Centos-redis配置redis.conf內容

 #Redis configuration file example.
 #
 # Note that in order to read the configuration file, Redis must be
 # started with the file path as first argument:
 #
 # ./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:
 #
 # 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.

 #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     # INCLUDES      #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #
 # 包含其他配置檔案
 # 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

 #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     # MODULES      #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #
 # 啟動時候載入其他模組
 # 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

 #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     # 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 lookback 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.
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 #繫結本地網路卡迴環介面，如果外網訪問則新增外網網路卡IP
 #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.
 #
 # 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.
 #是否開啟保護模式，預設開啟。要是配置裡沒有指定bind和密碼。開啟該引數後，redis只會本地進行訪問，拒絕外部訪問。
 #要是開啟了密碼 和bind，可以開啟。否則最好關閉，設定為no。
 protected-mode no

 # Accept connections on the specified port, default is 6379 (IANA      #815344).
 # If port 0 is specified Redis will not listen on a TCP socket.
 #埠號
 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.
 #此引數確定了TCP連線中已完成佇列(完成三次握手之後)的長度， 
 #當然此值必須不大於Linux系統定義的/proc/sys/net/core/somaxconn值，預設是511，
 #而Linux的預設引數值是128。當系統併發量大並且客戶端速度緩慢的時候，可以將這二個引數一起參考設定。
 #該核心引數預設值一般是128，對於負載很大的服務程式來說大大的不夠。一般會將它修改為2048或者更大。
 #在/etc/sysctl.conf中新增:net.core.somaxconn = 2048，然後在終端中執行sysctl -p。
 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)
 # 設定客戶端空閒超過timeout，服務端會斷開連線，為0則服務端不會主動斷開連線，不能小於0。
 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引數。如果設定不為0，就使用配置tcp的SO_KEEPALIVE值，
 #使用keepalive有兩個好處:檢測掛掉的對端。降低中間裝置出問題而導致網路看似連線卻已經與對端埠的問題。
 #在Linux核心中，設定了keepalive，redis會定時給對端傳送ack。檢測到對端關閉需要兩倍的設定值。
 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.
 #是否在守護程式執行
 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.
 #一般不用改，與daemonize選項配套，監控守護程式ID
 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.
 #redis的程式檔案
 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)
 # 日誌級別
 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
 #日誌檔案的位置，當指定為空字串時，為標準輸出，如果redis已守護程式模式執行，那麼日誌將會輸出到/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
 #資料庫數量
 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.
 #redis啟動時是否顯示Logo
 always-show-logo yes

 #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     # 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 ""
 # 過了900秒並且有1個key發生了改變，觸發save動作
 # 過了300秒並且有10個key發生了改變，觸發save動作
 # 過了60秒並且至少有10000個key發生了改變，觸發save動作
 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.
 # 如果使用者開啟了RDB快照功能，那麼在redis持久化資料到磁碟時如果出現失敗，預設情況下，redis會停止接受所有的寫請求。
 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.
 # 對於儲存到磁碟中的快照，可以設定是否進行壓縮儲存。
 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.
 #在儲存快照後，我們還可以讓redis使用CRC64演算法來進行資料校驗，但是這樣做會增加大約10%的效能消耗，
 rdbchecksum yes

