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From MySQL to GaussDB(for MySQL)

Supported Source and Destination Databases

Table 1 Supported databases

Source DB

Destination DB

  • On-premises MySQL databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • ECS-hosted MySQL databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • Other cloud MySQL databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • RDS for MySQL (5.5, 5.6, 5.7, 8.0)

GaussDB(for MySQL) Primary/Standby (version 8.0)

Database Account Permission Requirements

To start a synchronization task, the source and destination database users must meet the requirements in the following table. Different types of synchronization tasks require different permissions. For details, see Table 2. DRS automatically checks the database account permissions in the pre-check phase and provides handling suggestions.

Table 2 Database account permission

Type

Full+Incremental Synchronization and Incremental Synchronization

Source database user

SELECT, SHOW VIEW, EVENT, LOCK TABLES, REPLICATION SLAVE, and REPLICATION CLIENT

For a full+incremental task, if the source database version is 8.0.2 or later, the XA_RECOVER_ADMIN permission is required to prevent data loss caused by uncommitted XA transactions during startup or task editing.

Destination database user

The root account of GaussDB(for MySQL) has the following permissions by default: SELECT, CREATE, DROP, DELETE, INSERT, UPDATE, ALTER, CREATE VIEW, CREATE ROUTINE, and REFERENCES

If the destination database version is in the range 8.0.14 to 8.0.18, the SESSION_VARIABLES_ADMIN permission is required.

Note
  • You are advised to create an independent database account for DRS task connection to prevent task failures caused by database account password modification.
  • After changing the account passwords for the source and destination databases, modify the connection information of the DRS task by referring to Modifying Connection Information to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.

Supported Synchronization Objects

Table 3 lists the objects that can be synchronized in different scenarios. DRS will automatically check the objects you selected before the synchronization.

Table 3 Supported synchronization objects

Type

Precautions

Synchronization objects

  • Tables, primary key indexes, unique indexes, common indexes, stored procedures, views, and functions can be synchronized.
  • Only MyISAM and InnoDB tables can be synchronized.
  • Table names cannot be mapped for tables on which views, stored procedures, and functions depend.
  • Events and triggers cannot be synchronized.
  • Full and incremental synchronizations do not support invisible columns. Invisible columns can be synchronized since MySQL 8.0.23. For example:
    CREATE TABLE `test11` (
  `id` int NOT NULL,
  `c1` int DEFAULT NULL /*!80023 INVISIBLE */,
  PRIMARY KEY (`id`));

Precautions

To ensure tasks can run normally, DRS provides automatic pre-check. Before starting a DRS task, DRS checks the configurations and conditions of the source and destination databases. For details about the main check items and handling suggestions, see Pre-check Items. In addition to the pre-check items, you need to pay attention to the items listed in Table 4.

Table 4 Precautions

Type

Restrictions

Restrictions on the source database

  • The names of the source databases, tables, and views cannot contain non-ASCII characters, or the following characters: . > < / \ ' "
  • The column names in the source database tables cannot end with a backslash (\).
  • The source database does not support the reset master or reset master to command, which may cause DRS task failures or data inconsistency.
  • If the source MySQL database does not support TLS 1.2 or is a self-built database of an earlier version (earlier than 5.6.46 or between 5.7.0 and 5.7.28), you need to submit an O&M application for testing the SSL connection.

Restrictions on usage

General

  • Do not modify or delete the usernames, passwords, and permissions of the source and destination databases or change the ports of the source and destination databases.
  • During data synchronization, do not upgrade the source MySQL database across major versions. Otherwise, data may become inconsistent or the synchronization task may fail (data, table structures, and keywords may cause compatibility changes after the cross-version upgrade). You are advised to create a synchronization task again if the source MySQL database is upgraded across major versions.

Full synchronization

  • When a DRS task is being started or in the full synchronization phase, do not perform DDL operations on the source database. Otherwise, the task may be abnormal.
  • Modifying MyISAM tables may cause data inconsistency.
  • During database name mapping, function objects, views, and stored procedures may fail to be created because they are referenced by a database table name before the mapping. DRS ignores the error reported during the creation of these objects in the full synchronization phase. As a result, these objects are lost in the destination database.

