一、Redis简介

Redis ，是一个高性能(NOSQL)的key-value数据库,Redis是一个开源的使用ANSI C语言编写、支持网络、可基于内存亦可持久化的日志型、Key-Value数据库，并提供多种语言的API。Redis是完全开源免费的，遵守BSD协议。

二、Redis特点

● 性能极高：Redis能读的速度是110000次/s,写的速度是81000次/s 。

●Redis支持String, Hash,List, , Set 及 Ordered Set 数据类型操作。

● 原子性 – Redis的所有操作都是原子性的，意思就是要么成功执行要么失败完全不执行。单个操作是原子性的。多个操作也支持事务，即原子性，通过MULTI和EXEC指令包起来。

● 丰富的特性 – Redis还支持 publish/subscribe, 通知, key 过期等等特性。

● 高速读写，redis使用自己实现的分离器，代码量很短，没有使用lock（MySQL），因此效率非常高。

三、数据类型

● string（字符串）：最基本的k-v存储 ，适合验证码、配置信息等

● list（列表）：适合有序/固定的列表。比如行政区、字典表、消息队列等。

● set（集合）：支持交集、并集、差集等操作。可以用来找共同点等。

● hash（哈希）：类似于唯一标识，value对应详情。适合存储文章内容、商品内容等详情。

● zset（有序集合）：增强版本增加了一个score参数，用来排序，适合排行榜类的数据存储

四、Redis应用场景

3.1、缓存

缓存现在几乎是所有中大型网站都在用的必杀技，合理利用缓存不仅能够提升网站访问速度，还能大大降低数据库的压力。Redis提供了键过期功能，也提供了灵活的键淘汰策略，所以，现在Redis用在缓存的场合非常多。

3.2、排行榜

很多网站都有排行榜应用的，如京东的月度销量榜单、商品按时间的上新排行榜等。Redis提供的有序集合数据结构能实现各种复杂的排行榜应用。

3.3、计数器

什么是计数器，如电商网站商品的浏览量、视频网站视频的播放数等。为了保证数据实时效，每次浏览都得给+1，并发量高时如果每次都请求数据库操作无疑是种挑战和压力。Redis提供的incr命令来实现计数器功能，内存操作，性能非常好，非常适用于这些计数场景。

3.4、分布式会话

集群模式下，在应用不多的情况下一般使用容器自带的session复制功能就能满足，当应用增多相对复杂的系统中，一般都会搭建以Redis等内存数据库为中心的session服务，session不再由容器管理，而是由session服务及内存数据库管理。

3.5、分布式锁

在很多互联网公司中都使用了分布式技术，分布式技术带来的技术挑战是对同一个资源的并发访问，如全局ID、减库存、秒杀等场景，并发量不大的场景可以使用数据库的悲观锁、乐观锁来实现，但在并发量高的场合中，利用数据库锁来控制资源的并发访问是不太理想的，大大影响了数据库的性能。可以利用Redis的setnx功能来编写分布式的锁，如果设置返回1说明获取锁成功，否则获取锁失败，实际应用中要考虑的细节要更多。

3.6、 社交网络

点赞、踩、关注/被关注、共同好友等是社交网站的基本功能，社交网站的访问量通常来说比较大，而且传统的关系数据库类型不适合存储这种类型的数据，Redis提供的哈希、集合等数据结构能很方便的的实现这些功能。

3.7、最新列表

Redis列表结构，LPUSH可以在列表头部插入一个内容ID作为关键字，LTRIM可用来限制列表的数量，这样列表永远为N个ID，无需查询最新的列表，直接根据ID去到对应的内容页即可。

3.8、消息系统

消息队列是大型网站必用中间件，如ActiveMQ、RabbitMQ、Kafka等流行的消息队列中间件，主要用于业务解耦、流量削峰及异步处理实时性低的业务。Redis提供了发布/订阅及阻塞队列功能，能实现一个简单的消息队列系统。另外，这个不能和专业的消息中间件相比。

