vtbackup: disable redo log before starting replication

[maxenglander]

Description

According to MySQL docs:

As of MySQL 8.0.21, you can disable redo logging using the ALTER INSTANCE DISABLE INNODB REDO_LOG statement. This functionality is intended for loading data into a new MySQL instance. Disabling redo logging speeds up data loading by avoiding redo log writes and doublewrite buffering.

See: https://dev.mysql.com/doc/refman/8.0/en/innodb-redo-log.html#innodb-disable-redo-logging

We can take advantage of this in vtbackup. This change disables the redo log on MySQL >= 8.0.21 before starting replication, and re-enables the redo log after stopping replication.

Related Issue(s)

Checklist

• [ ] "Backport me!" label has been added if this change should be backported
• [ ] Tests were added or are not required
• [ ] Documentation was added or is not required

Deployment Notes

[vitess-bot[bot]]

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[maxenglander]

vtbackup_transform is failing consistently which is concerning, but I also see this test failing a bunch on main recently, so maybe it's a flake?

[mattlord]

vtbackup_transform is failing consistently which is concerning, but I also see this test failing a bunch on main recently, so maybe it's a flake?

vtbackup_transform has been VERY flaky so not likely related. @rsajwani has been looking into it but we haven't found the cause yet (only seems to happen in the CI).

[maxenglander]

Hey @mattlord I was able to address your suggestions. I tried adding some checks to the E2E test, ran into a challenge where the E2E test is executing the vtbackup binary, which starts and destroys a fresh mysqld instance and didn't really give me any way to inspect MySQL from the test code. Reworked the code a bit so that vtbackup optionally retains temporary files, so that I'm able to inspect them (in particular the error.log) from the test after the backup completes, and then delete the temporary files from the test. Not ideal, definitely open to better ideas.

[maxenglander]

@mattlord was able to do what you suggested:

• Connect to mysqld directly from the E2E test.
• Verify redo log changes with performance schema error sink.
• Remove those flags and the CNF cruft.

A bit worried about flakiness since mysqld could shut down before test is able to verify, but the test is passing consistently locally 👍

[deepthi]

@maxenglander your last commit needed to include changes to unit tests. It's good to run make unit_test locally before pushing changes. CI is a very expensive way to detect unit test failures.

[maxenglander]

Understood @deepthi, will do that going forward