Redis基础--Redis 4.0 常用配置

约定不等于承诺〃 2022-05-18 03:09 68阅读 0赞

# Redis configuration file example.
    #
    # Note that in order to read the configuration file, Redis must be
    # started with the file path as first argument:
    # 
    # 启动 Redis 时读取指定的 redis.conf 配置。
    # 配置文件的路径必须作为 Redis 启动命令后的第一个参数。
    # ./redis-server /path/to/redis.conf
    #
    # Note on units: when memory size is needed, it is possible to specify
    # it in the usual form of 1k 5GB 4M and so forth:
    #
    # 关于单位: 当为某个配置项指定内存大小的时候，必须要带上单位。
    # 常见的格式例如 1k 5GB 4M 等等:
    #
    # 1k => 1000 bytes
    # 1kb => 1024 bytes
    # 1m => 1000000 bytes
    # 1mb => 1024*1024 bytes
    # 1g => 1000000000 bytes
    # 1gb => 1024*1024*1024 bytes
    #
    # units are case insensitive so 1GB 1Gb 1gB are all the same.
    #
    # 单位是不区分大小写的，所以写 1GB 1Gb 1gB 效果都是一样的。
    
    ################################## INCLUDES ###################################
    
    # Include one or more other config files here.  This is useful if you
    # have a standard template that goes to all Redis servers but also need
    # to customize a few per-server settings.  Include files can include
    # other files, so use this wisely.
    #
    # Notice option "include" won't be rewritten by command "CONFIG REWRITE"
    # from admin or Redis Sentinel. Since Redis always uses the last processed
    # line as value of a configuration directive, you'd better put includes
    # at the beginning of this file to avoid overwriting config change at runtime.
    #
    # If instead you are interested in using includes to override configuration
    # options, it is better to use include as the last line.
    #
    # redis.conf 配置中还可以引用其他的配置文件，
    # 这在当你有一个标准配置模板要应用到所有 Redis 服务器，
    # 但又需要对其中的单个服务器做少量的个性化配置时会非常有用。
    # 
    # 注意：通过 "include" 引用的配置项将不能被来自 admin 和 哨兵 的 "CONFIG REWRITE" 命令重写。
    # 由于 Redis 总是使用最后处理的行作为配置指令的值，
    # 所以你最好把 INCLUDES 放在该配置文件的开头以避免覆盖掉运行期会发生变化的配置。
    #
    # 如果你是想要使用 "include" 来覆盖某些配置选项，那么把 INCLUDES 放在该配置文件的最后一行会比较好。
    #
    # include /path/to/local.conf
    # include /path/to/other.conf
    
    ################################## MODULES #####################################
    
    # Load modules at startup. If the server is not able to load modules
    # it will abort. It is possible to use multiple loadmodule directives.
    #
    # 启动时加载模块，如果服务器不能成功加载模块的话将会中止。
    # 此处允许执行多条 "loadmodule" 指令。
    # 
    # loadmodule /path/to/my_module.so
    # loadmodule /path/to/other_module.so
    
    ################################## NETWORK #####################################
    
    # By default, if no "bind" configuration directive is specified, Redis listens
    # for connections from all the network interfaces available on the server.
    # It is possible to listen to just one or multiple selected interfaces using
    # the "bind" configuration directive, followed by one or more IP addresses.
    #
    # 默认情况下，如果没有指定任何的 "bind" 指令，Redis 将监听来自该服务器所有可用网卡的连接请求。
    # 使用 "bind" 配置指令后面跟上一个或者多个 IP 地址来让 Redis 只监听选定的一个或者多个网卡。
    # 
    # Examples:
    #
    # bind 192.168.1.100 10.0.0.1
    # bind 127.0.0.1 ::1
    #
    # ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the
    # internet, binding to all the interfaces is dangerous and will expose the
    # instance to everybody on the internet. So by default we uncomment the
    # following bind directive, that will force Redis to listen only into
    # the IPv4 lookback interface address (this means Redis will be able to
    # accept connections only from clients running into the same computer it
    # is running).
    #
    # ~~~ 警告 ~~~ 如果运行 Redis 的服务器直接暴露在网络上，绑定所有的网卡是非常危险的，它会将 Redis 实例暴露给网络上的所有人。
    # 缺省情况下，我们并不建议使用下面这条 "bind" 配置指令，它会迫使 Redis 只监听 IPv4 回环网卡地址
    # （这就意味着， Redis 将只能接收那些与 Redis 服务器运行在同一台计算机上的客户端的连接请求）。
    #
    #
    # IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES
    # JUST COMMENT THE FOLLOWING LINE.
    # 如果你想要 Redis 监听所有的网卡，只需要注释掉下面这行"bind" 配置指令即可。
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    bind 127.0.0.1
    
