Include changes to the container's root file-system in the checkpoint archive #3443
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Can one of the admins verify this patch?
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adrianreber
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☔ The latest upstream changes (presumably #3442) made this pull request unmergeable. Please resolve the merge conflicts. |
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LGTM |
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Mind holding this until I get back? I want to do a pass over the API stuff
before merge
…On Thu, Jun 27, 2019, 20:37 Brent Baude ***@***.***> wrote:
LGTM
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/hold |
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☔ The latest upstream changes (presumably #3496) made this pull request unmergeable. Please resolve the merge conflicts. |
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The newly added function GetDiffTarStream() mirrors the GetDiff() function. It tries to get the correct layer ID from getLayerID() and it filters out containerMounts from the tarstream. Thus the behavior is the same as GetDiff(), but it returns a tarstream. This also adds the function ApplyDiffTarStream() to apply the tarstream generated by GetDiffTarStream(). These functions are targeted to support container migration with root file-system changes. Signed-off-by: Adrian Reber <[email protected]>
One of the last limitations when migrating a container using Podman's 'podman container checkpoint --export=/path/to/archive.tar.gz' was that it was necessary to manually handle changes to the container's root file-system. The recommendation was to mount everything as --tmpfs where the root file-system was changed. This extends the checkpoint export functionality to also include all changes to the root file-system in the checkpoint archive. The checkpoint archive now includes a tarstream of the result from 'podman diff'. This tarstream will be applied to the restored container before restoring the container. With this any container can now be migrated, even it there are changes to the root file-system. There was some discussion before implementing this to base the root file-system migration on 'podman commit', but it seemed wrong to do a 'podman commit' before the migration as that would change the parent layer the restored container is referencing. Probably not really a problem, but it would have meant that a migrated container will always reference another storage top layer than it used to reference during initial creation. Signed-off-by: Adrian Reber <[email protected]>
Signed-off-by: Adrian Reber <[email protected]>
The newly added functionality to include the container's root file-system changes into the checkpoint archive can now be explicitly disabled. Either during checkpoint or during restore. If a container changes a lot of files during its runtime it might be more effective to migrated the root file-system changes in some other way and to not needlessly increase the size of the checkpoint archive. If a checkpoint archive does not contain the root file-system changes information it will automatically be skipped. If the root file-system changes are part of the checkpoint archive it is also possible to tell Podman to ignore these changes. Signed-off-by: Adrian Reber <[email protected]>
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This adds three tests for the --ignore-rootfs option to verify that it works in all combination. 1. Not used at all 2. Only used during restore 3. Only used during checkpoint Signed-off-by: Adrian Reber <[email protected]>
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Rebased and all tests are green. Can the hold be removed? |
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/hold cancel Will review today or tomorrow |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: adrianreber, mheon The full list of commands accepted by this bot can be found here. The pull request process is described here
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@mheon I see that you are really busy with many other PRs, so this is just a friendly ping if you have a chance to look at this. |
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/lgtm |
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locked - please file new issue/PR
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One limitation of Podman's container migration feature was that it was problematic to migrate containers which changed their root file-system. The recommendation until now was to mount all directories which the container potentially changes with
--tmpfs. Everything in a--tmpfswas already included in the checkpoint archive.To make it easier for the users to migrate a container, without first mounting all directories with possible changes with
--tmpfs, this now adds container root file-system changes to the checkpoint archive.To extract the changes to the container's root file-system the functionality behind
podman diffis used. There were discussion about usingpodman commit, but that would mean that the restored container is now referencing another storage top layer than it was started with. Usingpodman diffmakes it possible to have the restored container the same as possible as the original container.If the root file-system changes are very large or unnecessary for the container migration there is now a new option for checkpoint and restore called:
--ignore-rootfs. This option tells Podman to not include the root file-system changes in the checkpoint archive during checkpointing, or if they are part of the checkpoint archive to ignore the root file-system changes during restore.