【Redis】通过 docker 快速搭建集群 Redis 环境

古城微笑少年丶 2022-12-17 01:18 214阅读 0赞

# 【Redis】通过 docker 快速搭建集群 Redis 环境 #

### 一、安装单机版 ###

#### 1.下载reids镜像 ####

docker pull redis:5.0.9

#### 2.创建文件夹 ####

mkdir -p /opt/redis

#### 3.配置文件 ####

vim /opt/redis/redis.conf
    #内容

#### 4.运行容器创建redis ####

sudo docker run -it --name redis \
    -p 16379:6379 \
    --restart always \
    --privileged=true \
    -m 2048m \
    -v /opt/redis/redis.conf:/etc/redis/redis.conf  \
    -v /opt/redis/data:/data  \
    -d  \
    redis:5.0.9 redis-server /etc/redis/redis.conf

#### 5.创建客户端 ####

*  客户端
    
        docker run -it -p 6379:6379  -d -m 125m  --restart always --name redis-client redis:5.0.9
 *  创建脚本
    
        vim /opt/redis/redisClient.sh
        ## 内容
        docker exec -it redis-client redis-cli -h [redisIP] -p [redis端口] -a [认证密码,没有就不需要]
        ## 例如 docker exec -it redis-client redis-cli -h 172.16.46.213 -p 16379 -a mscmredis
        
        
        docker exec -it redis-client redis-cli -h 172.16.46.213 -p 16379 -a mscmredis -c
        docker exec -it redis-client redis-cli -h 172.16.46.214 -p 16377 -a mscmredis -c
        
        docker exec -it redis-client redis-cli -h 172.16.46.214 -p 16379 -a mscmredis -c
        docker exec -it redis-client redis-cli -h 172.16.46.213 -p 16377 -a mscmredis -c
        
        docker exec -it redis-client redis-cli -h 172.16.46.213 -p 16378 -a mscmredis -c
        docker exec -it redis-client redis-cli -h 172.16.46.214 -p 16378 -a mscmredis -c
 *  给脚本执行权限
    
        chmod a+x /opt/redis/redisClient.sh

### 二、集群搭建 cluster ###

#### 1.创建文件夹 ####

mkdir -p /opt/redis

#### 2.配置文件修改,复制redis.conf修改一下信息 ####

#端口
    port 16379
    #设置集群节点间访问密码
    masterauth mscmredis
    #启动集群模式
    cluster-enabled yes
    #节点配置文件
    cluster-config-file nodes.conf
    #redis节点宕机被发现的时间毫秒
    cluster-node-timeout 5000
    #集群节点的汇报ip
    cluster-announce-ip 172.16.46.213
    #集群节点的汇报端口 防止nat
    cluster-announce-port 16379
    #集群节点的汇报bus-port 防止nat 注意:网络模式如果不是host模式,端口与转发端口一致
    cluster-announce-bus-port 26379

**配置文件需要在213 214两台主机上配置 redis\_16377.conf redis\_16378.conf redis\_16379.conf,不同点端口和IP**

#### 3.启动 ####

#分别在213 214主机执行
    #redis_16379
    sudo docker run -it --name redis_16379 \
    -p 16379:16379 \
    -p 26379:26379 \
    --restart always \
    --privileged=true \
    -m 1g \
    -v /opt/redis/redis_16379.conf:/etc/redis/redis.conf  \
    -v /opt/redis/data_16379:/data  \
    -d  \
    redis:5.0.9 redis-server /etc/redis/redis.conf
    
    #redis_16378
    sudo docker run -it --name redis_16378 \
    -p 16378:16378 \
    -p 26378:26378 \
    --restart always \
    --privileged=true \
    -m 1g \
    -v /opt/redis/redis_16378.conf:/etc/redis/redis.conf  \
    -v /opt/redis/data_16378:/data  \
    -d  \
    redis:5.0.9 redis-server /etc/redis/redis.conf
    
    #redis_16377
    sudo docker run -it --name redis_16377 \
    -p 16377:16377 \
    -p 26377:26377 \
    --restart always \
    --privileged=true \
    -m 1g \
    -v /opt/redis/redis_16377.conf:/etc/redis/redis.conf  \
    -v /opt/redis/data_16377:/data  \
    -d  \
    redis:5.0.9 redis-server /etc/redis/redis.conf

#创建集群主从节点
    redis-cli -a mscmredis --cluster create 172.16.46.213:16379 172.16.46.213:16378 172.16.46.213:16377 172.16.46.214:16379 172.16.46.214:16378 172.16.46.214:16377 --cluster-replicas 1

#### 4.Redis 5.0 redis-cli --cluster help说明 ####

https://www.cnblogs.com/zhoujinyi/p/11606935.html

redis-cli --cluster help
    Cluster Manager Commands:
      create         host1:port1 ... hostN:portN   #创建集群
                     --cluster-replicas <arg>      #从节点个数
      check          host:port                     #检查集群
                     --cluster-search-multiple-owners #检查是否有槽同时被分配给了多个节点
      info           host:port                     #查看集群状态
      fix            host:port                     #修复集群
                     --cluster-search-multiple-owners #修复槽的重复分配问题
      reshard        host:port                     #指定集群的任意一节点进行迁移slot，重新分slots
                     --cluster-from <arg>          #需要从哪些源节点上迁移slot，可从多个源节点完成迁移，以逗号隔开，传递的是节点的node id，还可以直接传递--from all，这样源节点就是集群的所有节点，不传递该参数的话，则会在迁移过程中提示用户输入
                     --cluster-to <arg>            #slot需要迁移的目的节点的node id，目的节点只能填写一个，不传递该参数的话，则会在迁移过程中提示用户输入
                     --cluster-slots <arg>         #需要迁移的slot数量，不传递该参数的话，则会在迁移过程中提示用户输入。
                     --cluster-yes                 #指定迁移时的确认输入
                     --cluster-timeout <arg>       #设置migrate命令的超时时间
                     --cluster-pipeline <arg>      #定义cluster getkeysinslot命令一次取出的key数量，不传的话使用默认值为10
                     --cluster-replace             #是否直接replace到目标节点
      rebalance      host:port                                      #指定集群的任意一节点进行平衡集群节点slot数量 
                     --cluster-weight <node1=w1...nodeN=wN>         #指定集群节点的权重
                     --cluster-use-empty-masters                    #设置可以让没有分配slot的主节点参与，默认不允许
                     --cluster-timeout <arg>                        #设置migrate命令的超时时间
                     --cluster-simulate                             #模拟rebalance操作，不会真正执行迁移操作
                     --cluster-pipeline <arg>                       #定义cluster getkeysinslot命令一次取出的key数量，默认值为10
                     --cluster-threshold <arg>                      #迁移的slot阈值超过threshold，执行rebalance操作
                     --cluster-replace                              #是否直接replace到目标节点
      add-node       new_host:new_port existing_host:existing_port  #添加节点，把新节点加入到指定的集群，默认添加主节点
                     --cluster-slave                                #新节点作为从节点，默认随机一个主节点
                     --cluster-master-id <arg>                      #给新节点指定主节点
      del-node       host:port node_id                              #删除给定的一个节点，成功后关闭该节点服务
      call           host:port command arg arg .. arg               #在集群的所有节点执行相关命令
      set-timeout    host:port milliseconds                         #设置cluster-node-timeout
      import         host:port                                      #将外部redis数据导入集群
                     --cluster-from <arg>                           #将指定实例的数据导入到集群
                     --cluster-copy                                 #migrate时指定copy
                     --cluster-replace                              #migrate时指定replace
      help           
    