    # Protected mode is a layer of security protection, in order to avoid that
    # Redis instances left open on the internet are accessed and exploited.
    #
    # 保护模式是一个安全防护层，其目的在于避免对互联网开放的 Redis 实例被访问和使用。
    # 
    # When protected mode is on and if:
    #
    # 1) The server is not binding explicitly to a set of addresses using the
    #    "bind" directive.
    # 2) No password is configured.
    # 
    # 当保护模式开启，并且满足以下条件:
    #
    # 1) 服务器并未使用 "bind" 配置指令明确地绑定某些地址。
    # 2) 未设置密码。
    #
    # The server only accepts connections from clients connecting from the
    # IPv4 and IPv6 loopback addresses 127.0.0.1 and ::1, and from Unix domain
    # sockets.
    #
    # Redis 服务器将只接收来自以下地址的连接请求：
    # IPv4 回环网卡地址 127.0.0.1 
    # IPv6 回环网卡地址 ::1
    # Unix domain 套接字
    #
    #
    # By default protected mode is enabled. You should disable it only if
    # you are sure you want clients from other hosts to connect to Redis
    # even if no authentication is configured, nor a specific set of interfaces
    # are explicitly listed using the "bind" directive.
    protected-mode yes
    
    # Accept connections on the specified port, default is 6379 (IANA #815344).
    # If port 0 is specified Redis will not listen on a TCP socket.
    # 
    # 接收指定端口的连接请求, 缺省 6379 。
    # 如果设置为 0 ，Redis  将不会监听任何 TCP socket 连接。
    port 6379
    
    # TCP listen() backlog.
    #
    # In high requests-per-second environments you need an high backlog in order
    # to avoid slow clients connections issues. Note that the Linux kernel
    # will silently truncate it to the value of /proc/sys/net/core/somaxconn so
    # make sure to raise both the value of somaxconn and tcp_max_syn_backlog
    # in order to get the desired effect.
    #
    # 在高并发的环境下，你需要把这个值调高以避免客户端连接缓慢的问题。
    # Linux 内核会自动地把这个值缩小成 /proc/sys/net/core/somaxconn 中的较小值，
    # 所以你需要同时调高 somaxconn 和 tcp_max_syn_backlog 的值来达到想要的效果。
    # 
    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.
    #
    # 指定用来监听连接的 Unix socket 的路径。
    # 该配置没有缺省值, 如果你未指定 Redis 将不会对 Unix socket 进行监听。
    #
    # unixsocket /tmp/redis.sock
    # unixsocketperm 700
    
    # Close the connection after a client is idle for N seconds (0 to disable)
    # 
    # 当客户端连接闲置 N 秒后关闭连接 (0 不关闭)
    timeout 0
    
    # TCP keepalive.
    #
    # If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
    # of communication. This is useful for two reasons:
    #
    # 1) Detect dead peers.
    # 2) Take the connection alive from the point of view of network
    #    equipment in the middle.
    #
    # On Linux, the specified value (in seconds) is the period used to send ACKs.
    # Note that to close the connection the double of the time is needed.
    # On other kernels the period depends on the kernel configuration.
    #
    # A reasonable value for this option is 300 seconds, which is the new
    # Redis default starting with Redis 3.2.1.
    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.
    # 
    # 缺省情况下，Redis 是作为非守护进程启动的. Redis 作为守护进程启动需要配置为 'yes' 。
    # 当 Redis 作为守护进程启动时会在 /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      - no supervision interaction
    #   supervised upstart - signal upstart by putting Redis into SIGSTOP mode
    #   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
    
    # If a pid file is specified, Redis writes it where specified at startup
    # and removes it at exit.
    #
    # 如果指定了 PID 文件，Redis 会在启动时写入并在退出时删除它。
    #
    # When the server runs non daemonized, no pid file is created if none is
    # specified in the configuration. When the server is daemonized, the pid file
    # is used even if not specified, defaulting to "/var/run/redis.pid".
    #
    # 如果 Redis 不是作为守护进程启动，如果不指定 PID 文件的话，将不会创建 PID 文件。
    # 当 Redis 作为守护进程启动时，即使不指定 PID 文件，也会默认在 "/var/run/redis.pid" 中创建 PID 文件。
    # is used even if not specified, defaulting to "/var/run/redis.pid".
    #
    # Creating a pid file is best effort: if Redis is not able to create it
    # nothing bad happens, the server will start and run normally.
    #
    # Redis 服务器会尽最大努力创建 PID 文件: 如果 PID 文件创建失败也不会产生什么坏影响，服务器依旧会正常启动和运行。
    pidfile /var/run/redis_6379.pid
    
    # Specify the server verbosity level.
    # 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
    
    # Specify the log file name. Also the empty string can be used to force
    # Redis to log on the standard output. Note that if you use standard
    # output for logging but daemonize, logs will be sent to /dev/null
    # 指定日志文件名称。如果指定的是空字符串的话，Redis 会使用标准输出记录日志。
    # 但是当 Redis 以守护进程启动时，依旧使用标准输出记录日志的话，日志将被发送到 /dev/null ，不作输出。
    # Redis to log on the standard output. Note that if you use standard
    # output for logging but daemonize, logs will be sent to /dev/null
    logfile ""
    
    # To enable logging to the system logger, just set 'syslog-enabled' to yes,
    # and optionally update the other syslog parameters to suit your needs.
    # syslog-enabled no
    
