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Ignore missing config.v2.json files on migration #303

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Ignore missing config.v2.json files on migration #303

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lmbarros
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@lmbarros lmbarros commented Jul 14, 2022 •
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TODO: One thing we should do in this PR: if every attempt of making the migration fails, simply remove all images and containers and let the device redownload everything. (This is actually how we designed the migration, but not the observed behavior.)

We have seen some cases in which the file
/var/lib/docker/containers/<UUID>/config.v2.json was not found for
certain UUIDs. This causes the whole migration to fail and, worse,
causes our migration cleanup code to fail.

A missing config.v2.json indicates that directory does not contain a
valid container, so we should not even try to migrate them. That's what
this commit does: it makes the migration ignore directories with a
missing config.v2.json.

I don't think we should have directories like this in the first place,
this is probably the side effect of some other issue. That said, Docker
itself ignores these directories (after logging a warning) during
startup, so here are just bringing the Engine in line with the standard
behavior.

Resolves #301

- What I did

- How I did it

- How to verify it

- Description for the changelog

@lmbarros lmbarros self-assigned this Jul 14, 2022
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ghost commented Jul 14, 2022

An error occurred whilst building your landr site preview:

{
  "name": "Error",
  "message": "Command failed with code undefined: /usr/src/app/node_modules/gatsby/cli.js build",
  "stack": "Error: Command failed with code undefined: /usr/src/app/node_modules/gatsby/cli.js build\n    at Object.exports.run (/usr/src/app/lib/build-runner.js:257:11)\n    at async build (/usr/src/app/bot/index.js:132:19)\n    at async /usr/src/app/bot/index.js:210:25\n    at async Promise.all (index 0)\n    at async middleware (/usr/src/app/node_modules/@octokit/webhooks/dist-node/index.js:355:5)"
}

@lmbarros
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Totally untested as of now, therefore keeping PR as a draft.

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[alexgg] This has attached https://jel.ly.fish/9aaf5f96-265c-4c52-9e59-074e973b53f8

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zoobot commented Nov 12, 2022

I added a test and some error handling but not quite ready to merge this as my tests aren't working when I run individual tests.

The migrate_test.go tests pass when I run all the tests: make test-unit

But these all fail with package errors and GOROOT/GOPATH errors so I need to sort that out.
make test-unit TESTDIRS=pkg
make test-unit TESTDIRS=pkg/storagemigration
make test-unit TESTDIRS=pkg/storagemigration/migrate_test.go

@zoobot zoobot self-assigned this Nov 12, 2022
@zoobot zoobot linked an issue Nov 12, 2022 that may be closed by this pull request
Aufs to overlay2 migration failure #301
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@lmbarros
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Hey @zoobot ! I think you need to include the ./ prefix:

make test-unit TESTDIRS=./pkg/storagemigration

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zoobot commented Nov 14, 2022

That . worked! :) thanks @lmbarros

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zoobot commented Nov 14, 2022

Adding this here as reference for all the changes to make this happen:
https://github.com/balena-os/balena-engine/pull/168/files

And the improvement:
https://jel.ly.fish/product-improvement-migrate-device-storage-driver-from-aufs-to-overlayfs-22cf335f-b1f7-44f8-853d-064681c69fd8

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zoobot commented Nov 21, 2022

Update on this @lmbarros :

Was hoping to get a rpi3 to test on, Ross is sending one.
Also trying to set up QEMU to test this on for quicker results, sorting out m1 QEMU issues.

Making changes today:
Don't just delete single container layer that has missing config.v2.json

On migration failure due to missing config.v2.json:
Remove all overlay2 layers, aufs layers remain

@lmbarros @zoobot
Ignore missing config.v2.json files on migration
5d01bf7 
We have seen some cases in which the file
`/var/lib/docker/containers/<UUID>/config.v2.json` was not found for
certain UUIDs. This causes the whole migration to fail and, worse,
causes our migration cleanup code to fail.

A missing `config.v2.json` indicates that directory does not contain a
valid container, so we should not even try to migrate them. That's what
this commit does: it makes the migration ignore directories with a
missing `config.v2.json`.

I don't think we should have directories like this in the first place,
this is probably the side effect of some other issue. That said, Docker
itself ignores these directories (after logging a warning) during
startup, so here are just bringing the Engine in line with the standard
behavior.

Signed-off-by: Leandro Motta Barros <[email protected]>
Change-type: patch
@zoobot zoobot force-pushed the lmb/dont-migrate-bad-containers branch 3 times, most recently from 8162043 to b71b5df Compare November 21, 2022 23:56
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zoobot commented Nov 21, 2022

@lmbarros
I made the changes to test and cleanup so it removes all the overlay2 folders/containers on rollback, instead of just removing the single layer with the missing config.v2.json.

Should we wait until I have a RP3 device or QEMU to test this on or roll it out with the current go test?
Do you always test on devices first?

Thanks for looking

lmbarros
lmbarros commented Nov 22, 2022
View reviewed changes
pkg/storagemigration/failcleanup.go Outdated
@@ -36,5 +31,23 @@ func failCleanup(root string) error {
return err
}

err = SwitchAllContainersStorageDriver(root, "aufs")
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If any of the removeDirIfExists() calls above fails, we'd return before reaching this call here, and I believe this could leave the device in an inconsistent state. (Specifically: if any containers were successfully migrated, they'd be tagged as being overlay2 containers, but the corresponding overlay2 data might have been deleted.)

pkg/storagemigration/failcleanup.go Outdated
return nil
}

func failCleanupContainer(root string, containerID string) error {
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I think this is not being currently called anywhere.

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Also there's a typo in the changelog entry: "Rollback to ausf..."

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Should we wait until I have a RP3 device or QEMU to test this on or roll it out with the current go test?
Do you always test on devices first?

I often do this because I am paranoid and like the ritual, but no, not necessarily. In fact, I think it's generally more important to have a good automated test case (either here or in meta-balena) capable of ensuring that we really fixed the issue.

@zoobot
Rollback to aufs and cleanup overlay2 in case of missing config.v2.json
3915950 
Add test for missing config.v2.json

Changelog-entry: Rollback to aufs and cleanup overlay2 in case of missing config.v2.json
Change-type: patch
Signed-off-by: zoobot <[email protected]>
@zoobot zoobot force-pushed the lmb/dont-migrate-bad-containers branch from b71b5df to 3915950 Compare November 22, 2022 17:51
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Aufs to overlay2 migration failure
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