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8.25. The tungsten_provision_thl Command

The tungsten_provision_thl command can be used to generate the THL required to provision a database with information from a MySQL master to a slave. Because of the way the tool works, the tool is most useful in heterogeneous deployments where the data must be formatted and processed by the replicator for effective loading into the target database.

The tool operates as follows:

  1. A mysqldump of the current database is taken from the current master.

  2. The generated SQL from mysqldump is then modified so that the data is loaded into tables using the BLACKHOLE engine type. These statements still generate information within the MySQL binary log, but do not create any data.

  3. A sandbox MySQL server is started, using the MySQL Sandbox tool.

  4. A duplicate replicator is started, pointing to the sandbox MySQL instance, but sharing the same THL port and THL directory.

  5. The modified SQL from mysqldump is loaded, generating events in the binary log which are extracted by the sandbox replicator.

Because the sandbox replicator works on the same THL port as the standard master replicator, the slaves will read the THL from the sandbox replicator. Also, because it uses the same THL directory, the THL will be written into additional THL files. It doesn't matter whether there are existing THL data files, the new THL will be appended into files in the same directory.

The tool has the following pre-requisites, in addition to the main Appendix B, Prerequisites for Tungsten Replicator:

  • A tarball of the Tungsten Replicator must be available so that the duplicate replicator can be created. The full path to the file should be used.

  • The MySQL Sandbox tool must have been installed. For more information, see MySQL Sandbox.

    Installing MySQL Sandbox requires the ExtUtils::MakeMaker and Test::Simple Perl modules. You may install these through CPAN or a package manager:

    shell> yum install -y perl-ExtUtils-MakeMaker perl-Test-Simple

    After those packages are available, you can proceed with building MySQL Sandbox and installing it. If you do not have sudo access, make sure that ~/MySQL-Sandbox-3.0.44/bin is added to $PATH

    shell> cd ~
    shell> wget https://launchpad.net/mysql-sandbox/mysql-sandbox-3/mysql-sandbox-3/+download/MySQL-Sandbox-3.0.44.tar.gz
    shell> tar -xzf MySQL-Sandbox-3.0.44.tar.gz
    shell> cd MySQL-Sandbox-3.0.44
    shell> perl Makefile.PL
    shell> make
    shell> make test
    shell> sudo make install
  • A tarball of a MySQL release must be available to create the sandbox MySQL environment. The release should match the installed version of MySQL. The full path to the file should be used.

  • The replicator deployment should already be installed. The master should be OFFLINE, but the command can place the replicator offline automatically as part of the provisioning process.

Once these prerequisites have been met, the basic method of executing the command is to specify the location of the Tungsten Replicator tarball, MySQL tarball and the databases that you want to provision:

shell> tungsten_provision_thl \
      --tungsten-replicator-package=/home/tungsten/tungsten-replicator-3.0.0-254.tar.gz \
      --mysql-package=/home/tungsten/mysql-5.6.20-linux-glibc2.5-x86_64.tar.gz \
      --schemas=test
NOTE >>The THL has been provisioned to mysql-bin.000025:493 on host1:3306

The command reports the MySQL binary log point and host on which the THL has been provisioned. Put the Tungsten Replicator back online from the reported position:

shell> trepctl online -from-event 000025:493

The Tungsten Replicator will start extracting from that position and continue with any additional changes. Check all slaves to be sure they are online. The slaves services will process all extracted entries.