From GaussDB Distributed to PostgreSQL

Supported Source and Destination Databases

Only whitelisted users can use this function.

Supported Synchronization Objects

Table 2 lists the objects that can be synchronized in different scenarios. DRS will automatically check the objects you selected before the synchronization.

Database User Permission Requirements

Before you 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 3. DRS automatically checks the database account permissions in the pre-check phase and provides handling suggestions.

• 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 or destination databases, modify the connection information in the DRS task as soon as possible to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.
• If a distributed database is the source database, the connectivity of each DN needs to be checked. You are advised to perform data synchronization as a non-root database user to prevent user locking due to incorrect password during DN connection.

Precautions

The full+incremental synchronization consists of four phases: task startup, full synchronization, incremental synchronization, and task completion. A single full or incremental synchronization task contains three phases. To ensure smooth synchronization, read the following notes before creating a synchronization task.

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 1 Synchronization task information
     

     Table 5 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 details
     Figure 2 Synchronization instance details
     

     Table 6 Synchronization instance settings

     Parameter	Description
     Data Flow	Select Out of the cloud.
     Source DB Engine	Select GaussDB Distributed.
     Destination DB Engine	Select PostgreSQL.
     Network Type	Public network is used as an example. Available options: Public network and VPN or Direct Connect Public network is suitable for data synchronization from on-premises or external cloud databases to the destination database 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.
     Source DB Instance	The distributed GaussDB instance you created.
     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	Available options: Full+Incremental, Full, and Incremental. 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. 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 In this mode, data is synchronized from the source to the destination at a time. Incremental Through log parsing, incremental data generated on the source database is synchronized to the destination database.
     Source DN Quantity	The value must be the same as the number of DNs in the distributed source database.
     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. The number of specified EIPs must be the consistent with that of DB instances. For details about the data transfer fee generated using a public network, see EIP Price Calculator.

   • AZ
     Figure 3 AZ
     

     Table 7 Task AZ

     Parameter	Description
     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
     Figure 4 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. 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. 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, click Next.

   Establish the connectivity between the DRS instance and the source and destination databases.

   • Network connectivity: Ensure that the source and destination databases accept connections from the DRS instance. To access databases over a public network, configure the database to accept connections from the EIP of the DRS instance. To access databases over a VPC, VPN, or Direct Connect network, configure the database to accept connections from the private IP address of the DRS instance. For details, see Network Preparations.
   • Account connectivity: Ensure that the source and destination databases allows connections from the DRS instance using the username and password.
   Figure 5 Source database information
   

   Table 9 Source database settings

   Parameter	Description
   DB Instance Name	The distributed GaussDB DB instance selected during synchronization task creation. This parameter cannot be changed.
   Database Username	The username for accessing the source database.
   Database Password	The password for the database username.

   

   The username and password of the source 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.

   Figure 6 Destination database information
   

   Table 10 Destination database settings

   Parameter	Description
   IP Address or Domain Name	The IP address or domain name of the destination database.
   Port	The port of the destination database. Range: 1 - 65535
   Database Name	Indicates whether to specify a database. If this option is enabled, enter the database name.
   Database Username	The username for accessing the destination database.
   Database Password	The password for the database username.
   SSL Connection	SSL encrypts the connections between the source and destination databases.

   

   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 synchronization policy and synchronization objects, and click Next.
   Figure 7 Synchronization Mode
   

   Table 11 Synchronization 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. Figure 8 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.
   Synchronization Object Type	Type of objects for full synchronization. Data is mandatory.
   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. The following conflict policies are supported: Ignore The system will skip the conflicting data and continue the subsequent synchronization process. Overwrite Conflicting data will be overwritten. If the synchronized data conflicts with the existing data in the destination database, selecting Ignore cannot ensure data consistency. To ensure data consistency, select Overwrite.
   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.
   Source Database Replication Slot Name	You can choose whether to specify the replication slot of the source database. After replication slot is enabled, enter the replication slot name. The name contains 63 characters and cannot start with a digit. Only lowercase letters, digits, and underscores (_) are allowed.
   Case Conversion Policy in the Destination Database	Case of schema names, table names, and column names can be converted. If you have specified the mapping name when selecting objects to be synchronized, ignore this parameter.
   Synchronization Object	The left pane displays the source database objects, and the right pane displays the selected objects. You can select Tables or Import object files for Synchronization Object based on your service requirements. 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). You can change object names when you select Import object file. For details, 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 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 you need to process columns or filter out data, set the corresponding rules by referring to 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.
     

     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 9 Task startup settings
   

   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. After enabled, select a SMN topic. 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. 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.
   • 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.