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MDEV-31527: Add --validate-config option to check configuration without starting the server#4716

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bodyhedia44 wants to merge 1 commit intoMariaDB:mainfrom
bodyhedia44:MDEV-31527-validate-config
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MDEV-31527: Add --validate-config option to check configuration without starting the server#4716
bodyhedia44 wants to merge 1 commit intoMariaDB:mainfrom
bodyhedia44:MDEV-31527-validate-config

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@bodyhedia44 bodyhedia44 commented Mar 1, 2026 •
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MDEV-31527: Add --validate-config option

Summary

Add a new --validate-config command-line option that validates the server
configuration (from config files and command line) and exits with exit code
0 on success or non-zero on failure, without actually starting the server.

Use case

mariadbd --defaults-file=/etc/my.cnf --validate-config

DBAs can verify configuration changes before restarting production servers.

Test cases (mysql-test/main/validate_config.test):

  1. Valid config → exit 0
  2. Unknown CLI option → exit non-zero
  3. No pid file created (server doesn't start)
  4. No help text output
  5. Bad option in config file → exit non-zero with error message
  6. Valid config file → exit 0 with success message

Exit codes

Scenario Exit code
Valid configuration 0
Unknown option 2
Unknown variable 7

How to use

Validate a config file before restarting

mariadbd --defaults-file=/etc/my.cnf --validate-config

Validate with additional command-line overrides

mariadbd --defaults-file=/etc/my.cnf --validate-config --max-connections=500

Matching MySQL 8.0 behavior

This is equivalent to MySQL 8.0's --validate-config option, adapted for
MariaDB's parsing architecture.

@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch 2 times, most recently from 82f19f2 to 99d166e Compare March 2, 2026 00:17
@gkodinov gkodinov added the External Contribution All PRs from entities outside of MariaDB Foundation, Corporation, Codership agreements. label Mar 2, 2026
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Thank you for your contribution. This is a preliminary review.

Comment thread sql/mysqld.cc
Comment thread mysql-test/main/validate_config.test Outdated
Comment thread mysql-test/main/validate_config.test Outdated
Comment thread mysql-test/main/validate_config.test
Comment thread mysql-test/main/validate_config.test Outdated
Comment thread mysql-test/main/validate_config.test Outdated
Comment thread mysql-test/main/validate_config.test
@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch from 99d166e to 7510e9e Compare March 4, 2026 20:07
@bodyhedia44 bodyhedia44 requested a review from gkodinov March 4, 2026 20:08
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bodyhedia44 commented Mar 4, 2026

Done

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gkodinov approved these changes Mar 5, 2026
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Thanks for working on this with me. LGTM. One question for the final reviewer.

Please update the jira and the commit message and stand by for the final review.

Comment thread sql/mysqld.cc
@gkodinov gkodinov requested a review from raghunandanbhat March 5, 2026 10:13
@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch 3 times, most recently from 8e832a0 to e2a0e86 Compare March 5, 2026 11:31
raghunandanbhat
raghunandanbhat reviewed Mar 9, 2026
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Comment thread mysql-test/main/validate_config.test
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What happens if someone tries to check the version while validating the config? (Version print should probably take precedence and exit 0). Add a test for this case.

Please make the suggested changes & thanks for contribution!

@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch from e2a0e86 to a7c374d Compare March 10, 2026 11:36
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bodyhedia44 commented Mar 10, 2026

Done

@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch from a7c374d to 4466433 Compare March 10, 2026 12:00
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When --help is present, mariadbd does not validate invalid configs, just prints the help text and exits (same with --version).

$ ./mariadbd --help --invalid-config
./mariadbd  Ver 13.0.0-MariaDB-debug for Linux on x86_64 (Source distribution)
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Starts the MariaDB database server.

Usage: ./mariadbd [OPTIONS]

For more help options (several pages), use mariadbd --verbose --help.

