Updated on 2024-03-28 GMT+08:00

Creating a Synchronization Task

Process

A complete real-time synchronization consists of creating a synchronization task, tracking task progress, analyzing synchronization logs, and comparing data consistency. By comparing multiple items and data, you can synchronize data between different service systems in real time.

A complete real-time synchronization involves the following procedures.

Figure 1 Flowchart

This section describes how to synchronize data from a MySQL database to an RDS for MySQL database. To configure other storage engines, you can refer to the following procedures.

Procedure

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

    • Task information description
      Figure 2 Synchronization task information
      Table 1 Task information

      Parameter

      Description

      Region

      The region where the replication instance is deployed. You can change the region.

      Project

      The project corresponds to the current region and can be changed.

      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
      Figure 3 Synchronization instance information

      Table 2 Synchronization instance settings

      Parameter

      Description

      Data Flow

      Select To the cloud. The destination database is a database in the current cloud.

      Source DB Engine

      Select MySQL.

      Destination DB Engine

      Select MySQL.

      Network Type

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

      • VPC is suitable for data synchronization between cloud databases of the same account in the same region.
      • 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 synchronization of data between on-premises databases and cloud databases, between cloud databases of different accounts in the same region, or between cloud databases across regions.

      DRS Task Type

      Type of the DRS task. The value can be Single-AZ or Dual-AZ.

      • Dual-AZ: This architecture provides HA, improving the reliability of DRS tasks. After a dual-AZ task is created, DRS creates two subtasks, each running in the primary and standby AZs. If the subtask in the primary AZ fails, DRS automatically starts the subtask in the standby AZ to continue the synchronization. This deployment is for scenarios where there is a lot of service data, long-term synchronization is required, and there are strict limits on how much service downtime can be tolerated.
      • Single-AZ: Single-node deployment is used. The synchronization task will be created on only one node to save money. This deployment is for scenarios where there is a small amount of service data, short-term synchronization is required, and there is no requirement on service downtime.

      This option is available only in specific scenarios. For details, see Performing a Switchover for a Dual-AZ Task.

      Destination DB Instance

      The RDS DB instance you created.

      NOTE:
      • The destination DB instance cannot be a read replica.
      • The source and destination DB instances can be the same DB instance.

      Synchronization Instance Subnet

      Select the subnet where the synchronization instance is located. You can also click View Subnet 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.

      Security Group

      Select a security group. You can use security group rules to allow or deny access to the instance.

      Synchronization Mode

      The synchronization mode supported by a DRS task. Full+Incremental is used as an example. For details about the underlying working principles for full or incremental synchronization, see Product Architecture and Function Principles.

      • 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.

        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.

      • Full

        All objects and data in non-system databases are synchronized to the destination database at a time. This mode is applicable to scenarios where service interruption is acceptable.

      • Incremental

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

    • Task Type
      Figure 4 Task type
      Table 3 Task type information

      Parameter

      Description

      Specifications

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

      NOTE:

      DRS allows you to upgrade specifications only for single-AZ synchronization tasks. Task specifications cannot be downgraded. For details, see Changing Specifications.

      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.

      If DRS Task Type is set to Dual-AZ, you can specify Primary AZ and Standby AZ.

      Figure 5 AZ
    • Enterprise Project and Tags
      Figure 6 Enterprise projects and tags
      Table 4 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.

      For more information about enterprise project, see Enterprise Management User Guide.

      To customize an enterprise project, click Enterprise in the upper right corner of the console. The Enterprise Project Management Service page is displayed. For details, see Creating an Enterprise Project in Enterprise Management User Guide.

      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.
      • If your organization has configured tag policies for DRS, add tags to tasks based on the policies. If a tag does not comply with the policies, task creation may fail. Contact your organization administrator to learn more about tag policies.
      • After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.

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

  3. After the synchronization instance is created, on the Configure Source and Destination Databases page, specify source and destination database information. Then, 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.

    In different data flow scenarios, the source and destination database settings are different. Specify the required parameters based on the GUI.
    • Source database information
      Figure 7 Source database information
      Table 5 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. You can change the password if necessary. To change the password, perform the following operation after the task is created:

      If the task is in the Starting, Full synchronization, Incremental synchronization, or Incremental synchronization failed status, in the Connection Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password.

      SSL Connection

      If SSL connection is required, enable SSL on the source database, ensure that related parameters have been correctly configured, and upload an SSL 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.

      The IP address, port, username, and password of the source database are encrypted and stored in the database and the synchronization instance, and will be cleared after the task is deleted.

