Not compatible with cgroupv2

[pkoelbl]

This is not compatible with cgroupv2 and causes an error when initializing Application Insights Kubernetes
KubeHttpClientSettingsProvider.cs line 25 string pathToCGroup = @"/proc/self/cgroup"

See this for details
https://stackoverflow.com/questions/68816329/how-to-get-docker-container-id-from-within-the-container-with-cgroup-v2

[xiaomi7732]

Hi @pkoelbl Thanks for the reporting.

I tried it on docker 20.10.10 with the latest alpine and it appears still working:

Is there anything else needed to reproduce the issue? Thanks!

[pkoelbl]

I am on a Mac using Docker Desktop 4.4.2(73395) Docker engine 20.10.12 with Kubernetes 1.22.5 enabled. Using kubernetes to create the pod. Using mcr.microsoft.com/dotnet/aspnet:5.0-buster-slim as the base image. When i connect to the pod and look at the cgroup file it is empty.

[pkoelbl]

The app is also running as a non-root user.

[xiaomi7732]

@pkoelbl Thanks for the update. We will look into that.

[xiaomi7732]

@pkoelbl I updated the env (Docker Desktop: 4.5.1, Engine: 20.10.12, K8s:1.22.5), am still able to access cgroups:

PS D:\> docker run -it mcr.microsoft.com/dotnet/aspnet:5.0-buster-slim
root@ca7739f0a9f1:/# cat /proc/self/cgroup
14:name=systemd:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
13:rdma:/
12:pids:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
11:hugetlb:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
10:net_prio:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
9:perf_event:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
8:net_cls:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
7:freezer:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
6:devices:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
5:blkio:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
4:cpuacct:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
3:cpu:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
2:cpuset:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
1:memory:/docker/ca7739f0a9f1ab77959378e36b48c22d68410adae6db2e44be7b04271e49a81c
0::/
root@ca7739f0a9f1:/# exit
exit

Yes, I am running as root there, and that makes me think, maybe the problem is not about cgroup, it is about permission. Do you mind run the same command in your environment just to see what if you have root?

docker pull mcr.microsoft.com/dotnet/aspnet:5.0-buster-slim
docker run -it mcr.microsoft.com/dotnet/aspnet:5.0-buster-slim

/# cat /proc/self/cgroup

[pkoelbl]

When running that I get

root@c70c50bfc108:/# cat /proc/self/cgroup   
0::/
root@c70c50bfc108:/# 

[pkoelbl]

This started happening when I did a clean install of docker after reloading my Mac. So it may be a matter of a setting that isn't there anymore in docker 20.10.12 but would be left over from an upgrade from a previous version

[pkoelbl]

In the file ~/Library/Group\ Containers/group.com.docker/settings.json
I set deprecatedCgroupv1 to true then restarted docker and it fixed the problem.

However given the name of that variable, it looks like Docker is in the process of deprecating cgroup v1. So this will become a problem again in the future.

[xiaomi7732]

@pkoelbl Thank you for figuring that out. You point about deprecating cgroupv1 is well taken. We will need to understand how to make it work with cgroupv2 or find out some other ways to get the same information. I will keep this issue active until we have a solution.