fix container_oom_events_total always returns 0.

In a Kubernetes pod, if a container is OOM-killed, it will be deleted and a new container will be created. Therefore, the `container_oom_events_total` metric will always be 0. It would be useful to preserve the metrics of the OOM-killed containers instead of deleting them.

Signed-off-by: joey <zchengjoey@gmail.com>

manager/manager.go

@@ -297,7 +297,7 @@ func (m *manager) Start() error {
 		return err
 	}
 	klog.V(2).Infof("Starting recovery of all containers")
-	err = m.detectSubcontainers("/")
+	err = m.detectSubContainers("/")
 	if err != nil {
 		return err
 	}
@@ -385,7 +385,7 @@ func (m *manager) globalHousekeeping(quit chan error) {
 			start := time.Now()
 
 			// Check for new containers.
-			err := m.detectSubcontainers("/")
+			err := m.detectSubContainers("/")
 			if err != nil {
 				klog.Errorf("Failed to detect containers: %s", err)
 			}
@@ -1009,6 +1009,10 @@ func (m *manager) destroyContainerLocked(containerName string) error {
 		// Already destroyed, done.
 		return nil
 	}
+	// If the container is OOM-killed, keep monitoring metrics for the container.
+	if cont.oomEvents != 0 {
+		return nil
+	}
 
 	// Tell the container to stop.
 	err := cont.Stop()
@@ -1045,7 +1049,7 @@ func (m *manager) destroyContainerLocked(containerName string) error {
 
 // Detect all containers that have been added or deleted from the specified container.
 func (m *manager) getContainersDiff(containerName string) (added []info.ContainerReference, removed []info.ContainerReference, err error) {
-	// Get all subcontainers recursively.
+	// Get all subContainers recursively.
 	m.containersLock.RLock()
 	cont, ok := m.containers[namespacedContainerName{
 		Name: containerName,
@@ -1067,8 +1071,8 @@ func (m *manager) getContainersDiff(containerName string) (added []info.Containe
 	// Determine which were added and which were removed.
 	allContainersSet := make(map[string]*containerData)
 	for name, d := range m.containers {
-		// Only add the canonical name.
-		if d.info.Name == name.Name {
+		// Only add the canonical name. Preserve containers that were deleted due to OOMKilled.
+		if d.info.Name == name.Name && d.oomEvents != 0 {
 			allContainersSet[name.Name] = d
 		}
 	}
@@ -1092,8 +1096,8 @@ func (m *manager) getContainersDiff(containerName string) (added []info.Containe
 	return
 }
 
-// Detect the existing subcontainers and reflect the setup here.
-func (m *manager) detectSubcontainers(containerName string) error {
+// Detect the existing subContainers and reflect the setup here.
+func (m *manager) detectSubContainers(containerName string) error {
 	added, removed, err := m.getContainersDiff(containerName)
 	if err != nil {
 		return err
@@ -1136,7 +1140,7 @@ func (m *manager) watchForNewContainers(quit chan error) error {
 	}
 
 	// There is a race between starting the watch and new container creation so we do a detection before we read new containers.
-	err := m.detectSubcontainers("/")
+	err := m.detectSubContainers("/")
 	if err != nil {
 		return err
 	}