Global Distributed Cache for Tair (Redis OSS-compatible) is an active geo-redundancy database system that is developed in-house by Alibaba Cloud. It provides geo-replication capabilities and can quickly synchronize data across instances in different regions to support active geo-redundancy and disaster recovery. A Global Distributed Cache instance can consist of up to three child instances. Data is automatically synchronized among child instances in real time. Global Distributed Cache is designed to reduce the physical distance between data and users, consequently lowering access latency and improving the response speed of applications.
Background information
As your business expands into multiple regions, cross-region and long-distance access can result in high latency and deteriorate user experience. Global Distributed Cache for Tair (Enterprise Edition) can help you reduce the high latency caused by cross-region access. Global Distributed Cache has the following benefits.
Benefit | Description |
High reliability |
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High performance |
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High accuracy |
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Scenarios
This feature can be used in cross-region data synchronization scenarios and global business deployments for industries such as multimedia, gaming, and e-commerce.
Scenario | Description |
Active geo-redundancy | In active geo-redundancy scenarios, multiple sites in different regions provide services at the same time. Active geo-redundancy is a type of high-availability architecture. The difference from the traditional disaster recovery design is that all sites provide services at the same time in the active geo-redundancy architecture. This allows applications to connect to nearby nodes. |
Data disaster recovery | Global Distributed Cache can synchronize data across child instances in both directions to support disaster recovery scenarios, such as zone-disaster recovery, disaster recovery based on three data centers across two regions, and three-region disaster recovery. |
Load balancing | In specific scenarios such as large promotional events where you expect ultra-high QPS and a large amount of access traffic, you can balance loads across child instances to mitigate the risk of overloading a single instance. |
Data synchronization | Two-way data synchronization is implemented across child instances in a Global Distributed Cache instance. This feature can be used in scenarios such as data analysis and testing. |
Feature overview
Global Distributed Cache for Tair (Enterprise Edition) is a logical collection of all Global Distributed Cache child instances (child instances for short) and links. Data is synchronized in real time across child instances by using synchronization channels. The synchronization occurs at the instance level, which means that all data in a child instance is synchronized. The following figure shows the architecture.
A Global Distributed Cache instance consists of the following components.
Component | Description |
Child instance | A child instance is the basic service unit that constitutes a Global Distributed Cache instance. Each child instance is an independent instance. All child instances support read and write operations and provide separate endpoints. Data consistency across child instances is maintained through real-time two-way synchronization, with the data being eventually consistent at any given point. Child instances must be classic Tair (Enterprise Edition) DRAM-based instances that are compatible with Redis 5.0. |
Synchronization channel | A synchronization channel is a one-way link that is used to synchronize data in real time from one child instance to another. Two opposite synchronization channels are required to implement two-way replication between two child instances. In addition to append-only files (AOFs) supported by open source Redis, Global Distributed Cache for Tair (Enterprise Edition) includes information such as server-id and opid for synchronization. Global Distributed Cache transmits binlogs over synchronization channels to synchronize data. |
Channel manager | The channel manager manages the lifecycle of synchronization channels and performs operations to handle exceptions that occur in child instances, such as master-replica switchover and replica reconstruction. |
Cross-border synchronization between the Chinese mainland and other regions is not supported. In a Global Distributed Cache instance, all child instances must be located either in the Chinese mainland or in other regions. For more information, see Limits.
Billing
This feature is free of charge. You are charged only for the Tair (Enterprise Edition) DRAM-based child instances based on their specifications. For more information, see Billable items.
Usage notes
Create the first Global Distributed Cache child instance by converting an existing classic Tair (Enterprise Edition) DRAM-based instance that is compatible with Redis 5.0 or creating a new instance.
After you create the first child instance, the Global Distributed Cache instance is automatically created.
In the Global Distributed Cache instance, add the second or third child instance by creating a new instance.
In your business code, direct requests from different regions to the endpoints of nearby child instances to provide users with a better service experience by ensuring access from a geographically closer location.
FAQ
Q: Can I update the minor versions of Global Distributed Cache child instances at the same time?
A: To ensure business continuity and stability, we recommend that you stagger the update time of child instances by more than 30 minutes. This helps avoid simultaneous service interruptions during the update process, reducing the impact on your business.
Q: Do Global Distributed Cache instances support multi-write operations?
A: You can write data to different child instances. However, you should avoid modifying the same key on multiple child instances at the same time or within a short period. Otherwise, data inconsistency may occur. For more information, see Limits on data consistency.