    • Destination database information
      Figure 8 Destination database information
      Table 6 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 password for the database username. You can change the password if necessary. To change the password, perform the following operation after the task is created:

      If the task is in the Starting, Full synchronization, Incremental synchronization, or Incremental synchronization failed status, in the Connection Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password.

      SSL Connection

      If SSL connection is required, enable SSL on the destination database, ensure that related parameters have been correctly configured, and upload an SSL 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.

      The username and password of the destination database are encrypted and stored in the database and the synchronization instance during the synchronization. After the task is deleted, the username and password are permanently deleted.

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

    Figure 9 Synchronization mode
    Table 7 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.

      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 All day. A maximum of three 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.

      Figure 10 Flow control
    • 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

    Normal indexes and incremental DDLs can be synchronized. You can determine whether to synchronize data based on service requirements.

    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.

    Data Synchronization Topology

    This parameter is available when Incremental DDLs is selected for Synchronize. Data synchronization supports multiple synchronization topologies. You can plan your synchronization instances based on service requirements. For details, see Data Synchronization Topologies.

    NOTE:

    Data Synchronization Topology can be selected only for whitelisted users. You need to submit a service ticket to apply for this function. In the upper right corner of the management console, choose Service Tickets > Create Service Ticket to submit a service ticket.

    Synchronize DDLs

    This parameter is available when Incremental DDLs is selected for Synchronize. Select DDL type for incremental synchronization. You can select Default or Custom based on your service requirements.

    • Default
      • During database-level synchronization, all DDL operations in the binlog related to database objects, except DDL related to permissions, are synchronized to the destination. Common DDL statements are CREATE_TABLE and RENAME_TABLE.
      • During table-level synchronization, only DDL operations in the binlog related to the selected tables are synchronized. Common DDL statements are ADD_COLUMN, MODIFY_COLUMN, and ALTER_COLUMN.
    • Custom: You can select the DDL type to be synchronized as required. The DDL types supported by different data flow types are displayed on the GUI.

      If Incremental DDLs is selected for Synchronize, but no DDL type is selected for Custom, DDLs will not be synchronized by default.

    NOTE:
    • Only whitelisted users can synchronize incremental DDL operations. You need to submit a service ticket to apply for this function. In the upper right corner of the management console, choose Service Tickets > Create Service Ticket to submit a service ticket.
    • One-to-one and one-to-many scenarios: If the DDL usage of the source and destination databases must be consistent, high-risk DDLs must be synchronized. If you do not want a high-risk DDL to be performed in the destination, deselect the high-risk DDL to protect destination data. However, this may cause the synchronization to fail. However, filtering DDL may cause synchronization to fail, for example, column deletion.
    • Many-to-one scenarios: Synchronize only the Add Column operation, or tasks may fail or data may be inconsistent due to changes in destination tables.

    Synchronization Object

    The left pane displays the source database objects, and the right pane displays the selected objects. You can select Tables, Import object file, 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 in the right pane. For details, see 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.
      • In the many-to-one scenario, if you want to change the saved database mapping name during table-level synchronization, you need to expand the database.
    • For details about how to import an object file, see Importing Synchronization Objects.
    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 the object name contains spaces, the spaces before and after the object name are not displayed. If there are multiple spaces between the object name and 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.
    Figure 11 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.

      For details about how to handle check failures, see Solutions to Failed Check Items in Data Replication Service User Guide.

    • If all check items are successful, click Next.
      Figure 12 Pre-check

      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, select the check box before the agreement, and click Submit to submit the task.

    Figure 13 Task startup settings
    Table 8 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. After enabled, select a SMN topic. If the status, latency metric, or data of the synchronization task is abnormal, DRS will send 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.

    For details, see Simple Message Notification User Guide.

    Delay Threshold (s)

    During an incremental synchronization, a synchronization delay indicates a time difference (in seconds) of synchronization between the source and destination database.

    If the synchronization delay exceeds the threshold you specify, DRS will send alarms to the specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes.

    NOTE:
    • If the delay threshold is set to 0, no notifications will be sent to the recipient.
    • In the early stages of an incremental synchronization, the synchronization delay is long because a large quantity of data is awaiting synchronization. In this case, no notifications will be sent.
    • Before setting the delay threshold, enable Send Notifications.

    Data Exception Notification

    This parameter is optional. After enabled, DRS will send a notification if the task data is abnormal.

    Stop Abnormal Tasks After

    Number of days after which an abnormal task is automatically stopped. The value must range from 14 to 100. The default value is 14.

    NOTE:
    • You can set this parameter only for pay-per-use tasks.
    • Tasks in the abnormal state are still charged. If tasks remain in the abnormal state for a long time, they cannot be resumed. Abnormal tasks run longer than the period you set (unit: day) will automatically stop to avoid unnecessary fees.

  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.