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Allow gathering of stats for root cgroup on v2 #2801

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Mar 2, 2021
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Allow gathering of stats for root cgroup on v2 #2801

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19 changes: 10 additions & 9 deletions container/libcontainer/handler.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,21 +71,22 @@ func NewHandler(cgroupManager cgroups.Manager, rootFs string, pid int, includedM

// Get cgroup and networking stats of the specified container
func (h *Handler) GetStats() (*info.ContainerStats, error) {
var cgroupStats *cgroups.Stats
readCgroupStats := true
ignoreStatsError := false
if cgroups.IsCgroup2UnifiedMode() {
// On cgroup v2 there are no stats at the root cgroup
// so check whether it is the root cgroup
// On cgroup v2 the root cgroup stats have been introduced in recent kernel versions,
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do you know from what kernel versions root cgroup stats are supported? That would be good to note.

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I think there has been a floating transition to add various stats to the root cgroups in different versions. I am running mainline right now, and there are still some stats lacking right now as well.

I can do a small digging job, but I guess it will take some time (unless I find the data in a structured format somewhere)... :)

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no biggie if it's hard to find, was just curious :)

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Will take a look anyway! Always nice with some background info.

// so not all kernel versions have all the data. This means that stat fetching can fail
// due to lacking cgroup stat files, but that some data is provided.
if h.cgroupManager.Path("") == fs2.UnifiedMountpoint {
readCgroupStats = false
ignoreStatsError = true
}
}
var err error
if readCgroupStats {
cgroupStats, err = h.cgroupManager.GetStats()
if err != nil {

cgroupStats, err := h.cgroupManager.GetStats()
if err != nil {
if !ignoreStatsError {
return nil, err
}
klog.V(4).Infof("Ignoring errors when gathering stats for root cgroup since some controllers don't have stats on the root cgroup: %v", err)
}
libcontainerStats := &libcontainer.Stats{
CgroupStats: cgroupStats,
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