    For check, fix, reshard, del-node, set-timeout you can specify the host and port of any working node in the cluster.

\*\*注意：Redis Cluster最低要求是3个主节点，如果需要集群需要认证，则在最后加入-a xx即可. \*\*

*  1.创建集群主节点

redis-cli --cluster create 172.16.46.214:16379 172.16.46.214:16378 172.16.46.214:16377

*  2.创建集群主从节点

redis-cli -a mscmredis --cluster create 172.16.46.213:16379 172.16.46.213:16378 172.16.46.213:16377 172.16.46.214:16379 172.16.46.214:16378 172.16.46.214:16377 --cluster-replicas 1

**说明：–cluster-replicas 参数为数字，1表示每个主节点需要1个从节点。**

**通过该方式创建的带有从节点的机器不能够自己手动指定主节点，所以如果需要指定的话，需要自己手动指定，先使用①或③创建好主节点后，再通过④来处理**

*  3.添加集群主节点

redis-cli --cluster add-node 192.168.163.132:6382 192.168.163.132:6379

**说明：为一个指定集群添加节点，需要先连到该集群的任意一个节点IP（192.168.163.132:6379），再把新节点加入。该2个参数的顺序有要求：新加入的节点放前**

*  4.添加集群从节点

redis-cli --cluster add-node 192.168.163.132:6382 192.168.163.132:6379 --cluster-slave --cluster-master-id 117457eab5071954faab5e81c3170600d5192270

**说明：把6382节点加入到6379节点的集群中，并且当做node\_id为 117457eab5071954faab5e81c3170600d5192270 的从节点。如果不指定 --cluster-master-id会随机分配到任意一个主节点。**

*  5.删除节点

redis-cli --cluster del-node 192.168.163.132:6384 f6a6957421b80409106cb36be3c7ba41f3b603ff

### 配置文件redis.conf ###

# redis 配置文件示例
     
    # 当你需要为某个配置项指定内存大小的时候，必须要带上单位，
    # 通常的格式就是 1k 5gb 4m 等酱紫：
    #
    # 1k => 1000 bytes
    # 1kb => 1024 bytes
    # 1m => 1000000 bytes
    # 1mb => 1024*1024 bytes
    # 1g => 1000000000 bytes
    # 1gb => 1024*1024*1024 bytes
    #
    # 单位是不区分大小写的，你写 1K 5GB 4M 也行
    
    ################################## INCLUDES ###################################
    
    # 假如说你有一个可用于所有的 redis server 的标准配置模板，
    # 但针对某些 server 又需要一些个性化的设置，
    # 你可以使用 include 来包含一些其他的配置文件，这对你来说是非常有用的。
    #
    # 但是要注意哦，include 是不能被 config rewrite 命令改写的
    # 由于 redis 总是以最后的加工线作为一个配置指令值，所以你最好是把 include 放在这个文件的最前面，
    # 以避免在运行时覆盖配置的改变，相反，你就把它放在后面（外国人真啰嗦）。
    #
    # include /path/to/local.conf
    # include /path/to/other.conf
    
    ################################## MODULES #####################################
    
    # 在启动时加载模块。如果服务器无法加载模块
    # 它会中止。可以使用多个loadmodule指令。
    #
    # loadmodule /path/to/my_module.so
    # loadmodule /path/to/other_module.so
    
    ################################## 网络 #####################################
    
    # 默认情况下，如果未指定“ bind”配置指令，则Redis会侦听用于来自服务器上所有可用网络接口的连接。
    #
    # 用于来自服务器上所有可用网络接口的连接。.
    # 使用以下功能可以只收听一个或多个选定的接口“bind”配置指令，后跟一个或多个IP地址。
    #
    # 示例，多个IP用空格隔开:
    #
    # bind 192.168.1.100 10.0.0.1
    # bind 127.0.0.1 ::1
    #
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    #bind 127.0.0.1
    
    
    # 是否开启保护模式，默认开启。要是配置里没有指定bind和密码。开启该参数后，redis只会本地进行访问，
    # 拒绝外部访问。要是开启了密码和bind，可以开启。否则最好关闭，设置为no
    protected-mode yes
    
    # 接受指定端口上的连接，默认值为6379（IANA＃815344）。
    # 如果指定了端口0，则Redis将不会在TCP套接字上侦听
    port 6379
    
    # TCP listen() backlog.
    #
    # 此参数确定了TCP连接中已完成队列(完成三次握手之后)的长度， 当然此值必须不大于Linux系统定义
    # 的/proc/sys/net/core/somaxconn值，默认是511，而Linux的默认参数值是128。当系统并发量大并且客户端
    # 速度缓慢的时候，可以将这二个参数一起参考设定。该内核参数默认值一般是128，对于负载很大的服务程序来说
    # 大大的不够。一般会将它修改为2048或者更大。在/etc/sysctl.conf中添加:net.core.somaxconn = 2048，
    # 然后在终端中执行sysctl -p
    
    tcp-backlog 511
    
    # Unix socket.
    #
    # 指定将用于侦听的Unix套接字的路径
    # 传入连接。没有默认设置，因此Redis不会收听
    # 在未指定的情况下，在UNIX套接字上。
    #
    # unixsocket /tmp/redis.sock
    # unixsocketperm 700
    
