InnoDB Exporter/Importer

Python script for exporting and importing InnoDB tables.

Vendor Websites:

• The cPanel Admin/TCA Server Solutions, LLC http://thecpaneladmin.com
• InMotion Hosting, Inc http://inmotionhosting.com

Author: Vanessa Vasile vanessa@thecpaneladmin.com

This script does a mass export and import of InnoDB tables for MySQL. Doing this can resolve a number of InnoDB-related MySQL issues, including:

• InnoDB log sequence mismatches
• Converting to innodb_file_per_table, and shrinking the shared ibdata1 file
• Restoring from InnoDB recovery mode where MySQL/InnoDB will not start without recovery being enabled

Usage Scenario Example:

• http://www.thecpaneladmin.com/how-to-convert-innodb-to-innodb_file_per_table-and-shrink-ibdata1/

DISCLAIMER:

As usual, before you make any drastic changes to MySQL data, you should make a backup. We are not responsible for any damage done to your system resulting from failure to back up data or follow instructions. While this script has been repeatedly tested and used in production environments, we must reiterate that you use this script at your own risk.

PREREQUISITES

A. Running MySQL instance

MySQL must be running for this script to be able to export tables properly. If You are having trouble starting MySQL, check the MySQL error log for anything obvious. If the issue is related to corrupted InnoDB data:

1. Open /etc/my.cnf in a text editor

2. Add the following line:

   innodb_force_recovery = 1

3. Attempt to start MySQL

If MySQL still does not start, keep increasing the recovery level up to 6 until it does. If MySQL still refuses to start, your issues are likely outside the scope of what this script would be able to do for you, and you should consult a professional.

More information: http://dev.mysql.com/doc/refman/5.6/en/forcing-innodb-recovery.html

If you recently upgraded from 5.5 to 5.6, also try downgrading back to 5.5, using this script to re-import all tables, then upgrading again.

Note: A lot of InnoDB problems can be resolved simply by starting InnoDB in recovery mode (1-4), restarting MySQL, then restarting again without recovery mode.

B. Backups

Make sure you have a backup of your MySQL data. Since you may be dealing with corrupted data, we'd recommend stopping MySQL and making a copy of your MySQL data directory (i.e. /var/lib/mysql). Again, MySQL should be stopped when you do this. This allows you to easily restore MySQL to the a previous state if needed.

If you prefer to use dumps for backups, you can use mysqldump:

http://webcheatsheet.com/sql/mysql_backup_restore.php

C. Miscellaneous

The following is also needed:

• MySQL 5.0 or higher, or MariaDB 10.0 or higher, with client packages installed
• Python 2.6 or 2.7 with standard modules includes, plus MySQLDB
• Enough free disk space on the partition this script will dump to (typically the size of your MySQL data folder)
• Root MySQL access
• Write permissions to the folder this script is dumping data to

Most standard systems already meet the above requirements. This script also works with MySQL running on cPanel servers.

USAGE

Exporting tables

The script will only export InnoDB tables, and does so by iterating through all databases and dumping only the ones listed as having InnoDB as their engine.

Export syntax:

./innodb_import_export.py --export [--dir=DIR] [--config=CONFIG]

Where:

--dir = The folder where you would like the dumps to be stored.  By default
    this is /home/innodb_data.  A child folder will becreated within this
    directory for each session, denoted in these examples as $SESSION
--config = The client configuration file for MySQL.  By default, this is
    /root/.my.cnf, but you can create your own

More information: http://dev.mysql.com/doc/refman/5.6/en/option-files.html

Export format:

/$DIR/$SESSION/$DATABASE_NAME/$TABLE_NAME.sql

Log file:

/$DIR/$SESSION/innodb_export.log

Importing tables

Before you import, you may need to do the following:

• If innodb_recovery_mode > 0, disable it and restart MySQL
• If you had corruption or are switching to innodb_file_per_table, move the ibdata1 and ib_logfile* files out of the MySQL data folder and restart MySQL. MySQL will automatically recreate these files at default sizes

When you exported, the script provided the name of the export location:

/$DIR/$SESSION

ie: /home/innodb_data/201407281740/

This is the location we are restoring from.

Import syntax:

./innodb_export_import.py --import --dir=DIR [--skip-working] [--config=CONFIG]

Where:

--dir = The directory containing the exports taken, as discussed above
--skip-working = Use this option if you do not want to import tables that
  are working.  This does not check data integrity, but rather whether
  MySQL recognizes that the table exists.  You would want to use this
  option when resuming from a previous restoration
--config = The client configuration file for MySQL.  By default, this is
  /root/.my.cnf, but you can create your own

More information:

http://dev.mysql.com/doc/refman/5.6/en/option-files.html

Notes:

• When restoring, the .ibd files for each table are moved into the respective table's export folder. This is to clear up tablespace for corrupted tables that would otherwise prevent an import from occurring.

• If you want to STOP an import, you should avoid using CTRL+C. Instead, touch a stop file in the import folder and the script will stop importing after the current table is done.

  Example:

  touch /$DIR/$SESSION/stop

  Make sure to remove this file before resuming, and consider using --skip-working as to prevent re-importing tables that were already imported.

• If you deleted the ibdata1 and ib_logfile* files, it may be necessary to also remove the .frm files for each table, since ibdata1 will no longer reference them. You'll know this is necessary if you are not able to import due to MySQL claiming the table could not be dropped or created because it already exists. A quick way to do this is to dump the below lines into a file and run:

  Note: You should stop MySQL before doing this.

    #!/bin/bash
    DIR='/home/innodb_data/$SESSION/' # PUT THE DIR NAME HERE, ie /$DIR/$SESSION/
    for file in $(find /var/lib/mysql -name *.frm)
    do
        DB=$(dirname $file | xargs basename)
        TABLE=$(basename $file .frm)
        /bin/mv -f /var/lib/mysql/$DB/$TABLE.frm $DIR/$DB/
    done

This is not coded into the script as doing this may be irreversible and dangerous. Again, make sure you have a backup.

Recreating InnoDB Stat Tables

When you nuke the InnoDB tablespace information and are running MySQL 5.6 or higher, you will need to recreate the InnoDB stat tables. These tables are:

• innodb_index_stats
• innodb_table_stats
• slave_master_info
• slave_relay_log_info
• slave_worker_info

WHILE MYSQL IS STOPPED, and you have deleted ibdata1 and ib_logfile*, go into the 'mysql' database folder and remove the .frm and .ibd files for these tables.

When you start MySQL, go into this script's source folder and re-import them:

mysql mysql < mysql_innodb_stat_tables.sql

Checking tables

This script can automate post-import sanity checks against InnoDB tables

Check syntax:

./innodb_export_import.py --verify

A summary and location of the log file will be given when the script run is completed. The log file will log failures at an ERROR level for review.

One thing to keep in mind here is that this script (and rather any script of of this nature, is incapable of verifying the integrity of data within the table itself. This script specifically checks that MySQL can access the table, even if it means the table contains partial or no data. If MySQL can at least access the table, it means that 1) data can be imported, and 2) The InnoDB engine will not be halted on startup due to the table being corrupted.

If you were running innodb_file_per_table prior to running this script and notice that the .ibd files are smaller than they were before, this does not mean you lost data, it may mean that unused space within the tablespace file was removed, resulting in a smaller file.