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

This topic explains the process of migrating a self-managed Redis database to a cloud database Tair (compatible with Redis) instance using Data Transmission Service (DTS). DTS facilitates both full data migration and incremental data migration, enabling a seamless transition of a self-managed Redis database to the cloud without interrupting the associated application.

Prerequisites

Both the source self-managed Redis instance and the destination cloud database Tair (compatible with Redis) are set up. For instructions on creating a cloud database Tair (compatible with Redis) instance, see Step 1: Create an instance.

Note
Currently, DTS supports only cloud database Tair instances (compatible with Redis) in direct connection mode.
The self-managed Redis version must be 2.8, 3.0, 3.2, 4.0, 5.0, or 6.0.
The self-managed Redis can properly execute the psync or sync command.
The destination cloud database Tair (compatible with Redis) instance must have more storage space than the source self-managed Redis database uses.

Notes

Type	Description
Limits on the source database	Bandwidth requirements: The server to which the source database belongs must have sufficient outbound bandwidth. Otherwise, the data migration speed is affected. Limits on operations: If you perform only full data migration, do not write data to the source instance during data migration. Otherwise, data will be inconsistent between the source and destination databases. To maintain real-time data consistency, we recommend that you select both full data migration and incremental data migration. Limits on migrating a single-node Redis instance to a destination database with a cluster architecture: Because a cluster allows only a single command to operate on a single slot, if you perform multi-key operations on the source database and the keys are not in the same slot or involve multiple slots, an error occurs. `CROSSSLOT Keys in request don't hash to the same slot` We recommend that you perform only single-key operations during DTS migration to avoid link interruptions. If an expiration policy is enabled for specific keys in the source database, these keys may not be deleted in a timely manner after they expired. Therefore, the number of keys in the destination database may be less than that in the source database. You can run the info command to view the number of keys in the destination database. Note The number of keys that do not have an expiration policy or have not expired is the same in the source and destination databases. To ensure migration quality, DTS inserts a key with the prefix DTS_REDIS_TIMESTAMP_HEARTBEAT into the source database to record update timestamps. If the source database uses a cluster architecture, DTS inserts the key into each shard. The key is filtered out during data migration. After the data migration task is completed, the key expires. If the source database is a read-only instance or the DTS account does not have write (SETEX) permissions, the reported latency may be inaccurate. If you need to migrate incremental data, the account used by the task on the source must have the `PSYNC` and `SYNC` permissions.
Other limits	DTS uses the resources of the source and destination databases during a full data migration. This may increase the loads on the database servers. If you migrate a large amount of data or if the server specifications are limited, database services may become unavailable. Before you migrate data, evaluate the impacts of data migration on the performance of the source and destination instances. We recommend that you migrate data during off-peak hours. If the memory of the destination database is insufficient and data eviction is triggered, the default data eviction policy (maxmemory-policy) of cloud database Tair (compatible with Redis) is volatile-lru. This may cause data inconsistency between the destination and source databases but does not affect the normal operation of the task. To avoid this situation, we recommend that you set the data eviction policy of the destination database to noeviction. When the memory of the destination database is insufficient, data fails to be written and the task fails. However, data is not lost due to data eviction. Note For more information about data eviction policies, see Introduction to Redis data eviction policies. For Lua scripts called by EVAL or EVALSHA, during incremental data migration, DTS cannot confirm whether the script is successfully executed because the destination does not explicitly return the execution result. For List lists, when DTS calls the `psync` or `sync` command to transfer data, it does not perform the `Flush` operation on the existing data on the destination. Therefore, duplicate data may appear. During data migration, if the self-managed Redis database is scaled in or out (for example, shards are added or removed) or its specifications are changed (for example, the memory is scaled up), you must reconfigure the task. To ensure data consistency, we recommend that you clear the data that has been migrated to the destination Redis database before you reconfigure the task. If the connection address of the self-managed Redis database changes during data migration, you must reconfigure the task. If a data migration task fails and stops, DTS automatically resumes the task. Before you switch your business to the destination instance, make sure that you stop or release the task to prevent the source data from overwriting the data in the destination instance after the task is automatically resumed. If the destination instance is deployed in a cluster architecture and the amount of memory used by a shard in the destination instance reaches the upper limit, or if the available storage space of the destination instance is insufficient, the data synchronization task fails due to out of memory (OOM). If transparent data encryption (TDE) is enabled for the destination instance, you cannot use DTS to migrate data. If any of the following situations occur during data migration, full data may be migrated again to the destination, resulting in data inconsistency. A transient connection occurs on the source or destination Redis, causing a breakpoint resume failure. A primary/secondary switch or failover occurs on the source or destination Redis. The connection address of the source or destination Redis changes. If the ApsaraDB Tair (compatible with Redis) instance has enabled the TLS (Transport Layer Security) encryption feature, you must connect to DTS using SSL-encrypted (does not support TLSv1.3). Currently, it is not supported to connect an ApsaraDB Tair (compatible with Redis) instance with SSL enabled to DTS as a Alibaba Cloud Instance. If the migration instance contains both full and incremental tasks, restarting the migration instance may cause DTS to re-execute the full and incremental tasks. If a DTS task fails to run, DTS technical support will try to restore the task within 8 hours. During the restoration, the task may be restarted, and the parameters of the task may be modified. Note Only the parameters of the task may be modified. The parameters of databases are not modified. The parameters that may be modified include but are not limited to the parameters in the "Modify instance parameters" section of the Modify the parameters of a DTS instance topic.

