PHP method to implement remote disaster recovery of Redis database

With the continuous development of Internet applications and the continuous growth of user traffic, the stability and reliability of the database have become increasingly important issues. As a high-performance in-memory database, Redis has been widely used in various Internet application scenarios. In this case, how to implement remote disaster recovery of the Redis database has become a problem that needs to be solved.

Off-site disaster recovery refers to backing up data to an off-site location to prevent data loss when a disaster occurs in the data center. Redis itself does not support remote disaster recovery, but it can be achieved in a variety of ways.

1. Redis replication mechanism

Redis uses a replication mechanism to achieve high availability. Redis high availability is achieved by synchronizing data from one Redis instance to another Redis instance. There are two ways to achieve Redis high availability: master-slave and sentinel mode.

1.1 master-slave mode

The Master-slave mode refers to one Redis instance as the master, and other Redis instances as slaves. The master instance is responsible for write operations, and the slave instance is responsible for read operations and failover. In master-slave mode, the master node asynchronously copies data to the slave node, and the slave node only serves as a reading library to read data, thereby achieving master-slave separation.

When the master performs data writing operations, it will synchronize the writing operations to all slave nodes to ensure data synchronization. The slave nodes will regularly send ping commands to the master node to ensure high availability. If the master node fails, one of the slave nodes can be switched to the master node to continue to provide services through manual switching or automatic failover.

1.2 sentinel mode

Sentinel mode is based on the master-slave mode and introduces the sentinel node, which is to complete the automatic switching function. Sentinel can monitor the status of data, including the status of master nodes and slave nodes. When the master node goes down, sentinel will automatically select the slave node as the new master node and change other slave nodes to copy data from the new Master node, thereby achieving fast failover.

2. Redis persistence mechanism

Redis supports two persistence mechanisms, RDB and AOF, which can persist data in memory to the hard disk to prevent data loss.

2.1 RDB mechanism

The RDB mechanism saves the snapshot of Redis data in memory to the hard disk, and the persistent content is data at a point in time. Redis will periodically dump snapshots in memory to disk files to facilitate data recovery when restarting after a crash.

2.2 AOF mechanism

The AOF mechanism records Redis write commands and persists them to the hard disk in an incremental form so that data can be recovered after a crash. The AOF mechanism has higher reliability and durability, but it will cause a certain write load and be slower when recovering data.

3. Redis’ remote disaster recovery implementation

3.1 Redis’ remote disaster recovery architecture model

Redis’ remote disaster recovery model is divided into active-standby mode and active-active model.

1) active-standby mode

active-standby mode is the active-standby mode. The master node and the slave node are in different regions, and the data of the master node is synchronized to the slave node. The slave node is only used as a backup machine and does not perform read or write operations. When the master node fails, the slave node will take over the business of the master node.

2) active-active mode

The active-active mode is the multi-active mode. Multiple Redis nodes process requests at the same time and adopt a strong consistency data replication method. Multiple Redis instances are master nodes and serve different business areas. When a business request is made, Redis will find the corresponding Redis instance for processing based on the business area where the request is located.

3.2 Implementation method

1) Use the Redis replication mechanism to implement remote disaster recovery

In the remote disaster recovery architecture, the master node and slave nodes are distributed in different locations. In regions, the Redis replication mechanism is used to ensure the consistency of node data in different regions. At the same time, by pointing SLB or DNS resolution to the IP corresponding to the master node, load balancing of user requests is achieved, thereby achieving remote disaster recovery.

2) Introduce high-availability components to achieve remote disaster recovery

Introduce high-availability components (such as Alibaba Cloud's Redis version) into the architecture to achieve remote disaster recovery, high availability, data synchronization, Failover and other functions improve system reliability and scalability.

3.3 Summary

Through Redis’s replication mechanism, persistence mechanism and off-site disaster recovery architecture model, Redis’ off-site disaster recovery is realized to ensure the high availability and data reliability of Redis. At the same time, during actual use, it is also necessary to select appropriate off-site disaster recovery solutions based on specific needs and business scenarios, and carry out reasonable applications and configurations.

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