Retrieving the PID of a specific container

[danielkleinstein]

Hi all, I'm trying to understand if I can use cAdvisor to monitor for newly created containers and then retrieve the PID of those specific containers.

I am using this API:

http://localhost:8080/api/v1.3/events?stream=true&all_events=true&subcontainers=true

Which allows me to monitor for new containers. I then receive a message such as:

{"container_name":"/system.slice/docker-394b73cdd59f26778a19868b9f960837914c12392177f76a54841df6f9f20586.scope","timestamp":"2024-02-21T13:23:55.844120129Z","event_type":"containerCreation","event_data":{}}

i.e. a container with a name of /system.slice/docker-394b73cdd59f26778a19868b9f960837914c12392177f76a54841df6f9f20586.scope, which I've learned is the name of the container's cgroup.

If I query the (undocumented) /ps endpoint at:

http://localhost:8080/api/v2.0/ps

Then I see my container in the output:

...
{"user":"root","pid":337870,"parent_pid":337850,"start_time":"13:23","percent_cpu":0,"percent_mem":0,"rss":3801088,"virtual_size":4739072,"status":"Ss+","running_time":"00:00:00","cgroup_path":"/../docker-394b73cdd59f26778a19868b9f960837914c12392177f76a54841df6f9f20586.scope","cmd":"bash","fd_count":4,"psr":5},
...

Which has the PID I want - 337870. However this involves retrieving the entirety of /ps output to retrieve the PID of a specific container, which has non-trivial performance implications in my usecase. I tried to do this:

http://localhost:8080/api/v2.0/ps/system.slice/docker-394b73cdd59f26778a19868b9f960837914c12392177f76a54841df6f9f20586.scope

To retrieve the specific container's information, but then I just get an empty list:

[]

And trying variations of the name (e.g. copying the /../docker-394b73cdd59f26778a19868b9f960837914c12392177f76a54841df6f9f20586.scope cgroup_path specified in the /ps output above) invariably results in a:

process listing failed: unknown container 

Would really appreciate help on this, thanks in advance!