Help Center/ Data Replication Service/ Real-Time Synchronization/ To the Cloud/ From Redis to GeminiDB Redis

Updated on 2024-12-01 GMT+08:00

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From Redis to GeminiDB Redis

Supported Source and Destination Databases

**Table 1** Supported databases
Source DB	Destination DB
On-premises official open-source single-node or primary/standby Redis (versions 2.8.x, 3.0.x, 3.2.x, 4.0.x, and 5.0.x) ECS-hosted official open-source single-node or primary/standby Redis (versions 2.8.x, 3.0.x, 3.2.x, 4.0.x, and 5.0.x)	GeminiDB Redis NOTE: The destination database version must be the same as or later than the source database version.

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.

**Table 2** Supported synchronization objects
Type	Precautions
Synchronization objects	Object level: database level Supported synchronization objects: Data of the String, Hash, List, Set, and Sorted Set types can be synchronized. Lua scripts can be migrated (except in a single full migration task). Transactions cannot be synchronized. Stream, BitMap, HyperLogLog, and GEO data types cannot be synchronized. User-defined types are not supported. Commands that are not supported by the destination GeminiDB Redis instance cannot be synchronized.

Suggestions

To maintain data consistency before and after the synchronization, ensure that no data is written to your source and destination databases during a full synchronization. In the full+incremental synchronization mode, you can continue the synchronization while data is still being written to the source database.

The success of database synchronization depends on environment and manual operations. To ensure a smooth synchronization, perform a synchronization trial before you start the synchronization to help you detect and resolve problems in advance.
During the synchronization, ensure that no data is written to the destination database to keep data consistency before and after the synchronization.
You are advised to start your synchronization task during off-peak hours by setting Start Time to Start at a specified time. A less active database is easier to synchronize successfully. If the data is fairly static, there is less likely to be any severe performance impacts during the synchronization.
- If network bandwidth is not limited, the query rate of the source database increases by about 20 MB/s during full synchronization, and two to four CPUs are occupied.
- When DRS concurrently reads data from a database, it will use about 6 to 10 sessions. The impact of the connections on services must be considered.
- For more information about the impact of DRS on databases, see How Does DRS Affect the Source and Destination Databases?

Precautions

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

**Table 3** Precautions
Type	Restrictions
Starting a task	Source database object requirements: To create a full+incremental task, the PSYNC command must be supported. Destination database object requirements: The destination must be a GeminiDB Redis instance on the current cloud. The destination GeminiDB Redis instance must be empty before the migration. The version of the destination database instance must be the same as or later than that of the source database. Other notes: A full migration task reads data in SCAN mode. A full+incremental task read data by parsing RDB files. If the source database does not support the PSYNC command, use the full synchronization type. If the source database supports the PSYNC command, use the full+incremental synchronization type. The expiration time settings of the full synchronization task cannot be synchronized. In a full migration task, Lua scripts cannot be migrated. When synchronizing Lua scripts, ensure that the source database contains other data. Otherwise, Lua scripts in RDB cannot be parsed, causing the Lua script migration failure. If the source is a self-managed single-node Redis database, the following data types can be migrated during the incremental migration phase: append, blpop, brpop, decr, decrby, del, expire, expireat, flushall, flushdb, getset, hdel, hincrby, hincrbyfloat, hmset, hset, hsetnx, incr, incrby, incrbyfloat, linsert, lpop, lpush, lpushx, lrem, lset, ltrim, move, mset, msetnx, multi, persist, pexpire, pexpireat, psetex, publish, rename, rpop, rpush, rpushx, sadd, select, set, setbit, setex, setnx, setrange, smove, spop, srem, zadd, zincrby, zrem, zremrangebylex, zremrangebyrank and zremrangebyscore. GeminiDB Redis does not support multi-key commands. If the source is a standalone Redis database and keys involved in an operation aren't in the same hash-slot, the following error message will appear: CROSSSLOT Keys in request don't hash to the same slot DRS does not perform high-risk operations such as FLUSH on the destination database, so data of the List type may be duplicated. To ensure a successful incremental synchronization, increase the value of repl-backlog-size in the redis.conf configuration file of the source database before the synchronization. During the synchronization, if the self-built Redis database is scaled in or out (for example, shards are added or deleted) or the specifications are changed (for example, the memory is scaled up), reconfigure the synchronization task. To ensure data consistency, clear the data that has been migrated to the destination GeminiDB Redis before reconfiguring the task. If the expire policy is configured for some keys in the source database, the number of keys in the destination database (for example, by running the info command) may be less than that in the source database because the keys may have expired but are not deleted. To ensure data consistency, you are advised to prolong the key expiration time.
Full migration	During synchronization, do not change the passwords or ports of the source and destination databases. During the synchronization, do not modify the destination database.
Incremental migration	During synchronization, do not change the passwords or ports of the source and destination databases. During the synchronization, do not modify the destination database.

