vm/gce: always ignore serial relay errors

GCE serial reply seems to be buggy, we see lots of "serialport: VM disconnected"
and "packet_write_wait: Connection to 1.2.3.4 port 9600: Broken pipe"
errors, which do not have any explanation.
Ignore all serial relay errors.

2 files changed, 16 insertions, 3 deletions

diff --git a/vm/vmimpl/merger.go b/vm/vmimpl/merger.go
index b189a40f0..2de32e53b 100644
--- a/vm/vmimpl/merger.go
+++ b/vm/vmimpl/merger.go
@@ -18,6 +18,16 @@ type OutputMerger struct {
 	wg     sync.WaitGroup
 }
 
+type MergerError struct {
+	Name string
+	R    io.ReadCloser
+	Err  error
+}
+
+func (err MergerError) Error() string {
+	return fmt.Sprintf("failed to read from %v: %v", err.Name, err.Err)
+}
+
 func NewOutputMerger(tee io.Writer) *OutputMerger {
 	return &OutputMerger{
 		Output: make(chan []byte, 1000),
@@ -84,7 +94,7 @@ func (merger *OutputMerger) AddDecoder(name string, r io.ReadCloser,
 				}
 				r.Close()
 				select {
-				case merger.Err <- fmt.Errorf("failed to read from %v: %v", name, err):
+				case merger.Err <- MergerError{name, r, err}:
 				default:
 				}
 				merger.wg.Done()
diff --git a/vm/vmimpl/merger_test.go b/vm/vmimpl/merger_test.go
index 335dcb228..dd44af57f 100644
--- a/vm/vmimpl/merger_test.go
+++ b/vm/vmimpl/merger_test.go
@@ -5,6 +5,7 @@ package vmimpl
 
 import (
 	"bytes"
+	"io"
 	"testing"
 	"time"
 
@@ -61,8 +62,10 @@ func TestMerger(t *testing.T) {
 		t.Fatalf("bad line: '%s', want '%s'", got, want)
 	}
 
-	if err := <-merger.Err; err == nil || err.Error() != "failed to read from pipe1: EOF" {
-		t.Fatalf("merger did not produce io.EOF: %v", err)
+	if err := <-merger.Err; err == nil {
+		t.Fatalf("merger did not produce an error on pipe close")
+	} else if merr := err.(MergerError); merr.Name != "pipe1" || merr.R != rp1 || merr.Err != io.EOF {
+		t.Fatalf("merger produced wrong error: %v", err)
 	}
 
 	wp2.Close()