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sdjournal: please add support for journal namespaces #413

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klaernie opened this issue Nov 9, 2022 · 2 comments · May be fixed by #421
Open

sdjournal: please add support for journal namespaces #413

klaernie opened this issue Nov 9, 2022 · 2 comments · May be fixed by #421

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@klaernie
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klaernie commented Nov 9, 2022

I am using sdjournal indirectly with the filebeat journald input, and was wondering if reading from a non-default journald namespace is supported directly. I know that I can point filebeat to the namespace's systemd.journal file residing in /var/lib/journal/machine-id.namespace, but this requires knowledge of the machine-id for each individual server.
I solved the problem for our system by symlinking the machine-id.namespace directory to a machine-independent path, but this still feels hacked together.

Looking at the code it doesn't seem like, so I just wanted to confirm.

Thanks a lot and all the best!
@lucab lucab changed the title sdjournal: is reading from journald namespaces supported? sdjournal: please add support for journal namespaces Nov 10, 2022
@lucab
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lucab commented Nov 10, 2022

Good question! There are multiple levels to cover on this:

  • The sdjournal package is built on top of C primitives provided by libsystemd.so, so it could in theory support namespaced journals without much troubles by wrapping the relevant API.
  • It looks like we are not currently binding the libsystemd function sd_journal_open_namespace() to a Go wrapper. This is likely not on purpose, but because the Go package is older than the journal namespace logic.
  • We should add a NewJournalFromNamespace(...) wrapper (or similar name), I've retitled this ticket accordingly. I don't currently have bandwidth to tackle this myself this month, but I can happily review PRs.
  • The sd_journal_open_namespace() API has been added only recently in systemd (>= 245, 2020/03). We'll need to make consumers aware that this helper won't work or be available on older environments.

@klaernie
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Thanks for letting me know!

While I'd love to just dig in and implement this, I sadly have no golang skills, but I don't expect you or any contributor to jump at that anyway.

Regarding the behaviour with systemd<245 I'd probably just expect a "does not exist" error, after all you only start reading logs from a namespace if you already write to one, which wouldn't work there as well (I even had to make a minor OS upgrade to get a namespaced journal available for my application). So unless the golang-c interaction breaks on that I'd consider this all the awareness needed.

igor-tsiglyar pushed a commit to igor-tsiglyar/go-systemd that referenced this issue May 17, 2023
sdjournal: add sd_journal_open_namespace wrapper
2665651 
wrap sd_journal_open_namespace C call to enable reading
journal records in non-default namespace

fixes coreos#413
@igor-tsiglyar igor-tsiglyar linked a pull request May 17, 2023 that will close this issue
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igor-tsiglyar pushed a commit to igor-tsiglyar/go-systemd that referenced this issue Jun 5, 2023
sdjournal: add sd_journal_open_namespace wrapper
00cf474 
wrap sd_journal_open_namespace C call to enable reading
journal records in non-default namespace

fixes coreos#413
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sdjournal: add sd_journal_open_namespace wrapper igor-tsiglyar/go-systemd
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@lucab @klaernie