Redis配置文件简介

- 日理万妓 2023-06-04 10:57 100阅读 0赞

这里呢，主要讲的是redis.conf（版本是基于redis-5.0.0）

我们需要注意的是，奇数的版本，是测试版本，偶数的版本，是稳定的版本。

## 1.开头说明 ##

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################################## 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.
    #
    # include /path/to/local.conf
    # include /path/to/other.conf

这里没什么好说的，需要注意的是后面需要使用内存大小时，可以指定单位，通常是以 k,gb,m的形式出现，并且**单位不区分大小写**。

## 2.INCLUDES ##

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我们知道Redis只有一个配置文件，如果多个人进行开发维护，那么就需要多个这样的配置文件，这时候多个配置文件就可以在此通过 include /path/to/local.conf 配置进来，而原本的 redis.conf 配置文件就作为一个总闸。

ps:如果用过struts2 开发的同学，在项目组中多人开发的情况下，通常会有多个struts2.xml 文件，这时候也会通过类时的配置引入进来。

另外需要注意的时，如果将此配置写在redis.conf 文件的开头，那么后面的配置会覆盖引入文件的配置，如果想以引入文件的配置为主，那么需要将 include 配置写在 redis.conf 文件的末尾。

3.MODULES

################################## 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.
    #
    # loadmodule /path/to/my_module.so
    # loadmodule /path/to/other_module.so

redis3.0的爆炸功能是新增了集群，而redis4.0就是在3.0的基础上新增了许多功能，其中这里的 自定义模块配置就是其中之一。通过这里的 loadmodule 配置将引入自定义模块来新增一些功能。

## 4.NETWORK ##

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################################## 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.
    #
    # 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 loopback interface address (this means Redis will be able to
    # accept connections only from clients running into the same computer it
    # is running).
    #
    # IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES
    # JUST COMMENT THE FOLLOWING LINE.
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    bind 0.0.0.0
    
    # Protected mode is a layer of security protection, in order to avoid that
    # Redis instances left open on the internet are accessed and exploited.
    #
    # 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.
    #
    # 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.
    #
    # 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.
    port 6380
    
    # 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.
    tcp-backlog 511
    
    # Unix socket.
    #
    # Specify the path for the Unix socket that will be used to listen for
    # incoming connections. There is no default, so Redis will not listen
    # on a unix socket when not specified.
    #
    # unixsocket /tmp/redis.sock
    # unixsocketperm 700
    
    # Close the connection after a client is idle for N seconds (0 to disable)
    timeout 0
    
    # TCP keepalive.
    #
    # 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

ps:这里的配置较长，我只截取了一部分，下同。

①、bind:绑定redis服务器网卡IP，默认为127.0.0.1,即本地回环地址。这样的话，访问redis服务只能通过本机的客户端连接，而无法通过远程连接。如果bind选项为空的话，那会接受所有来自于可用网络接口的连接。

②、port：指定redis运行的端口，默认是6379。由于Redis是单线程模型，因此单机开多个Redis进程的时候会修改端口。

③、timeout：设置客户端连接时的超时时间，单位为秒。当客户端在这段时间内没有发出任何指令，那么关闭该连接。默认值为0，表示不关闭。

④、tcp-keepalive ：单位是秒，表示将周期性的使用SO\_KEEPALIVE检测客户端是否还处于健康状态，避免服务器一直阻塞，官方给出的建议值是300s，如果设置为0，则不会周期性的检测。

## 5.GENERAL ##

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################################# GENERAL #####################################
    
    # By default Redis does not run as a daemon. Use 'yes' if you need it.
    # Note that Redis will write a pid file in /var/run/redis.pid when daemonized.
    daemonize yes
    
    # 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.
    #
    # 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".
    #
    # 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.
    pidfile /var/run/redis_6380.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
    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
    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

具体配置详解：

①、daemonize:设置为yes表示指定Redis以守护进程的方式启动（后台启动）。默认值为 no

②、pidfile:配置PID文件路径，当redis作为守护进程运行的时候，它会把 pid 默认写到 /var/redis/run/redis\_6379.pid 文件里面