    # 此参数为设置客户端空闲超过timeout，服务端会断开连接，为0则服务端不会主动断开连接，不能小于0
    timeout 0
    
    # TCP keepalive.
    #
    # tcp keepalive参数。如果设置不为0，就使用配置tcp的SO_KEEPALIVE值，使用keepalive有两个好处:检测挂
    # 掉的对端。降低中间设备出问题而导致网络看似连接却已经与对端端口的问题。在Linux内核中，设置了
    # keepalive，redis会定时给对端发送ack。检测到对端关闭需要两倍的设置值
    tcp-keepalive 300
    
    ################################# 一般 #####################################
    
    # 默认情况下，Redis不会作为守护程序运行。如果需要，请使用“是”。
    # 请注意，Redis守护进程将在/var/run/redis.pid中写入一个pid文件。
    daemonize no
    
    # If you run Redis from upstart or systemd, Redis can interact with your
    # supervision tree. Options:
    # supervised no - 没有监督互动
    # supervised upstart - 通过将Redis置于SIGSTOP模式来发出信号以指示upstart
    # supervised systemd - signal systemd by writing READY=1 to $NOTIFY_SOCKET
    # supervised auto - detect upstart or systemd method based on
    # UPSTART_JOB or NOTIFY_SOCKET environment variables
    # Note: these supervision methods only signal "process is ready."
    # They do not enable continuous liveness pings back to your supervisor.
    supervised no
    
    # 如果指定了pid文件，则Redis会在启动时将其写入指定位置
    # 并在退出时将其删除。
    #
    # 当服务器以非守护进程运行时，如果没有，则不创建pid文件
    # 在配置中指定。守护服务器时，pid文件
    # 即使未指定，也使用，默认为“ /var/run/redis.pid”。
    #
    # 创建pid文件是最大的努力：如果Redis无法创建它
    # 不会发生任何不良情况，服务器将启动并正常运行。
    #
    pidfile /var/run/redis_6379.pid
    
    # 指定了服务端日志的级别。
    # 级别包括：
    # debug（很多信息，方便开发、测试），
    # verbose（许多有用的信息，但是没有debug级别信息多），
    # notice（适当的日志级别，适合生产环境），
    # warn（只有非常重要的信息）
    loglevel notice
    
    # 指定日志文件名。也可以使用空字符串强制
    # Redis登录到标准输出。请注意，如果您使用标准
    # 输出用于日志记录但要守护进程，日志将发送到/dev/null
    logfile ""
    
    # 要启用到系统记录器的日志记录，只需将“ syslog-enabled”设置为yes，
    # 并根据需要更新其他syslog参数。
    # syslog-enabled no
    
    # 指定系统日志标识。
    # syslog-ident redis
    
    # 日志的来源、设备
    # syslog-facility local0
    
    # 数据库的数量，默认使用的数据库是0。可以通过”SELECT 【数据库序号】“命令选择一个数据库，序号从0开始
    databases 16
    
    # 默认情况下，Redis仅在开始登录时才显示ASCII艺术徽标。
    # 标准输出，如果标准输出是TTY。基本上这意味着
    # 通常徽标仅在交互式会话中显示。
    #
    # 但是，可以强制4.0之前的行为并始终显示
    # 通过将以下选项设置为yes，可以在启动日志中显示ASCII艺术徽标。
    always-show-logo yes
    
    ################################ 快照 ################################
    #
    # 存 DB 到磁盘：
    #
    # 格式：save <间隔时间（秒）> <写入次数>
    #
    # 根据给定的时间间隔和写入次数将数据保存到磁盘
    #
    # 下面的例子的意思是：
    # 900 秒内如果至少有 1 个 key 的值变化，则保存
    # 300 秒内如果至少有 10 个 key 的值变化，则保存
    # 60 秒内如果至少有 10000 个 key 的值变化，则保存
    #　　
    # 注意：你可以注释掉所有的 save 行来停用保存功能。
    # 也可以直接一个空字符串来实现停用：
    # save ""
    
    save 900 1
    save 300 10
    save 60 10000
    
    # 默认情况下，如果 redis 最后一次的后台保存失败，redis 将停止接受写操作，
    # 这样以一种强硬的方式让用户知道数据不能正确的持久化到磁盘，
    # 否则就会没人注意到灾难的发生。
    #
    # 如果后台保存进程重新启动工作了，redis 也将自动的允许写操作。
    #
    # 然而你要是安装了靠谱的监控，你可能不希望 redis 这样做，那你就改成 no 好了。
    # 当RDB持久化出现错误后，是否依然进行继续进行工作，yes：不能进行工作，no：可以继续进行工作，可以通
    # 过info中的rdb_last_bgsave_status了解RDB持久化是否有错误
    stop-writes-on-bgsave-error yes
    
    # 配置存储至本地数据库时是否压缩数据，默认为yes。Redis采用LZF压缩方式，但占用了一点CPU的时间。
    # 若关闭该选项，但会导致数据库文件变的巨大。建议开启
    rdbcompression yes
    
    # 是否校验rdb文件;从rdb格式的第五个版本开始，在rdb文件的末尾会带上CRC64的校验和。这跟有利于文件的
    # 容错性，但是在保存rdb文件的时候，会有大概10%的性能损耗，所以如果你追求高性能，可以关闭该配置
    rdbchecksum yes
    
    # 指定本地数据库文件名，一般采用默认的 dump.rdb
    dbfilename dump.rdb
    
    #数据目录，数据库的写入会在这个目录。rdb、aof文件也会写在这个目录
    dir /data
    
    ################################# 主从复制 #################################
    
    # 主副本复制。使用copyof作为Redis实例的副本
    # 另一个Redis服务器。尽快了解有关Redis复制的几件事。
    #
    # +------------------+ +---------------+
    # | Master | ---> | Replica |
    # | (receive writes) | | (exact copy) |
    # +------------------+ +---------------+
    #
    # 1) Redis复制是异步的，但是您可以将主服务器配置为
    # 如果看起来与至少没有连接，则停止接受写入
    # 给定数量的副本。
    # 2) Redis副本能够与以下服务器执行部分重新同步
    # 如果复制链接丢失相对较少的数量，则为master
    # 时间。您可能需要配置复制积压大小（请参阅下一个
    # 文件的各个部分），并根据您的需要提供合理的价值。
    # 3) 复制是自动的，不需要用户干预。之后
    # 网络分区副本会自动尝试重新连接到主服务器
    # 并与他们重新同步。
    #
    # 复制选项，slave复制对应的master
    # replicaof <masterip> <masterport>
    
    # 如果master设置了requirepass，那么slave要连上master，需要有master的密码才行。masterauth就是用来
    # 配置master的密码，这样可以在连上master后进行认证
    # masterauth <master-password>
    
