Data Transmission Service:Migrate data from a self-managed Redis database to a Tair instance

Prerequisites

• A self-managed Redis database and a Tair instance are created. For more information about how to create a Tair instance, see Step 1: Create a Tair instance.

  Note

  • DTS supports only Tair instances for which the direct connection mode is enabled.

  • DTS also allows you to migrate data from an Tair (Redis OSS-Compatible) instance to a Tair instance or between Tair instances. You can refer to the procedure that is described in this topic to configure the migration task.

• The engine version of the self-managed Redis database is 2.8, 3.0, 3.2, 4.0, 5.0, or 6.0.

• The PSYNC or SYNC command can be run on the self-managed Redis database.

• The available storage space of the destination Tair instance is larger than the total size of the data in the source self-managed Redis database.

Limits

Billing rules

Migration types

• Full data migration

  DTS migrates existing data of objects from the source self-managed Redis database to the destination Tair instance.

  Note

  If you perform only full data migration, we recommend that you do not write data to the self-managed Redis database during the full data migration. This ensures data consistency.

• Incremental data migration

  After full data migration is complete, DTS migrates incremental data from the self-managed Redis database to the Tair instance. Incremental data migration allows data to be smoothly migrated without interrupting services of self-managed applications during data migration.

Commands that can be incrementally migrated

• APPEND

• BITOP, BLPOP, BRPOP, and BRPOPLPUSH

• DECR, DECRBY, and DEL

• EVAL, EVALSHA, EXEC, EXPIRE, and EXPIREAT

• FLUSHALL and FLUSHDB

• GEOADD and GETSET

• HDEL, HINCRBY, HINCRBYFLOAT, HMSET, HSET, and HSETNX

• INCR, INCRBY, and INCRBYFLOAT

• LINSERT, LPOP, LPUSH, LPUSHX, LREM, LSET, and LTRIM

• MOVE, MSET, MSETNX, and MULTI

• PERSIST, PEXPIRE, PEXPIREAT, PFADD, PFMERGE, PSETEX, and PUBLISH

• RENAME, RENAMENX, RESTORE, RPOP, RPOPLPUSH, RPUSH, and RPUSHX

• SADD, SDIFFSTORE, SELECT, SET, SETBIT, SETEX, SETNX, SETRANGE, SINTERSTORE, SMOVE, SPOP, SREM, and SUNIONSTORE

• ZADD, ZINCRBY, ZINTERSTORE, ZREM, ZREMRANGEBYLEX, ZUNIONSTORE, ZREMRANGEBYRANK, and ZREMRANGEBYSCORE

• XADD, XCLAIM, XDEL, XAUTOCLAIM, XGROUP CREATECONSUMER, and XTRIM

Preparations before incremental data migration

To ensure that the incremental data migration task runs as expected, we recommend that you remove the limit on the replication output buffer. In this topic, a server that runs on Linux is used in the example.

1. Use the redis-cli program to connect to the self-managed Redis database.

   Note

   You can use the redis-cli program after you install the Redis client. For more information, visit Redis community official website.

   redis-cli -h <host> -p <port> -a <password>

   Note

   • <host>: the endpoint that is used to connect to the self-managed Redis database. You can use 127.0.0.1 in this example.

   • <port>: the service port number used to connect to the self-managed Redis database. The default port number is 6379.

   • <password>: the password used to connect to the self-managed Redis database.

   Example:

   redis-cli -h 127.0.0.1 -p 6379 -a Test123456

2. Run the following command to remove the limit on the replication output buffer:

   config set client-output-buffer-limit 'slave 0 0 0'

Procedure

1. Go to the Data Migration Tasks page.

   1. Log on to the Data Management (DMS) console.

   2. In the top navigation bar, move the pointer over DTS.

   3. Choose DTS (DTS) > Data Migration.

   Note

   • The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.

   • You can also go to the Data Migration page of the new DTS console.

2. From the drop-down list on the right side of Data Migration Tasks, select the region in which your data migration instance resides.

   Note

   If you use the new DTS console, you must select the region in which the data migration instance resides in the upper-left corner.

3. Click Create Task. On the Create Task page, configure the source and destination databases. The following table describes the parameters.