③、loglevel ：定义日志级别。默认值为notice，有如下4种取值：

debug（记录大量日志信息，适用于开发、测试阶段）

verbose（较多日志信息）

notice（适量日志信息，使用于生产环境）

warning（仅有部分重要、关键信息才会被记录）

④、logfile ：配置log文件地址,默认打印在命令行终端的窗口上

⑤、databases：设置数据库的数目。默认的数据库是DB 0 ，可以在每个连接上使用select  <dbid> 命令选择一个不同的数据库，dbid是一个介于0到databases - 1 之间的数值。默认值是 16，也就是说默认Redis有16个数据库。

##  6.SNAPSHOTTING ##

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################################ SNAPSHOTTING  ################################
    #
    # Save the DB on disk:
    #
    #   save <seconds> <changes>
    #
    #   Will save the DB if both the given number of seconds and the given
    #   number of write operations against the DB occurred.
    #
    #   In the example below the behaviour will be to save:
    #   after 900 sec (15 min) if at least 1 key changed
    #   after 300 sec (5 min) if at least 10 keys changed
    #   after 60 sec if at least 10000 keys changed
    #
    #   Note: you can disable saving completely by commenting out all "save" lines.
    #
    #   It is also possible to remove all the previously configured save
    #   points by adding a save directive with a single empty string argument
    #   like in the following example:
    #
    #   save ""
    
    save 900 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.
    #
    # 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.
    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.
    #
    # 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
    dbfilename dump_6380.rdb
    
    # The working directory.
    #
    # The DB will be written inside this directory, with the filename specified
    # above using the 'dbfilename' configuration directive.
    #
    # The Append Only File will also be created inside this directory.
    #
    # Note that you must specify a directory here, not a file name.
    dir ./

这里的配置主要用来做持久化操作。

①、save：这里是用来配置触发 Redis的持久化条件，也就是什么时候将内存中的数据保存到硬盘。默认如下配置：

save 900 1：表示900 秒内如果至少有 1 个 key 的值变化，则保存
    save 300 10：表示300 秒内如果至少有 10 个 key 的值变化，则保存
    save 60 10000：表示60 秒内如果至少有 10000 个 key 的值变化，则保存

当然如果你只是用Redis的缓存功能，不需要持久化，那么你可以注释掉所有的 save 行来停用保存功能。可以直接一个空字符串来实现停用：save ""

②、stop-writes-on-bgsave-error ：默认值为yes。当启用了RDB且最后一次后台保存数据失败，Redis是否停止接收数据。这会让用户意识到数据没有正确持久化到磁盘上，否则没有人会注意到灾难（disaster）发生了。如果Redis重启了，那么又可以重新开始接收数据了

③、rdbcompression ；默认值是yes。对于存储到磁盘中的快照，可以设置是否进行压缩存储。如果是的话，redis会采用LZF算法进行压缩。如果你不想消耗CPU来进行压缩的话，可以设置为关闭此功能，但是存储在磁盘上的快照会比较大。

④、rdbchecksum ：默认值是yes。在存储快照后，我们还可以让redis使用CRC64算法来进行数据校验，但是这样做会增加大约10%的性能消耗，如果希望获取到最大的性能提升，可以关闭此功能。

⑤、dbfilename ：设置快照的文件名，默认是 dump.rdb

⑥、dir：设置快照文件的存放路径，这个配置项一定是个目录，而不能是文件名。使用上面的 dbfilename 作为保存的文件名。

## 7.REPLICATION ##

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################################# REPLICATION #################################
    
    # Master-Replica replication. Use replicaof to make a Redis instance a copy of
    # another Redis server. A few things to understand ASAP about Redis replication.
    #
    #   +------------------+      +---------------+
    #   |      Master      | ---> |    Replica    |
    #   | (receive writes) |      |  (exact copy) |
    #   +------------------+      +---------------+
    #
    # 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 replicas.
    # 2) Redis replicas 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 replicas automatically try to reconnect to masters
    #    and resynchronize with them.
    #
    # replicaof <masterip> <masterport>
    
    # If the master is password protected (using the "requirepass" configuration
    # directive below) it is possible to tell the replica to authenticate before
    # starting the replication synchronization process, otherwise the master will
    # refuse the replica request.
    #
    # masterauth <master-password>
    
    # When a replica loses its connection with the master, or when the replication
    # is still in progress, the replica can act in two different ways:
    #
    # 1) if replica-serve-stale-data is set to 'yes' (the default) the replica 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 replica-serve-stale-data is set to 'no' the replica will reply with
    #    an error "SYNC with master in progress" to all the kind of commands
    #    but to INFO, replicaOF, AUTH, PING, SHUTDOWN, REPLCONF, ROLE, CONFIG,
    #    SUBSCRIBE, UNSUBSCRIBE, PSUBSCRIBE, PUNSUBSCRIBE, PUBLISH, PUBSUB,
    #    COMMAND, POST, HOST: and LATENCY.
    #
    replica-serve-stale-data yes
    
