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BUILDING_MYSQL.md

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MySQL replication setup

Many thanks to this article from Booking.com: https://medium.com/booking-com-infrastructure/mysql-5-6-gtids-evaluation-and-online-migration-139693719ff2

We use a patched version of MySQL as an inbetween slave/master machine. This allows us to have the following setup:

        |---------------------------|
        |           Aurora          |
        |             --            |
        |  non GTID capable master  |
        |---------------------------|
                     |
     |---------------------------------|
     |        Our patched MySQL        |
     |           -----------           |
     | This acts as a slave to aurora  |
     |   and acts as a GTID capable    |
     |       master for Cloud SQL      |
     |---------------------------------|
                     |
          |------------------------|
          |    Google Cloud SQL    |
          |       ----------       |
          | Acts as a slave to our |
          |  patched MySQL so we   |
          | can use standard MySQL |
          |      replication       |
          |------------------------|

Installing

We have built a version of MySQL that includes a patch that makes this setup possible.

This guide is based on the latest available version of MySQL 5.6, currently 5.6.41.

Building a new copy

Start a Linux VM and download a source RPM from the MySQL website, it's under the source code downloads section and put it in your home directory.

E.g. wget https://dev.mysql.com/get/Downloads/MySQL-5.6/MySQL-5.6.41-1.el6.src.rpm

Install the source rpm by running rpm -i <your-rpm.rpm>, this will create a folder in your home directory called rpmbuild. The tree looks like this:

rpmbuild/
├── SOURCES
│   └── mysql-5.6.41.tar.gz
└── SPECS
    └── mysql.spec

Applying the patch

  • Extract the mysql-5.6.41.tar.gz file, tar -zxf mysql-5.6.41.tar.gz

  • Open the mysql-5.6.41/sql/rpl_slave.cc file, and look for the following piece of code in the get_master_version_and_clock() function.

    if (mi->master_gtid_mode > gtid_mode + 1 ||
  gtid_mode > mi->master_gtid_mode + 1)
{
  mi->report(ERROR_LEVEL, ER_SLAVE_FATAL_ERROR,
             "The slave IO thread stops because the master has "
             "@@GLOBAL.GTID_MODE %s and this server has "
             "@@GLOBAL.GTID_MODE %s",
             gtid_mode_names[mi->master_gtid_mode],
             gtid_mode_names[gtid_mode]);
  DBUG_RETURN(1);
}

    This piece of code needs to be commented out (using /* */) or removed.

  • Now, zip everything back together:

    rm mysql-5.6.41.tar.gz
tar -czf mysql-5.6.41.tar.gz mysql-5.6.41/
rm -rf mysql-5.6.41/

  • And install the build dependencies:

    sudo yum install -y rpm-build gcc gperf ncurses-devel zlib-devel gcc-c++ libaio-devel cmake openssl-devel cyrus-sasl-devel openldap-devel perl-Data-Dumper perl-JSON

  • Now build a new RPM (this will take a while):

    rpmbuild -ba SPECS/mysql.spec

  • Fetch the new RPMs (there are several) from the rpmbuild/RPMS directory and store them in a place that will be accessible from the AWS machine we will be using to replicate.