How to configure Azure Database for MySQL Data-in Replication

01/13/2021
8 minutes to read

This article describes how to set up Data-in Replication in Azure Database for MySQL by configuring the source and replica servers. This article assumes that you have some prior experience with MySQL servers and databases.

Note

This article contains references to the term slave, a term that Microsoft no longer uses. When the term is removed from the software, we'll remove it from this article.

To create a replica in the Azure Database for MySQL service, Data-in Replication synchronizes data from a source MySQL server on-premises, in virtual machines (VMs), or in cloud database services. Data-in Replication is based on the binary log (binlog) file position-based replication native to MySQL. To learn more about binlog replication, see the MySQL binlog replication overview.

Review the limitations and requirements of Data-in replication before performing the steps in this article.

Create a MySQL server to be used as replica

Create a new Azure Database for MySQL server

Create a new MySQL server (ex. "replica.mysql.database.azure.com"). Refer to Create an Azure Database for MySQL server by using the Azure portal for server creation. This server is the "replica" server in Data-in Replication.

Important

The Azure Database for MySQL server must be created in the General Purpose or Memory Optimized pricing tiers.
Create same user accounts and corresponding privileges

User accounts aren't replicated from the source server to the replica server. If you plan on providing users with access to the replica server, you need to create all accounts and corresponding privileges manually on this newly created Azure Database for MySQL server.
Add the source server's IP address to the replica's firewall rules.

Update firewall rules using the Azure portal or Azure CLI.

Configure the source server

The following steps prepare and configure the MySQL server hosted on-premises, in a virtual machine, or database service hosted by other cloud providers for Data-in Replication. This server is the "source" in Data-in replication.

Review the source server requirements before proceeding.
Ensure that the source server allows both inbound and outbound traffic on port 3306, and that it has a public IP address, the DNS is publicly accessible, or has a fully qualified domain name (FQDN).

Test connectivity to the source server by attempting to connect from a tool such as the MySQL command line hosted on another machine or from the Azure Cloud Shell available in the Azure portal.

If your organization has strict security policies and won't allow all IP addresses on the source server to enable communication from Azure to your source server, you can potentially use the below command to determine the IP address of your MySQL server.
1. Sign in to your Azure Database for MySQL using a tool such as the MySQL command line.
2. Execute the below query.
```
mysql> SELECT @@global.redirect_server_host;
```
  Below is some sample output:
```
+-----------------------------------------------------------+
| @@global.redirect_server_host                             |
+-----------------------------------------------------------+
| e299ae56f000.tr1830.westus1-a.worker.database.windows.net |
 +-----------------------------------------------------------+
```
3. Exit from the MySQL command line.
4. Execute the following command in the ping utility to get the IP address.
```
ping <output of step 2b>
```
  For example:
```
C:\Users\testuser> ping e299ae56f000.tr1830.westus1-a.worker.database.windows.net
Pinging tr1830.westus1-a.worker.database.windows.net (**11.11.111.111**) 56(84) bytes of data.
```
5. Configure your source server's firewall rules to include the previous step's outputted IP address on port 3306.
Note

This IP address may change due to maintenance/deployment operations. This method of connectivity is only for customers who cannot afford to allow all IP address on 3306 port.
Turn on binary logging

Check to see if binary logging has been enabled on the source by running the following command:
```
SHOW VARIABLES LIKE 'log_bin';
```
If the variable log_bin is returned with the value "ON", binary logging is enabled on your server.

If log_bin is returned with the value "OFF", turn on binary logging by editing your my.cnf file so that log_bin=ON and restart your server for the change to take effect.
Source server settings

Data-in Replication requires parameter lower_case_table_names to be consistent between the source and replica servers. This parameter is 1 by default in Azure Database for MySQL.
```
SET GLOBAL lower_case_table_names = 1;
```
Create a new replication role and set up permission

Create a user account on the source server that is configured with replication privileges. This can be done through SQL commands or a tool like MySQL Workbench. Consider whether you plan on replicating with SSL as this will need to be specified when creating the user. Refer to the MySQL documentation to understand how to add user accounts on your source server.

In the following commands, the new replication role created can access the source from any machine, not just the machine that hosts the source itself. This is done by specifying "syncuser@'%'" in the create user command. See the MySQL documentation to learn more about specifying account names.

SQL Command

Replication with SSL

To require SSL for all user connections, use the following command to create a user:
```
CREATE USER 'syncuser'@'%' IDENTIFIED BY 'yourpassword';
GRANT REPLICATION SLAVE ON *.* TO ' syncuser'@'%' REQUIRE SSL;
```
Replication without SSL

If SSL isn't required for all connections, use the following command to create a user:
```
CREATE USER 'syncuser'@'%' IDENTIFIED BY 'yourpassword';
GRANT REPLICATION SLAVE ON *.* TO ' syncuser'@'%';
```
MySQL Workbench

To create the replication role in MySQL Workbench, open the Users and Privileges panel from the Management panel, and then select Add Account.