    # You can configure a replica instance to accept writes or not. Writing against
    # a replica instance may be useful to store some ephemeral data (because data
    # written on a replica 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 replicas are read-only.
    #
    # Note: read only replicas 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 replica 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 replicas using 'rename-command' to shadow all the
    # administrative / dangerous commands.
    replica-read-only yes
    
    # Replication SYNC strategy: disk or socket.
    #
    # -------------------------------------------------------
    # WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
    # -------------------------------------------------------
    #
    # New replicas and reconnecting replicas 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 replicas.
    # 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 replicas incrementally.
    # 2) Diskless: The Redis master creates a new process that directly writes the
    #              RDB file to replica sockets, without touching the disk at all.
    #
    # With disk-backed replication, while the RDB file is generated, more replicas
    # 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 replicas 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 replicas
    # 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 replicas.
    #
    # This is important since once the transfer starts, it is not possible to serve
    # new replicas arriving, that will be queued for the next RDB transfer, so the server
    # waits a delay in order to let more replicas 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
    
    # Replicas send PINGs to server in a predefined interval. It's possible to change
    # this interval with the repl_ping_replica_period option. The default value is 10
    # seconds.
    #
    # repl-ping-replica-period 10
    
    # The following option sets the replication timeout for:
    #
    # 1) Bulk transfer I/O during SYNC, from the point of view of replica.
    # 2) Master timeout from the point of view of replicas (data, pings).
    # 3) Replica 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-replica-period otherwise a timeout will be detected
    # every time there is low traffic between the master and the replica.
    #
    # repl-timeout 60
    
    # Disable TCP_NODELAY on the replica socket after SYNC?
    #
    # If you select "yes" Redis will use a smaller number of TCP packets and
    # less bandwidth to send data to replicas. But this can add a delay for
    # the data to appear on the replica side, up to 40 milliseconds with
    # Linux kernels using a default configuration.
    #
    # If you select "no" the delay for data to appear on the replica 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 replicas 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
    # replica data when replicas are disconnected for some time, so that when a replica
    # wants to reconnect again, often a full resync is not needed, but a partial
    # resync is enough, just passing the portion of data the replica missed while
    # disconnected.
    #
    # The bigger the replication backlog, the longer the time the replica can be
    # disconnected and later be able to perform a partial resynchronization.
    #
    # The backlog is only allocated once there is at least a replica connected.
    #
    # repl-backlog-size 1mb
    
    # After a master has no longer connected replicas 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 replica disconnected, for
    # the backlog buffer to be freed.
    #
    # Note that replicas never free the backlog for timeout, since they may be
    # promoted to masters later, and should be able to correctly "partially
    # resynchronize" with the replicas: hence they should always accumulate backlog.
    #
    # A value of 0 means to never release the backlog.
    #
    # repl-backlog-ttl 3600
    
    # The replica priority is an integer number published by Redis in the INFO output.
    # It is used by Redis Sentinel in order to select a replica to promote into a
    # master if the master is no longer working correctly.
    #
    # A replica with a low priority number is considered better for promotion, so
    # for instance if there are three replicas with priority 10, 100, 25 Sentinel will
    # pick the one with priority 10, that is the lowest.
    #
    # However a special priority of 0 marks the replica as not able to perform the
    # role of master, so a replica with priority of 0 will never be selected by
    # Redis Sentinel for promotion.
    #
    # By default the priority is 100.
    replica-priority 100
    
    # It is possible for a master to stop accepting writes if there are less than
    # N replicas connected, having a lag less or equal than M seconds.
    #
    # The N replicas 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 replica, 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 replicas
    # are available, to the specified number of seconds.
    #
    # For example to require at least 3 replicas with a lag <= 10 seconds use:
    #
    # min-replicas-to-write 3
    # min-replicas-max-lag 10
    #
    # Setting one or the other to 0 disables the feature.
    #
    # By default min-replicas-to-write is set to 0 (feature disabled) and
    # min-replicas-max-lag is set to 10.
    
