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

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

View PDF

From GeminiDB Redis to Redis Cluster

Supported Source and Destination Databases

**Table 1** Supported databases
Source DB	Destination DB
GeminiDB Redis	ECS-hosted Redis Cluster (open-source Redis 4.0 or later) On-premises Redis Cluster (open-source Redis 4.0 or later)

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: All Supported synchronization objects: Data of the String, Hash, List, Set, and Sorted Set types can be synchronized. Lua scripts and transactions cannot be synchronized. Stream, Exhash, and Bloomfilter data types cannot be synchronized. User-defined types are not supported. Commands that are not supported by the destination database cannot be synchronized. Batch operation commands without hash_tag 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	Constraints
Starting a task	Source database requirements: The source must be a GeminiDB Redis instance on the current cloud. A GeminiDB Redis instance can be used as the source database of only one DRS task. The source GeminiDB Redis instance kernel version (gemini version) must be 4.2.0 or later. To use data synchronization, disable the configuration item notify-keyspace-events. To create a full+incremental task, the PSYNC command must be supported. The replication function must be enabled for the source GeminiDB Redis instance. set config set enable-replication 1 Destination database requirements: The destination database must be empty before the synchronization. The destination DB instance must have sufficient storage space. The username cannot be entered in Redis 6.0. If the destination cluster instance is created using containers, ECSs, or NAT, ensure that the config settings of the cluster allow DRS to discover all master and standby nodes. Other notes: A full+incremental task read data by parsing RDB files. If the replication timeout interval of the source GeminiDB Redis is too short (the default value is 3600s), you can increase the value of repl-timeout to prevent task resuming failure due to a long task failure. During the synchronization, if the task fails due to configuration increase of the source GeminiDB Redis, you need to reset the task. To ensure data consistency, clear the data that has been migrated to the destination database before reconfiguring the task. (You do not need to reset the task if the task is in the incremental state and the source database kernel version (Gemini version) is 6.3.0 or later.) During the synchronization, the specifications of the source GeminiDB Redis cannot be downgraded. If the specifications of the source database needs to be downgraded, create a synchronization task again. (You do not need to reset the task if the task is in the incremental state and the source database kernel version (Gemini version) is 6.3.0 or later.) For List objects, duplicated data may occur because the existing data on the destination end is not cleared when PSYNC is invoked for retransmission. If the source is a master/standby GeminiDB Redis instance, commands containing multiple keys (such as mset) cannot be executed in the source database. Otherwise, the error message "CROSSSLOT Keys in request don't hash to the same slot" may be displayed because the keys are not in the same slot or involve multiple slots.
Full synchronization	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 synchronization	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 GeminiDB Redis to Redis Cluster 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 information

**Table 5** Synchronization instance settings
Parameter	Description
Data Flow	Select Out of the cloud. The source database is a database on the current cloud.
Source DB Engine	Select GeminiDB Redis.
Destination DB Engine	Select Redis cluster.
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.
Source DB Instance	Select the source GeminiDB Redis instance you have 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	Incremental: Through log parsing, incremental data generated on the source database is 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.
DRS Task Nodes	Specifies the number of nodes to be migrated using DRS. One DRS task node connects to two to three shards on the source database. If the source GeminiDB Redis database is a master/standby instance, the number of DRS task nodes can only be 1.
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 settings
Parameter	Description
DB Instance Name	The GeminiDB Redis instance selected when you created the migration task. This parameter cannot be changed.
Database Password	Password of the source database administrator.

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
IP Address or Domain Name	IP address or domain name of the destination database in the IP address/Domain name:Port format. Enter the IP addresses and ports of all master and slave nodes in the Redis Cluster instance. A maximum of 32 IP addresses or domain names can be entered. Use commas (,) to separate multiple values. For example: 192.168.0.1:8080,192.168.0.2:8080.
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, select the objects to be synchronized, and then click Next.

Figure 8 Synchronization objects

**Table 11** Synchronization Object
Parameter	Description
Synchronization Object	All database objects can be synchronized.

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.