    # Specify the syslog identity.
    # syslog-ident redis
    
    # Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
    # syslog-facility local0
    
    # Set the number of databases. The default database is DB 0, you can select
    # a different one on a per-connection basis using SELECT <dbid> where
    # dbid is a number between 0 and 'databases'-1
    # 
    # 设置数据库数量。默认会使用 0 数据库，也可以使用  SELECT <dbid> 指令为每个连接选择不同的数据库，
    # 其中 dbid 的取值在 0 和 （'databases' 设置值）-1 之间
    databases 16
    
    # By default Redis shows an ASCII art logo only when started to log to the
    # standard output and if the standard output is a TTY. Basically this means
    # that normally a logo is displayed only in interactive sessions.
    #
    # However it is possible to force the pre-4.0 behavior and always show a
    # ASCII art logo in startup logs by setting the following option to yes.
    always-show-logo yes
    
    ################################ SNAPSHOTTING  ################################
    #
    # Save the DB on disk（将数据保存到磁盘）:
    #
    #   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 1
    save 300 10
    save 60 10000
    
    # By default Redis will stop accepting writes if RDB snapshots are enabled
    # (at least one save point) and the latest background save failed.
    # This will make the user aware (in a hard way) that data is not persisting
    # on disk properly, otherwise chances are that no one will notice and some
    # disaster will happen.
    # 
    # 缺省情况下，如果 RDB 快照被启用（至少有一个存储点）时，若后台保存快照失败，Redis 将拒绝接受写入。
    # 这将会促使用户发现（以一种强硬的方式）数据持久化到磁盘出问题了，否则，很有可能没人会注意到这一点，最终带来灾难性的后果。
    #
    # If the background saving process will start working again Redis will
    # automatically allow writes again.
    #
    # However if you have setup your proper monitoring of the Redis server
    # and persistence, you may want to disable this feature so that Redis will
    # continue to work as usual even if there are problems with disk,
    # permissions, and so forth.
    stop-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.
    # 
    # 当导出 .rdb 数据库时，是否对字符串对象采用 LZF 进行压缩。
    # 由于进行压缩在多数情况下效果都比较好，所以，该配置的缺省值为 'yes' 。
    # 如果你想要节省点 CPU ，可以将其改为  'no' ，相应地，如果你的数据集里面包含较多可压缩的键或值时，保存的数据集很有可能会比较大。
    rdbcompression yes
    
    # Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
    # This makes the format more resistant to corruption but there is a performance
    # hit to pay (around 10%) when saving and loading RDB files, so you can disable it
    # for maximum performances.
    #
    # 从 RDB 5 版开始，CRC64 和校验被添加到了 .rdb 文件的末尾。
    # 这样做可以使 .rdb 文件变得更加不容易损坏，但相应地，在文件保存和加载的时候也会消耗更多服务器性能（大概10%）。
    # 所以，如果你想要追求最佳的服务器性能，你可以将它关闭掉。
    #
    # RDB files created with checksum disabled have a checksum of zero that will
    # tell the loading code to skip the check.
    rdbchecksum yes
    
    # The filename where to dump the DB
    # 导出的 .rdb 文件名称
    dbfilename dump.rdb
    
    # The working directory.
    #
    # The DB will be written inside this directory, with the filename specified
    # above using the 'dbfilename' configuration directive.
    # 
    # 导出的 .rdb 文件将会被写入到此目录，文件名称即为  'dbfilename' 配置的文件名。
    #
    # The Append Only File will also be created inside this directory.
    #
    # Note that you must specify a directory here, not a file name.
    dir ./
    
    ################################# REPLICATION #################################
    
    # Master-Slave replication. Use slaveof to make a Redis instance a copy of
    # another Redis server. A few things to understand ASAP about Redis replication.
    #
    # 1) Redis replication is asynchronous, but you can configure a master to
    #    stop accepting writes if it appears to be not connected with at least
    #    a given number of slaves.
    # 2) Redis slaves are able to perform a partial resynchronization with the
    #    master if the replication link is lost for a relatively small amount of
    #    time. You may want to configure the replication backlog size (see the next
    #    sections of this file) with a sensible value depending on your needs.
    # 3) Replication is automatic and does not need user intervention. After a
    #    network partition slaves automatically try to reconnect to masters
    #    and resynchronize with them.
    #
    # 主从复制，可以通过 "slaveof" 配置指令将某个 Redis 节点设置为另外一个 Redis 节点的备份。
    #
    # slaveof <masterip> <masterport>
    
    # If the master is password protected (using the "requirepass" configuration
    # directive below) it is possible to tell the slave to authenticate before
    # starting the replication synchronization process, otherwise the master will
    # refuse the slave request.
    #
    # 如果主节点开启了密码保护 (使用下面的 "requirepass" 配置指令进行配置)， 
    # 主节点在从节点在开始同步复制过程之前可能会通知从节点进行认证，否则，主节点将会拒绝从节点的请求。
    #
    # masterauth <master-password>
    
