Re: Question about LTTng Context

[Amir Najafi Zadeh via lttng-dev <lttng-dev@lists.lttng.org>]

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I'll try that too. Thanks for mentioning it.

Cheers,
Amir

On Thu, 11 Dec 2025, 11:14 Michael Jeanson, <mjeanson@efficios.com> wrote:

> On 12/11/25 10:51, Amir Najafi Zadeh wrote:
> > Michael, Kienan, Thank you both for your replies. As you mentioned the
> > cgroup namespace, it isn’t very helpful in some cases. Containers may
> > share the same cgroup namespace, and the container runtime often avoids
> > giving each container a private cgroup namespace for performance and
> > security reasons. Because of this, the cgroup namespace can’t be used as
> > a reliable or unique label for filtering trace logs.
> >
> > In my case, with container-d you can inspect a container, find its PID,
> > and then check /proc/<pid>/ns/cgroup, but you’ll see that different
> > containers often have the same cgroup namespace ID (e.g., in the
> > following logs you can see the calico-node and kube-proxy containers
> > sharing a cgroup ns).
>
> If you want to track containers, the pid namespace is the one used by
> most container runtimes but I don't know specifically for container-d.
>
> >
> > ```
> > Name: calico-node  CID:
> > b5624afe31b005725f4ba53c7b6fe758f3c09fabf013085231ff8b97588f6ace  PID:
> > 2243  cgroup_ns_inode: 4026531835
> > Name: kube-proxy  CID:
> > 52f3c12def7a680f61a925ac92dd5ebd5eba6cad17d671efbfd1d40db7dff624  PID:
> > 1851  cgroup_ns_inode: 4026531835
> >    >> MATCH FOUND: shares ns with container:
> > b5624afe31b005725f4ba53c7b6fe758f3c09fabf013085231ff8b97588f6ace
> > (calico-node)
> > ```
> >
> > Thanks again for your answers. I hope this feature appears in a future
> > patch.
> >
> > Best,
> > Amir
> >
> > On Thu, Dec 11, 2025 at 9:57 AM Michael Jeanson <mjeanson@efficios.com
> > <mailto:mjeanson@efficios.com>> wrote:
> >
> >     On 12/11/25 09:30, Kienan Stewart via lttng-dev wrote:
> >      > Hi Amir,
> >      >
> >      > On 12/10/25 9:40 PM, Amir Najafi Zadeh via lttng-dev wrote:
> >      >> Hello everyone,
> >      >>
> >      >> I hope you’re doing well. My name is Amir, and I’m a PhD student
> in
> >      >> the Computer Science department at Stony Brook University, New
> York.
> >      >>
> >      >> I have a question about the LTTng context that I haven’t been
> >     able to
> >      >> find an answer for in the docs or man pages. Does LTTng support
> >     adding
> >      >> the cgroup ID or cgroup path as a context field? I want to
> >     filter my
> >      >> trace results based on cgroups.
> >      >>
> >      >
> >      > I think you're looking for the `cgroup_ns` context which adds the
> >     inum
> >      > of the cgroup namespace as a context field.
> >
> >     This will give you the ID of the cgroup namespace but we don't have
> >     contexts for cgroups themselves. It's probably something we would
> like
> >     to have but there is no concrete plans on implementing this at the
> >     moment.
> >
> >      >
> >      >> If this isn’t supported, are there any plans to add it in future
> >      >> versions, such as 2.14?
> >      >>
> >      >> For reference, I’m currently using LTTng 2.13 on Ubuntu 24.04
> with
> >      >> kernel 6.8.0-87-generic.
> >      >>
> >      >> Cheers,
> >      >> Amir
> >      >> --
> >      >> *Amirhossein Najafizadeh*
> >      >> *PhD Student, Computer Science Department, Stony Brook
> >     University, N.Y.
> >      >> File systems and Storage Lab (FSL)
> >
>
>

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