 # The filename where to dump the DB
 #設定快照的檔名
 dbfilename dump.rdb

 # The working directory.
 #
 # The DB will be written inside this directory, with the filename specified
 # above using the `dbfilename` configuration directive.
 #
 # The Append Only File will also be created inside this directory.
 #
 # Note that you must specify a directory here, not a file name.
 #設定檔案儲存路徑
 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.
 #  主從複製，使用 slaveof 來讓一個 redis 例項成為另一個reids 例項的副本，預設關閉
 # 注意這個只需要在 slave 上配置
 # 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 master 需要密碼認證，就在這裡設定，預設不設定
 # 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.
 # 當一個 slave 與 master 失去聯絡，或者複製正在進行的時候，
   #slave 可能會有兩種表現：
   #1) 如果為 yes ，slave 仍然會應答客戶端請求，但返回的資料可能是過時，
   #   或者資料可能是空的在第一次同步的時候 
   #2) 如果為 no ，在你執行除了 info he salveof 之外的其他命令時，
   #   slave 都將返回一個 "SYNC with master in progress" 的錯誤
 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 實體是否接受寫入操作。一般不更改
 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.
 #   主從資料複製是否使用無硬碟複製功能。
 #   新的從站和重連後不能繼續備份的從站，需要做所謂的“完全備份”，即將一個RDB檔案從主站傳送到從站。
 #   這個傳送有以下兩種方式：
 #   1）硬碟備份：redis主站建立一個新的程式，用於把RDB檔案寫到硬碟上。過一會兒，其父程式遞增地將檔案傳送給從站。
 #   2）無硬碟備份：redis主站建立一個新的程式，子程式直接把RDB檔案寫到從站的套接字，不需要用到硬碟。
 #   在硬碟備份的情況下，主站的子程式生成RDB檔案。一旦生成，多個從站可以立即排成佇列使用主站的RDB檔案。
 #   在無硬碟備份的情況下，一次RDB傳送開始，新的從站到達後，需要等待現在的傳送結束，才能開啟新的傳送。
 #   如果使用無硬碟備份，主站會在開始傳送之間等待一段時間（可配置，以秒為單位），希望等待多個子站到達後並行傳送。
 #   在硬碟低速而網路高速（高頻寬）情況下，無硬碟備份更好。
 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.
 # 當啟用無硬碟備份，伺服器等待一段時間後才會通過套接字向從站傳送RDB檔案，這個等待時間是可配置的。
 #   這一點很重要，因為一旦傳送開始，就不可能再為一個新到達的從站服務。從站則要排隊等待下一次RDB傳送。因此伺服器等待一段
 #   時間以期更多的從站到達。
 #   延遲時間以秒為單位，預設為5秒。要關掉這一功能，只需將它設定為0秒，傳送會立即啟動。
 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.
 #  從redis會週期性的向主redis發出PING包，你可以通過repl_ping_slave_period指令來控制其週期，預設是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.
 # 接下來的選項為以下內容設定備份的超時時間：
 #   1）從從站的角度，同步期間的批量傳輸的I/O
 #   2）從站角度認為的主站超時（資料，ping）
 #   3）主站角度認為的從站超時（REPLCONF ACK pings)
 #   確認這些值比定義的repl-ping-slave-period要大，否則每次主站和從站之間通訊低速時都會被檢測為超時。
 # 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.
 #
 # 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.
 #   同步之後是否禁用從站上的TCP_NODELAY
 #   如果你選擇yes，redis會使用較少量的TCP包和頻寬向從站傳送資料。但這會導致在從站增加一點資料的延時。
 #   Linux核心預設配置情況下最多40毫秒的延時。
 #   如果選擇no，從站的資料延時不會那麼多，但備份需要的頻寬相對較多。
 #   預設情況下我們將潛在因素優化，但在高負載情況下或者在主從站都跳的情況下，把它切換為yes是個好主意。
 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.
 #
 # The backlog is only allocated once there is at least a slave connected.
 #  設定備份的工作儲備大小。工作儲備是一個緩衝區，當從站斷開一段時間的情況時，它替從站接收儲存資料，
 #   因此當從站重連時，通常不需要完全備份，只需要一個部分同步就可以，即把從站斷開時錯過的一部分資料接收。
 #   工作儲備越大，從站可以斷開並稍後執行部分同步的斷開時間就越長。
 #   只要有一個從站連線，就會立刻分配一個工作儲備。
 # 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.
 #  主站有一段時間沒有與從站連線，對應的工作儲備就會自動釋放。
 #   這個選項用於配置釋放前等待的秒數，秒數從斷開的那一刻開始計算，值為0表示不釋放。
 # 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.
 #
 # 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.
 #   從站優先順序是可以從redis的INFO命令輸出中查到的一個整數。當主站不能正常工作時
 #   redis sentinel使用它來選擇一個從站並將它提升為主站。
 #   低優先順序的從站被認為更適合於提升，因此如果有三個從站優先順序分別是10， 
 #   100，25，sentinel會選擇優先順序為10的從站，因為它的優先順序最低。
 #   然而優先順序值為0的從站不能執行主站的角色，因此優先順序為0的從站永遠不會被redis sentinel提升。
 #   預設優先順序是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.
 #
 # 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:
 #
 # 主站可以停止接受寫請求，當與它連線的從站少於N個，滯後少於M秒，N個從站必須是線上狀態。
 #   延遲的秒數必須<=所定義的值，延遲秒數是從最後一次收到的來自從站的ping開始計算。ping通常是每秒一次。
 #   這一選項並不保證N個備份都會接受寫請求，但是會限制在指定秒數內由於從站數量不夠導致的寫操作丟失的情況。
 #   如果想要至少3個從站且延遲少於10秒，如上配置即可
 # 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.

