[lxc-devel] [lxd/master] DO NOT MERGE (jenkins failure debugging)

[stgraber on Github]

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From 0cd61ff147e3853f8fcfa18e7a0fcc11b0688ced Mon Sep 17 00:00:00 2001
From: Tycho Andersen <tycho.andersen at canonical.com>
Date: Thu, 13 Oct 2016 19:17:17 -0600
Subject: [PATCH] Log errors from `lxd netcat` to a temp file

Hopefully this will help with debugging.

Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
---
 lxd/main_netcat.go | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/lxd/main_netcat.go b/lxd/main_netcat.go
index f5be1b3..00833f8 100644
--- a/lxd/main_netcat.go
+++ b/lxd/main_netcat.go
@@ -3,11 +3,26 @@ package main
 import (
 	"fmt"
 	"io"
+	"io/ioutil"
 	"net"
 	"os"
 	"sync"
 )
 
+type logErrorReader struct {
+	r io.Reader
+	f *os.File
+}
+
+func (le logErrorReader) Read(p []byte) (int, error) {
+	n, err := le.r.Read(p)
+	if err != nil {
+		fmt.Fprintf(le.f, "Error reading netcat stream: %v", err)
+	}
+
+	return n, err
+}
+
 // Netcat is called with:
 //
 //    lxd netcat /path/to/unix/socket
@@ -20,6 +35,12 @@ func cmdNetcat(args []string) error {
 		return fmt.Errorf("Bad arguments %q", args)
 	}
 
+	f, err := ioutil.TempFile("", "lxd_netcat_")
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
 	uAddr, err := net.ResolveUnixAddr("unix", args[1])
 	if err != nil {
 		return err
@@ -34,13 +55,19 @@ func cmdNetcat(args []string) error {
 	wg.Add(1)
 
 	go func() {
-		io.Copy(os.Stdout, conn)
+		_, err := io.Copy(os.Stdout, logErrorReader{conn, f})
+		if err != nil {
+			fmt.Fprintf(f, "Error netcatting to stdout: %v", err)
+		}
 		conn.Close()
 		wg.Done()
 	}()
 
 	go func() {
-		io.Copy(conn, os.Stdin)
+		_, err := io.Copy(conn, os.Stdin)
+		if err != nil {
+			fmt.Fprintf(f, "Error netcatting to stdout: %v", err)
+		}
 	}()
 
 	wg.Wait()