(listeners []net.Listener) {
 	}
 }
 
+func (proxy *Proxy) ListenAndServeStatus(socket string) {
+	listener, err := net.Listen("unix", socket)
+	if err != nil {
+		Log.Fatalf("ListenAndServeStatus failed: %s", err)
+	}
+	handler := http.HandlerFunc(proxy.StatusHTTP)
+	if err := (&http.Server{Handler: handler}).Serve(listener); err != nil {
+		Log.Fatalf("ListenAndServeStatus failed: %s", err)
+	}
+}
+
+func (proxy *Proxy) StatusHTTP(w http.ResponseWriter, r *http.Request) {
+	for _, addr := range proxy.normalisedAddrs {
+		fmt.Fprintln(w, addr)
+	}
+}
+
 func copyOwnerAndPermissions(from, to string) error {
 	stat, err := os.Stat(from)
 	if err != nil {

weave

@@ -662,6 +662,17 @@ http_call() {
     curl --connect-timeout 3 -s -S -X $http_verb "$@" http://$addr$url
 }
 
+http_call_unix() {
+    container="$1"
+    socket="$2"
+    http_verb="$3"
+    url="$4"
+    shift 4
+    output=$(docker exec $container curl -s -S -X $http_verb --unix-socket $socket "$@" http:$url)
+    [ -n "$output" ] || return 1
+    echo $output
+}
+
 call_weave() {
     container_ip $CONTAINER_NAME \
         "$CONTAINER_NAME container is not present. Have you launched it?" \
@@ -692,17 +703,19 @@ wait_for_status() {
     done
 }
 
-# Wait until container $1 outputs a line containing $2 in its log
-wait_for_log() {
-    fifo=/tmp/tmpfifo.$$
-    mkfifo $fifo || exit 1
-    docker logs -f $1 >$fifo 2>&1 &
-    res=0
-    grep -q "$2" $fifo || res=1
-    kill $! 2>/dev/null || true
-    rm $fifo
-    [ $res -eq 1 ] && echo "$(death_msg $1)" >&2
-    return $res
+# Wait until container $1 is alive enough to respond to "GET /status"
+# http request is to unix socket "status.sock", we assume the container
+# has curl >= 7.40
+wait_for_status_unix() {
+    err_msg=$(death_msg $1)
+    while true ; do
+        http_call_unix $1 status.sock GET /status >/dev/null 2>&1 && return 0
+        if ! container_id $1 >/dev/null 2>&1 ; then
+            echo "$err_msg" >&2
+            return 1
+        fi
+        fractional_sleep 3.1
+    done
 }
 
 # Call $1 for all containers, passing container ID, all MACs and all IPs
@@ -1051,8 +1064,8 @@ proxy_args() {
 }
 
 proxy_addr() {
-    if addr=$(docker logs $PROXY_CONTAINER_NAME 2>&1 | head -n4 | grep -oE "proxy listening on .*") ; then
-      echo "${addr##* }" | sed "s/0.0.0.0/$PROXY_HOST/g"
+    if addr=$(http_call_unix $PROXY_CONTAINER_NAME status.sock GET /status 2>&1) ; then
+      echo "$addr" | head -n1 | sed "s/0.0.0.0/$PROXY_HOST/g"
     else
       echo "$PROXY_CONTAINER_NAME container is not present. Have you launched it?" >&2
       return 1
@@ -1209,7 +1222,7 @@ launch_proxy() {
         -e DOCKER_BRIDGE \
         --entrypoint=/home/weave/weaveproxy \
         $WEAVEPROXY_DOCKER_ARGS $EXEC_IMAGE $COVERAGE_ARGS $PROXY_ARGS)
-    wait_for_log $PROXY_CONTAINER_NAME "proxy listening"
+    wait_for_status_unix $PROXY_CONTAINER_NAME
 }
 
 ##########################################################################################