    # 当副本失去与主数据库的连接或复制时
    # 该副本仍在进行中，可以以两种不同的方式起作用：
    #
    # 1) 如果复制副本服务过时数据设置为“是”（默认值），则复制副本将
    # 仍会回复客户请求，可能带有过期数据，或者
    # 如果这是第一次同步，则数据集可能只是空的。
    #
    # 2) 如果slave-serve-stale-data设置为no ,
    # INFO, replicaOF, AUTH, PING, SHUTDOWN, REPLCONF, ROLE, CONFIG,
    # SUBSCRIBE, UNSUBSCRIBE, PSUBSCRIBE, PUNSUBSCRIBE, PUBLISH, PUBSUB,
    # COMMAND, POST, HOST: and LATENCY.命令之外的任何请求都会返回一个错误”SYNC with master in progress”。
    #
    replica-serve-stale-data yes
    
    #作为从服务器，默认情况下是只读的（yes），可以修改成NO，用于写（不建议）
    replica-read-only yes
    
    
    # 是否使用socket方式复制数据。目前redis复制提供两种方式，disk和socket。
    # 如果新的slave连上来或者重连的slave无法部分同步，就会执行全量同步，master会生成rdb文件。
    # disk方式是master创建一个新的进程把rdb文件保存到磁盘，
    # 再把磁盘上的rdb文件传递给slave。socket是master创建一个新的进程，
    # 直接把rdb文件以socket的方式发给slave。disk方式的时候，当一个rdb保存的过程中，多个slave都能共享这个rdb文件。
    # socket的方式就的一个个slave顺序复制。在磁盘速度缓慢，网速快的情况下推荐用socket方式。
    repl-diskless-sync no
    
    # diskless复制的延迟时间，防止设置为0。一旦复制开始，节点不会再接收新slave的复制请求直到下一个rdb传输。
    # 所以最好等待一段时间，等更多的slave连上来
    repl-diskless-sync-delay 5
    
    # slave根据指定的时间间隔向服务器发送ping请求。时间间隔可以通过 repl_ping_slave_period 来设置，默认10秒
    # repl-ping-replica-period 10
    
    # 复制连接超时时间。
    # master和slave都有超时时间的设置。master检测到slave上次发送的时间超过repl-timeout，
    # 即认为slave离线，清除该slave信息。slave检测到上次和master交互的时间超过repl-timeout，
    # 则认为master离线。需要注意的是repl-timeout需要设置一个比repl-ping-slave-period更大的值，不然会经常检测到超时
    # repl-timeout 60
    
    # 是否禁止复制tcp链接的tcp nodelay参数，可传递yes或者no。默认是no，即使用tcp nodelay。
    # 如果master设置了yes来禁止tcp nodelay设置，在把数据复制给slave的时候，会减少包的数量和更小的网络带宽。
    # 但是这也可能带来数据的延迟。默认我们推荐更小的延迟，但是在数据量传输很大的场景下，建议选择yes
    repl-disable-tcp-nodelay no
    
    # 复制缓冲区大小，这是一个环形复制缓冲区，用来保存最新复制的命令。
    # 这样在slave离线的时候，不需要完全复制master的数据，如果可以执行部分同步，
    # 只需要把缓冲区的部分数据复制给slave，就能恢复正常复制状态。缓冲区的大小越大，slave离线的时间可以更长，
    # 复制缓冲区只有在有slave连接的时候才分配内存。没有slave的一段时间，内存会被释放出来，默认1m
    # repl-backlog-size 1mb
    
    # master没有slave一段时间会释放复制缓冲区的内存，repl-backlog-ttl用来设置该时间长度。单位为秒。
    # repl-backlog-ttl 3600
    
    # 当master不可用，Sentinel会根据slave的优先级选举一个master。最低的优先级的slave，
    # 当选master。而配置成0，永远不会被选举
    replica-priority 100
    
    # redis提供了可以让master停止写入的方式，
    # 如果配置了min-replicas-to-write，健康的slave的个数小于N，mater就禁止写入。
    # master最少得有多少个健康的slave存活才能执行写命令。这个配置虽然不能保证N个slave都一定能接收到master的写操作，但是能避免没有足够健康的slave的时候，master不能写入来避免数据丢失。设置为0是关闭该功能
    # min-replicas-to-write 3
    
    ## 延迟小于min-replicas-max-lag秒的slave才认为是健康的slave
    # min-replicas-max-lag 10
    #
    # 将一个或另一个设置为0将禁用该功能。
    #
    # 默认情况下，最小写入分钟数设置为0（禁用功能），并且
    # min-replicas-max-lag is set to 10.
    
    # Redis主服务器能够列出附件的地址和端口
    # 复制品的方式不同。例如，“ INFO复制”部分
    # 提供此信息，除其他工具外，该信息还用于
    # Redis Sentinel以发现副本实例。
    # 此信息可用的另一个地方是
    # 主机的“角色”命令。
    #
    # The listed IP and address normally reported by a replica is obtained
    # in the following way:
    #
    # IP: The address is auto detected by checking the peer address
    # of the socket used by the replica to connect with the master.
    #
    # Port: The port is communicated by the replica during the replication
    # handshake, and is normally the port that the replica is using to
    # listen for connections.
    #
    # However when port forwarding or Network Address Translation (NAT) is
    # used, the replica may be actually reachable via different IP and port
    # pairs. The following two options can be used by a replica in order to
    # report to its master a specific set of IP and port, so that both INFO
    # and ROLE will report those values.
    #
    # There is no need to use both the options if you need to override just
    # the port or the IP address.
    #
    # replica-announce-ip 5.5.5.5
    # replica-announce-port 1234
    
    ################################## 安全 ###################################
    
    # requirepass配置可以让用户使用AUTH命令来认证密码，才能使用其他命令。这让redis可以使用在不受信任的网络中。为了保持向后的兼容性，可以注释该命令，因为大部分用户也不需要认证。使用requirepass的时候需要
    requirepass mscmredis
    
    # Command renaming.
    #
    # It is possible to change the name of dangerous commands in a shared
    # environment. For instance the CONFIG command may be renamed into something
    # hard to guess so that it will still be available for internal-use tools
    # but not available for general clients.
    #
    # Example:
    #
    # rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
    #
    # It is also possible to completely kill a command by renaming it into
    # an empty string:
    #
    # rename-command CONFIG ""
    #
    # Please note that changing the name of commands that are logged into the
    # AOF file or transmitted to replicas may cause problems.
    