@bodyhedia44, your tests suggest that --help should take precedence over --validate-config. What if all three - --invalid-option, --help and --validate-confg are present? Should this validate the invalid config or just print help text and exit?

the current behavior is, it validates and prints the error indicating unknown option

$ ./mariadbd --help --invalid-config --validate-config
2026-03-10 23:02:11 0 [ERROR] ./mariadbd: unknown option '--invalid-config'
./mariadbd  Ver 13.0.0-MariaDB-debug for Linux on x86_64 (Source distribution)
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Starts the MariaDB database server.

Usage: ./mariadbd [OPTIONS]

For more help options (several pages), use mariadbd --verbose --help.

Same is true for --version, --validate-config and --invalid-option as well.

maybe @vuvova or @sanja-byelkin can comment on this?

Comment thread mysql-test/main/validate_config.test Outdated
@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch from 4466433 to 2cedcbc Compare March 11, 2026 13:23
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To be clear on the existing behavior (before this patch):

  • mariadbd --help --invalid-option - prints help and exits cleanly. it does not evaluate the invalid config.
  • mariadbd --version --invalid-option - prints version and exits cleanly. it does not evaluate the invalid config.
  • mariadbd --help --verbose --invalid-option - takes the long path to load plugins for the verbose help menu, evaluates the config, and crashes with an "unknown option" error. it is the only exception.

currently, the PR breaks this behavior. if a user runs mariadbd --help --validate-config --invalid-option, the server incorrectly takes the long initialization path, evaluates the config, and crashes with an "unknown option" error, rather than short-circuiting to print the help text. please fix this.

add two more tests to ensure we don't regress. they verify that --help and --version correctly ignore invalid configurations and exit cleanly, even when --validate-config is present.

  • --exec $MYSQLD_BOOTSTRAP_CMD --help --validate-config --invalid-config
  • --exec $MYSQLD_BOOTSTRAP_CMD --version --validate-config --invalid-config

Comment thread mysql-test/main/validate_config.test Outdated
@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch from 2cedcbc to 8d367a6 Compare March 13, 2026 12:48
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bodyhedia44 commented Mar 13, 2026

Done

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code looks good; please make the change in the test and it is ready for testing.

Comment thread mysql-test/main/validate_config.test Outdated
@bodyhedia44
MDEV-31527: Add --validate-config option to check configuration witho…
c259355 
…ut starting the server

Add a new --validate-config command-line option that validates the server
configuration (from config files and command line) and exits with 0 on
success or non-zero on failure, without actually starting the server.

This is useful for DBAs to verify configuration changes before restarting:
  mariadbd --defaults-file=/etc/my.cnf --validate-config

The validation checks the following:
- Config files explicitly specified via --defaults-file or --defaults-extra-file
  must exist and be readable
- There are no unknown options specified (in config files or on the command line)
- Option values are type-checked (e.g. numeric options reject non-numeric input).
  Out-of-range values are adjusted to valid limits with a warning, not rejected.

The implementation reuses the existing --help code path (opt_abort),
which already loads plugins to validate their variables and runs a
final parsing pass with skip_unknown=0 to detect unknown options.
The only difference is that --validate-config suppresses help output.

Note: this is intentionally named --validate-config (not --validate-defaults)
for MySQL compatibility, although --validate-defaults would be more consistent
with MariaDB's existing defaults-related options (--defaults-file,
--no-defaults, my_print_defaults, etc.).
@bodyhedia44 bodyhedia44 force-pushed the MDEV-31527-validate-config branch from 8d367a6 to c259355 Compare March 16, 2026 20:38
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bodyhedia44 commented Mar 16, 2026

Done

raghunandanbhat
raghunandanbhat approved these changes Mar 17, 2026
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looks good. thanks @bodyhedia44

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@sanja-byelkin sanja-byelkin sanja-byelkin left review comments

@gkodinov gkodinov gkodinov approved these changes

@raghunandanbhat raghunandanbhat raghunandanbhat approved these changes

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