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

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bodyhedia44:MDEV-31527-validate-config

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`):

Valid config → exit 0
Unknown CLI option → exit non-zero
No pid file created (server doesn't start)
No help text output
Bad option in config file → exit non-zero with error message
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 force-pushed the MDEV-31527-validate-config branch 2 times, most recently from 82f19f2 to 99d166e Compare

March 2, 2026 00:17

gkodinov added the External Contribution label

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gkodinov left a comment

Thank you for your contribution. This is a preliminary review.

sql/mysqld.cc Show resolved Hide resolved

mysql-test/main/validate_config.test Outdated

+              --echo #
+              --echo # Test 1: --validate-config with valid configuration should succeed (exit 0)
+              --echo #
+              --exec $MYSQLD_BOOTSTRAP_CMD --skip-networking --datadir=$MYSQLTEST_VARDIR/tmp/validate_config --skip-grant-tables --validate-config >$MYSQLTEST_VARDIR/tmp/validate_config/test1.log 2>&1

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gkodinov Mar 2, 2026

Why do you need --skip-grant-tables and --skip-networking? It's not supposed to matter.

mysql-test/main/validate_config.test Outdated

+              --exec $MYSQLD_BOOTSTRAP_CMD --skip-networking --datadir=$MYSQLTEST_VARDIR/tmp/validate_config --skip-grant-tables --validate-config >$MYSQLTEST_VARDIR/tmp/validate_config/test5.log 2>&1
+              # The log should NOT contain the --help option listing
+              --let SEARCH_FILE=$MYSQLTEST_VARDIR/tmp/validate_config/test5.log
+              --let SEARCH_PATTERN=To see what values a running

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gkodinov Mar 2, 2026

I'd find a better, more stable text to search.
Note that on my computer, this is never produced. I get:

blackbook:~$dev/server-main/bld/sql/mariadbd --help
dev/server-main/bld/sql/mariadbd  Ver 13.0.0-MariaDB-debug for osx10.21 on arm64 (Source distribution)
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Starts the MariaDB database server.

Usage: dev/server-main/bld/sql/mariadbd [OPTIONS]

For more help options (several pages), use mariadbd --verbose --help.
blackbook:~$

I'd suggest using either "^Usage:.*mariadbd" or "Starts the MariaDB database server.".

mysql-test/main/validate_config.test Show resolved Hide resolved

mysql-test/main/validate_config.test Outdated

+              # mysqld refuses to run as root normally.
+              --source include/not_as_root.inc
+              mkdir $MYSQLTEST_VARDIR/tmp/validate_config;

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gkodinov Mar 2, 2026

Why do you need a specific tmp subdir with your files? Why not just use the base tmp but prefix the files with the mdev number as suggested below?

mysql-test/main/validate_config.test Outdated

+              [mariadb]
+              max_connections=50
+              EOF
+              --exec $MYSQLD --defaults-file=$MYSQLTEST_VARDIR/tmp/validate_config/good.cnf --skip-networking --skip-grant-tables --validate-config --lc-messages-dir=$MYSQL_SHAREDIR --datadir=$MYSQLTEST_VARDIR/tmp/validate_config --plugin-dir=$MYSQLTEST_VARDIR/plugins --character-sets-dir=$MYSQL_CHARSETSDIR --console --core-file >$MYSQLTEST_VARDIR/tmp/validate_config/test7.log 2>&1

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gkodinov Mar 2, 2026

lots of options you do not need here too.

mysql-test/main/validate_config.test Show resolved Hide resolved

bodyhedia44 force-pushed the MDEV-31527-validate-config branch from 99d166e to 7510e9e Compare

March 4, 2026 20:07

bodyhedia44 requested a review from gkodinov

March 4, 2026 20:08

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bodyhedia44 commented Mar 4, 2026

Done

gkodinov approved these changes

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gkodinov left a comment

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.

sql/mysqld.cc

                 {"help", '?', "Display this help and exit",
                  &opt_help, &opt_help, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
 , 0},
+                {"validate-config", 0, "Validate the server configuration specified by the user "

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gkodinov Mar 5, 2026

One final nitpick: Looking at https://mariadb.com/docs/server/server-management/install-and-upgrade-mariadb/configuring-mariadb/configuring-mariadb-with-option-files it seems like all of the configuration file related options contain the word "defaults" in some shape or form: --defaults-file, --no-defaults etc. Even the related tool is called https://mariadb.com/docs/server/clients-and-utilities/administrative-tools/my_print_defaults.

What the new option added does in essence is basically what my_print_defaults does, but without the printing. I'd name the option --validate-defaults to be consistent with the naming used so far. But, since this is a MySQL compatible option, I'd not insist on it. And leave the decision to the final approver.

I'd also be prudent to spell out exactly what kind of "validation" is happening. To me this is a check that:

all the config files specified or defaulted are reachable.
the syntax of these config files is consistent.
there are no unknown options specified
the values for the options fall within the compiled validity limits

I'd put all of the above in the jira and into the commit message itself.

gkodinov assigned raghunandanbhat

gkodinov requested a review from raghunandanbhat

March 5, 2026 10:13

bodyhedia44 force-pushed the MDEV-31527-validate-config branch 2 times, most recently from 3300ee2 to 8e832a0 Compare

March 5, 2026 11:29


          MDEV-31527: Add --validate-config option to check configuration witho…

e2a0e86

…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 force-pushed the MDEV-31527-validate-config branch from 8e832a0 to e2a0e86 Compare

March 5, 2026 11:31

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