From 7821412bf786844919afd2d104671cbf11fd214b Mon Sep 17 00:00:00 2001
From: Paul Bellamy <paul.a.bellamy@gmail.com>
Date: Thu, 2 Jul 2015 15:43:03 +0100
Subject: [PATCH] [proxy] print all stderr from callWeave to the proxy logs,
 even if successful

---
 proxy/common.go                      | 9 ++++++---
 proxy/proxy.go                       | 4 ++--
 proxy/start_container_interceptor.go | 8 +++++---
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/proxy/common.go b/proxy/common.go
index 7231226c..985fae9a 100644
--- a/proxy/common.go
+++ b/proxy/common.go
@@ -18,13 +18,16 @@ var (
 	weaveWaitEntrypoint = []string{"/w/w"}
 )
 
-func callWeave(args ...string) ([]byte, error) {
+func callWeave(args ...string) ([]byte, []byte, error) {
 	args = append([]string{"--local"}, args...)
 	Log.Debug("Calling weave", args)
 	cmd := exec.Command("./weave", args...)
 	cmd.Env = []string{"PROCFS=/hostproc", "PATH=/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"}
-	out, err := cmd.CombinedOutput()
-	return out, err
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	err := cmd.Run()
+	return stdout.Bytes(), stderr.Bytes(), err
 }
 
 func marshalRequestBody(r *http.Request, body interface{}) error {
diff --git a/proxy/proxy.go b/proxy/proxy.go
index 0812ab4b..2993d00d 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -57,9 +57,9 @@ func NewProxy(c Config) (*Proxy, error) {
 	p.client = client
 
 	if !p.WithoutDNS {
-		dockerBridgeIP, err := callWeave("docker-bridge-ip")
+		dockerBridgeIP, stderr, err := callWeave("docker-bridge-ip")
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf(string(stderr))
 		}
 		p.dockerBridgeIP = string(dockerBridgeIP)
 	}
diff --git a/proxy/start_container_interceptor.go b/proxy/start_container_interceptor.go
index b7da0505..1a4de456 100644
--- a/proxy/start_container_interceptor.go
+++ b/proxy/start_container_interceptor.go
@@ -30,9 +30,11 @@ func (i *startContainerInterceptor) InterceptResponse(r *http.Response) error {
 	args := []string{"attach"}
 	args = append(args, cidrs...)
 	args = append(args, "--or-die", container.ID)
-	if output, err := callWeave(args...); err != nil {
-		Log.Warningf("Attaching container %s to weave network failed: %s", container.ID, string(output))
-		return errors.New(string(output))
+	if _, stderr, err := callWeave(args...); err != nil {
+		Log.Warningf("Attaching container %s to weave network failed: %s", container.ID, string(stderr))
+		return errors.New(string(stderr))
+	} else if len(stderr) > 0 {
+		Log.Warningf("Attaching container %s to weave network: %s", container.ID, string(stderr))
 	}
 
 	return i.proxy.client.KillContainer(docker.KillContainerOptions{ID: container.ID, Signal: docker.SIGUSR2})