   Section	Parameter	Description
   N/A	Task Name	The name of the DTS task. DTS automatically generates a task name. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.
   Source Database	Select a DMS database instance	The database that you want to use. You can choose whether to use an existing database based on your business requirements. If you select an existing database, DTS automatically populates the parameters for the database. If you do not select an existing database, you must configure the following database information.
   	Database Type	The type of the source database. Select Tair/Redis.
   	Access Method	The access method of the source database. In this example, Self-managed Database on ECS is selected. Note If your source database is a self-managed database, you must deploy the network environment for the database. For more information, see Preparation overview.
   	Instance Region	The region in which the source self-managed Redis database resides.
   	Replicate Data Across Alibaba Cloud Accounts	Specifies whether to migrate data across Alibaba Cloud accounts. In this example, No is selected.
   	ECS Instance ID	The ID of the Elastic Compute Service (ECS) instance that hosts the source self-managed Redis database. Note If the source Redis database is deployed in a cluster architecture, select the ID of the ECS instance on which a master node resides.
   	Instance Mode	The architecture in which the source Redis database is deployed. Select Standalone or Cluster.
   	Port Number	The service port number of the source self-managed Redis database. Default value: 6379. Note If the source self-managed Redis database is deployed in a cluster architecture, enter the service port number of a master node.
   	Database Password	The password of the source self-managed Redis database. Note This parameter is optional and can be left empty if no password is set. The database password is in the <user>:<password> format. For example, if the username of the account that you use to log on to the source self-managed Redis database is admin and the password is Rp829dlwa, the database password is admin:Rp829dlwa.
   	Encryption	Specifies whether to encrypt the connection to the source database. Select Non-encrypted or SSL-encrypted based on your business requirements. If the SSL encryption feature is disabled for the source self-managed Redis instance, select Non-encrypted. If the SSL encryption feature is enabled for the source self-managed Redis database, select SSL-encrypted. In this case, you must upload a CA Certificate and configure the CA Key parameter.
   Destination Database	Select a DMS database instance	The database that you want to use. You can choose whether to use an existing database based on your business requirements. If you select an existing database, DTS automatically populates the parameters for the database. If you do not select an existing database, you must configure the following database information.
   	Database Type	The type of the destination database. Set this parameter to Tair/Redis.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the destination Tair instance resides.
   	Instance ID	The ID of the destination Tair instance.
   	Database Password	The database password of the destination Tair instance. Note The database password is in the <user>:<password> format. For example, if the username of the account that you use to log on to the destination Tair instance is admin and the password is Rp829dlwa, the database password is admin:Rp829dlwa.

4. In the lower part of the page for this step, click Test Connectivity and Proceed.

   Warning

   • If the source or destination database is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the instance. If the source or destination database is a self-managed database hosted on an Elastic Compute Service (ECS) instance, DTS automatically adds the CIDR blocks of DTS servers to the security group rules of the ECS instance. For more information, see Add the CIDR blocks of DTS servers. If the source or destination database is a self-managed database that is deployed in a data center or provided by a third-party cloud service provider, you must manually add the CIDR blocks of DTS servers to the whitelist of the database to allow DTS to access the database.

   • If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database, Alibaba Cloud database instance, or ECS security group rules, security risks may arise. Therefore, before you use DTS to migrate data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhancing the security of your username and password, limiting the ports that are exposed, authenticating API calls, regularly checking the whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, or connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

   • After the DTS task is complete or released, we recommend that you manually detect and remove the added CIDR blocks from the whitelist or ECS security group rules.

5. Configure the objects to be migrated and advanced settings.

   Parameter	Description
   Migration Types	The migration type. Select Full Data Migration and Incremental Data Migration. Note If you do not have the permissions to run the SYNC or PSYNC command on the source database, select Full Data Migration.
   Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database is empty. If the destination database is empty, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started. Ignore Errors and Proceed: skips the Check the existence of objects in the destination database. check item. Warning If you select Ignore Errors and Proceed, the data in the source database overwrites the data in the destination database that has the same keys as the source data. This may cause data loss in the destination database. Proceed with caution.
   Source Objects	Select one or more objects from the Source Objects section. Click the icon to add the objects to the Selected Objects section. Note You can select only databases as the objects to be migrated. Keys cannot be selected as the objects to be migrated.
   Selected Objects	If you want to select a database to which data is migrated from DB 0 to DB 255 or filter the data to be migrated by prefix, you can use the object name mapping feature or the filtering feature. In the Selected Objects section, right-click the database that you want to migrate. In the Edit Schema dialog box, configure the parameters. For more information, see Map object names and Set filter conditions. Note You cannot map multiple object names at a time.

6. Click Next: Advanced Settings to configure advanced settings.

   • Data Verification Settings

     For more information about how to configure the data verification feature, see Configure a data verification task.

   • Advanced Settings

     Parameter	Description
     Monitoring and Alerting	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see the Configure monitoring and alerting when you create a DTS task section of the Configure monitoring and alerting topic.
     Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the parameter to a value greater than 30. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you set different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is set later takes precedence. When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at the earliest opportunity after the source database and destination instance are released.
     Retry Time for Other Issues	The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Important The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
     Enable Throttling for Incremental Data Migration	The load on the destination instance may increase when DTS migrates incremental data to the destination instance. You can configure throttling thresholds for the number of rows and the amount of data that can be incrementally migrated per second based on your business requirements. This helps reduce the load on the destination instance.
     Environment Tag	The environment tag that is used to identify the DTS instance. You can select an environment tag based on your business requirements. In this example, you do not need to select an environment tag.
     Extend Expiration Time of Destination Database Key	The extended time period for keys migrated from the source database to the destination database to remain valid. Unit: seconds. If specific commands such as the following commands are run, we recommend that you set the value of the parameter to 600 to ensure data consistency. EXPIRE key seconds PEXPIRE key milliseconds EXPIREAT key timestamp PEXPIREAT key timestampMs
     Use Slave Node	Specifies whether to read data from replica nodes. If the Instance Mode parameter of the source self-managed Redis database is set to Cluster, you can specify whether to read data from the replica nodes. By default, No is selected, which indicates that DTS reads data from the master nodes.
     Configure ETL	Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: does not configure the ETL feature.

7. In the lower part of the page, click Next: Save Task Settings and Precheck.

   Note

   • Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.

   • If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.

   • If an alert is triggered for an item during the precheck:

     • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.

     • If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.

8. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.

9. On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

   Section	Parameter	Description
   New Instance Class	Resource Group	The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
   	Instance Class	DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Instance classes of data migration instances.

10. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.

11. Click Buy and Start. In the message that appears, click OK.

    You can view the progress of the task on the Data Migration page.