五、Centos环境部署Redis

更新系统的软件包列表和已安装的软件包

sudo yum update

使用以下命令安装 Redis：

sudo yum install epel-releasesudo yum install redis

启动 Redis 服务

安装完成后，启动 Redis 服务并设置开机启动：

sudo systemctl start redissudo systemctl enable redis

验证安装

可以使用以下命令检查 Redis 是否成功安装并运行：

redis-cli ping

如果 Redis 正常运行，会返回 "PONG"。

六、常见参数整理

# protected-mode用于控制 Redis 服务器是否运行在保护模式下。保护模式是为了防止未经授权访问而设计的一种安全特性。# 当 protected-mode 被设置为 yes 时，Redis 服务器只会监听来自本地环回接口（127.0.0.1）的连接，拒绝来自外部网络的连接。这可以保护 Redis  务器免受未经授权的访问。# 当 protected-mode 被设置为 no 时，Redis 服务器将接受来自任何网络接口的连接，这意味着可以从外部网络进行访问。protected-mode no# redis 端口port 6379# tcp-backlog 参数用于设置 TCP 监听套接字的连接队列的长度tcp-backlog 511# Unix socket.## Specify the path for the Unix socket that will be used to listen for# incoming connections. There is no default, so Redis will not listen# on a unix socket when not specified.## unixsocket /tmp/redis.sock# unixsocketperm 700# Close the connection after a client is idle for N seconds (0 to disable)timeout 0# tcp-keepalive 参数用于设置 TCP keepalive 功能的开关。TCP keepalive 是一种机制，用于在长时间没有数据交换的情况下，检测连接是否仍然有效tcp-keepalive 300################################# GENERAL ###################################### By default Redis does not run as a daemon. Use 'yes' if you need it.# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.daemonize yes# 设置 Redis 访问密码# requirepass yourpassword  # supervised 参数用于指定 Redis 服务器的启动和关闭行为。这个参数允许你指定 Redis 服务器是作为一个常规程序（no），一个守护进程（systemd），一个 Upstart 任务（upstart），或者一个 SysV init 脚本（sysv）来运行。supervised no# pidfile 是一个用于指定 Redis 服务器进程 ID（PID）文件路径的配置参数pidfile /var/run/redis_6379.pid# 日志等级# This can be one of:# debug (a lot of information, useful for development/testing)# verbose (many rarely useful info, but not a mess like the debug level)# notice (moderately verbose, what you want in production probably)# warning (only very important / critical messages are logged)loglevel notice#redis日志路径logfile /var/log/redis/redis.log# 默认数据库数量为16个databases 16################################ SNAPSHOTTING  ################################## Save the DB on disk:##   save <seconds> <changes>##   Will save the DB if both the given number of seconds and the given#   number of write operations against the DB occurred.##   In the example below the behaviour will be to save:#   after 900 sec (15 min) if at least 1 key changed#   after 300 sec (5 min) if at least 10 keys changed#   after 60 sec if at least 10000 keys changed##   Note: you can disable saving completely by commenting out all "save" lines.##   It is also possible to remove all the previously configured save#   points by adding a save directive with a single empty string argument#   like in the following example:##   save ""save 900 1save 300 10save 60 10000stop-writes-on-bgsave-error yes# Compress string objects using LZF when dump .rdb databases?# For default that's set to 'yes' as it's almost always a win.# If you want to save some CPU in the saving child set it to 'no' but# the dataset will likely be bigger if you have compressible values or keys.rdbcompression yesrdbchecksum yes# The filename where to dump the DBdbfilename dump.rdb# The working directory.## The DB will be written inside this directory, with the filename specified# above using the 'dbfilename' configuration directive.## The Append Only File will also be created inside this directory.## Note that you must specify a directory here, not a file name.dir /var/lib/redisslave-serve-stale-data yesslave-read-only yesrepl-diskless-sync norepl-diskless-sync-delay 5repl-disable-tcp-nodelay noslave-priority 100# 设置redis的最大内存maxmemory 3GB# maxmemory-policy allkeys-lru # MAXMEMORY POLICY: how Redis will select what to remove when maxmemory# is reached. You can select among five behaviors:## volatile-lru -> remove the key with an expire set using an LRU algorithm# allkeys-lru -> remove any key according to the LRU algorithm# volatile-random -> remove a random key with an expire set# allkeys-random -> remove a random key, any key# volatile-ttl -> remove the key with the nearest expire time (minor TTL)# noeviction -> don't expire at all, just return an error on write operationsappendonly no# The name of the append only file (default: "appendonly.aof")appendfilename "appendonly.aof"appendfsync everysecno-appendfsync-on-rewrite noauto-aof-rewrite-percentage 100auto-aof-rewrite-min-size 64mbaof-load-truncated yeslua-time-limit 5000slowlog-log-slower-than 10000# There is no limit to this length. Just be aware that it will consume memory.# You can reclaim memory used by the slow log with SLOWLOG RESET.slowlog-max-len 128################################ LATENCY MONITOR ############################### The Redis latency monitoring subsystem samples different operations# at runtime in order to collect data related to possible sources of# latency of a Redis instance.## Via the LATENCY command this information is available to the user that can# print graphs and obtain reports.## The system only logs operations that were performed in a time equal or# greater than the amount of milliseconds specified via the# latency-monitor-threshold configuration directive. When its value is set# to zero, the latency monitor is turned off.## By default latency monitoring is disabled since it is mostly not needed# if you don't have latency issues, and collecting data has a performance# impact, that while very small, can be measured under big load. Latency# monitoring can easily be enabled at runtime using the command# "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.latency-monitor-threshold 0notify-keyspace-events ""############################### ADVANCED CONFIG ################################ Hashes are encoded using a memory efficient data structure when they have a# small number of entries, and the biggest entry does not exceed a given# threshold. These thresholds can be configured using the following directives.hash-max-ziplist-entries 512hash-max-ziplist-value 64# Lists are also encoded in a special way to save a lot of space.# The number of entries allowed per internal list node can be specified# as a fixed maximum size or a maximum number of elements.# For a fixed maximum size, use -5 through -1, meaning:# -5: max size: 64 Kb  <-- not recommended for normal workloads# -4: max size: 32 Kb  <-- not recommended# -3: max size: 16 Kb  <-- probably not recommended# -2: max size: 8 Kb   <-- good# -1: max size: 4 Kb   <-- good# Positive numbers mean store up to _exactly_ that number of elements# per list node.# The highest performing option is usually -2 (8 Kb size) or -1 (4 Kb size),# but if your use case is unique, adjust the settings as necessary.list-max-ziplist-size -2list-compress-depth 0# Sets have a special encoding in just one case: when a set is composed# of just strings that happen to be integers in radix 10 in the range# of 64 bit signed integers.# The following configuration setting sets the limit in the size of the# set in order to use this special memory saving encoding.set-max-intset-entries 512# Similarly to hashes and lists, sorted sets are also specially encoded in# order to save a lot of space. This encoding is only used when the length and# elements of a sorted set are below the following limits:zset-max-ziplist-entries 128zset-max-ziplist-value 64hll-sparse-max-bytes 3000activerehashing yesclient-output-buffer-limit normal 0 0 0client-output-buffer-limit slave 256mb 64mb 60client-output-buffer-limit pubsub 32mb 8mb 60hz 10aof-rewrite-incremental-fsync yes

然后可以客户端访问测试