Creating a DR Task_Data Replication Service

Scenario

To prevent service unavailability caused by regional faults, DRS provides disaster recovery to ensure service continuity. If the region where the primary instance is located encounters a natural disaster and cannot be connected, you can switch the remote instance to the primary instance. To reconnect to the primary instance, you only need to change the connection address on the application side. DRS allows you to perform cross-region real-time synchronization between a primary instance and a DR instance during disaster recovery

A complete online disaster recovery consists of creating a DR task, tracking task progress, analyzing DR logs, and comparing data consistency. By comparing multiple items and data, you can synchronize data between different service systems.

Process

The following flowchart shows the basic processes for disaster recovery.

Figure 1 Disaster recovery process

Step 1: Create a DR task. Select the service and DR databases as required and create a DR task.
Step 2: Query the DR progress. During the disaster recovery, you can view the DR progress.
Step 3: View DR logs. Disaster recovery logs contain alarms, errors, and prompt information. You can analyze system problems based on such information.
Step 4: Compare DR items. The DR system supports object-level, data-level comparison to ensure data consistency.

This section uses disaster recovery from a MySQL instance to an RDS for MySQL instance as an example describes how to configure a DR task on the DRS console over a public network.

You can create a DR task that will walk you through each step of the process. After a DR task is created, you can manage it on the DRS console.

Prerequisites

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

Procedure

On the Disaster Recovery Management page, click Create Disaster Recovery Task.

On the Create Disaster Recovery Instance page, select a region and project, specify the task name, description, and the DR instance details, and click Create Now.

Task information description

Figure 2 DR task information

**Table 1** Task and recipient description
Parameter	Description
Region	The region where your service is running. 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 !=<>'&"\

DR instance information

Figure 3 DR instance information

**Table 2** DR instance settings
Parameter	Description
DR Type	Select Single-active. The DR type can be single-active or dual-active. If Dual-active is selected, two subtasks are created by default, a forward DR task and a backward DR task. NOTE: Only whitelisted users can use dual-active DR. To use this function, submit a service ticket. In the upper right corner of the management console, choose Service Tickets > Create Service Ticket to submit a service ticket.
Disaster Recovery Relationship	Select Current cloud as standby. This parameter is available only when you select Single-active. By default, Current cloud as standby is selected. You can also select Current cloud as active. Current cloud as standby: The DR database is on the current cloud. Current cloud as active: The service database is on the current cloud.
Service DB Engine	Select MySQL.
DR DB Engine	Select MySQL.
Network Type	The public network is used as an example. Available options: VPN or Direct Connect and Public network. By default, the value is Public network.
DR DB Instance	RDS DB instance you have created as the destination database of the DR task.
Disaster Recovery Instance Subnet	Select the subnet where the disaster recovery 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 DR 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 disaster recovery instance is successfully created, only subnets with DHCP enabled are displayed.
Destination DB Instance Access	Select Read-only. This parameter is available when you select Single-active for DR Type and Current cloud as standby for Disaster Recovery Relationship. During disaster recovery, the entire DR database instance becomes read-only. To change the DR database to Read/Write, you can change the DR database (or destination database) to a service database by clicking Promote Current Cloud on the Disaster Recovery Monitoring tab. If a DR task fails, the DR database does not automatically change to the read/write state. If a DR task is paused, you can disable read-only for the DR database. For details, see Disabling or Enabling Read-Only. After read-only is disabled and the DR task is resumed, the DR database automatically changes to read-only. The read-only settings of the DR DB instance are also affected by the access settings of the DB instance itself. Therefore, you are advised not to set the access settings of the DB instance on the RDS console. After the DR task is complete, the DR database changes to Read/Write. When the external database functions as the DR database, the user with the superuser permission can set the database to read-only. If a DRS instance node is rebuilt due to a fault, to ensure data consistency during the DRS task restoration, the current cloud standby database is set to read-only before the task is restored. After the task is restored, the synchronization relationship recovers.
Enable Binlog Cleanup	This parameter is available when you set Disaster Recovery Relationship to Current cloud as standby. It indicates whether to enable the function of quickly clearing binlogs of the destination database. After this function is enabled, binlog clearing is enabled for the DR database during the full synchronization and disabled during the incremental synchronization.
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.