Billing

Migration type	Instance configuration fee	Internet traffic fee
Full data migration	Free of charge.	When the Access Method parameter of the destination database is set to Public IP Address, you are charged for Internet traffic. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Full data migration

DTS migrates historical data from objects within the self-managed Redis database to the Tair (compatible with Redis) cloud database instance.

Note
To ensure data consistency, avoid writing data to the self-managed Redis database during the full data migration process.
Incremental data migration

Leveraging full data migration, DTS transfers both the full data and incremental updates from the self-managed Redis database to the cloud database Tair (compatible with Redis) instance. This process of incremental data migration ensures a seamless transition of the Redis database to the cloud without interrupting the application.

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.

Note

If you perform only full data migration, skip the following steps.

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
```
Run the following command to remove the limit on the replication output buffer:
```
config set client-output-buffer-limit 'slave 0 0 0'
```

Procedure

Use one of the following methods to go to the Data Migration page and select the region in which the data migration instance resides.
DTS console
1. Log on to the DTS console.
2. In the left-side navigation pane, click Data Migration.
3. In the upper-left corner of the page, select the region in which the data migration instance resides.
DMS console
Note
The actual operation 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.
1. Log on to the DMS console.
2. In the top navigation bar, move the pointer over Data + AI > DTS (DTS) > Data Migration .
3. From the drop-down list to the right of Data Migration Tasks, select the region in which the data synchronization instance resides.
Click Create Task to go to the task configuration page.

Configure the source and destination databases. The following table describes the parameters.

Category	Configuration	Description
None	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 Existing Connection	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not use an existing instance, you must configure the database information below. Note You can register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
	Database Type	Select Tair/Redis.
	Access Method	Select a connection type based on the deployment location of the source database. In this example, select ECS Self-managed Database. Note If the source instance is a self-managed database, you must perform the corresponding preparations. For more information, see Preparations Overview.
	Instance Region	Select the region where the ECS instance to which the source Redis belongs is located.
	Replicate Data Across Alibaba Cloud Accounts	In this example, the migration is performed between the same Alibaba Cloud account. Select No.
	ECS Instance ID	Select the ID of the ECS instance to which the source Redis belongs. Note If the source Redis has a cluster architecture, select the ECS instance ID of the Master node of any shard. You must also manually add the IP address range of the DTS service in the corresponding region to the security rules of each ECS instance. For more information, see Create a Security Group, Associate a Security Group with an Instance (Primary Network Interface Card), and Add the IP Address Range of the DTS Server.
	Instance Mode	Select Basic Edition or Cluster based on the architecture of the source Redis.
	Port	Enter the service port of the source Redis. The default port number is 6379. Note If the source Redis database has a cluster architecture, enter the service port of the Master node of any shard.
	Authentication Method	Select an authentication mode based on your business requirements. In this example, select Password Login. Note If you select Secret-free login, make sure that password-free access is enabled for the Redis database. For more information about how to enable password-free access for a cloud database Tair (compatible with Redis) instance, see Enable Password-free Access for a Virtual Private Cloud.
	Database Password	Enter the password of the source Redis database. Note This parameter is optional and can be left empty if no database password is configured. Specify the database password in the <user>:<password> format. For example, if the username of the account that you use to log on to the source Redis database is admin and the password is Rp829dlwa, the database password is admin:Rp829dlwa.
	Encryption	Select Non-encrypted or SSL-encrypted based on your business requirements. Note If the source database is a self-managed Redis database (Access Method is not Alibaba Cloud Instance) and you select SSL-encrypted, you must upload the CA Certificate and enter the CA Key.
Destination Database	Select Existing Connection	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not use an existing instance, you must configure the database information below. Note You can register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