    # When a slave loses its connection with the master, or when the replication
    # is still in progress, the slave can act in two different ways:
    #
    # 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will
    #    still reply to client requests, possibly with out of date data, or the
    #    data set may just be empty if this is the first synchronization.
    #
    # 2) if slave-serve-stale-data is set to 'no' the slave will reply with
    #    an error "SYNC with master in progress" to all the kind of commands
    #    but to INFO and SLAVEOF.
    #
    # 当一个从节点与主节点失去连接时，或者当复制还在进行时，从节点可以有以下两种表现方式：
    #
    # 1) 当 slave-serve-stale-data 被设置为 'yes' (默认值) ，从节点将仍然能够回复客户端的请求，
    #    但有可能回复的是过期的数据，亦或者如果这是第一次数据同步的话将只会返回空值。
    #
    # 2) 当 slave-serve-stale-data 被设置为 'no' ，从节点对于除 INFO 和 SLAVEOF 之外的所有请求命令，
    #    都将返回一个 "SYNC with master in progress" 错误。
    #
    slave-serve-stale-data yes
    
    # You can configure a slave instance to accept writes or not. Writing against
    # a slave instance may be useful to store some ephemeral data (because data
    # written on a slave will be easily deleted after resync with the master) but
    # may also cause problems if clients are writing to it because of a
    # misconfiguration.
    #
    # Since Redis 2.6 by default slaves are read-only.
    #
    # Note: read only slaves are not designed to be exposed to untrusted clients
    # on the internet. It's just a protection layer against misuse of the instance.
    # Still a read only slave exports by default all the administrative commands
    # such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
    # security of read only slaves using 'rename-command' to shadow all the
    # administrative / dangerous commands.
    slave-read-only yes
    
    # Replication SYNC strategy: disk or socket.
    #
    # -------------------------------------------------------
    # WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
    # -------------------------------------------------------
    #
    # New slaves and reconnecting slaves that are not able to continue the replication
    # process just receiving differences, need to do what is called a "full
    # synchronization". An RDB file is transmitted from the master to the slaves.
    # The transmission can happen in two different ways:
    #
    # 1) Disk-backed: The Redis master creates a new process that writes the RDB
    #                 file on disk. Later the file is transferred by the parent
    #                 process to the slaves incrementally.
    # 2) Diskless: The Redis master creates a new process that directly writes the
    #              RDB file to slave sockets, without touching the disk at all.
    #
    # With disk-backed replication, while the RDB file is generated, more slaves
    # can be queued and served with the RDB file as soon as the current child producing
    # the RDB file finishes its work. With diskless replication instead once
    # the transfer starts, new slaves arriving will be queued and a new transfer
    # will start when the current one terminates.
    #
    # When diskless replication is used, the master waits a configurable amount of
    # time (in seconds) before starting the transfer in the hope that multiple slaves
    # will arrive and the transfer can be parallelized.
    #
    # With slow disks and fast (large bandwidth) networks, diskless replication
    # works better.
    repl-diskless-sync no
    
    # When diskless replication is enabled, it is possible to configure the delay
    # the server waits in order to spawn the child that transfers the RDB via socket
    # to the slaves.
    #
    # This is important since once the transfer starts, it is not possible to serve
    # new slaves arriving, that will be queued for the next RDB transfer, so the server
    # waits a delay in order to let more slaves arrive.
    #
    # The delay is specified in seconds, and by default is 5 seconds. To disable
    # it entirely just set it to 0 seconds and the transfer will start ASAP.
    repl-diskless-sync-delay 5
    
    # Slaves send PINGs to server in a predefined interval. It's possible to change
    # this interval with the repl_ping_slave_period option. The default value is 10
    # seconds.
    #
    # 从节点按照一个预先定义的时间间隔来向主节点发送 PING 指令，
    # 时间间隔可以通过 repl_ping_slave_period 选项来配置，缺省值是 10 秒。
    #
    # repl-ping-slave-period 10
    
    # The following option sets the replication timeout for:
    #
    # 1) Bulk transfer I/O during SYNC, from the point of view of slave.
    # 2) Master timeout from the point of view of slaves (data, pings).
    # 3) Slave timeout from the point of view of masters (REPLCONF ACK pings).
    #
    # It is important to make sure that this value is greater than the value
    # specified for repl-ping-slave-period otherwise a timeout will be detected
    # every time there is low traffic between the master and the slave.
    #
    # 注意一定要确保复制超时时间必须大于 repl-ping-slave-period 选项的配置时间，
    # 否则，主节点和从节点的每一次同步都会被检测到超时。
    #
    # repl-timeout 60
    