Incremental synchronization

  • If the session variable character_set_client is set to binary, some data may include garbled characters.
  • If database name mapping is required, DDL operations (including CREATE, MODIFY, and DELETE) related to function objects, views, and stored procedures are not synchronized to the destination database.
  • Some DDL operations are supported.
    • In one-to-one synchronization, the following DDL operations are synchronized by default: CREATE_TABLE, RENAME_TABLE, ADD_COLUMN, MODIFY_COLUMN, CHANGE_COLUMN, DROP_COLUMN, DROP_INDEX, ADD_INDEX, CREATE_INDEX, RENAME_INDEX, DROP_TABLE, TRUNCATE_TABLE, DROP_PARTITION, RENAME_COLUMN, DROP_PRIMARY_KEY and ADD_PRIMARY_KEY. You can select the DDL operations to be synchronized on the object selection page as required.
    • Incremental synchronization supports table renaming. Ensure that both the source and destination tables are selected.

Other restrictions

  • When table name mapping is used in a synchronization task, foreign key constraints of the table cannot be synchronized.
  • The DDL operation of renaming an unselected table is filtered out during the synchronization. As a result, the task may fail or data may be inconsistent.
    • If you rename table A to the name of table B and tables A and B are selected for synchronization, this RENAME statement will not be filtered out.
    • If you rename table A to the name of table B but table B is not synchronized, this RENAME statement will be filtered out.
    • You are not advised to perform the rename operation in the many-to-one synchronization scenario. Otherwise, the task may fail or data may be inconsistent.
  • If a physically generated column in a table is generated based on a time type, the data in the column may be inconsistent.
  • The source and destination databases cannot contain tables that have the same names but do not have primary keys.
  • If the source database contains non-standard floating-point data and the data can be written in loose mode but cannot be written in strict mode, there may be data inconsistency during synchronization.
  • If Transparent Data Encryption (TDE) is enabled for the source database table, TDE must also be enabled for the destination database. Otherwise, the table structure fails to be created and the task will be abnormal. You can create an unencrypted table structure in the destination database to avoid this problem.
  • Before creating a DRS task, if concurrency control rules of SQL statements are configured for the source or destination database, the DRS task may fail.
  • Resumable upload is supported, but data may be repeatedly inserted into a table that does not have a primary key.
  • The destination table can contain more columns than the source table. However, the following failures must be avoided:
    • Assume that extra columns on the destination database cannot be null or have default values. If newly inserted data records are synchronized from the source database to the destination database, the extra columns will become null, which does not meet the requirements of the destination database and will cause the task to fail.
    • Assume that extra columns on the destination database must be fixed at a default value and have a unique constraint. If newly inserted data records are synchronized from the source database to the destination database, the extra columns will contain multiple default values. That does not meet the unique constraint of the destination database and will cause the task to fail.
  • The source database does not support point-in-time recovery (PITR).
  • The destination database cannot be restored to a point in time when a full synchronization was being performed.
  • Cascade operations cannot be performed on tables with foreign keys. If the foreign key index of a table is a common index, the table structure may fail to be created. You are advised to use a unique index.
  • Binlogs cannot be forcibly deleted. Otherwise, the synchronization task fails.
  • After a task is created, the destination database cannot be set to read-only.
  • If index synchronization is required for a DRS task, the destination database table cannot contain indexes with the same name but different columns. In the full phase, DRS ignores the existing indexes with the same name. In the incremental phase, DDL operations on indexes based on the index name trigger misplacement.
  • If you use additional columns and the number of columns in a single table exceeds 500, adding additional columns may lead to the number of columns in a table to reach an upper limit and cause the task to fail.

Procedure

This section uses real-time synchronization from MySQL to GaussDB(for MySQL) as an example to describe how to configure a real-time synchronization task.

  1. On the Data Synchronization Management page, click Create Synchronization Task.
  2. On the Create Synchronization Instance page, specify the task name, description, and the synchronization instance details, and click Create Now.

    • Task information description
      Table 5 Task information

      Parameter

      Description

      Task Name

      The task name must start with a letter and consist of 4 to 50 characters. It can contain only letters, digits, hyphens (-), and underscores (_).

      Description

      The description consists of a maximum of 256 characters and cannot contain special characters !=<>'&"\

    • Synchronization instance information
      Table 6 Synchronization instance settings

      Parameter

      Description

      Data Flow

      Select To the cloud.

      Source DB Engine

      Select MySQL.

      Destination DB Engine

      Select GaussDB(for MySQL).

