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NewSystemd handles UnitExists when starting units #290

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merged 1 commit into from
Jul 16, 2023

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mmerkes
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@mmerkes mmerkes commented Apr 23, 2023

As done in this runc PR
opencontainers/runc#3782,
UnitExists errors are no longer ignored when starting units. If it already exists, we attempt to reset the failed unit and retry once. Otherwise, we fail. See #279 for more context.

Fixes #279

In generally, I'm following runc's example and making this code more robust. See code and commit for more details. Ideally, we'd reuse the code, but don't currently have a dependency on runc as a library here and I don't have enough context to know if that would be reasonable or not.

@mmerkes mmerkes force-pushed the unitexists branch 2 times, most recently from 699e348 to 8565c75 Compare May 20, 2023 21:30
@mmerkes mmerkes changed the title [WIP] NewSystemd handles UnitExists when starting units NewSystemd handles UnitExists when starting units May 20, 2023
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mmerkes commented May 20, 2023

@kolyshkin Let me know if you have feedback here since you opened the original issue and made the runc change. Tx!

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Alas, I am not a maintainer and can't say which uses/users this method has.

But nevertheless a fix needs to be made, because the current behavior (of not adding the container into a proper cgroup) is totally unacceptable (and can, in some circumstances, be qualified as a security issue).

So, I'm adding my non-binding LGTM, but this needs a review from the actual maintainers of this package.

.gitignore Outdated
@@ -1,2 +1,5 @@
example/example
cmd/cgctl/cgctl

*.swp
coverage.txt
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These settings should be in your home directory

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Please squash commits

As done in opencontainers/runc#3782,
UnitExists errors are no longer ignored when starting units.
This change makes the logic more robust like in runc:

1. Attempts to reset a failed unit if it already exists
2. Verifies via the unit status that it successfully starts
3. Waits longer for unit to start
4. Continues to ignore unit existing when pid is -1 to
accommodate kubelet use case
5. Otherwise, returns an error if it already exists

Signed-off-by: Matt Merkes <[email protected]>

Update .gitignore

Signed-off-by: Matt <[email protected]>
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mmerkes commented Jun 28, 2023

Please squash commits

Updated. Falsely assumed that the merge would squash. @AkihiroSuda

@AkihiroSuda AkihiroSuda requested a review from thaJeztah June 28, 2023 17:49
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LGTM

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mmerkes commented Jul 14, 2023

@AkihiroSuda This good to be merged?

@AkihiroSuda AkihiroSuda merged commit a0ae1c2 into containerd:main Jul 16, 2023
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NewSystemd must not ignore UnitExists
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