    # Disable TCP_NODELAY on the slave socket after SYNC?
    #
    # If you select "yes" Redis will use a smaller number of TCP packets and
    # less bandwidth to send data to slaves. But this can add a delay for
    # the data to appear on the slave side, up to 40 milliseconds with
    # Linux kernels using a default configuration.
    #
    # 当 repl-disable-tcp-nodelay 被设置为 "yes" ，Redis 将使用更小的 TCP 包和更少的带宽向从节点发送数据。
    # 但是这样做会使得数据在从节点中的出现增加一定延迟时间，在 Linux 内核缺省配置下延迟可达 40 毫秒。
    #
    # If you select "no" the delay for data to appear on the slave side will
    # be reduced but more bandwidth will be used for replication.
    #
    # By default we optimize for low latency, but in very high traffic conditions
    # or when the master and slaves are many hops away, turning this to "yes" may
    # be a good idea.
    repl-disable-tcp-nodelay no
    
    # Set the replication backlog size. The backlog is a buffer that accumulates
    # slave data when slaves are disconnected for some time, so that when a slave
    # wants to reconnect again, often a full resync is not needed, but a partial
    # resync is enough, just passing the portion of data the slave missed while
    # disconnected.
    #
    # The bigger the replication backlog, the longer the time the slave can be
    # disconnected and later be able to perform a partial resynchronization.
    #
    # 复制储备的空间越大，从节点能够和主节点断开的时间就越长，能够执行部分再同步的时间就越晚。
    #
    # The backlog is only allocated once there is at least a slave connected.
    #
    # repl-backlog-size 1mb
    
    # After a master has no longer connected slaves for some time, the backlog
    # will be freed. The following option configures the amount of seconds that
    # need to elapse, starting from the time the last slave disconnected, for
    # the backlog buffer to be freed.
    #
    # Note that slaves never free the backlog for timeout, since they may be
    # promoted to masters later, and should be able to correctly "partially
    # resynchronize" with the slaves: hence they should always accumulate backlog.
    #
    # A value of 0 means to never release the backlog.
    #
    # repl-backlog-ttl 3600
    
    # The slave priority is an integer number published by Redis in the INFO output.
    # It is used by Redis Sentinel in order to select a slave to promote into a
    # master if the master is no longer working correctly.
    #
    # A slave with a low priority number is considered better for promotion, so
    # for instance if there are three slaves with priority 10, 100, 25 Sentinel will
    # pick the one with priority 10, that is the lowest.
    #
    # 优先级数字越小的从节点会被认为是更应被提拔，
    # 所以如果有三个优先级数字分别为 10 、100、25的从节点的话，将会选择提拔优先级数字为 10 的从节点，
    # 将会选择提拔优先级数字为 10 的从节点。
    #
    # However a special priority of 0 marks the slave as not able to perform the
    # role of master, so a slave with priority of 0 will never be selected by
    # Redis Sentinel for promotion.
    #
    # By default the priority is 100.
    slave-priority 100
    
    # It is possible for a master to stop accepting writes if there are less than
    # N slaves connected, having a lag less or equal than M seconds.
    #
    # 当与一个主节点相连接的从节点数量在 M 秒时间间隔内少于 N 的话，主节点将停止接收写操作。
    #
    # The N slaves need to be in "online" state.
    #
    # The lag in seconds, that must be <= the specified value, is calculated from
    # the last ping received from the slave, that is usually sent every second.
    #
    # This option does not GUARANTEE that N replicas will accept the write, but
    # will limit the window of exposure for lost writes in case not enough slaves
    # are available, to the specified number of seconds.
    #
    # For example to require at least 3 slaves with a lag <= 10 seconds use:
    #
    # min-slaves-to-write 3
    # min-slaves-max-lag 10
    #
    # Setting one or the other to 0 disables the feature.
    #
    # By default min-slaves-to-write is set to 0 (feature disabled) and
    # min-slaves-max-lag is set to 10.
    # min-slaves-to-write 缺省值为 0 (禁用此特性) and min-slaves-max-lag 缺省值为 10。
    
    # A Redis master is able to list the address and port of the attached
    # slaves in different ways. For example the "INFO replication" section
    # offers this information, which is used, among other tools, by
    # Redis Sentinel in order to discover slave instances.
    # Another place where this info is available is in the output of the
    # "ROLE" command of a master.
    #
    # The listed IP and address normally reported by a slave is obtained
    # in the following way:
    #
    #   IP: The address is auto detected by checking the peer address
    #   of the socket used by the slave to connect with the master.
    #
    #   Port: The port is communicated by the slave during the replication
    #   handshake, and is normally the port that the slave is using to
    #   list for connections.
    #
    # However when port forwarding or Network Address Translation (NAT) is
    # used, the slave may be actually reachable via different IP and port
    # pairs. The following two options can be used by a slave 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.
    #
    # slave-announce-ip 5.5.5.5
    # slave-announce-port 1234
    
    ################################## SECURITY ###################################
    
    
    # Require clients to issue AUTH <PASSWORD> before processing any other
    # commands.  This might be useful in environments in which you do not trust
    # others with access to the host running redis-server.
    #
    # 客户端在处理任何命令的时候都必须先执行 AUTH <PASSWORD> 进行认证。
    # 
    # This should stay commented out for backward compatibility and because most
    # people do not need auth (e.g. they run their own servers).
    #
    # Warning: since Redis is pretty fast an outside user can try up to
    # 150k passwords per second against a good box. This means that you should
    # use a very strong password otherwise it will be very easy to break.
    #
    # requirepass foobared
    
    # 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.
    #
    # 在一个公共环境下，我们还可以对一些危险操作的命令进行改名。
    # 以 CONFIG 命令为例，我们可以把它改成一些很难被猜到的内容，
    # 这样做的话，CONFIG 命令仍然能够被内部专用的工具所使用，但普通的客户端就不能再使用它了。
    #
    # 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 slaves may cause problems.
    
