【Redis - 0】Introduction to Redis

Introduction to Redis

Redis is an open source (BSD licensed), in-memory data structure store, used as a database, cache and message broker. It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs(超重对数), geospatial(n. 地理空间) indexes with radius(n. 半径，半径范围；) queries and streams. Redis has built-in replication(n. 复制；回答；反响), Lua scripting, LRU eviction(n. 逐出；赶出；收回), transactions and different levels of on-disk persistence, and provides high availability via Redis Sentinel(n. 哨兵 vt. 守卫，放哨) and automatic partitioning with Redis Cluster.

You can run atomic operations on these types, like appending(vt. 附加；贴上；盖章) to a string; incrementing(n. [数] 增量；增加；增额；盈余) the value in a hash; pushing an element to a list; computing set intersection, union and difference; or getting the member with highest ranking in a sorted set.

In order to achieve its outstanding performance, Redis works with an in-memory dataset. Depending on your use case, you can persist it either by dumping(n. 倾销；倾泻) the dataset to disk every once in a while, or by appending each command to a log. Persistence can be optionally disabled, if you just need a feature-rich, networked, in-memory cache.

Redis also supports trivial(adj. 不重要的，琐碎的；琐细的)-to-setup master-slave(n. 奴隶；从动装置;vi. 苦干；拼命工作) asynchronous replication, with very fast non-blocking first synchronization, auto-reconnection with partial resynchronization on net split.

Other features include:

• Transactions
• Pub/Sub(发布/订阅)
• Lua scripting
• Keys with a limited time-to-live
• LRU eviction of keys
• Automatic failover(n. 失效备援（为系统备援能力的一种，当系统中其中一项设备失效而无法运作时，另一项设备即可自动接手原失效系统所执行的工作）)

You can use Redis from most programming languages out there.

Redis is written in ANSI C and works in most POSIX(n. 可移植性操作系统接口) systems like Linux, *BSD, OS X without external dependencies. Linux and OS X are the two operating systems where Redis is developed and more tested, and we recommend using Linux for deploying. Redis may work in Solaris-derived systems like SmartOS, but the support is best effort(n. 努力；成就). There is no official support for Windows builds, but Microsoft develops and maintains a Win-64 port of Redis.