      Network Type

      Public network is used as an example. Available options: VPC, Public network and VPN or Direct Connect

      • VPC is suitable for data synchronization between cloud databases of the same account in the same region and VPC.
      • Public network is suitable for data synchronization from on-premises or external cloud databases to the destination databases bound with an EIP.
      • VPN or Direct Connect is suitable for data synchronization from on-premises databases to cloud databases, between databases of different accounts in the same region on the cloud, or between databases across regions on the cloud using a VPN, Direct Connect, Cloud Connect, VPCEP, or a VPC peering connection.

      Destination DB Instance

      An available GaussDB(for MySQL) instance.

      Synchronization Instance Subnet

      Select the subnet where the synchronization instance is located. You can also click View Subnets to go to the network console to view the subnet where the instance resides.

      By default, the DRS instance and the destination DB instance are in the same subnet. You need to select the subnet where the DRS instance resides, and there are available IP addresses for the subnet. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.

      Synchronization Mode

      The synchronization mode supported by a DRS task. Full+Incremental is used as an example.

      • Full+Incremental

      This synchronization mode allows you to synchronize data in real time. After a full synchronization initializes the destination database, an incremental synchronization parses logs to ensure data consistency between the source and destination databases.

      • Incremental

      Through log parsing, incremental data generated on the source database is synchronized to the destination database.

      NOTE:

      If you select Full+Incremental, data generated during the full synchronization will be continuously synchronized to the destination database, and the source remains accessible.

      Specify EIP

      This parameter is available when you select Public network for Network Type. Select an EIP to be bound to the DRS instance. DRS will automatically bind the specified EIP to the DRS instance and unbind the EIP after the task is complete.

    • Task Type
      Table 7 Task type information

      Parameter

      Description

      Specifications

      DRS instance specifications. Different specifications have different performance upper limits. For details, see Real-Time Synchronization.

      AZ

      Select the AZ where you want to create the DRS task. Selecting the one housing the source or destination database can provide better performance.

    • Enterprise Project and Tags

      Table 8 Enterprise Project and Tags

      Parameter

      Description

      Enterprise Project

      An enterprise project you would like to use to centrally manage your cloud resources and members. Select an enterprise project from the drop-down list. The default project is default.

      Tags

      • Tags a task. This configuration is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 20 tags.
      • After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.
    Note

    If a task fails to be created, DRS retains the task for three days by default. After three days, the task automatically stops.

  3. On the Configure Source and Destination Databases page, wait until the synchronization instance is created. Then, specify source and destination database information and click Test Connection for both the source and destination databases to check whether they have been connected to the synchronization instance. After the connection tests are successful, select the check box before the agreement and click Next.

    Table 9 Source database settings

    Parameter

    Description

    IP Address or Domain Name

    The IP address or domain name of the source database.

    Port

    The port of the source database. Range: 1 – 65535

    Database Username

    The username for accessing the source database.

    Database Password

    The password for the database username.

    SSL Connection

    SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate.

    NOTE:
    • The maximum size of a single certificate file that can be uploaded is 500 KB.
    • If SSL is disabled, your data may be at risk.
    Note

    The username and password of the source database are encrypted and stored in DRS and will be cleared after the task is deleted.

    Table 10 Destination database settings

    Parameter

    Description

    DB Instance Name

    The RDS DB instance selected during synchronization task creation. This parameter cannot be changed.

    Database Username

    The username for accessing the destination database.

    Database Password

    The database username and password are encrypted and stored in the system and will be cleared after the task is deleted.

  4. On the Set Synchronization Task page, select synchronization objects and click Next.

    Table 11 Synchronization mode and object

    Parameter

    Description

    Flow Control

    You can choose whether to control the flow. Flow Control takes effect in the full phase only.

    • Yes

      You can customize the maximum synchronization speed. During the full synchronization, the synchronization speed of each task (or each subtask in multi-task mode) does not exceed the value of this parameter.

      In addition, you can set the time range based on your service requirements. The traffic rate setting usually includes setting of a rate limiting time period and a traffic rate value. Flow can be controlled all day or during specific time ranges. The default value is Always. A maximum of 10 time ranges can be set, and they cannot overlap.

      The flow rate must be set based on the service scenario and cannot exceed 9,999 MB/s.

    • No

      The synchronization speed is not limited and the outbound bandwidth of the source database is maximally used, which will increase the read burden on the source database. For example, if the outbound bandwidth of the source database is 100 MB/s and 80% bandwidth is used, the I/O consumption on the source database is 80 MB/s.

      NOTE:
      • The flow control mode takes effect only in the full synchronization phase.
      • You can also change the flow control mode after creating a task. For details, see Modifying the Flow Control Mode.

