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plugin/localbinary: Exit output stream goroutines when plugin closes

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This commit ensures that when a plugin instance is closed the goroutines
responsible for streaming stdout and stderr of the called binary will
also exit, preventing a goroutines leak.

Before this commit these goroutines could stay blocked forever if
Close() was called while the binary still had some pending output.

I found this bug after debugging a real world goroutine leak, the
goroutines dump would show thousands of goroutines at:

```
github.com/tsuru/tsuru/vendor/github.com/docker/machine/libmachine/drivers/plugin/localbinary.stream(0xc023013d80, 0xc0000aad20)
	/home/travis/gopath/src/github.com/tsuru/tsuru/vendor/github.com/docker/machine/libmachine/drivers/plugin/localbinary/plugin.go:177 +0x7c
created by github.com/tsuru/tsuru/vendor/github.com/docker/machine/libmachine/drivers/plugin/localbinary.(*Plugin).AttachStream
	/home/travis/gopath/src/github.com/tsuru/tsuru/vendor/github.com/docker/machine/libmachine/drivers/plugin/localbinary/plugin.go:183 +0x67
```

Signed-off-by: Cezar Sa Espinola <cezarsa@gmail.com>
This commit is contained in:
Cezar Sa Espinola
2018-12-28 16:02:20 -02:00
committed by Joffrey F
parent 5a8ce1ae43
commit 55bfb59b67
2 changed files with 14 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
libmachine/drivers/plugin/localbinary/plugin.go
View File

@@ -72,7 +72,7 @@ type Plugin struct {
Addr string
MachineName string
addrCh chan string
stopCh chan bool
stopCh chan struct{}
timeout time.Duration
}
@@ -121,7 +121,7 @@ func NewPlugin(driverName string) (*Plugin, error) {
log.Debugf("Found binary path at %s", binaryPath)
return &Plugin{
stopCh: make(chan bool),
stopCh: make(chan struct{}),
addrCh: make(chan string, 1),
Executor: &Executor{
DriverName: driverName,
@@ -168,19 +168,23 @@ func (lbe *Executor) Close() error {
return nil
}
func stream(scanner *bufio.Scanner, streamOutCh chan<- string) {
func stream(scanner *bufio.Scanner, streamOutCh chan<- string, stopCh <-chan struct{}) {
for scanner.Scan() {
line := scanner.Text()
if err := scanner.Err(); err != nil {
log.Warnf("Scanning stream: %s", err)
}
streamOutCh <- strings.Trim(line, "\n")
select {
case streamOutCh <- strings.Trim(line, "\n"):
case <-stopCh:
return
}
}
}
func (lbp *Plugin) AttachStream(scanner *bufio.Scanner) <-chan string {
streamOutCh := make(chan string)
go stream(scanner, streamOutCh)
go stream(scanner, streamOutCh, lbp.stopCh)
return streamOutCh
}
@@ -241,6 +245,6 @@ func (lbp *Plugin) Address() (string, error) {
}
func (lbp *Plugin) Close() error {
lbp.stopCh <- true
close(lbp.stopCh)
return nil
}

8
libmachine/drivers/plugin/localbinary/plugin_test.go
View File

@@ -71,10 +71,10 @@ func TestLocalBinaryPluginAddressTimeout(t *testing.T) {
func TestLocalBinaryPluginClose(t *testing.T) {
lbp := &Plugin{}
lbp.stopCh = make(chan bool, 1)
lbp.stopCh = make(chan struct{})
go lbp.Close()
stopped := <-lbp.stopCh
if !stopped {
_, isOpen := <-lbp.stopCh
if isOpen {
t.Fatal("Close did not send a stop message on the proper channel")
}
}
@@ -106,7 +106,7 @@ func TestExecServer(t *testing.T) {
MachineName: machineName,
Executor: fe,
addrCh: make(chan string, 1),
stopCh: make(chan bool, 1),
stopCh: make(chan struct{}),
}
finalErr := make(chan error)