Migrate MySQL to Azure Database for MySQL online using DMS

You can use the Azure Database Migration Service to migrate the databases from an on-premises MySQL instance to Azure Database for MySQL with minimal downtime. In other words, migration can be achieved with minimum downtime to the application. In this tutorial, you migrate the Employees sample database from an on-premises instance of MySQL 5.7 to Azure Database for MySQL by using an online migration activity in the Azure Database Migration Service.

In this tutorial, you learn how to:

  • Migrate the sample schema using mysqldump utility.
  • Create an instance of the Azure Database Migration Service.
  • Create a migration project by using the Azure Database Migration Service.
  • Run the migration.
  • Monitor the migration.

Important

For an optimal migration experience, Microsoft recommends creating an instance of the Azure Database Migration Service in the same Azure region as the target database. Moving data across regions or geographies can slow down the migration process and introduce errors.

Prerequisites

To complete this tutorial, you need to:

  • Download and install MySQL community edition 5.6 or 5.7. The on-premises MySQL version must match with Azure Database for MySQL version. For example, MySQL 5.6 can only migrate to Azure Database for MySQL 5.6 and not upgraded to 5.7.
  • Create an instance in Azure Database for MySQL. Refer to the article Use MySQL Workbench to connect and query data for details about how to connect and create a database using the Azure portal.
  • Create a VNET for the Azure Database Migration Service by using the Azure Resource Manager deployment model, which provides site-to-site connectivity to your on-premises source servers by using either ExpressRoute or VPN.
  • Ensure that your Azure Virtual Network (VNET) Network Security Group rules do not block the following communication ports 443, 53, 9354, 445, 12000. For more detail on Azure VNET NSG traffic filtering, see the article Filter network traffic with network security groups.
  • Configure your Windows Firewall for database engine access.
  • Open your Windows firewall to allow the Azure Database Migration Service to access the source MySQL Server, which by default is TCP port 3306.
  • When using a firewall appliance in front of your source database(s), you may need to add firewall rules to allow the Azure Database Migration Service to access the source database(s) for migration.
  • Create a server-level firewall rule for Azure Database for MySQL to allow the Azure Database Migration Service access to the target databases. Provide the subnet range of the VNET used for the Azure Database Migration Service.
  • The source MySQL must be on supported MySQL community edition. To determine the version of MySQL instance, in the MySQL utility or MySQL Workbench, run the following command: SELECT @@version;
  • Azure Database for MySQL supports only InnoDB tables. To convert MyISAM tables to InnoDB, see the article Converting Tables from MyISAM to InnoDB

  • Enable binary logging in the my.ini (Windows) or my.cnf (Unix) file in source database by using the following configuration:

  • The user must have the ReplicationAdmin role with the following privileges:
    • REPLICATION CLIENT - Required for Change Processing tasks only. In other words, Full Load only tasks don't require this privilege.
    • REPLICATION REPLICA - Required for Change Processing tasks only. In other words, Full Load only tasks don't require this privilege.
    • SUPER - Only required in versions earlier than MySQL 5.6.6.

Migrate the sample schema

To complete all the database objects like table schemas, indexes and stored procedures, we need to extract schema from the source database and apply to the database. To extract schema, you can use mysqldump with - - no-data parameter.

Assuming you have MySQL employees sample database in the on-premise system, the command to do schema migration using mysqldump is:

mysqldump -h [servername] -u [username] -p[password] --databases [db name] --no-data > [schema file path]

For example:

mysqldump -h 10.10.123.123 -u root -p --databases employees --no-data > d:\employees.sql

To import schema to Azure Database for MySQL target, run the following command:

mysql.exe -h [servername] -u [username] -p[password] [database]< [schema file path]

For example:

mysql.exe -h shausample.mysql.database.azure.com -u dms@shausample -p employees < d:\employees.sql

If you have foreign keys in your schema, the initial load and continuous sync of the migration will fail. Execute the following script in MySQL workbench to extract the drop foreign key script and add foreign key script.

SET group_concat_max_len = 8192;
    SELECT SchemaName, GROUP_CONCAT(DropQuery SEPARATOR ';\n') as DropQuery, GROUP_CONCAT(AddQuery SEPARATOR ';\n') as AddQuery
    FROM
    (SELECT 
    KCU.REFERENCED_TABLE_SCHEMA as SchemaName,    
    KCU.TABLE_NAME,
    KCU.COLUMN_NAME,
    CONCAT('ALTER TABLE ', KCU.TABLE_NAME, ' DROP FOREIGN KEY ', KCU.CONSTRAINT_NAME) AS DropQuery,
    CONCAT('ALTER TABLE ', KCU.TABLE_NAME, ' ADD CONSTRAINT ', KCU.CONSTRAINT_NAME, ' FOREIGN KEY (`', KCU.COLUMN_NAME, '`) REFERENCES `', KCU.REFERENCED_TABLE_NAME, '` (`', KCU.REFERENCED_COLUMN_NAME, '`) ON UPDATE ',RC.UPDATE_RULE, ' ON DELETE ',RC.DELETE_RULE) AS AddQuery
    FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU, information_schema.REFERENTIAL_CONSTRAINTS RC
    WHERE
      KCU.CONSTRAINT_NAME = RC.CONSTRAINT_NAME
      AND KCU.REFERENCED_TABLE_SCHEMA = RC.UNIQUE_CONSTRAINT_SCHEMA
  AND KCU.REFERENCED_TABLE_SCHEMA = 'SchemaName') Queries
  GROUP BY SchemaName;

Run the drop foreign key (which is the second column) in the query result to drop foreign key.

