Creating a Synchronization Task_Data Replication Service

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

Step 1: Create a synchronization task. Select the source and destination databases as required and create a synchronization task.

Step 2: Check the synchronization progress. During synchronization, you can view the synchronization progress.
Step 3: View synchronization logs. Synchronization logs contain alarms, errors, and prompt information. You can analyze system problems based on such information.
Step 4: Compare synchronization items. You can compare objects and data to be synchronized to ensure data consistency.

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.

Prerequisites

You have logged in to the DRS console.
Your account balance is greater than or equal to $0 USD.
For details about the DB types and versions supported by real-time synchronization, see Supported Databases.
If a subaccount is used to create a DRS task, ensure that an agency has been added. To create an agency, see Agency Management.

Procedure

On the Data Synchronization Management page, click Create Synchronization Task.

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 and recipient description
Parameter	Description
Region	The region where the synchronization 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	The public network is used as an example. Available options: Public network, VPC, VPN or Direct Connect
Instance Type	DRS instance type. The value can be Single or Primary/Standby. Primary/Standby: This architecture provides HA, improving the reliability of DRS instances. After a primary/standby instance is created, DRS creates two subtasks, each running on the primary and standby nodes. If the subtask on the primary node fails, DRS automatically starts the subtask on the standby node to continue the synchronization. Single: The single-node deployment architecture is used, which is cost-effective. This option is available only in specific scenarios. For details, see Performing a Primary/Standby Switchover.
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 ensure that there are available IP addresses. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.
Synchronization Mode	Available options: Full+Incremental and Incremental 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. Incremental Through log parsing, incremental data generated on the source database is synchronized to the destination database.
AZ	This parameter is available only when you select primary/standby for Instance Type. It indicates the AZ where the DRS instance is created. If the source or destination database is in the same AZ as the DRS instance, you can get better performance. If Instance Type is set to primary/standby, you can specify Primary AZ and Standby AZ. Figure 4 AZ

DRS instance specifications

Figure 5 Specifications

**Table 3** Specifications
Parameter	Description
Specifications	DRS instance specifications. Different specifications have different performance upper limits. For details, see Real-Time Synchronization. NOTE: Currently, DRS supports specification upgrade only in MySQL-to-MySQL synchronization tasks with single-node DRS instances configured. Task specifications cannot be downgraded. For details, see Changing Specifications.

Enterprise Projects and Tags

Figure 6 Enterprise projects and tags

**Table 4** Enterprise Projects and Tags
Parameter	Description
Enterprise Project	An enterprise project you would like to use to centrally manage your Global Accelerator resources. 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 Management page is displayed. For details, see Creating an Enterprise Project in Enterprise Management User Guide.
Tags	This setting is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 10 tags. 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 ends.

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 not enabled, 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 not enabled, 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.

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. Yes You can customize the maximum migration 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. 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 start point during an incremental synchronization. Run show master status to obtain the source database position 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. 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. 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. 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.

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 Column, or Processing Columns. For details about how to configure related rules, see Processing Data.
Figure 11 Processing data
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 Checking Whether the Source Database Is Connected 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.

On the displayed page, specify Start Time, Send Notification, SMN Topic, Synchronization Delay Threshold, 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
Started 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	SMN topic. This parameter is optional. If an exception occurs during synchronization, the system will send a notification to the specified recipients.
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.
Synchronization Delay Threshold	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 Notification.
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: 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.

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, and the task status remains unchanged. When you restart the task configuration, DRS applies for resources again.

Creating a Synchronization Task

Process

Prerequisites

Procedure

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