How is the redis cluster implemented

Redis cluster is a distributed deployment model that allows horizontal expansion of Redis instances to be achieved through inter-node communication, hash slot division key space, node election, master-slave replication and command redirection: inter-node communication: virtual network communication is realized through cluster bus. Hash slot: divides the key space into hash slots to determine the node responsible for the key. Node election: At least three master nodes are required, and only one active master node is ensured through the election mechanism. Master-slave replication: The master node is responsible for writing requests, and the slave node is responsible for reading requests and data replication. Command redirection: The client connects to the node responsible for the key, and the node redirects incorrect requests. Troubleshooting: fault detection, marking off line and re-

Implementation of Redis cluster

Redis clustering is a distributed deployment model that allows horizontal scaling of Redis instances on multiple servers. The following describes how Redis cluster is implemented:

Internode communication

Nodes in the Redis cluster communicate through a virtual network called the cluster bus. Cluster bus is an abstract concept that encapsulates the underlying network connection and communication protocol. Each node has a specific bus address that identifies and locates other nodes.

Hash slot

Redis clusters use hash slots to divide key space. The key space is divided into 16384 hash slots, each storing a specific range of keys. When the client performs an operation, the hash slot to which the key belongs is calculated by the hash value of the key, thereby determining the node responsible for the key.

Node election

At least three master nodes are required in the cluster to work properly. The master node is responsible for handling write requests and replication to the slave node. When a node starts, it participates in an election process to determine whether it is a master or slave. The election mechanism ensures that there is only one active master node in the cluster.

Master-slave copy

For high availability, Redis clusters use master-slave replication. Each master node has one or more slave nodes, responsible for replicating the master node's data and processing read requests. If the master node fails, the cluster will automatically select a new master node from the slave node.

Command redirection

When a client issues a command, it first connects to the node responsible for the hash slot of that command key. If the node is the correct receiving node, it executes the command and returns the result. If the node is not the correct receiving node, it redirects the client to the correct node.

Troubleshooting

Redis clusters provide fault detection and recovery mechanisms to ensure data consistency in the event of a node failure. When a node fails, the cluster marks it as offline from the cluster. Other nodes detect the failure and re-elect a new master node.

Through these mechanisms, Redis clusters can achieve level of scalability, high availability, and data consistency, making it ideal for large-scale deployment of Redis in distributed environments.

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