    ################################### CLIENTS ####################################
    
    # Set the max number of connected clients at the same time. By default
    # this limit is set to 10000 clients, however if the Redis server is not
    # able to configure the process file limit to allow for the specified limit
    # the max number of allowed clients is set to the current file limit
    # minus 32 (as Redis reserves a few file descriptors for internal uses).
    #
    # Once the limit is reached Redis will close all the new connections sending
    # an error 'max number of clients reached'.
    #
    # maxclients 10000
    
    ############################## MEMORY MANAGEMENT ################################
    
    # Set a memory usage limit to the specified amount of bytes.
    # When the memory limit is reached Redis will try to remove keys
    # according to the eviction policy selected (see maxmemory-policy).
    #
    # If Redis can't remove keys according to the policy, or if the policy is
    # set to 'noeviction', Redis will start to reply with errors to commands
    # that would use more memory, like SET, LPUSH, and so on, and will continue
    # to reply to read-only commands like GET.
    #
    # This option is usually useful when using Redis as an LRU or LFU cache, or to
    # set a hard memory limit for an instance (using the 'noeviction' policy).
    #
    # WARNING: If you have slaves attached to an instance with maxmemory on,
    # the size of the output buffers needed to feed the slaves are subtracted
    # from the used memory count, so that network problems / resyncs will
    # not trigger a loop where keys are evicted, and in turn the output
    # buffer of slaves is full with DELs of keys evicted triggering the deletion
    # of more keys, and so forth until the database is completely emptied.
    #
    # In short... if you have slaves attached it is suggested that you set a lower
    # limit for maxmemory so that there is some free RAM on the system for slave
    # output buffers (but this is not needed if the policy is 'noeviction').
    #
    # maxmemory <bytes>
    
    # MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
    # is reached. You can select among five behaviors:
    #
    # volatile-lru -> Evict using approximated LRU among the keys with an expire set.
    # allkeys-lru -> Evict any key using approximated LRU.
    # volatile-lfu -> Evict using approximated LFU among the keys with an expire set.
    # allkeys-lfu -> Evict any key using approximated LFU.
    # volatile-random -> Remove a random key among the ones 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 evict anything, just return an error on write operations.
    #
    # LRU means Least Recently Used
    # LFU means Least Frequently Used
    #
    # Both LRU, LFU and volatile-ttl are implemented using approximated
    # randomized algorithms.
    #
    # Note: with any of the above policies, Redis will return an error on write
    #       operations, when there are no suitable keys for eviction.
    #
    #       At the date of writing these commands are: 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
    #
    # The default is:
    #
    # maxmemory-policy noeviction
    
    # LRU, LFU and minimal TTL algorithms are not precise algorithms but approximated
    # algorithms (in order to save memory), so you can tune it for speed or
    # accuracy. For default Redis will check five keys and pick the one that was
    # used less recently, you can change the sample size using the following
    # configuration directive.
    #
    # The default of 5 produces good enough results. 10 Approximates very closely
    # true LRU but costs more CPU. 3 is faster but not very accurate.
    #
    # maxmemory-samples 5
    
    ############################# 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 slave performs a full resynchronization with
    #    its master, the content of the whole database is removed in order to
    #    load the RDB file just transfered.
    #
    # 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:
    
    lazyfree-lazy-eviction no
    lazyfree-lazy-expire no
    lazyfree-lazy-server-del no
    slave-lazy-flush no
    
    ############################## APPEND ONLY MODE ###############################
    
    # By default Redis asynchronously dumps the dataset on disk. This mode is
    # good enough in many applications, but an issue with the Redis process or
    # a power outage may result into a few minutes of writes lost (depending on
    # the configured save points).
    #
    # The Append Only File is an alternative persistence mode that provides
    # much better durability. For instance using the default data fsync policy
    # (see later in the config file) Redis can lose just one second of writes in a
    # dramatic event like a server power outage, or a single write if something
    # wrong with the Redis process itself happens, but the operating system is
    # still running correctly.
    #
    # AOF and RDB persistence can be enabled at the same time without problems.
    # If the AOF is enabled on startup Redis will load the AOF, that is the file
    # with the better durability guarantees.
    #
    # Please check http://redis.io/topics/persistence for more information.
    
    appendonly no
    
    # The name of the append only file (default: "appendonly.aof")
    
    appendfilename "appendonly.aof"
    
    # The fsync() call tells the Operating System to actually write data on disk
    # instead of waiting for more data in the output buffer. Some OS will really flush
    # data on disk, some other OS will just try to do it ASAP.
    #
    # Redis supports three different modes:
    #
    # no: don't fsync, just let the OS flush the data when it wants. Faster.
    # always: fsync after every write to the append only log. Slow, Safest.
    # everysec: fsync only one time every second. Compromise.
    #
    # The default is "everysec", as that's usually the right compromise between
    # speed and data safety. It's up to you to understand if you can relax this to
    # "no" that will let the operating system flush the output buffer when
    # it wants, for better performances (but if you can live with the idea of
    # some data loss consider the default persistence mode that's snapshotting),
    # or on the contrary, use "always" that's very slow but a bit safer than
    # everysec.
    #
    # More details please check the following article:
    # http://antirez.com/post/redis-persistence-demystified.html
    #
    # If unsure, use "everysec".
    