    Incremental Conflict Policy

    The conflict policy refers to the conflict handling policy during incremental synchronization. By default, conflicts in the full synchronization phase are ignored. Select any of the following conflict policies:

    • Ignore

      The system will skip the conflicting data and continue the subsequent synchronization process. If you select Ignore, data in the source database may be inconsistent with that in the destination database.

    • Overwrite

      Conflicting data will be overwritten.

    Filter DROP DATABASE

    During real-time synchronization, executing DDL operations on the source database may affect the synchronization performance. To reduce the risk of synchronization failure, DRS allows you to filter out DDL operations. Currently, only the delete operations on databases can be filtered by default.

    • If you select Yes, the database deletion operation performed on the source database is not synchronized during data synchronization.
    • If you select No, related operations are synchronized to the destination database during data synchronization.

    Synchronize

    Whether to synchronize normal indexes.

    By default, DRS synchronizes the primary key or unique index. A normal index refers to an index other than the primary key or unique index. If you select normal index, all indexes will be synchronized. If you do not select normal index, only the primary key and unique index will be synchronized.

    Create Indexes Along With Table Structure

    Indicates whether to create indexes along with the table structure in the full synchronization phase.

    • Yes: Indexes are migrated when the table structure is migrated in the full synchronization phase.
    • No: Indexes are migrated separately after data synchronization.

    Synchronize DML

    Select the DML operations to be synchronized. By default, all DML operations are selected.

    If you do not select Delete, DELETE statements in the incremental data of the source database will not be synchronized, which may cause a data inconsistency. As a result, there may be a data conflict or the task may fail.

    Start Point

    This option is available if you select Incremental in 2. The logs of the source database are obtained from the position after the start point during an incremental synchronization.

    Run show master status to obtain the start point of the source database and set File, Position, and Executed_Gtid_Set as prompted.

    Synchronization Object

    The left pane displays the source database objects, and the right pane displays the selected objects. You can select Tables or Databases for Synchronization Object as required.

    • If the synchronization objects in source and destination databases have different names, you can map the source object name to the destination one. For details, see Changing Object Names (Mapping Object Names).
      • If the database table name contains characters other than letters, digits, and underscores (_), or the mapped database table name contains hyphens (-) and number signs (#), the name length cannot exceed 42 characters.
    NOTE:
    • To quickly select the desired database objects, you can use the search function.
    • If there are changes made to the source databases or objects, click in the upper right corner to update the objects to be synchronized.
    • If an object name contains spaces, the spaces before and after the object name are not displayed. If there are two or more consecutive spaces in the middle of the object name, only one space is displayed.
    • The name of the selected synchronization object cannot contain spaces.

  5. On the Process Data page, set the filtering rules for data processing.

    • If data processing is not required, click Next.
    • If data processing is required, select Data filtering, Additional Columns, or Processing Columns. For details about how to configure related rules, see Processing Data.

  6. On the Check Task page, check the synchronization task.

    • If any check fails, review the cause and rectify the fault. After the fault is rectified, click Check Again.
    • If all check items are successful, click Next.
      Note

      You can proceed to the next step only when all checks are successful. If there are any items that require confirmation, view and confirm the details first before proceeding to the next step.

  7. On the displayed page, specify Start Time, Send Notifications, SMN Topic, Delay Threshold (s), and Stop Abnormal Tasks After, confirm that the configured information is correct, and click Submit to submit the task.

    Table 12 Task startup settings

    Parameter

    Description

    Start Time

    Set Start Time to Start upon task creation or Start at a specified time based on site requirements.

    NOTE:

    After a synchronization task is started, the performance of the source and destination databases may be affected. You are advised to start a synchronization task during off-peak hours.

    Send Notifications

    This parameter is optional. If the status, latency metric, or data of the migration task is abnormal, DRS will send you a notification.

    SMN Topic

    This parameter is available only after you enable Send Notifications and create a topic on the SMN console and add a subscriber.

  8. After the task is submitted, you can view and manage it on the Data Synchronization Management page.

    • You can view the task status. For more information about task status, see Task Statuses.
    • You can click in the upper right corner to view the latest task status.
    • By default, DRS retains a task in the Configuration state for three days. After three days, DRS automatically deletes background resources, but the task status remains unchanged. When you configure the task again, DRS applies for resources for the task again. In this case, the IP address of the DRS instance changes.
    • For a public network task, DRS needs to delete background resources after you stop the task. The EIP bound to the task cannot be restored to the Unbound state until background resources are deleted.

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