Cannot call GetContainerStats through varlink for rootless containers

[marusak]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description
I cannot call GetContainerStats through varlink for rootless containers. It works for root containers.

Steps to reproduce the issue:

1. Execute

/usr/bin/podman varlink -t 100000 unix:/run/user/1000/podman/io.podman

in one terminal

2. Start a new user owned container in another terminal
   podman run -dit --name foobar fedora

3. Try to get stats
   varlink call unix:/run/user/1000/podman/io.podman/io.podman.GetContainerStats '{ "name": "foobar" }'

Describe the results you received:

{
  "reason": "unable to load cgroup at /libpod_parent/libpod-4e9f3f856cdd2d1cb9d50d5daa12d06d1a258f0ad2c692316c438e2586399163: cgroups: cgroup deleted"
}

Describe the results you expected:
Expected proper stats about the container

Additional information you deem important (e.g. issue happens only occasionally):
Works fine for root contianers:

$ sudo /usr/bin/podman varlink -t 100000 unix:/run/podman/io.podman
$ sudo podman run -dit --name foobar fedora
$ sudo  varlink call unix:/run/podman/io.podman/io.podman.GetContainerStats '{ "name": "foobar" }'
{
  "container": {
    "block_input": 0,
    "block_output": 0,
    "cpu": 5.325716717611001679778e-08,
    "cpu_nano": 208393314,
    "id": "f2b57dda297602034f20fb6f9e73e39dfbd866201374eab172384659bbe12e8a",
    "mem_limit": 16452386816,
    "mem_perc": 1.481316982913319715842e-02,
    "mem_usage": 2437120,
    "name": "foobar",
    "net_input": 628,
    "net_output": 11184,
    "pids": 1,
    "system_nano": 0
  }
}

Also works fine for other methods like ListContainers for rootless containers.

Output of podman version:

Version:            1.4.4
RemoteAPI Version:  1
Go Version:         go1.12.7
OS/Arch:            linux/amd64

Output of podman info --debug:

debug:
  compiler: gc
  git commit: ""
  go version: go1.12.7
  podman version: 1.4.4
host:
  BuildahVersion: 1.9.0
  Conmon:
    package: podman-1.4.4-4.fc30.x86_64
    path: /usr/libexec/podman/conmon
    version: 'conmon version 1.0.0-dev, commit: 164df8af4e62dc759c312eab4b97ea9fb6b5f1fc'
  Distribution:
    distribution: fedora
    version: "30"
  MemFree: 4705746944
  MemTotal: 16452386816
  OCIRuntime:
    package: containerd.io-1.2.1-2.0.rc.0.1.fc29.x86_64
    path: /usr/sbin/runc
    version: |-
      runc version 1.0.0-rc5+dev
      commit: 10d38b660a77168360df3522881e2dc2be5056bd
      spec: 1.0.1-dev
  SwapFree: 0
  SwapTotal: 0
  arch: amd64
  cpus: 4
  hostname: trv1819.localdomain
  kernel: 5.1.20-300.fc30.x86_64
  os: linux
  rootless: true
  uptime: 21h 36m 54.73s (Approximately 0.88 days)
registries:
  blocked: null
  insecure: null
  search:
  - docker.io
  - registry.fedoraproject.org
  - quay.io
  - registry.access.redhat.com
  - registry.centos.org
store:
  ConfigFile: /home/mmarusak/.config/containers/storage.conf
  ContainerStore:
    number: 6
  GraphDriverName: overlay
  GraphOptions:
  - overlay.mount_program=/usr/bin/fuse-overlayfs
  GraphRoot: /home/mmarusak/.local/share/containers/storage
  GraphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  ImageStore:
    number: 6
  RunRoot: /run/user/1000
  VolumePath: /home/mmarusak/.local/share/containers/storage/volumes

[mheon]

Stats does not work for rootless right now, as it requires the container to have CGroups - rootless containers presently do not have privileges to create their own.

With the crun OCI runtime and a CGroups v2 enabled system, this may work - @giuseppe

[baude]

i will add a proper error response.