    # appendfsync always
    appendfsync everysec
    # appendfsync no
    
    # When the AOF fsync policy is set to always or everysec, and a background
    # saving process (a background save or AOF log background rewriting) is
    # performing a lot of I/O against the disk, in some Linux configurations
    # Redis may block too long on the fsync() call. Note that there is no fix for
    # this currently, as even performing fsync in a different thread will block
    # our synchronous write(2) call.
    #
    # In order to mitigate this problem it's possible to use the following option
    # that will prevent fsync() from being called in the main process while a
    # BGSAVE or BGREWRITEAOF is in progress.
    #
    # This means that while another child is saving, the durability of Redis is
    # the same as "appendfsync none". In practical terms, this means that it is
    # possible to lose up to 30 seconds of log in the worst scenario (with the
    # default Linux settings).
    #
    # If you have latency problems turn this to "yes". Otherwise leave it as
    # "no" that is the safest pick from the point of view of durability.
    
    no-appendfsync-on-rewrite no
    
    # Automatic rewrite of the append only file.
    # Redis is able to automatically rewrite the log file implicitly calling
    # BGREWRITEAOF when the AOF log size grows by the specified percentage.
    #
    # This is how it works: Redis remembers the size of the AOF file after the
    # latest rewrite (if no rewrite has happened since the restart, the size of
    # the AOF at startup is used).
    #
    # This base size is compared to the current size. If the current size is
    # bigger than the specified percentage, the rewrite is triggered. Also
    # you need to specify a minimal size for the AOF file to be rewritten, this
    # is useful to avoid rewriting the AOF file even if the percentage increase
    # is reached but it is still pretty small.
    #
    # Specify a percentage of zero in order to disable the automatic AOF
    # rewrite feature.
    
    auto-aof-rewrite-percentage 100
    auto-aof-rewrite-min-size 64mb
    
    # An AOF file may be found to be truncated at the end during the Redis
    # startup process, when the AOF data gets loaded back into memory.
    # This may happen when the system where Redis is running
    # crashes, especially when an ext4 filesystem is mounted without the
    # data=ordered option (however this can't happen when Redis itself
    # crashes or aborts but the operating system still works correctly).
    #
    # Redis can either exit with an error when this happens, or load as much
    # data as possible (the default now) and start if the AOF file is found
    # to be truncated at the end. The following option controls this behavior.
    #
    # If aof-load-truncated is set to yes, a truncated AOF file is loaded and
    # the Redis server starts emitting a log to inform the user of the event.
    # Otherwise if the option is set to no, the server aborts with an error
    # and refuses to start. When the option is set to no, the user requires
    # to fix the AOF file using the "redis-check-aof" utility before to restart
    # the server.
    #
    # Note that if the AOF file will be found to be corrupted in the middle
    # the server will still exit with an error. This option only applies when
    # Redis will try to read more data from the AOF file but not enough bytes
    # will be found.
    aof-load-truncated yes
    
    # When rewriting the AOF file, Redis is able to use an RDB preamble in the
    # AOF file for faster rewrites and recoveries. When this option is turned
    # on the rewritten AOF file is composed of two different stanzas:
    #
    #   [RDB file][AOF tail]
    #
    # When loading Redis recognizes that the AOF file starts with the "REDIS"
    # string and loads the prefixed RDB file, and continues loading the AOF
    # tail.
    #
    # This is currently turned off by default in order to avoid the surprise
    # of a format change, but will at some point be used as the default.
    aof-use-rdb-preamble no
    
    ################################ 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.
    #
    # 一个 Lua 脚本执行的最多毫秒数。
    #
    # 如果一个 Lua 脚本执行的时间达到了设置的最大允许时间，
    # Redis 将在日志中记录下一个脚本超过了最大允许时间后依旧在执行，并开始向请求回复一个错误。
    #
    # 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.
    lua-time-limit 5000
    
    ################################ REDIS CLUSTER  ###############################
    #
    # ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    # WARNING EXPERIMENTAL: Redis Cluster is considered to be stable code, however
    # in order to mark it as "mature" we need to wait for a non trivial percentage
    # of users to deploy it in production.
    # ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    #
    # Normal Redis instances can't be part of a Redis Cluster; only nodes that are
    # started as cluster nodes can. In order to start a Redis instance as a
    # cluster node enable the cluster support uncommenting the following:
    #
    # cluster-enabled yes
    