    ################################### 客户 ####################################
    
    # 设置能连上redis的最大客户端连接数量
    # 默认是10000个客户端连接。由于redis不区分连接是客户端连接还是内部打开文件或者和slave连接等，所以maxclients最小建议设置到32。如果超过了maxclients，redis会给新的连接发送’max number of clients reached’，并关闭连接
    # maxclients 10000
    
    ############################## 内存管理 ################################
    
    # redis配置的最大内存容量。当内存满了，需要配合maxmemory-policy策略进行处理。注意slave的输出缓冲区是不计算在maxmemory内的。所以为了防止主机内存使用完，建议设置的maxmemory需要更小一些
    # maxmemory <bytes>
    
    # 内存容量超过maxmemory后的处理策略。
    # volatile-lru：利用LRU算法移除设置过过期时间的key。
    # volatile-random：随机移除设置过过期时间的key。
    # volatile-ttl：移除即将过期的key，根据最近过期时间来删除（辅以TTL）
    # allkeys-lru：利用LRU算法移除任何key。
    # allkeys-random：随机移除任何key。
    # noeviction：不移除任何key，只是返回一个写错误。
    #上面的这些驱逐策略，如果redis没有合适的key驱逐，对于写命令，还是会返回错误。redis将不再接收写请求，只接收get请求。写命令包括：set setnx setex append incr decr rpush lpush rpushx lpushx linsert lset rpoplpush sadd sinter sinterstore sunion sunionstore sdiff sdiffstore zadd zincrby zunionstore zinterstore hset hsetnx hmset hincrby incrby decrby getset mset msetnx exec sort。
    # maxmemory-policy noeviction
    
    # lru检测的样本数。使用lru或者ttl淘汰算法，从需要淘汰的列表中随机选择sample个key，选出闲置时间最长的key移除
    # maxmemory-samples 5
    
    # 是否开启salve的最大内存
    # replica-ignore-maxmemory yes
    
    ############################# LAZY FREEING ####################################
    
    # Redis has two primitives to delete keys. One is called DEL and is a blocking
    # deletion of the object. It means that the server stops processing new commands
    # in order to reclaim all the memory associated with an object in a synchronous
    # way. If the key deleted is associated with a small object, the time needed
    # in order to execute the DEL command is very small and comparable to most other
    # O(1) or O(log_N) commands in Redis. However if the key is associated with an
    # aggregated value containing millions of elements, the server can block for
    # a long time (even seconds) in order to complete the operation.
    #
    # For the above reasons Redis also offers non blocking deletion primitives
    # such as UNLINK (non blocking DEL) and the ASYNC option of FLUSHALL and
    # FLUSHDB commands, in order to reclaim memory in background. Those commands
    # are executed in constant time. Another thread will incrementally free the
    # object in the background as fast as possible.
    #
    # DEL, UNLINK and ASYNC option of FLUSHALL and FLUSHDB are user-controlled.
    # It's up to the design of the application to understand when it is a good
    # idea to use one or the other. However the Redis server sometimes has to
    # delete keys or flush the whole database as a side effect of other operations.
    # Specifically Redis deletes objects independently of a user call in the
    # following scenarios:
    #
    # 1) On eviction, because of the maxmemory and maxmemory policy configurations,
    # in order to make room for new data, without going over the specified
    # memory limit.
    # 2) Because of expire: when a key with an associated time to live (see the
    # EXPIRE command) must be deleted from memory.
    # 3) Because of a side effect of a command that stores data on a key that may
    # already exist. For example the RENAME command may delete the old key
    # content when it is replaced with another one. Similarly SUNIONSTORE
    # or SORT with STORE option may delete existing keys. The SET command
    # itself removes any old content of the specified key in order to replace
    # it with the specified string.
    # 4) During replication, when a replica performs a full resynchronization with
    # its master, the content of the whole database is removed in order to
    # load the RDB file just transferred.
    #
    # In all the above cases the default is to delete objects in a blocking way,
    # like if DEL was called. However you can configure each case specifically
    # in order to instead release memory in a non-blocking way like if UNLINK
    # was called, using the following configuration directives:
    # 以非阻塞方式释放内存
    # 使用以下配置指令调用了
    lazyfree-lazy-eviction no
    lazyfree-lazy-expire no
    lazyfree-lazy-server-del no
    replica-lazy-flush no
    
    ############################## AOP持久化 ###############################
    
    # Redis 默认不开启。它的出现是为了弥补RDB的不足（数据的不一致性），
    # 所以它采用日志的形式来记录每个写操作，并追加到文件中。
    # Redis 重启的会根据日志文件的内容将写指令从前到后执行一次以完成数据的恢复工作默认redis使用的是rdb方式持久化，这种方式在许多应用中已经足够用了。
    # 但是redis如果中途宕机，会导致可能有几分钟的数据丢失，根据save来策略进行持久化，Append Only File是另一种持久化方式，可以提供更好的持久化特性。
    # Redis会把每次写入的数据在接收后都写入 appendonly.aof 文件，每次启动时Redis都会先把这个文件的数据读入内存里，先忽略RDB文件。若开启rdb则将no改为yes
    
    appendonly yes
    
    # The name of the append only file (default: "appendonly.aof")
    
    appendfilename "appendonly.aof"
    
    # aof持久化策略的配置
    # no表示不执行fsync，由操作系统保证数据同步到磁盘，速度最快
    # always表示每次写入都执行fsync，以保证数据同步到磁盘
    # everysec表示每秒执行一次fsync，可能会导致丢失这1s数据
    
    # appendfsync always
    appendfsync everysec
    # appendfsync no
    
    # 在aof重写或者写入rdb文件的时候，会执行大量IO，此时对于everysec和always的aof模式来说，执行fsync会造成阻塞过长时间，no-appendfsync-on-rewrite字段设置为默认设置为no。
    # 如果对延迟要求很高的应用，这个字段可以设置为yes，否则还是设置为no，这样对持久化特性来说这是更安全的选择。
    # 设置为yes表示rewrite期间对新写操作不fsync,暂时存在内存中,等rewrite完成后再写入，默认为no，建议yes。
    # Linux的默认fsync策略是30秒。可能丢失30秒数据
    no-appendfsync-on-rewrite no
    
    # aof自动重写配置。当目前aof文件大小超过上一次重写的aof文件大小的百分之多少进行重写，即当aof文件增长到一定大小的时候Redis能够调用bgrewriteaof对日志文件进行重写。
    # 当前AOF文件大小是上次日志重写得到AOF文件大小的二倍（设置为100）时，自动启动新的日志重写过程
    auto-aof-rewrite-percentage 100
    
