ApsaraDB for Redis 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. This topic describes ApsaraDB for Redis cluster master-replica instances.
You cannot enable both the proxy mode and the direct connection mode simultaneously for cloud disk-based cluster instances.
If a cluster master-replica instance runs in proxy mode, you can connect to the instance by using a unified endpoint (or domain name). Requests from clients 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. For more information about the architecture and components of a cluster master-replica instance in proxy mode, see the following figure and table.
A cluster master-replica instance contains multiple proxy nodes. Each proxy node uses a single-node architecture. The cluster master-replica instance automatically balances loads and performs failover between the configured proxy nodes.
For more information about the features of proxy nodes, see Features of proxy nodes.
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.
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 cluster master-replica instance vary based on the specifications of the instance. You cannot change the component 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
The proxy mode simplifies application development but decreases response speed because all requests must be forwarded by proxy nodes. If you require quick response, we recommend that you enable the direct connection mode. In direct connection mode, you can bypass proxy nodes and directly connect to data shards. This reduces network overheads and increases the response speed. For more information about the architecture of a cluster master-replica instance in direct connection mode, see the following figure and table.
Compared with the proxy mode, the direct connection mode does not provide features such as load balancing or hotkey caching. For more information, see Features of proxy nodes.
In direct connection mode, you can connect to an ApsaraDB for Redis 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 by using the Redis Cluster protocol. 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 an ApsaraDB for Redis instance.
Large volumes of data
Compared with a standard master-replica instance, a cluster master-replica instance supports a storage capacity of up to 4,096 GB.
A standard master-replica instance cannot support scenarios that require high queries per second (QPS). A 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 used by open source Redis. For more information, see Cluster master-replica instances.
Compared with a standard master-replica instance, 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 Redis protocols
A cluster master-replica instance contains multiple components. As a result, cluster master-replica instances are not as compatible with Redis protocols as standard master-replica instances. For more information, see Limits on commands supported by cluster instances and read/write splitting instances.
For information about how to analyze the distribution of data in memory, see Use the offline key analysis feature.