Prerequisites

You have logged in to the DRS console.
Your account balance is greater than or equal to $0 USD.
For details about the DB types and versions supported by real-time synchronization, 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

This section describes how to use DRS to synchronize data from a Redis database to GeminiDB Redis over a public network.

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

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 4** 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 can contain up to 256 characters and cannot contain special characters !=<>&'\"

Synchronization instance information

Figure 2 Synchronization instance details

**Table 5** Synchronization instance settings
Parameter	Description
Data Flow	Select To the cloud. The destination database must be a database on the current cloud.
Source DB Engine	Select Single-Node or Master/Standby Redis.
Destination DB Engine	Select GeminiDB Redis.
Network Type	Public network is used as an example. Available options: Public network, VPC, VPN or Direct Connect VPC is suitable for data synchronization between cloud databases of the same account in the same region and VPC. Public network is suitable for data synchronization from on-premises or external cloud databases to the destination databases 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.
Destination DB Instance	Select the DB 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	Full: All objects and data in non-system databases are synchronized to the destination database at a time. This mode is applicable to scenarios where service interruption is acceptable. NOTE: If you are performing a full synchronization, do not perform operations on the source database. Otherwise, data generated in the source database during the synchronization will not be synchronized to the destination database. Full+Incremental: This synchronization mode allows you to synchronize data without interrupting services. After a full synchronization initializes the destination database, an incremental synchronization initiates and 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.
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.

Figure 3 AZ

**Table 6** 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 7** 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.

On the Configure Source and Destination Databases page, wait until the synchronization instance is created. Then, configure your own DNS server, 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, select the check box before the agreement and click Next.

Configuring your own DNS server

Figure 5 DNS Server

**Table 8** DNS server information
Parameter	Description
DNS Server	Enable this option if you need to use your own private domain name as the source or destination database IP address.
DNS Server IP Address	Add the IP address of your own DNS server to DNS Server IP Address. Then, you can also enter this IP address in IP Address or Domain Name in the Source Database or Destination Database area for data synchronization.

Only whitelisted users can use this function. You need to submit a service ticket to apply for this function. In the upper right corner of the management console, choose Service Tickets > Create Service Ticket to submit a service ticket.

Source database information

Figure 6 Source database information

**Table 9** Source database information
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 Password	Password used to log in to the source database.

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

Destination database configuration

Figure 7 Destination database information

**Table 10** Destination database settings
Parameter	Description
DB Instance Name	The DB instance you selected when creating the synchronization task. This parameter cannot be changed.
Database Password	The password for the database username.

The password of the destination database is encrypted and stored in the database and the synchronization instance during the synchronization. After the task is deleted, the password are permanently deleted.

On the Set Synchronization Task page, configure the objects to be synchronized, and then click Next.

Figure 8 Synchronization objects

**Table 11** Synchronization Object
Parameter	Description
Synchronization Object	The left pane displays the source database objects, and the right pane displays the selected objects. DRS supports database-level synchronization. You can select the databases to be synchronized based on service requirements. If there are changes made to the source databases or objects, click in the upper right corner to update the objects to be synchronized. NOTE: 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. To quickly select the desired database objects, you can use the search function.

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 the check is complete and the check success rate is 100%, 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, Send Notifications, SMN Topic, Delay Threshold (s), and Stop Abnormal Tasks After, confirm that the configured information is correct, 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. The Start at a specified time option is recommended. NOTE: The synchronization task may affect the performance of the source and destination databases. You are advised to start the task in off-peak hours and reserve two to three days for data verification.
Send Notifications	This parameter is optional. After enabled, select a SMN topic. If the task billing is about to start, the status, latency metric, or data of the synchronization 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: 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. If the delay threshold is set to 0, no notifications will be sent to the recipient.
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: 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.

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.