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Replicate data into Azure Database for MySQL - Flexible Server

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Data-in replication allows you to synchronize data from an external MySQL server into an Azure Database for MySQL Flexible Server instance. The external server can be on-premises, in virtual machines, Azure Database for MySQL single server, or a database service hosted by other cloud providers. Data-in replication is based on the binary log (binlog) file position or GTID-based replication. To learn more about binlog replication, see the MySQL Replication.

Note

Configuring Data-in replication for servers enabled with high-availability is supported only through GTID-based replication.

When to use Data-in replication

The main scenarios to consider about using Data-in replication are:

  • Hybrid Data Synchronization: With Data-in replication, you can keep data synchronized between your on-premises servers and Azure Database for MySQL Flexible Server. This synchronization helps create hybrid applications. This method is appealing when you have an existing local database server but want to move the data to a region closer to end users.
  • Multi-Cloud Synchronization: For complex cloud solutions, use Data-in replication to synchronize data between Azure Database for MySQL Flexible Server and different cloud providers, including virtual machines and database services hosted in those clouds.
  • Migration: Customers can migrate in Minimal Time using open-source tools such as MyDumper/MyLoader with Data-in replication. A selective cutover of production load from source to destination database is possible with Data-in replication.

For migration scenarios, use the Azure Database Migration Service(DMS).

Limitations and considerations

Data not replicated

The mysql system database on the source server isn't replicated. In addition, changes to accounts and permissions on the source server aren't replicated. If you create an account on the source server and this account needs to access the replica server, manually create the same account on the replica server. To understand the tables in the system database, see the MySQL manual.

Data-in replication is supported on High Availability (HA) enabled servers

Support for data-in replication for high availability (HA) enabled server is available only through GTID-based replication.

The stored procedure for replication using GTID is available on all HA-enabled servers by the name mysql.az_replication_change_master_with_gtid.

Filter

The parameter replicate_wild_ignore_table creates a replication filter for tables on the replica server. To modify this parameter from the Azure portal, navigate to the Azure Database for MySQL Flexible Server instance used as replica and select "Server Parameters" to view/edit the replicate_wild_ignore_table parameter.

Requirements

  • The source server version must be at least MySQL version 5.7.

  • Our recommendation is to have the same version for source and replica server versions. For example, both must be MySQL version 5.7, or both must be MySQL version 8.0.

  • Our recommendation is to have a primary key in each table. If we have a table without a primary key, you might face slowness in replication.

  • The source server should use the MySQL InnoDB engine.

  • The user must have the right permissions to configure binary logging and create new users on the source server.

  • Binary log files on the source server shouldn't be purged before the replica applies those changes. If the source is Azure Database for MySQL Flexible Server, refer to how to configure binlog_expire_logs_seconds for Flexible Server or Single server

  • If the source server has SSL enabled, ensure the SSL CA certificate provided for the domain has been included in the mysql.az_replication_change_master stored procedure. Refer to the following examples and the master_ssl_ca parameter.

  • Ensure that the machine hosting the source server allows both inbound and outbound traffic on port 3306.

  • With public access, ensure that the source server has a public IP address, that DNS is publicly accessible, or that the source server has a fully qualified domain name (FQDN). If you have a private endpoint and have disabled public access, data-in replication is not supported

  • With private access (VNet Integration), ensure that the source server name can be resolved and is accessible from the VNet where the Azure Database for MySQL Flexible Server instance is running. (For more details, visit Name resolution for resources in Azure virtual networks).

Generated Invisible Primary Key

For MySQL version 8.0 and above, Generated Invisible Primary Keys (GIPK) is enabled by default for all the Azure Database for MySQL Flexible Server instances. MySQL 8.0+ servers adds the invisible column my_row_id to the tables and a primary key on that column, where the InnoDB table is created without an explicit primary key. This feature, when enabled might affect some of the data-in replication use cases, as described below:

  • Data-in replication fails with replication error: "ERROR 1068 (42000): Multiple primary key defined" if source server creates a Primary key on the table without Primary Key. For mitigation, run the following sql command, skip replication error and restart data-in replication.

    alter table <table name> drop column my_row_id, add primary key <primary key name>(<column name>);

  • Data-in replication fails with replication error: "ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key" if source server adds an auto_increment column as Unique Key. For mitigation, run the following sql command, set "sql_generate_invisible_primary_key" as OFF, skip replication error and restart data-in replication.

    alter table <table name> drop column my_row_id, modify <column name> int auto_increment;

  • Data-in replication fails if source server runs any other SQL that isn't supported when "sql_generate_invisible_primary_key" is ON. For example, create a partition table. In such a scenario mitigation is to set "sql_generate_invisible_primary_key" as OFF and restart data-in replication.

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