This topic describes ApsaraDB for Redis cluster master-replica instances. They 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.

Proxy mode

By default, cluster master-replica instances run in proxy mode. 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 of the instance. The proxy nodes, data shards, and config server 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.

Figure 1. Architecture of a cluster master-replica instance in proxy mode
Table 1. Components of a cluster master-replica instance in proxy mode
Component Description
Proxy node A cluster master-replica instance contains multiple proxy nodes. Each proxy node works in a single-node architecture. The cluster master-replica instance automatically balances loads and can fail over among the configured proxy nodes.
Note For more information about the features of proxy nodes, see Features of proxy nodes.
Data shard A cluster master-replica instance contains multiple data shards. Each data shard works in 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 cluster master-replica instance fails over to the replica node to ensure high availability.
Config server The config server of a cluster master-replica instance works in a high availability architecture in which a master node and a replica node are deployed. The config server stores the configuration data and partitioning policies of the cluster master-replica instance.

The component quantities and configurations in a cluster master-replica instance vary with 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 about instance specifications, specification change, and architecture change, 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 this mode, you can bypass proxy nodes and directly connect to data shards. This reduces network overheads and increases response speed. For more information about the architecture of a cluster master-replica instance in direct connection mode, see the following figure and description.

Note Compared with the proxy mode, the direct connection mode does not provide features such as load balancing or hotkey cache. For more information, see Features of proxy nodes.
Figure 2. Architecture of a cluster master-replica instance in direct connection mode
Architecture of a cluster master-replica instance in direct connection mode

To use the direct connection mode on a cluster instance, you must enable the direct connection mode, obtain the private endpoint, and then connect to the instance in the same method as you connect to a native Redis cluster. For more information about how to enable the direction connection mode, see Enable the direct connection mode. 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. Direct connection mode and proxy mode are quite different from each other. For more information about the precautions and connection examples, see Use a private endpoint to connect to an ApsaraDB for Redis instance.

Scenarios

  • Large amounts of data

    Compared with a standard master-replica instance, a cluster master-replica instance supports a storage capacity of up to 4,096 GB.

  • High QPS

    A standard master-replica instance cannot support high queries per second (QPS) scenarios. A cluster master-replica instance allows you to deploy multiple data shards. These data shards can work together to eliminate the performance bottleneck of the single-threading model used by open source Redis. For more information, see Master-replica cluster instances.

  • Throughput-intensive applications

    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 such, cluster master-replica instances are not as compatible with Redis protocols as standard master-replica instances. For information, see Limits on commands supported by cluster instances.

References

  • For more information about how to troubleshoot abnormal memory usage of data shards in a cluster master-replica instance, see How do I search for large keys?
  • For more information about how to analyze the distribution of data in memory, see Offline key analysis.

FAQ

Q: Can I enable both the direct connection mode and the proxy mode?

A: Yes, you can enable both the direct connection mode and the proxy mode. If you use a local disk-based cluster instance, you can enable the two modes at the same time. However, if you use a cloud disk-based one, you can only enable a single mode.