Cassandra代替Redis?
最近用Cassandra的又逐渐多了，除了之前的360案例，在月初的QCon Shanghai 2013 篱笆网也介绍了其使用案例。而这篇百万用户时尚分享网站feed系统扩展实践文章则提到了Fashiolista和Instagram从Redis迁移到Cassandra的案例。考虑到到目前仍然有不少网友在讨论
最近用Cassandra的又逐渐多了，除了之前的360案例，在月初的QCon Shanghai 2013 篱笆网也介绍了其使用案例。而这篇百万用户时尚分享网站feed系统扩展实践文章则提到了Fashiolista和Instagram从Redis迁移到Cassandra的案例。考虑到到目前仍然有不少网友在讨论Redis的用法问题，Redis是一个数据库、内存、还是Key value store?以及Redis和memcache在实际场景的抉择问题，因此简单谈下相关区别。
首先，Redis和Cassandra完全是适合不同的使用场景的NoSQL产品。前者是适用小规模内存型的key value或者key list数据，后者适合存储大规模数据。因此这篇文章提到切换主要原因或许还是前期Redis使用场景不合适，在初创公司项目初期，以顺手的工具快速实现功能的做法也可以理解。
Redis的几种使用场景
- 访问量大
- key value或者key list数据结构
- 容量小，可控，可以全部放入内存。由于Redis是单线程设计，因此大value会导致后续的请求一定的堵塞。另外hashset当hgetall时候由于存在遍历操作，也不适合集合太大。如果数据超过单机容量可以使用常规的sharding方法分布到多台机
- 需持久化的场景
上面四点一般情况下应是必要条件。因此常见网站的用户资料、好友列表就适用用Redis来保存。由于Redis具有memcached所有的特性，也有讨论说memcache是否可以退出了？在以下情况下，我会倾向于选择memcached而非redis
- 简单无需持久化的key value，比如100字节以下。这种情况下使用memcached空间更节约且维护更简便。
- 有滚动过期需求，如网站的session，每个新登录的用户定期过期。
相关观点也可参考Memcached真的过时了吗
几个问题
- 既然Redis可以持久化，用Redis保存的好友列表是否还需要保存到关系数据库？
- 手机游戏Clash of Clans中的城堡属性、及用户的金币、圣水、奖杯适用用什么数据结构保存？
原文地址：Cassandra代替Redis?, 感谢原作者分享。
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1387
52
How to build the redis cluster mode
Apr 10, 2025 pm 10:15 PM
Redis cluster mode deploys Redis instances to multiple servers through sharding, improving scalability and availability. The construction steps are as follows: Create odd Redis instances with different ports; Create 3 sentinel instances, monitor Redis instances and failover; configure sentinel configuration files, add monitoring Redis instance information and failover settings; configure Redis instance configuration files, enable cluster mode and specify the cluster information file path; create nodes.conf file, containing information of each Redis instance; start the cluster, execute the create command to create a cluster and specify the number of replicas; log in to the cluster to execute the CLUSTER INFO command to verify the cluster status; make
How to clear redis data
Apr 10, 2025 pm 10:06 PM
How to clear Redis data: Use the FLUSHALL command to clear all key values. Use the FLUSHDB command to clear the key value of the currently selected database. Use SELECT to switch databases, and then use FLUSHDB to clear multiple databases. Use the DEL command to delete a specific key. Use the redis-cli tool to clear the data.
How to use the redis command
Apr 10, 2025 pm 08:45 PM
Using the Redis directive requires the following steps: Open the Redis client. Enter the command (verb key value). Provides the required parameters (varies from instruction to instruction). Press Enter to execute the command. Redis returns a response indicating the result of the operation (usually OK or -ERR).
How to read redis queue
Apr 10, 2025 pm 10:12 PM
To read a queue from Redis, you need to get the queue name, read the elements using the LPOP command, and process the empty queue. The specific steps are as follows: Get the queue name: name it with the prefix of "queue:" such as "queue:my-queue". Use the LPOP command: Eject the element from the head of the queue and return its value, such as LPOP queue:my-queue. Processing empty queues: If the queue is empty, LPOP returns nil, and you can check whether the queue exists before reading the element.
How to use redis lock
Apr 10, 2025 pm 08:39 PM
Using Redis to lock operations requires obtaining the lock through the SETNX command, and then using the EXPIRE command to set the expiration time. The specific steps are: (1) Use the SETNX command to try to set a key-value pair; (2) Use the EXPIRE command to set the expiration time for the lock; (3) Use the DEL command to delete the lock when the lock is no longer needed.
How to read the source code of redis
Apr 10, 2025 pm 08:27 PM
The best way to understand Redis source code is to go step by step: get familiar with the basics of Redis. Select a specific module or function as the starting point. Start with the entry point of the module or function and view the code line by line. View the code through the function call chain. Be familiar with the underlying data structures used by Redis. Identify the algorithm used by Redis.
How to solve data loss with redis
Apr 10, 2025 pm 08:24 PM
Redis data loss causes include memory failures, power outages, human errors, and hardware failures. The solutions are: 1. Store data to disk with RDB or AOF persistence; 2. Copy to multiple servers for high availability; 3. HA with Redis Sentinel or Redis Cluster; 4. Create snapshots to back up data; 5. Implement best practices such as persistence, replication, snapshots, monitoring, and security measures.
How to use the redis command line
Apr 10, 2025 pm 10:18 PM
Use the Redis command line tool (redis-cli) to manage and operate Redis through the following steps: Connect to the server, specify the address and port. Send commands to the server using the command name and parameters. Use the HELP command to view help information for a specific command. Use the QUIT command to exit the command line tool.
