Backups: Add Support for Backup Init SQL Queries

[mattlord]

Description

This PR adds a new feature to Vitess Backups that is similar to these MySQL features

• --init-file: https://dev.mysql.com/doc/refman/en/server-system-variables.html#sysvar_init_file
• --init-connect: https://dev.mysql.com/doc/refman/en/server-system-variables.html#sysvar_init_connect

It allows users to specify a set of flags — via automated backups using vtbackup or via the vtctldclient Backup and BackupShard commands — which then support the ability to run a set of SQL commands on the mysqld instance before we back it up:

1. --init-backup-sql-queries - Queries to execute before initializing the backup (flag can be specified multiple times or you can provide a CSV string)
2. --init-backup-tablet-types - Tablet types used for the backup where the init SQL queries (--init-backup-sql-queries) will be executed before initializing the backup (flag can be specified multiple times or you can provide a CSV string)
3. --init-backup-sql-timeout - At what point should we time out the init SQL query (--init-backup-sql-queries) work and either fail the backup job (--init-backup-sql-fail-on-error) or continue on with the backup
4. --init-backup-sql-fail-on-error - Whether or not to fail the backup if the init SQL queries (--init-backup-sql-queries) fail, which includes if they fail to complete before the specified timeout (--init-backup-sql-timeout) (defaults to FALSE)

If any queries are specified then non-default values for the tablet-types and timeout flags must also be provided.

This supports any number of uses cases for users, including the one mentioned in the issue.

Note

Once the PR gets approval I will create a website PR to update the docs.

Related Issue(s)

• Fixes: Feature Request: Add support for executing SQL queries prior to taking a backup #18886

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation: docs: Document backup init SQL queries feature website#2039

Deployment Notes

AI Disclosure

My man Claude did the bulk of the unit test work.

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

❌ Patch coverage is 47.42268% with 51 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.82%. Comparing base (1f49de4) to head (fd9fe8e).
⚠️ Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vttablet/tabletmanager/rpc_backup.go	0.00%	21 Missing ⚠️
go/cmd/vtctldclient/command/backups.go	46.66%	16 Missing ⚠️
go/cmd/vtbackup/cli/vtbackup.go	0.00%	13 Missing ⚠️
go/vt/mysqlctl/backup.go	96.55%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18883      +/-   ##
==========================================
+ Coverage   69.77%   69.82%   +0.05%     
==========================================
  Files        1608     1610       +2     
  Lines      214908   215299     +391     
==========================================
+ Hits       149953   150339     +386     
- Misses      64955    64960       +5     

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[arthurschreiber]

Changes look good to me. I'm only a bit confused about the usefulness of the --init-backup-tablet-types flag. How do you intend for it to be used? 🙇‍♂️

[mattlord]

Changes look good to me. I'm only a bit confused about the usefulness of the --init-backup-tablet-types flag. How do you intend for it to be used? 🙇‍♂️

Thanks! ❤️

You may only want to backup RDONLY tablets -- at least when available. Same for REPLICA tablets. And there are times where you might be forced to backup a PRIMARY tablet. The init statements may only be applicable/desirable/safe on a subset of those tablet types. That's the thinking behind it. Does that make sense?

[timvaillancourt]

Added one question that should not change my review. LGTM 👍

[mattlord]

Docs PR: vitessio/website#2039