Tair cluster master-replica instances can address the bottlenecks of the single-threading model of open source Redis and provide large capacity and high performance. Cluster master-replica instances support two connection modes: proxy mode and direct connection mode. You can select a connection mode based on your business requirements.
Usage notes
You cannot enable both the proxy mode and the direct connection mode simultaneously for cloud-native cluster instances.
Proxy mode
If a cluster master-replica instance runs in proxy mode, requests from clients to the instance are sent to the configured proxy nodes. Then, the proxy nodes forward the requests to the data shards. The proxy nodes, data shards, and Configserver of the instance do not provide separate endpoints. This simplifies application development and coding. Proxy nodes automatically balance loads, route commands, and perform failover after they receive client requests. For more information about the features of proxy nodes, see Features of proxy nodes.
For more information about the architecture and components of a cluster master-replica instance in proxy mode, see the following figure and table.
Figure 1. Architecture of a cluster master-replica instance in proxy mode
Component | Description |
Proxy node | A cluster master-replica instance contains multiple proxy nodes. |
Data shard | A cluster master-replica instance contains multiple data shards. Each data shard uses a high availability architecture in which a master node and a replica node are deployed on different hosts. If the master node is faulty, the master-replica cluster instance fails over to the replica node to ensure high service availability. |
Configserver | The Configserver of a cluster master-replica instance uses a high availability architecture in which a master node and a replica node are deployed. The Configserver stores the configuration data and partitioning policies of the cluster master-replica instance. |
The component quantities and configurations on a Tair cluster master-replica instance vary based on the specifications of the instance. You cannot change the quantities or configurations. However, you can change the specifications and architecture of the instance. For more information, see Overview, Change the configurations of an instance, and Overview.
Direct connection mode
In direct connection mode, you can connect to a cluster master-replica instance in a similar manner as you connect to an open source Redis cluster. The first time a client connects to the instance, the Domain Name System (DNS) resolves the private endpoint of the instance into a random virtual IP address (VIP). Then, the client can connect to the data shards of the instance over the Redis Cluster protocol. For more information about the architecture of a cluster master-replica instance in direct connection mode, see the following figure and description.
The direct connect mode and the proxy mode are significantly different from each other. For information about the usage notes and usage examples of these connection modes, see Use a private endpoint to connect to a Tair instance.
Figure 2. Architecture of a cluster master-replica instance in direct connection mode
Scenarios
Large volumes of data
Compared with a standard master-replica instance of Tair, a cluster master-replica instance supports a storage capacity of up to 4,096 GB.
High QPS
A Tair standard master-replica instance cannot support scenarios that involve high queries per second (QPS). A Tair cluster master-replica instance allows you to deploy multiple data shards. These data shards can work together to eliminate the performance bottlenecks of the single-threading model. For more information, see DRAM-based cluster instances.
Throughput-intensive applications
Compared with a standard master-replica instance of Tair, a cluster master-replica instance provides higher throughput over an internal network. You can efficiently read hot data and manage high-throughput workloads.
Applications that do not require high compatibility with the Redis protocol
A cluster master-replica instance contains multiple components. As a result, cluster master-replica instances are not as compatible with the Redis protocol as standard master-replica instances. For more information, see Limits on commands supported by cluster instances and read/write splitting instances.
References
For information about how to troubleshoot abnormal memory usage of data shards in a cluster master-replica instance, see Identify and handle large keys and hotkeys.
For information about how to analyze the distribution of data in memory, see Use the offline key analysis feature.