    # A Redis master is able to list the address and port of the attached
    # replicas 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 replica 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 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

①、slave-serve-stale-data：默认值为yes。当一个 slave 与 master 失去联系，或者复制正在进行的时候，slave 可能会有两种表现：

1) 如果为 yes ，slave 仍然会应答客户端请求，但返回的数据可能是过时，或者数据可能是空的在第一次同步的时候

2) 如果为 no ，在你执行除了 info he salveof 之外的其他命令时，slave 都将返回一个 "SYNC with master in progress" 的错误

②、slave-read-only：配置Redis的Slave实例是否接受写操作，即Slave是否为只读Redis。默认值为yes。

③、repl-diskless-sync：主从数据复制是否使用无硬盘复制功能。默认值为no。

④、repl-diskless-sync-delay：当启用无硬盘备份，服务器等待一段时间后才会通过套接字向从站传送RDB文件，这个等待时间是可配置的。  这一点很重要，因为一旦传送开始，就不可能再为一个新到达的从站服务。从站则要排队等待下一次RDB传送。因此服务器等待一段  时间以期更多的从站到达。延迟时间以秒为单位，默认为5秒。要关掉这一功能，只需将它设置为0秒，传送会立即启动。默认值为5。

⑤、repl-disable-tcp-nodelay：同步之后是否禁用从站上的TCP\_NODELAY 如果你选择yes，redis会使用较少量的TCP包和带宽向从站发送数据。但这会导致在从站增加一点数据的延时。  Linux内核默认配置情况下最多40毫秒的延时。如果选择no，从站的数据延时不会那么多，但备份需要的带宽相对较多。默认情况下我们将潜在因素优化，但在高负载情况下或者在主从站都跳的情况下，把它切换为yes是个好主意。默认值为no。

## 8.SECURITY ##

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################################## 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.
    #
    # 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 123456
    
    # 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.

①、rename-command：命令重命名，对于一些危险命令例如：

flushdb（清空数据库）

flushall（清空所有记录）

config（客户端连接后可配置服务器）

keys（客户端连接后可查看所有存在的键）

作为服务端redis-server，常常需要禁用以上命令来使得服务器更加安全，禁用的具体做法是是：

*  rename-command FLUSHALL ""

也可以保留命令但是不能轻易使用，重命名这个命令即可：

*  rename-command FLUSHALL abcdefg

这样，重启服务器后则需要使用新命令来执行操作，否则服务器会报错unknown command。

## 9.CLIENTS ##

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################################### 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

①、maxclients ：设置客户端最大并发连接数，默认无限制，Redis可以同时打开的客户端连接数为Redis进程可以打开的最大文件。  描述符数-32（redis server自身会使用一些），如果设置 maxclients为0 。表示不作限制。当客户端连接数到达限制时，Redis会关闭新的连接并向客户端返回max number of clients reached错误信息

## 10.MEMORY MANAGEMENT ##

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############################## 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 replicas attached to an instance with maxmemory on,
    # the size of the output buffers needed to feed the replicas 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 replicas 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 replicas attached it is suggested that you set a lower
    # limit for maxmemory so that there is some free RAM on the system for replica
    # 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
    
    # Starting from Redis 5, by default a replica will ignore its maxmemory setting
    # (unless it is promoted to master after a failover or manually). It means
    # that the eviction of keys will be just handled by the master, sending the
    # DEL commands to the replica as keys evict in the master side.
    #
    # This behavior ensures that masters and replicas stay consistent, and is usually
    # what you want, however if your replica is writable, or you want the replica to have
    # a different memory setting, and you are sure all the writes performed to the
    # replica are idempotent, then you may change this default (but be sure to understand
    # what you are doing).
    #
    # Note that since the replica by default does not evict, it may end using more
    # memory than the one set via maxmemory (there are certain buffers that may
    # be larger on the replica, or data structures may sometimes take more memory and so
    # forth). So make sure you monitor your replicas and make sure they have enough
    # memory to never hit a real out-of-memory condition before the master hits
    # the configured maxmemory setting.
    #
    # replica-ignore-maxmemory yes

①、maxmemory：设置客户端最大并发连接数，默认无限制，Redis可以同时打开的客户端连接数为Redis进程可以打开的最大文件。描述符数-32（redis server自身会使用一些），如果设置 maxclients为0 。表示不作限制。当客户端连接数到达限制时，Redis会关闭新的连接并向客户端返回max number of clients reached错误信息。