    # 设置允许重写的最小aof文件大小，避免了达到约定百分比但尺寸仍然很小的情况还要重写
    auto-aof-rewrite-min-size 64mb
    
    # aof文件可能在尾部是不完整的，当redis启动的时候，aof文件的数据被载入内存。
    # 重启可能发生在redis所在的主机操作系统宕机后，尤其在ext4文件系统没有加上data=ordered选项（redis宕机或者异常终止不会造成尾部不完整现象。）出现这种现象，可以选择让redis退出，或者导入尽可能多的数据。如果选择的是yes，当截断的aof文件被导入的时候，会自动发布一个log给客户端然后load。如果是no，用户必须手动redis-check-aof修复AOF文件才可以
    aof-load-truncated yes
    
    # 加载redis时，可以识别AOF文件以“redis”开头。
    # 字符串并加载带前缀的RDB文件，然后继续加载AOF尾巴
    aof-use-rdb-preamble yes
    
    ################################ LUA SCRIPTING ###############################
    
    # Max execution time of a Lua script in milliseconds.
    #
    # If the maximum execution time is reached Redis will log that a script is
    # still in execution after the maximum allowed time and will start to
    # reply to queries with an error.
    #
    # When a long running script exceeds the maximum execution time only the
    # SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
    # used to stop a script that did not yet called write commands. The second
    # is the only way to shut down the server in the case a write command was
    # already issued by the script but the user doesn't want to wait for the natural
    # termination of the script.
    #
    # Set it to 0 or a negative value for unlimited execution without warnings.
    # 如果达到最大时间限制（毫秒），redis会记个log，然后返回error。当一个脚本超过了最大时限。只有SCRIPT KILL和SHUTDOWN NOSAVE可以用。第一个可以杀没有调write命令的东西。要是已经调用了write，只能用第二个命令杀
    lua-time-limit 5000
    
    ################################ REDIS 集群 ###############################
    
    # 集群开关，默认是不开启集群模式
    # cluster-enabled yes
    
    # 集群配置文件的名称，每个节点都有一个集群相关的配置文件，持久化保存集群的信息。
    # 这个文件并不需要手动配置，这个配置文件有Redis生成并更新，
    # 每个Redis集群节点需要一个单独的配置文件，请确保与实例运行的系统中配置文件名称不冲突
    # cluster-config-file nodes-6379.conf
    
    # 节点互连超时的阀值。集群节点超时毫秒数
    # cluster-node-timeout 15000
    
    # 在进行故障转移的时候，全部slave都会请求申请为master，
    # 但是有些slave可能与master断开连接一段时间了，导致数据过于陈旧，这样的slave不应该被提升为master。
    # 该参数就是用来判断slave节点与master断线的时间是否过长。判断方法是：
    # 比较slave断开连接的时间和
    # (node-timeout * cluster-replica-validity-factor) + cluster-replica-validity-factor
    # 如果节点超时时间为三十秒, 并且slave-validity-factor为10 30*10+10=310
    # 假设默认的repl-ping-slave-period是10秒，即如果超过310秒slave将不会尝试进行故障转移
    # cluster-replica-validity-factor 10
    
    # master的slave数量大于该值，slave才能迁移到其他孤立master上，如这个参数若被设为2，那么只有当一个主节点拥有2 个可工作的从节点时，它的一个从节点会尝试迁移
    # cluster-migration-barrier 1
    
    # 默认情况下，集群全部的slot有节点负责，集群状态才为ok，才能提供服务。设置为no，可以在slot没有全部分配的时候提供服务。不建议打开该配置，这样会造成分区的时候，小分区的master一直在接受写请求，而造成很长时间数据不一致
    # cluster-require-full-coverage yes
    
    # This option, when set to yes, prevents replicas from trying to failover its
    # master during master failures. However the master can still perform a
    # manual failover, if forced to do so.
    #
    # This is useful in different scenarios, especially in the case of multiple
    # data center operations, where we want one side to never be promoted if not
    # in the case of a total DC failure.
    #
    # cluster-replica-no-failover no
    
    # In order to setup your cluster make sure to read the documentation
    # available at http://redis.io web site.
    
    ########################## CLUSTER DOCKER/NAT support ########################
    
    # In certain deployments, Redis Cluster nodes address discovery fails, because
    # addresses are NAT-ted or because ports are forwarded (the typical case is
    # Docker and other containers).
    #
    # In order to make Redis Cluster working in such environments, a static
    # configuration where each node knows its public address is needed. The
    # following two options are used for this scope, and are:
    #
    # * cluster-announce-ip
    # * cluster-announce-port
    # * cluster-announce-bus-port
    #
    # Each instruct the node about its address, client port, and cluster message
    # bus port. The information is then published in the header of the bus packets
    # so that other nodes will be able to correctly map the address of the node
    # publishing the information.
    #
    # If the above options are not used, the normal Redis Cluster auto-detection
    # will be used instead.
    #
    # Note that when remapped, the bus port may not be at the fixed offset of
    # clients port + 10000, so you can specify any port and bus-port depending
    # on how they get remapped. If the bus-port is not set, a fixed offset of
    # 10000 will be used as usually.
    #
    # Example:
    #
    # 群集公告IP
    # 群集公告端口
    # 群集公告总线端口
    # cluster-announce-ip 10.1.1.5
    # cluster-announce-port 6379
    # cluster-announce-bus-port 6380
    
    ################################## SLOW LOG ###################################
    
    # slog log是用来记录redis运行中执行比较慢的命令耗时。当命令的执行超过了指定时间，就记录在slow log中，slog log保存在内存中，所以没有IO操作。
    # 执行时间比slowlog-log-slower-than大的请求记录到slowlog里面，单位是微秒，所以1000000就是1秒。注意，负数时间会禁用慢查询日志，而0则会强制记录所有命令。
    slowlog-log-slower-than 10000
    
    # 慢查询日志长度。当一个新的命令被写进日志的时候，最老的那个记录会被删掉。这个长度没有限制。只要有足够的内存就行。你可以通过 SLOWLOG RESET 来释放内存
    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.
    # 延迟监控功能是用来监控redis中执行比较缓慢的一些操作，用LATENCY打印redis实例在跑命令时的耗时图表。只记录大于等于下边设置的值的操作。0的话，就是关闭监视。默认延迟监控功能是关闭的，如果你需要打开，也可以通过CONFIG SET命令动态设置
    latency-monitor-threshold 0
    