Specifications

Figure 4 Specifications

**Table 3** Specifications
Parameter	Description
Specifications	DRS instance specifications. Different specifications have different performance upper limits. For details, see Real-Time DR. NOTE: DRS allows you to upgrade specifications only for real-time DR tasks from MySQL to MySQL, from MySQL to GaussDB(for MySQL), and from GaussDB(for MySQL) to GaussDB(for MySQL). 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.

Enterprise Project and Tags

Figure 5 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 projects, 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.

On the Configure Source and Destination Databases page, wait until the DR 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 DR instance. After the connection tests are successful, select the check box before the agreement and click Next.

Select Current cloud as standby for Disaster Recovery Relationship in 2.

Figure 6 Service database information

**Table 5** Service database settings
Parameter	Description
Database Type	By default, Self-built on ECS is selected. The source database can be a Self-built on ECS or an RDS DB instance. After selecting RDS DB instance, select the region where the source database resides and the region cannot be the same as the region where the destination database resides. The region where the destination database is located is the region where you log in to the management console. To use the RDS DB instance option, submit a service ticket.
IP Address or Domain Name	The IP address or domain name of the service database.
Port	The port of the service database. Range: 1 – 65535
Database Username	The username for accessing the service database.
Database Password	The password for the service 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, Initializing, Disaster recovery in progress, or Disaster recovery 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	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.
Region	The region where the source database is located. This parameter is available only when Database Type for the source database is set to RDS DB instance. The region cannot be the region where the destination database is located.
DB Instance Name	The name of the service DB instance. This parameter is available only when the source database is an RDS DB instance.
Database Username	The username for accessing the service database.
Database Password	The password for the service database username.

The IP address, domain name, username, and password of the service database are encrypted and stored in DRS and will be cleared after the task is deleted.

Figure 7 DR database information

**Table 6** DR database settings
Parameter	Description
DB Instance Name	The DB instance you selected when creating the DR task and cannot be changed.
Database Username	The username for accessing the DR database.
Database Password	The password for the database username. The password can be changed after a task is created. If the task is in the Starting, Initializing, Disaster recovery in progress, or Disaster recovery failed status, in the DR Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password. The database username and password are encrypted and stored in DRS, and will be cleared after the task is deleted.
SSL Connection	If SSL connection is required, enable SSL on the DR 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.

Select Current cloud as active for Disaster Recovery Relationship in 2.

Figure 8 Service database information

**Table 7** Service database settings
Parameter	Description
DB Instance Name	The RDS instance selected when you created the DR task. This parameter cannot be changed.
Database Username	The username for accessing the service 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, Initializing, Disaster recovery in progress, or Disaster recovery failed status, in the DR Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password. The database username and password are encrypted and stored in the system and will be cleared after the task is deleted.
SSL Connection	If SSL connection is required, enable SSL on the service 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.

Figure 9 DR database information

**Table 8** DR database settings
Parameter	Description
Database Type	By default, Self-built on ECS is selected. The destination database can be a Self-built on ECS or an RDS DB instance. If you select RDS DB instance, you need to select the region where the destination database is located. To use the RDS DB instance option, submit a service ticket.
IP Address or Domain Name	The IP address or domain name of the DR database.
Port	The port of the DR database. Range: 1 – 65535
Region	The region where the RDS DB instance is located. This parameter is available only when the destination database is an RDS DB instance.
DB Instance Name	DR instance name. This parameter is available only when the destination database is an RDS DB instance. NOTE: When the DB instance is used as the DR database, it is set to read-only. After the task is complete, the DB instance can be readable and writable.
Database Username	Username for logging in to the DR database.
Database Password	Password for the database username.
SSL Connection	If SSL connection is required, enable SSL on the DR 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, domain name, username, and password of the DR database are encrypted and stored in DRS and will be cleared after the task is deleted.

On the Configure DR page, specify flow control and click Next.