	Database Type	Select Tair/Redis.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination cloud database Tair (compatible with Redis) instance resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, the migration is performed between the same Alibaba Cloud account. Select No.
	Instance ID	Select the ID of the destination cloud database Tair (compatible with Redis) instance.
	Authentication Method	Select an authentication mode based on your business requirements. In this example, select Password Login. Note If you select Secret-free login, make sure that password-free access is enabled for the Redis database. For more information about how to enable password-free access for a cloud database Tair (compatible with Redis) instance, see Enable Password-free Access for a Virtual Private Cloud.
	Database Password	Enter the password of the destination cloud database Tair (compatible with Redis) instance. Note Specify the database password in the <user>:<password> format. For example, if the username of the account that you use to log on to the Tair instance is admin and the password is Rp829dlwa, the database password is admin:Rp829dlwa.
	Encryption	Select Non-encrypted or SSL-encrypted based on your business requirements. Note If the source database is a self-managed Redis database (Access Method is not Alibaba Cloud Instance) and you select SSL-encrypted, you must upload the CA Certificate and enter the CA Key.

In the lower part of the page, click Test Connectivity and Proceed.
Note
- Make sure that the CIDR blocks of DTS servers can be automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add the CIDR blocks of DTS servers.
- If the source or destination database is a self-managed database and its Access Method is not set to Alibaba Cloud Instance, click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

Configure the objects to be migrated.

On the Configure Objects page, configure the objects that you want to migrate.

Configuration	Description
Migration Types	Select Full Data Migration + Incremental Data Migration. Note If the source database does not have the SYNC or PSYNC permission, 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 databases as the objects to be migrated. You cannot select keys as 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.

Click Next: Advanced Settings to configure advanced settings.

Configuration	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data migration tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
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 retry time range. Valid values: 10 to 1,440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified 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 Full Data Migration	Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. This reduces the loads of the destination database server. Note This configuration item is available only if Migration Types includes Full Data Migration.
Enable Throttling for Incremental Data Migration	Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server. Note This configuration item is available only if Migration Types includes Incremental Data Migration.
Extend Expiration Time of Destination Database Key	Set the period during which keys migrated from the source instance to the destination instance remain valid. If specific commands, including but not limited to the following commands, are used, configure this parameter to ensure data consistency. Note In scenarios involving distributed locks, the locks may not be released in time. `expire key seconds pexpire key milliseconds expireat key timestamp pexpireat key timestampMs`
Use Slave Node	When the source self-built Redis Instance Mode is a Cluster, you can opt to read data from either the master or the slave node. By default, the setting is No, indicating that data is read from the master node.
Environment Tag	The environment tag used to identify the instance. You can select an environment tag based on your business requirements. In this example, no environment tag is selected.
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.
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.

Click Next Step: Data Verification to configure data verification.
For more information about how to use the data verification feature, see Configure a data verification task.

Save the task settings and run a precheck.
- To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.
- If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.
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.

Purchase an instance.

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

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?
New Instance Class	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.

Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.
Click Purchase And Start, and in the pop-up OK dialog box, click OK.

You can monitor the progress of the data migration task on the Data Migration page.

Note
If your configured DTS instance includes both full migration and incremental migration tasks (the Migration Types comprises Full Data Migration and Incremental Data Migration), these will be combined and presented as Incremental Data Migration on the migration task list page.