    # Every cluster node has a cluster configuration file. This file is not
    # intended to be edited by hand. It is created and updated by Redis nodes.
    # Every Redis Cluster node requires a different cluster configuration file.
    # Make sure that instances running in the same system do not have
    # overlapping cluster configuration file names.
    #
    # cluster-config-file nodes-6379.conf
    
    # Cluster node timeout is the amount of milliseconds a node must be unreachable
    # for it to be considered in failure state.
    # Most other internal time limits are multiple of the node timeout.
    #
    # cluster-node-timeout 15000
    
    # A slave of a failing master will avoid to start a failover if its data
    # looks too old.
    #
    # There is no simple way for a slave to actually have an exact measure of
    # its "data age", so the following two checks are performed:
    #
    # 1) If there are multiple slaves able to failover, they exchange messages
    #    in order to try to give an advantage to the slave with the best
    #    replication offset (more data from the master processed).
    #    Slaves will try to get their rank by offset, and apply to the start
    #    of the failover a delay proportional to their rank.
    #
    # 2) Every single slave computes the time of the last interaction with
    #    its master. This can be the last ping or command received (if the master
    #    is still in the "connected" state), or the time that elapsed since the
    #    disconnection with the master (if the replication link is currently down).
    #    If the last interaction is too old, the slave will not try to failover
    #    at all.
    #
    # The point "2" can be tuned by user. Specifically a slave will not perform
    # the failover if, since the last interaction with the master, the time
    # elapsed is greater than:
    #
    #   (node-timeout * slave-validity-factor) + repl-ping-slave-period
    #
    # So for example if node-timeout is 30 seconds, and the slave-validity-factor
    # is 10, and assuming a default repl-ping-slave-period of 10 seconds, the
    # slave will not try to failover if it was not able to talk with the master
    # for longer than 310 seconds.
    #
    # A large slave-validity-factor may allow slaves with too old data to failover
    # a master, while a too small value may prevent the cluster from being able to
    # elect a slave at all.
    #
    # For maximum availability, it is possible to set the slave-validity-factor
    # to a value of 0, which means, that slaves will always try to failover the
    # master regardless of the last time they interacted with the master.
    # (However they'll always try to apply a delay proportional to their
    # offset rank).
    #
    # Zero is the only value able to guarantee that when all the partitions heal
    # the cluster will always be able to continue.
    #
    # cluster-slave-validity-factor 10
    
    # Cluster slaves are able to migrate to orphaned masters, that are masters
    # that are left without working slaves. This improves the cluster ability
    # to resist to failures as otherwise an orphaned master can't be failed over
    # in case of failure if it has no working slaves.
    #
    # Slaves migrate to orphaned masters only if there are still at least a
    # given number of other working slaves for their old master. This number
    # is the "migration barrier". A migration barrier of 1 means that a slave
    # will migrate only if there is at least 1 other working slave for its master
    # and so forth. It usually reflects the number of slaves you want for every
    # master in your cluster.
    #
    # Default is 1 (slaves migrate only if their masters remain with at least
    # one slave). To disable migration just set it to a very large value.
    # A value of 0 can be set but is useful only for debugging and dangerous
    # in production.
    #
    # cluster-migration-barrier 1
    
    # By default Redis Cluster nodes stop accepting queries if they detect there
    # is at least an hash slot uncovered (no available node is serving it).
    # This way if the cluster is partially down (for example a range of hash slots
    # are no longer covered) all the cluster becomes, eventually, unavailable.
    # It automatically returns available as soon as all the slots are covered again.
    #
    # However sometimes you want the subset of the cluster which is working,
    # to continue to accept queries for the part of the key space that is still
    # covered. In order to do so, just set the cluster-require-full-coverage
    # option to no.
    #
    # cluster-require-full-coverage yes
    
    # This option, when set to yes, prevents slaves 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-slave-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:
    #
    # cluster-announce-ip 10.1.1.5
    # cluster-announce-port 6379
    # cluster-announce-bus-port 6380
    
    ################################## SLOW LOG ###################################
    
    # The Redis Slow Log is a system to log queries that exceeded a specified
    # execution time. The execution time does not include the I/O operations
    # like talking with the client, sending the reply and so forth,
    # but just the time needed to actually execute the command (this is the only
    # stage of command execution where the thread is blocked and can not serve
    # other requests in the meantime).
    #
    # You can configure the slow log with two parameters: one tells Redis
    # what is the execution time, in microseconds, to exceed in order for the
    # command to get logged, and the other parameter is the length of the
    # slow log. When a new command is logged the oldest one is removed from the
    # queue of logged commands.
    
    # The following time is expressed in microseconds, so 1000000 is equivalent
    # to one second. Note that a negative number disables the slow log, while
    # a value of zero forces the logging of every command.
    slowlog-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 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
    
    # 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
    # slave  -> slave 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 slave clients, since
    # subscribers and slaves 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 slave 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
    
    # 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
    
    # 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 25
    
    # Maximal effort for defrag in CPU percentage
    # active-defrag-cycle-max 75