Figure 10 DR settings

**Table 9** DR settings
Parameter	Description
Flow Control	You can choose whether to control the flow. Yes You can customize the maximum disaster recovery speed. During the disaster recovery, the 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 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 11 Flow control No The DR speed is not limited and the outbound bandwidth of the source database is maximally used, which causes read consumption on the source database accordingly. 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: Flow control mode takes effect only in the DR initialization phase. You can also change the flow control mode when the task is in the Configuration state. For details, see Modifying the Flow Control Mode.
Migrate Definer to User	Indicates whether to migrate the Definers of all source database objects to the destination database user entered during the connection test. Yes The Definers of all source database objects will be migrated to the user. Other users do not have permissions for database objects unless these users are authorized. For details about authorization, see How Do I Maintain the Original Service User Permission System After Definer Is Forcibly Converted During MySQL Migration? For example, if the view is CREATE ALGORITHM=UNDEFINED DEFINER=`username`@`%` SQL SECURITY DEFINER VIEW `test_db`.`view5` AS select 1 AS `1` before migration, it is converted to CREATE ALGORITHM=UNDEFINED DEFINER=`drsUser`@`%` SQL SECURITY DEFINER VIEW `test_db`.`view5` AS select 1 AS `1` after the migration. drsUser indicates the destination database user used for testing the connection. No The Definers of all source database objects will not be changed. You need to migrate all accounts and permissions of the source database in the next step. Note that if the Definer account is not found in the destination database, unavailable objects will be created. For details about Definer, see the MySQL official document.

On the Check Task page, check the DR task.
- If any check fails, review the failure 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 the check is complete and the check success rate is 100%, go to the Compare Parameter page.
  
  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.
Compare the parameters.
The parameter comparison function helps you check the consistency of common parameters and performance parameters between service and DR databases and show inconsistent values. You can determine whether to use this function based on service requirements. It mainly ensures that services are not affected after the DR task is completed.
- This process is optional, so you can click Next to skip the comparison.
- Compare common parameters:
  - For common parameters, if the parameters in the service database are different from those in the DR database, click Save Change to make the parameters of the DR database be the same as those in the service database.
    Figure 12 Modifying common parameters
  - Performance parameter values in both the service and DR databases can be the same or different.
    - If you need to adjust the performance parameters, enter the value in the Change to column and click Save Change.
    - If you want to make the performance parameter values of the source and destination database be the same:
      
      Click Use Source Database Value.
      DRS automatically makes the DR database values the same as those of the service database.
      
      Figure 13 One-click modification
      
      You can also manually enter the value as required.
      
      Click Save Change.
      DRS changes the DR database parameter values based on your settings. After the modification, the comparison results are automatically updated.
      
      Figure 14 One-click modification
      
      Some parameters in the DR database cannot take effect immediately, so the comparison result is temporarily inconsistent. Restart the DR database before the DR task is started or after the DR task is completed for the modification to take effect. To minimize the impact of database restart on your services, restart the DR database at the scheduled time after the disaster recovery is complete.
      
      For details about parameter comparison, see Parameters for Comparison in the Data Replication Service User Guide.
      
      Click Next.

On the Confirm Task page, specify Start Time, Send Notifications, SMN Topic, Delay Threshold, RPO Delay Threshold, RTO Delay Threshold, Stop Abnormal Tasks After. After confirming that the configured information about the DR task is correct, click Submit.

Figure 15 Task startup settings

**Table 10** Task settings
Parameter	Description
Start Time	Set Start Time to Start upon task creation or Start at a specified time based on site requirements. NOTE: Starting a DR task may slightly affect the performance of the service and DR databases. You are advised to start a DR task during off-peak hours.
Send Notifications	This parameter is optional. After enabled, select a SMN topic. If the status or latency metric of the DR 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 disaster recovery, a synchronization delay indicates a time difference (in seconds) of synchronization between the service and DR 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: Before setting the delay threshold, enable Send Notifications. If the delay threshold is set to 0, no notifications will be sent to the recipient.
RTO Delay Threshold (s)	If the synchronization delay from the DRS instance to the DR database exceeds the threshold you specify, DRS will notify 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: Before setting the RTO delay threshold, enable Send Notifications. If the delay threshold is set to 0, no notifications will be sent to the recipient.
RPO Delay Threshold (s)	If the synchronization delay from the DRS instance to the service database exceeds the threshold you specify, DRS will notify 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: Before setting the delay threshold, enable Send Notifications. If the delay threshold is set to 0, no notifications will be sent to the recipient. In the early stages of an incremental DR, more delay is normal because more data is waiting to be synchronized. In this situation, no notifications will be sent.
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. Any task in the abnormal state that has run for longer than the period you set here (in days) will automatically stop to avoid unnecessary fees.

After the task is submitted, view and manage it on the Disaster Recovery 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 reconfigure the task, DRS applies for resources again.
- 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.
- For a task that is in the Disaster recovery in progress state, you can use data comparison to check whether data is consistent before and after the disaster recovery.

Creating a DR Task

Scenario

Process

Prerequisites

Procedure

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