 # 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.
 # Redis master能夠以不同的方式列出所連線slave的地址和埠。 
 #  例如，“INFO replication”部分提供此資訊，除了其他工具之外，Redis Sentinel還使用該資訊來發現slave例項。
 #  此資訊可用的另一個地方在masterser的“ROLE”命令的輸出中。
 #  通常由slave報告的列出的IP和地址,通過以下方式獲得：
 #  IP：通過檢查slave與master連線使用的套接字的對等體地址自動檢測地址。
 #  埠：埠在複製握手期間由slavet通訊，並且通常是slave正在使用列出連線的埠。
 #  然而，當使用埠轉發或網路地址轉換（NAT）時，slave實際上可以通過(不同的IP和埠對)來到達。 slave可以使用以下兩個選項，以便向master報告一組特定的IP和埠，
 #  以便INFO和ROLE將報告這些值。
 #  如果你需要僅覆蓋埠或IP地址，則沒必要使用這兩個選項。
 # 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.
 #
 # 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.
 #   設定redis連線密碼
 # 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.
 #
 # Example:
 #
 # rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
 #
 # It is also possible to completely kill a command by renaming it into
 # an empty string:
 #將命令重新命名，為了安全考慮，可以將某些重要的、危險的命令重新命名。
 #當你把某個命令重新命名成空字串的時候就等於取消了這個命令。
 # 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`.
 # 設定客戶端最大併發連線數，預設無限制，Redis可以同時開啟的客戶端連線數為Redis程式可以開啟的最大檔案
 #   描述符數-32（redis server自身會使用一些），如果設定 maxclients為0 
 #   表示不作限制。當客戶端連線數到達限制時，Redis會關閉新的連線並向客戶端返回max number of clients reached錯誤資訊
 # 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`).
 # 指定Redis最大記憶體限制，Redis在啟動時會把資料載入到記憶體中，達到最大記憶體後，Redis會先嚐試清除已到期或即將到期的Key
 #   當此方法處理 後，仍然到達最大記憶體設定，將無法再進行寫入操作，但仍然可以進行讀取操作。Redis新的vm機制，
 #   會把Key存放記憶體，Value會存放在swap區，格式：maxmemory <bytes>
 # 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:
 #  當記憶體使用達到最大值時，redis使用的清楚策略。有以下幾種可以選擇：
 #   1）volatile-lru   利用LRU演算法移除設定過過期時間的key (LRU:最近使用 Least Recently Used ) 
 #   2）allkeys-lru   利用LRU演算法移除任何key 
 #   3）volatile-random 移除設定過過期時間的隨機key 
 #   4）allkeys-random  移除隨機ke
 #   5）volatile-ttl   移除即將過期的key(minor TTL) 
 #   6）noeviction  noeviction   不移除任何key，只是返回一個寫錯誤 ，預設選項
 # 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.
 #   LRU 和 minimal TTL 演算法都不是精準的演算法，但是相對精確的演算法(為了節省記憶體)
 #   隨意你可以選擇樣本大小進行檢，redis預設選擇3個樣本進行檢測，你可以通過maxmemory-samples進行設定樣本數
 # 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.
 # 預設redis使用的是rdb方式持久化，這種方式在許多應用中已經足夠用了。但是redis如果中途當機，
 #   會導致可能有幾分鐘的資料丟失，根據save來策略進行持久化，Append Only File是另一種持久化方式，
 #   可以提供更好的持久化特性。Redis會把每次寫入的資料在接收後都寫入appendonly.aof檔案，
 #   每次啟動時Redis都會先把這個檔案的資料讀入記憶體裡，先忽略RDB檔案。
 appendonly no

