Fix a bug in shim log on Windows that can cause 100% CPU utilization

jterry75 · jterry75 · commit 828f6eb84245 · 2019-02-27T16:51:52.000-08:00
With the change to unified shims (ie: 1 shim per multiple tasks) the shimLog
on Windows for the 2nd-Nth worload containers will not have an associated
named pipe listener.

Due to a subtle bug in errors.Wrap passing a nil error we would unblock the
disconnected listener and return 0 byte successfull reads which would cause go
to continually read and cap the CPU.

Signed-off-by: Justin Terry (VM) &lt;juterry@microsoft.com&gt;
diff --git a/runtime/v2/shim_windows.go b/runtime/v2/shim_windows.go
@@ -78,7 +78,7 @@ func openShimLog(ctx context.Context, bundle *Bundle) (io.ReadCloser, error) {
 			time.Second*10,
 		)
 		if conerr != nil {
-			dpc.conerr = errors.Wrap(err, "failed to connect to shim log")
+			dpc.conerr = errors.Wrap(conerr, "failed to connect to shim log")
 		}
 		dpc.c = c
 		dpc.wg.Done()

Original file line number	Diff line number	Diff line change
`@@ -78,7 +78,7 @@ func openShimLog(ctx context.Context, bundle *Bundle) (io.ReadCloser, error) {`
`78`	`78`	`time.Second*10,`
`79`	`79`	`)`
`80`	`80`	`if conerr != nil {`
`81`		`- dpc.conerr = errors.Wrap(err, "failed to connect to shim log")`
	`81`	`+ dpc.conerr = errors.Wrap(conerr, "failed to connect to shim log")`
`82`	`82`	`}`
`83`	`83`	`dpc.c = c`
`84`	`84`	`dpc.wg.Done()`