Type in the username into the Login Name field.

Select the Administrative Roles panel and then select Replication Slave from the list of Global Privileges. Then select Apply to create the replication role.
Set the source server to read-only mode

Before starting to dump out the database, the server needs to be placed in read-only mode. While in read-only mode, the source will be unable to process any write transactions. Evaluate the impact to your business and schedule the read-only window in an off-peak time if necessary.
```
FLUSH TABLES WITH READ LOCK;
SET GLOBAL read_only = ON;
```
Get binary log file name and offset

Run the show master status command to determine the current binary log file name and offset.
```
 show master status;
```
The results should appear similar to the following. Make sure to note the binary file name, as it will be used in later steps.

Dump and restore source server

Determine which databases and tables you want to replicate into Azure Database for MySQL and perform the dump from the source server.

You can use mysqldump to dump databases from your master. For details, refer to Dump & Restore. It's unnecessary to dump MySQL library and test library.
Set source server to read/write mode.

After the database has been dumped, change the source MySQL server back to read/write mode.
```
SET GLOBAL read_only = OFF;
UNLOCK TABLES;
```
Restore dump file to new server.

Restore the dump file to the server created in the Azure Database for MySQL service. Refer to Dump & Restore for how to restore a dump file to a MySQL server. If the dump file is large, upload it to a virtual machine in Azure within the same region as your replica server. Restore it to the Azure Database for MySQL server from the virtual machine.

Link source and replica servers to start Data-in Replication

Set source server.

All Data-in Replication functions are done by stored procedures. You can find all procedures at Data-in Replication Stored Procedures. The stored procedures can be run in the MySQL shell or MySQL Workbench.

To link two servers and start replication, login to the target replica server in the Azure DB for MySQL service and set the external instance as the source server. This is done by using the mysql.az_replication_change_master stored procedure on the Azure DB for MySQL server.
```
CALL mysql.az_replication_change_master('<master_host>', '<master_user>', '<master_password>', 3306, '<master_log_file>', <master_log_pos>, '<master_ssl_ca>');
```
- master_host: hostname of the source server
- master_user: username for the source server
- master_password: password for the source server
- master_log_file: binary log file name from running show master status
- master_log_pos: binary log position from running show master status
- master_ssl_ca: CA certificate's context. If not using SSL, pass in empty string.
  
  It's recommended to pass this parameter in as a variable. For more information, see the following examples.
Note

If the source server is hosted in an Azure VM, set "Allow access to Azure services" to "ON" to allow the source and replica servers to communicate with each other. This setting can be changed from the Connection security options. For more information, see Manage firewall rules using the portal .

Examples

Replication with SSL

The variable @cert is created by running the following MySQL commands:
```
SET @cert = '-----BEGIN CERTIFICATE-----
PLACE YOUR PUBLIC KEY CERTIFICATE'`S CONTEXT HERE
-----END CERTIFICATE-----'
```
Replication with SSL is set up between a source server hosted in the domain "companya.com" and a replica server hosted in Azure Database for MySQL. This stored procedure is run on the replica.
```
CALL mysql.az_replication_change_master('master.companya.com', 'syncuser', 'P@ssword!', 3306, 'mysql-bin.000002', 120, @cert);
```
Replication without SSL

Replication without SSL is set up between a source server hosted in the domain "companya.com" and a replica server hosted in Azure Database for MySQL. This stored procedure is run on the replica.
```
CALL mysql.az_replication_change_master('master.companya.com', 'syncuser', 'P@ssword!', 3306, 'mysql-bin.000002', 120, '');
```
Filtering.

If you want to skip replicating some tables from your master, update the replicate_wild_ignore_table server parameter on your replica server. You can provide more than one table pattern using a comma-separated list.

Review the MySQL documentation to learn more about this parameter.

To update the parameter, you can use the Azure portal or Azure CLI.
Start replication.

Call the mysql.az_replication_start stored procedure to start replication.
```
CALL mysql.az_replication_start;
```
Check replication status.

Call the show slave status command on the replica server to view the replication status.
```
show slave status;
```
If the state of Slave_IO_Running and Slave_SQL_Running are "yes" and the value of Seconds_Behind_Master is "0", replication is working well. Seconds_Behind_Master indicates how late the replica is. If the value isn't "0", it means that the replica is processing updates.

Other stored procedures

Stop replication

To stop replication between the source and replica server, use the following stored procedure:

CALL mysql.az_replication_stop;

Remove replication relationship

To remove the relationship between source and replica server, use the following stored procedure:

CALL mysql.az_replication_remove_master;

Skip replication error

To skip a replication error and allow replication to continue, use the following stored procedure:

CALL mysql.az_replication_skip_counter;

Next steps

Learn more about Data-in Replication for Azure Database for MySQL.