    ############################# EVENT NOTIFICATION ##############################
    
    # Redis can notify Pub/Sub clients about events happening in the key space.
    # This feature is documented at http://redis.io/topics/notifications
    #
    # For instance if keyspace events notification is enabled, and a client
    # performs a DEL operation on key "foo" stored in the Database 0, two
    # messages will be published via Pub/Sub:
    #
    # PUBLISH __keyspace@0__:foo del
    # PUBLISH __keyevent@0__:del foo
    #
    # It is possible to select the events that Redis will notify among a set
    # of classes. Every class is identified by a single character:
    #
    # K Keyspace events, published with __keyspace@<db>__ prefix.
    # E Keyevent events, published with __keyevent@<db>__ prefix.
    # g Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
    # $ String commands
    # l List commands
    # s Set commands
    # h Hash commands
    # z Sorted set commands
    # x Expired events (events generated every time a key expires)
    # e Evicted events (events generated when a key is evicted for maxmemory)
    # A Alias for g$lshzxe, so that the "AKE" string means all the events.
    #
    # The "notify-keyspace-events" takes as argument a string that is composed
    # of zero or multiple characters. The empty string means that notifications
    # are disabled.
    #
    # Example: to enable list and generic events, from the point of view of the
    # event name, use:
    #
    # notify-keyspace-events Elg
    #
    # Example 2: to get the stream of the expired keys subscribing to channel
    # name __keyevent@0__:expired use:
    #
    # notify-keyspace-events Ex
    #
    # By default all notifications are disabled because most users don't need
    # this feature and the feature has some overhead. Note that if you don't
    # specify at least one of K or E, no events will be delivered.
    notify-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 512
    hash-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 -2
    
    # Lists may also be compressed.
    # Compress depth is the number of quicklist ziplist nodes from *each* side of
    # the list to *exclude* from compression. The head and tail of the list
    # are always uncompressed for fast push/pop operations. Settings are:
    # 0: disable all list compression
    # 1: depth 1 means "don't start compressing until after 1 node into the list,
    # going from either the head or tail"
    # So: [head]->node->node->...->node->[tail]
    # [head], [tail] will always be uncompressed; inner nodes will compress.
    # 2: [head]->[next]->node->node->...->node->[prev]->[tail]
    # 2 here means: don't compress head or head->next or tail->prev or tail,
    # but compress all nodes between them.
    # 3: [head]->[next]->[next]->node->node->...->node->[prev]->[prev]->[tail]
    # etc.
    list-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 128
    zset-max-ziplist-value 64
    
    # HyperLogLog sparse representation bytes limit. The limit includes the
    # 16 bytes header. When an HyperLogLog using the sparse representation crosses
    # this limit, it is converted into the dense representation.
    #
    # A value greater than 16000 is totally useless, since at that point the
    # dense representation is more memory efficient.
    #
    # The suggested value is ~ 3000 in order to have the benefits of
    # the space efficient encoding without slowing down too much PFADD,
    # which is O(N) with the sparse encoding. The value can be raised to
    # ~ 10000 when CPU is not a concern, but space is, and the data set is
    # composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
    hll-sparse-max-bytes 3000
    
    # Streams macro node max size / items. The stream data structure is a radix
    # tree of big nodes that encode multiple items inside. Using this configuration
    # it is possible to configure how big a single node can be in bytes, and the
    # maximum number of items it may contain before switching to a new node when
    # appending new stream entries. If any of the following settings are set to
    # zero, the limit is ignored, so for instance it is possible to set just a
    # max entires limit by setting max-bytes to 0 and max-entries to the desired
    # value.
    stream-node-max-bytes 4096
    stream-node-max-entries 100
    
    # Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
    # order to help rehashing the main Redis hash table (the one mapping top-level
    # keys to values). The hash table implementation Redis uses (see dict.c)
    # performs a lazy rehashing: the more operation you run into a hash table
    # that is rehashing, the more rehashing "steps" are performed, so if the
    # server is idle the rehashing is never complete and some more memory is used
    # by the hash table.
    #
    # The default is to use this millisecond 10 times every second in order to
    # actively rehash the main dictionaries, freeing memory when possible.
    #
    # If unsure:
    # use "activerehashing no" if you have hard latency requirements and it is
    # not a good thing in your environment that Redis can reply from time to time
    # to queries with 2 milliseconds delay.
    #
    # use "activerehashing yes" if you don't have such hard requirements but
    # want to free memory asap when possible.
    activerehashing yes
    
    # The client output buffer limits can be used to force disconnection of clients
    # that are not reading data from the server fast enough for some reason (a
    # common reason is that a Pub/Sub client can't consume messages as fast as the
    # publisher can produce them).
    #
    # The limit can be set differently for the three different classes of clients:
    #
    # normal -> normal clients including MONITOR clients
    # replica -> replica clients
    # pubsub -> clients subscribed to at least one pubsub channel or pattern
    #
    # The syntax of every client-output-buffer-limit directive is the following:
    #
    # client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
    #
    # A client is immediately disconnected once the hard limit is reached, or if
    # the soft limit is reached and remains reached for the specified number of
    # seconds (continuously).
    # So for instance if the hard limit is 32 megabytes and the soft limit is
    # 16 megabytes / 10 seconds, the client will get disconnected immediately
    # if the size of the output buffers reach 32 megabytes, but will also get
    # disconnected if the client reaches 16 megabytes and continuously overcomes
    # the limit for 10 seconds.
    #
    # By default normal clients are not limited because they don't receive data
    # without asking (in a push way), but just after a request, so only
    # asynchronous clients may create a scenario where data is requested faster
    # than it can read.
    #
    # Instead there is a default limit for pubsub and replica clients, since
    # subscribers and replicas receive data in a push fashion.
    #
    # Both the hard or the soft limit can be disabled by setting them to zero.
    client-output-buffer-limit normal 0 0 0
    client-output-buffer-limit replica 256mb 64mb 60
    client-output-buffer-limit pubsub 32mb 8mb 60
    
    # Client query buffers accumulate new commands. They are limited to a fixed
    # amount by default in order to avoid that a protocol desynchronization (for
    # instance due to a bug in the client) will lead to unbound memory usage in
    # the query buffer. However you can configure it here if you have very special
    # needs, such us huge multi/exec requests or alike.
    #
    # client-query-buffer-limit 1gb
    
    # In the Redis protocol, bulk requests, that are, elements representing single
    # strings, are normally limited ot 512 mb. However you can change this limit
    # here.
    #
    # proto-max-bulk-len 512mb
    
