Retain a copy of container exit file on cleanup

When cleaning up containers, we presently remove the exit file
created by Conmon, to ensure that if we restart the container, we
won't have conflicts when Conmon tries writing a new exit file.

Unfortunately, we need to retain that exit file (at least until
we get a workable events system), so we can read it in cases
where the container has been removed before 'podman run' can read
its exit code.

So instead of removing it, rename it, so there's no conflict with
Conmon, and we can still read it later.

Fixes: #1640

Signed-off-by: Matthew Heon <mheon@redhat.com>

2 files changed, 14 insertions, 3 deletions

diff --git a/cmd/podman/run.go b/cmd/podman/run.go
index 6002578ff..86dc02dea 100644
--- a/cmd/podman/run.go
+++ b/cmd/podman/run.go
@@ -160,7 +160,7 @@ func runCmd(c *cliconfig.RunValues) error {
 
 // Read a container's exit file
 func readExitFile(runtimeTmp, ctrID string) (int, error) {
-	exitFile := filepath.Join(runtimeTmp, "exits", ctrID)
+	exitFile := filepath.Join(runtimeTmp, "exits", fmt.Sprintf("%s-old", ctrID))
 
 	logrus.Debugf("Attempting to read container %s exit code from file %s", ctrID, exitFile)
 
diff --git a/libpod/container_internal.go b/libpod/container_internal.go
index b0dcc853e..f82cbd674 100644
--- a/libpod/container_internal.go
+++ b/libpod/container_internal.go
@@ -489,9 +489,20 @@ func (c *Container) removeConmonFiles() error {
 		return errors.Wrapf(err, "error removing container %s OOM file", c.ID())
 	}
 
+	// Instead of outright deleting the exit file, rename it (if it exists).
+	// We want to retain it so we can get the exit code of containers which
+	// are removed (at least until we have a workable events system)
 	exitFile := filepath.Join(c.runtime.ociRuntime.exitsDir, c.ID())
-	if err := os.Remove(exitFile); err != nil && !os.IsNotExist(err) {
-		return errors.Wrapf(err, "error removing container %s exit file", c.ID())
+	oldExitFile := filepath.Join(c.runtime.ociRuntime.exitsDir, fmt.Sprintf("%s-old", c.ID()))
+	if _, err := os.Stat(exitFile); err != nil {
+		if !os.IsNotExist(err) {
+			return errors.Wrapf(err, "error running stat on container %s exit file", c.ID())
+		}
+	} else if err == nil {
+		// Rename should replace the old exit file (if it exists)
+		if err := os.Rename(exitFile, oldExitFile); err != nil {
+			return errors.Wrapf(err, "error renaming container %s exit file", c.ID())
+		}
 	}
 
 	return nil