Redis methods and application examples for implementing distributed caching

With the rapid development of the Internet, there are problems of massive data and high concurrency. In order to improve website performance and user experience, caching technology is widely used. One of the more popular caching technologies is distributed caching, and Redis is an excellent tool for implementing distributed caching. This article will introduce the basic concepts of Redis, the principles and application examples of distributed cache, so that everyone can better understand the role of Redis in distributed cache.

1. Overview of Redis

Redis (Remote Dictionary Server) is an open source in-memory data storage system that can be used as a database, cache and message middleware. The data structures supported by Redis include strings, hashes, lists, sets, ordered sets, etc. It is a single-threaded application, but multiplexing technology can handle multiple connections concurrently. Redis can support replication, high availability and distribution.

Basic features of Redis:

1. High performance

Redis is an in-memory database, the data is stored in the memory, and the reading and writing speed is very fast. At the same time, it uses a single-threaded model to avoid issues such as lock competition and context switching caused by multi-threading, thus improving performance.

2. Multiple data structure support

Redis supports multiple data structures including strings, hashes, lists, sets, ordered sets, etc., which can meet the needs of different application scenarios.

3. Good scalability

Redis is a distributed database that can be expanded through clustering and supports functions such as read-write separation and master-slave replication.

4. Rich functions

Redis has a rich function library that can implement a series of application functions such as counters, speed limits, and queues.

2. Principle of distributed cache

1. The meaning and role of cache

Cache is a technical means to improve application efficiency and reduce load. The cache stores reused data in memory. When the application needs the data, it can be read directly from the memory, avoiding the time consumption of reading the data from the disk.

2. Advantages of distributed caching

Distributed caching, as the name suggests, is to manage cached data distributed among multiple servers. Compared with a single server managing cache, it has the following advantages:

1) Large cache space

Multiple servers can share the cache pressure, the cache capacity has been greatly improved, and the cache hit rate has also been improved.

2) High Availability

The data between multiple servers are backed up to each other, which avoids the problem of data loss when a node goes down or other failures occur, and improves the availability of the system.

3) Load balancing

Multiple servers share requests, effectively balancing the system load and improving the stability and scalability of the system.

3. How Redis implements distributed caching

Redis uses sharding technology to divide cache data into different node nodes. Each node is an independent Redis instance, and all nodes form a cluster. The access method of the cluster is determined by the client, which can be random access or directed access. Redis cluster uses hash slots for data sharding. There are 16384 hash slots in total, and each slot can store a key-value pair. When nodes are added or removed, hash slots are automatically reallocated and new data is evenly distributed to different nodes. Redis has a complete set of built-in data migration mechanisms to ensure data integrity and availability during the entire process.

3. Application examples of Redis distributed cache

1. Cluster architecture diagram

The following figure is the Redis cluster architecture diagram, including 6 nodes (can be configured as needed expansion), each node can store multiple slots.

2. Redis cluster configuration steps

1) Install Redis

The normal installation method can be installed through the official document https://redis.io/download.

2) Configuring the Redis cluster

The configuration of the Redis cluster is relatively complex and can be automatically completed through the open source software redis-trib.rb script.

3) Start the Redis cluster

After initializing and configuring through the redis-trib.rb script, you can start the Redis cluster through the redis-trib.rb tool. The command is:

redis-trib.rb start

4) Use Redis cluster

After completing the above steps, you can use Redis cluster in your application. The client first needs to connect to any node in the Redis cluster. This node will return which node the currently requested data is on, and then the client will send the request to the corresponding node.

Summary: Redis is a powerful, high-performance, and scalable in-memory database that supports a variety of data structures and data types. It implements distributed caching through sharding technology, which greatly improves the cache capacity, reliability and performance of the system. Using Redis to implement distributed caching can not only improve the data reading and writing speed and system stability, but also improve the efficiency and user experience of the website. It is a very excellent caching technology.

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