Add an id for Docker containers #3
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Usual Linux images for Docker containers, does not have the originally listed files. Following the conversation at denisbrodbeck/machineid#10, I am including the following: Because `/proc/self/cgroup` seams to not be working on same Docker versions, I am also including `/proc/self/mountinfo`. Tested on `Python 3.11` running on `Debian GNU/Linux 11 (bullseye)` inside a Docker.
machineid/__init__.py
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| if not id: | ||
| id = __exec__('head -1 /proc/self/cgroup|cut -d/ -f3') | ||
| if not id: | ||
| id = __exec__("grep 'systemd' /proc/self/mountinfo|cut -d/ -f3") |
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| id = __exec__("grep 'systemd' /proc/self/mountinfo|cut -d/ -f3") | |
| id = __exec__("grep 'systemd' /proc/self/mountinfo | cut -d/ -f3") |
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Can you give me more detail on what /proc/self/mountinfo is and how it can be used as a unique ID? I don't think mountinfo is Docker-specific.
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@ezekg , this idea of using mountinfo, came from this post: https://stackoverflow.com/a/71823877/3780957
This post mentions, some versions do not have the ID at /proc/self/cgroup.
I am not sure if this is Docker specific. I can confirm that I check on a Docker instance, and that file has the same ID as /proc/self/cgroup.
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Got more info here. I think this is fine as long as you add a similar if 'docker' in mountinfo check as above.
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Also more discussion with the above workarounds is at opencontainers/runtime-spec#1105.
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Quick question, if __read__('/proc/self/mountinfo') returns None (because the file does not exist).
Will if 'docker' in mountinfo: return an exception?
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You’re right. I was only supplying pseudo code. I guess we should also check if mountinfo and 'docker' in mountinfo:. We shouldn’t raise an exception.
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You also need to fix the indentation (you're using 4 spaces but the rest of the file uses 2 spaces).
Please make sure the code runs.
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You’re right. I was only supplying pseudo code. I guess we should also check
if mountinfo and 'docker' in mountinfo:. We shouldn’t raise an exception.
There is no additional exception.
Currently on a Docker container the if 'docker' in cgroup: does not find docker, the ending Exception works as intended. Same test with mountinfo.
When the full code does not find an ID raises the following:
Python 3.11.0 (main, Nov 15 2022, 19:58:01) [GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import machineid
>>> print(machineid.id())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.11/site-packages/machineid/__init__.py", line 90, in id
raise Exception('failed to obtain id on platform {}'.format(platform))
Exception: failed to obtain id on platform linux
Following your review, I made some updates on the patch.
* Fixed the indentation to 2.
* Checked on a Docker container the `if 'docker' in cgroup:` works when the `docker` is not found. Same test with `mountinfo`.
* When the full code does not find an ID raises the following:
`Python 3.11.0 (main, Nov 15 2022, 19:58:01) [GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import machineid
>>> print(machineid.id())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.11/site-packages/machineid/__init__.py", line 90, in id
raise Exception('failed to obtain id on platform {}'.format(platform))
Exception: failed to obtain id on platform linux`
Check if `cgroup` and `mountinfo` are not None, before checking if `docker` is inside the file. To not rise a possible error when is trying to check `if 'docker' in None` (when the file does not exist).
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Released in v0.3.0: https://pypi.org/project/py-machineid/0.3.0/ |
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Great! Now is time to update my app and its dependencies :) |
Usual Linux images for Docker containers, does not have the originally listed files. Following the conversation at denisbrodbeck/machineid#10, I am including the following: Because
/proc/self/cgroupseams to not be working on same Docker versions, I am also including/proc/self/mountinfo.Tested on
Python 3.11running onDebian GNU/Linux 11 (bullseye)inside a Docker.