If you have trigger in the data (insert or update trigger), it will enforce data integrity in the target ahead of the replicated data from the source. The recommendation is to disable triggers in all the tables at the target during migration, and then enable the triggers after migration is done.

To disable triggers in target database, use the following command:

SELECT Concat('DROP TRIGGER ', Trigger_Name, ';') FROM  information_schema.TRIGGERS WHERE TRIGGER_SCHEMA = 'your_schema';

Register the Microsoft.DataMigration resource provider

  1. Sign in to the Azure portal, select All services, and then select Subscriptions.

    Show portal subscriptions

  2. Select the subscription in which you want to create the instance of the Azure Database Migration Service, and then select Resource providers.

    Show resource providers

  3. Search for migration, and then to the right of Microsoft.DataMigration, select Register.

    Register resource provider

Create a DMS instance

  1. In the Azure portal, select + Create a resource, search for Azure Database Migration Service, and then select Azure Database Migration Service from the drop-down list.

    Azure Marketplace

  2. On the Azure Database Migration Service screen, select Create.

    Create Azure Database Migration Service instance

  3. On the Create Migration Service screen, specify a name for the service, the subscription, and a new or existing resource group.

  4. Select an existing virtual network (VNET) or create a new one.

    The VNET provides the Azure Database Migration Service with access to the source SQL Server and the target Azure SQL Database instance.

    For more information about how to create a VNET in the Azure portal, see the article Create a virtual network using the Azure portal.

  5. Select a pricing tier.

    For more information on costs and pricing tiers, see the pricing page.

    If you need help in choosing the right Azure Database Migration Service tier, refer to the recommendations in the blog posting Choosing an Azure Database Migration Service (Azure DMS) tier.

    Configure Azure Database Migration Service instance settings

  6. Select Create to create the service.

Create a migration project

After the service is created, locate it within the Azure portal, open it, and then create a new migration project.

  1. In the Azure portal, select All services, search for Azure Database Migration Service, and then select Azure Database Migration Services.

    Locate all instances of the Azure Database Migration Service

  2. On the Azure Database Migration Services screen, search for the name of the Azure Database Migration Service instance that you created, and then select the instance.

    Locate your instance of the Azure Database Migration Service

  3. Select + New Migration Project.

  4. On the New migration project screen, specify a name for the project, in the Source server type text box, select MySQL, in the Target server type text box, select AzureDbForMySQL.
  5. In the Choose type of activity section, select Online data migration

    Create Database Migration Service Project

    Note

    Alternately, you can chose Create project only to create the migration project now and execute the migration later.

  6. Select Save, note the requirements to successfully use DMS to migrate data, and then select Create and run activity.

Specify source details

  1. On the Add Source Details screen, specify the connection details for the source MySQL instance.

    Add Source Details screen

Specify target details

  1. Select Save, and then on the Target details screen, specify the connection details for the target Azure Database for MySQL server, which is the pre-provisioned instance of Azure Database for MySQL to which the Employees schema was deployed by using mysqldump.

    Target details screen

  2. Select Save, and then on the Map to target databases screen, map the source and the target database for migration.

    If the target database contains the same database name as the source database, the Azure Database Migration Service selects the target database by default.

    Map to target databases

  3. Select Save, on the Migration summary screen, in the Activity name text box, specify a name for the migration activity, and then review the summary to ensure that the source and target details match what you previously specified.

    Migration Summary

Run the migration

  • Select Run migration.

    The migration activity window appears, and the Status of the activity is initializing.

Monitor the migration

  1. On the migration activity screen, select Refresh to update the display until the Status of the migration shows as Complete.

    Activity Status - complete

  2. Under Database Name, select specific database to get to the migration status for Full data load and Incremental data sync operations.

    Full data load will show the initial load migration status while Incremental data sync will show change data capture (CDC) status.

    Activity Status - Full load completed

    Activity Status - Incremental data sync

Perform migration cutover

After the initial Full load is completed, the databases are marked Ready to cutover.

  1. When you're ready to complete the database migration, select Start Cutover.

    Start cutover

  2. Make sure to stop all the incoming transactions to the source database; wait until the Pending changes counter shows 0.

  3. Select Confirm, and the select Apply.
  4. When the database migration status shows Completed, connect your applications to the new target Azure SQL Database.

Next steps