    # Redis calls an internal function to perform many background tasks, like
    # closing connections of clients in timeout, purging expired keys that are
    # never requested, and so forth.
    #
    # Not all tasks are performed with the same frequency, but Redis checks for
    # tasks to perform according to the specified "hz" value.
    #
    # By default "hz" is set to 10. Raising the value will use more CPU when
    # Redis is idle, but at the same time will make Redis more responsive when
    # there are many keys expiring at the same time, and timeouts may be
    # handled with more precision.
    #
    # The range is between 1 and 500, however a value over 100 is usually not
    # a good idea. Most users should use the default of 10 and raise this up to
    # 100 only in environments where very low latency is required.
    hz 10
    
    # Normally it is useful to have an HZ value which is proportional to the
    # number of clients connected. This is useful in order, for instance, to
    # avoid too many clients are processed for each background task invocation
    # in order to avoid latency spikes.
    #
    # Since the default HZ value by default is conservatively set to 10, Redis
    # offers, and enables by default, the ability to use an adaptive HZ value
    # which will temporary raise when there are many connected clients.
    #
    # When dynamic HZ is enabled, the actual configured HZ will be used as
    # as a baseline, but multiples of the configured HZ value will be actually
    # used as needed once more clients are connected. In this way an idle
    # instance will use very little CPU time while a busy instance will be
    # more responsive.
    dynamic-hz yes
    
    # When a child rewrites the AOF file, if the following option is enabled
    # the file will be fsync-ed every 32 MB of data generated. This is useful
    # in order to commit the file to the disk more incrementally and avoid
    # big latency spikes.
    aof-rewrite-incremental-fsync yes
    
    # When redis saves RDB file, if the following option is enabled
    # the file will be fsync-ed every 32 MB of data generated. This is useful
    # in order to commit the file to the disk more incrementally and avoid
    # big latency spikes.
    rdb-save-incremental-fsync yes
    
    # Redis LFU eviction (see maxmemory setting) can be tuned. However it is a good
    # idea to start with the default settings and only change them after investigating
    # how to improve the performances and how the keys LFU change over time, which
    # is possible to inspect via the OBJECT FREQ command.
    #
    # There are two tunable parameters in the Redis LFU implementation: the
    # counter logarithm factor and the counter decay time. It is important to
    # understand what the two parameters mean before changing them.
    #
    # The LFU counter is just 8 bits per key, it's maximum value is 255, so Redis
    # uses a probabilistic increment with logarithmic behavior. Given the value
    # of the old counter, when a key is accessed, the counter is incremented in
    # this way:
    #
    # 1. A random number R between 0 and 1 is extracted.
    # 2. A probability P is calculated as 1/(old_value*lfu_log_factor+1).
    # 3. The counter is incremented only if R < P.
    #
    # The default lfu-log-factor is 10. This is a table of how the frequency
    # counter changes with a different number of accesses with different
    # logarithmic factors:
    #
    # +--------+------------+------------+------------+------------+------------+
    # | factor | 100 hits | 1000 hits | 100K hits | 1M hits | 10M hits |
    # +--------+------------+------------+------------+------------+------------+
    # | 0 | 104 | 255 | 255 | 255 | 255 |
    # +--------+------------+------------+------------+------------+------------+
    # | 1 | 18 | 49 | 255 | 255 | 255 |
    # +--------+------------+------------+------------+------------+------------+
    # | 10 | 10 | 18 | 142 | 255 | 255 |
    # +--------+------------+------------+------------+------------+------------+
    # | 100 | 8 | 11 | 49 | 143 | 255 |
    # +--------+------------+------------+------------+------------+------------+
    #
    # NOTE: The above table was obtained by running the following commands:
    #
    # redis-benchmark -n 1000000 incr foo
    # redis-cli object freq foo
    #
    # NOTE 2: The counter initial value is 5 in order to give new objects a chance
    # to accumulate hits.
    #
    # The counter decay time is the time, in minutes, that must elapse in order
    # for the key counter to be divided by two (or decremented if it has a value
    # less <= 10).
    #
    # The default value for the lfu-decay-time is 1. A Special value of 0 means to
    # decay the counter every time it happens to be scanned.
    #
    # lfu-log-factor 10
    # lfu-decay-time 1
    
    ########################### ACTIVE DEFRAGMENTATION #######################
    #
    # WARNING THIS FEATURE IS EXPERIMENTAL. However it was stress tested
    # even in production and manually tested by multiple engineers for some
    # time.
    #
    # What is active defragmentation?
    # -------------------------------
    #
    # Active (online) defragmentation allows a Redis server to compact the
    # spaces left between small allocations and deallocations of data in memory,
    # thus allowing to reclaim back memory.
    #
    # Fragmentation is a natural process that happens with every allocator (but
    # less so with Jemalloc, fortunately) and certain workloads. Normally a server
    # restart is needed in order to lower the fragmentation, or at least to flush
    # away all the data and create it again. However thanks to this feature
    # implemented by Oran Agra for Redis 4.0 this process can happen at runtime
    # in an "hot" way, while the server is running.
    #
    # Basically when the fragmentation is over a certain level (see the
    # configuration options below) Redis will start to create new copies of the
    # values in contiguous memory regions by exploiting certain specific Jemalloc
    # features (in order to understand if an allocation is causing fragmentation
    # and to allocate it in a better place), and at the same time, will release the
    # old copies of the data. This process, repeated incrementally for all the keys
    # will cause the fragmentation to drop back to normal values.
    #
    # Important things to understand:
    #
    # 1. This feature is disabled by default, and only works if you compiled Redis
    # to use the copy of Jemalloc we ship with the source code of Redis.
    # This is the default with Linux builds.
    #
    # 2. You never need to enable this feature if you don't have fragmentation
    # issues.
    #
    # 3. Once you experience fragmentation, you can enable this feature when
    # needed with the command "CONFIG SET activedefrag yes".
    #
    # The configuration parameters are able to fine tune the behavior of the
    # defragmentation process. If you are not sure about what they mean it is
    # a good idea to leave the defaults untouched.
    
    # Enabled active defragmentation
    # activedefrag yes
    
    # Minimum amount of fragmentation waste to start active defrag
    # active-defrag-ignore-bytes 100mb
    
    # Minimum percentage of fragmentation to start active defrag
    # active-defrag-threshold-lower 10
    
    # Maximum percentage of fragmentation at which we use maximum effort
    # active-defrag-threshold-upper 100
    
    # Minimal effort for defrag in CPU percentage
    # active-defrag-cycle-min 5
    
    # Maximal effort for defrag in CPU percentage
    # active-defrag-cycle-max 75
    
    # Maximum number of set/hash/zset/list fields that will be processed from
    # the main dictionary scan
    # active-defrag-max-scan-fields 1000