②、maxmemory-policy ：当内存使用达到最大值时，redis使用的清楚策略。有以下几种可以选择：

1）volatile-lru   利用LRU算法移除设置过过期时间的key (LRU:最近使用 Least Recently Used )

2）allkeys-lru   利用LRU算法移除任何key

3）volatile-random 移除设置过过期时间的随机key

4）allkeys-random  移除随机ke

5）volatile-ttl   移除即将过期的key(minor TTL)

6）noeviction  noeviction   不移除任何key，只是返回一个写错误 ，默认选项

③、maxmemory-samples ：LRU 和 minimal TTL 算法都不是精准的算法，但是相对精确的算法(为了节省内存)。随意你可以选择样本大小进行检，redis默认选择3个样本进行检测，你可以通过maxmemory-samples进行设置样本数。

## 11.LAZY FREEING（待补充。。。） ##

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############################# 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:
    
    lazyfree-lazy-eviction no
    lazyfree-lazy-expire no
    lazyfree-lazy-server-del no
    replica-lazy-flush no

## 12.APPEND ONLY MODE ##

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############################## 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.
    aof-use-rdb-preamble yes

①、appendonly：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。默认值为no。

②、appendfilename ：aof文件名，默认是"appendonly.aof"

③、appendfsync：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

④、no-appendfsync-on-rewrite：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。默认值为no。

⑤、auto-aof-rewrite-percentage：默认值为100。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。

⑥、auto-aof-rewrite-min-size：64mb。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。

⑦、aof-load-truncated：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，出现这种现象  redis宕机或者异常终止不会造成尾部不完整现象，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。默认值为 yes。

## 13.LUA SCRIPTING ##

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################################ 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.
    lua-time-limit 5000

①、lua-time-limit：一个lua脚本执行的最大时间，单位为ms。默认值为5000.

## 14.REDIS CLUSTER ##

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################################ 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 replica of a failing master will avoid to start a failover if its data
    # looks too old.
    #
    # There is no simple way for a replica to actually have an exact measure of
    # its "data age", so the following two checks are performed:
    #
    # 1) If there are multiple replicas able to failover, they exchange messages
    #    in order to try to give an advantage to the replica with the best
    #    replication offset (more data from the master processed).
    #    Replicas 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 replica 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 replica will not try to failover
    #    at all.
    #
    # The point "2" can be tuned by user. Specifically a replica will not perform
    # the failover if, since the last interaction with the master, the time
    # elapsed is greater than:
    #
    #   (node-timeout * replica-validity-factor) + repl-ping-replica-period
    #
    # So for example if node-timeout is 30 seconds, and the replica-validity-factor
    # is 10, and assuming a default repl-ping-replica-period of 10 seconds, the
    # replica will not try to failover if it was not able to talk with the master
    # for longer than 310 seconds.
    #
    # A large replica-validity-factor may allow replicas with too old data to failover
    # a master, while a too small value may prevent the cluster from being able to
    # elect a replica at all.
    #
    # For maximum availability, it is possible to set the replica-validity-factor
    # to a value of 0, which means, that replicas 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-replica-validity-factor 10
    
    # Cluster replicas are able to migrate to orphaned masters, that are masters
    # that are left without working replicas. 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 replicas.
    #
    # Replicas migrate to orphaned masters only if there are still at least a
    # given number of other working replicas for their old master. This number
    # is the "migration barrier". A migration barrier of 1 means that a replica
    # will migrate only if there is at least 1 other working replica for its master
    # and so forth. It usually reflects the number of replicas you want for every
    # master in your cluster.
    #
    # Default is 1 (replicas migrate only if their masters remain with at least
    # one replica). 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 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:
    #
    # cluster-announce-ip 10.1.1.5
    # cluster-announce-port 6379
    # cluster-announce-bus-port 6380

①、cluster-enabled：集群开关，默认是不开启集群模式。

②、cluster-config-file：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。默认配置为nodes-6379.conf。

③、cluster-node-timeout ：可以配置值为15000。节点互连超时的阀值，集群节点超时毫秒数

④、cluster-slave-validity-factor ：可以配置值为10。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 \* slave-validity-factor) + repl-ping-slave-period     如果节点超时时间为三十秒, 并且slave-validity-factor为10,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

⑤、cluster-migration-barrier ：可以配置值为1。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。

⑥、cluster-require-full-coverage：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。

转载于:https://www.cnblogs.com/lys-lyy/p/11610065.html

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