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

Step 1: Create a synchronization task. Select the source and destination databases as needed to create the 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 MySQL database. To configure other storage engines, you can refer to the following procedures.

Prerequisites

You have logged in to the DRS console.

Procedure

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

On the Create Synchronization Instance page, specify the task name, description, and the synchronization instance details, and click Next.

**Table 1** Task and recipient description
Parameter	Description
Task Name	The task name consists of 4 to 50 characters, starts with a letter, and can contain only letters (case-insensitive), digits, hyphens (-), and underscores (_).
Description	The description consists of a maximum of 256 characters and cannot contain the following special characters: !=<>'&"\

**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
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.

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.

Source database information

**Table 3** 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 Synchronization Information area on the Basic Information page, click Update Password next to the Source Database Password field. In the displayed dialog box, change the password. This action only updates DRS with the changed password.
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 the SSL certificate is not used, 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

**Table 4** 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 Synchronization Information area on the Basic Information page, click Update Password next to the Destination Database Password field. In the displayed dialog box, change the password. This action only updates DRS with the changed password.

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.

**Table 5** 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. 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. Report error The synchronization task will be stopped and fail. Overwrite Conflicting data will be overwritten. If data conflicts occur, you can select Ignore, Overwrite, or Report error in any of the following scenarios. Data exists in the destination database. Multiple source databases are synchronized to one destination database. Data in the destination database is updated manually.
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. If gtid_mode is disabled, you do not need to specify Executed_Gtid_Set.
Data Synchronization Topology	Data synchronization supports multiple synchronization topologies. You can plan your synchronization instances based on service requirements. For details, see Data Synchronization Topologies.
Synchronize DDLs	You can select the DDL types for incremental synchronization as required. The DDL type depends on the application scenario. 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	Select Tables or Databases as required. The search function can help you quickly select the required database objects. If the source database is changed, click in the upper right corner before selecting synchronization objects to ensure that the objects to be selected are from the changed source database. 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.

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.
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.
  
  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, confirm that the configured information is correct, and click Submit to submit the task.

**Table 6** 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.

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.