 # The name of the append only file (default: "appendonly.aof")
 #aof檔名
 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".
 #   aof持久化策略的配置
 #   no表示不執行fsync，由作業系統保證資料同步到磁碟，速度最快。
 #   always表示每次寫入都執行fsync，以保證資料同步到磁碟。
 #   everysec表示每秒執行一次fsync，可能會導致丟失這1s資料
 # 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.
 #    在aof重寫或者寫入rdb檔案的時候，會執行大量IO，此時對於everysec和always的aof模式來說，
 #    執行fsync會造成阻塞過長時間，no-appendfsync-on-rewrite欄位設定為預設設定為no。
 #    如果對延遲要求很高的應用，這個欄位可以設定為yes，否則還是設定為no，這樣對持久化特性來說這是更安全的選擇。
 #    設定為yes表示rewrite期間對新寫操作不fsync,暫時存在記憶體中,等rewrite完成後再寫入，預設為no，建議yes。
 #    Linux的預設fsync策略是30秒。可能丟失30秒資料。
 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.
 #   aof自動重寫配置，當目前aof檔案大小超過上一次重寫的aof檔案大小的百分之多少進行重寫，
 #   即當aof檔案增長到一定大小的時候，Redis能夠呼叫bgrewriteaof對日誌檔案進行重寫。
 #   當前AOF檔案大小是上次日誌重寫得到AOF檔案大小的二倍（設定為100）時，自動啟動新的日誌重寫過程。
 auto-aof-rewrite-percentage 100
 
 #  設定允許重寫的最小aof檔案大小，避免了達到約定百分比但尺寸仍然很小的情況還要重寫
 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檔案可能在尾部是不完整的，當redis啟動的時候，aof檔案的資料被載入記憶體。
 #   重啟可能發生在redis所在的主機作業系統當機後，尤其在ext4檔案系統沒有加上data=ordered選項，出現這種現象
 #   redis當機或者異常終止不會造成尾部不完整現象，可以選擇讓redis退出，或者匯入儘可能多的資料。
 #   如果選擇的是yes，當截斷的aof檔案被匯入的時候，會自動釋出一個log給客戶端然後load。
 #   如果是no，使用者必須手動redis-check-aof修復AOF檔案才可以。
 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.
 # 是否啟用混合持久化
 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.
 #
 # When a long running script exceeds the maximum execution time only the
 # SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
 # used to stop a script that did not yet called write commands. The second
 # is the only way to shut down the server in the case a write command was
 # already issued by the script but the user doesn`t want to wait for the natural
 # termination of the script.
 #
 # Set it to 0 or a negative value for unlimited execution without warnings.
 #   如果達到最大時間限制（毫秒），redis會記個log，然後返回error。當一個指令碼超過了最大時限。
 #   只有SCRIPT KILL和SHUTDOWN NOSAVE可以用。第一個可以殺沒有調write命令的東西。
 #   要是已經呼叫了write，只能用第二個命令殺
 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:
 # 叢集開關，預設是不開啟叢集模式
 # 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.
 # 叢集配置檔案的名稱，每個節點都有一個叢集相關的配置檔案，持久化儲存叢集的資訊。
 #  這個檔案並不需要手動配置，這個配置檔案有Redis生成並更新，每個Redis叢集節點需要一個單獨的配置檔案
 #  請確保與例項執行的系統中配置檔名稱不衝突
 # 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.
 #  節點互連超時的閥值，叢集節點超時毫秒數
 # 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.
 #
 #   在進行故障轉移的時候，全部slave都會請求申請為master，但是有些slave可能與master斷開連線一段時間了，
 #   導致資料過於陳舊，這樣的slave不應該被提升為master。該引數就是用來判斷slave節點與master斷線的時間是否過長。
 #   判斷方法是：
 #      比較slave斷開連線的時間和(node-timeout * slave-validity-factor) + repl-ping-slave-period
 #      如果節點超時時間為三十秒, 並且slave-validity-factor為10,
 #      假設預設的repl-ping-slave-period是10秒，即如果超過310秒slave將不會嘗試進行故障轉移
 # 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.
 #   master的slave數量大於該值，slave才能遷移到其他孤立master上，如這個引數若被設為2，
 #   那麼只有當一個主節點擁有2 個可工作的從節點時，它的一個從節點會嘗試遷移。
 # 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.
 #   預設情況下，叢集全部的slot有節點負責，叢集狀態才為ok，才能提供服務。
 #   設定為no，可以在slot沒有全部分配的時候提供服務。
 #   不建議開啟該配置，這樣會造成分割槽的時候，小分割槽的master一直在接受寫請求，而造成很長時間資料不一致
 # cluster-require-full-coverage yes

 # 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.
 # slog log是用來記錄redis執行中執行比較慢的命令耗時。
 #  當命令的執行超過了指定時間，就記錄在slow log中，slog log儲存在記憶體中，所以沒有IO操作。
 #  執行時間比slowlog-log-slower-than大的請求記錄到slowlog裡面，單位是微秒，所以1000000就是1秒。
 #  注意，負數時間會禁用慢查詢日誌，而0則會強制記錄所有命令。
 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.
 #  慢查詢日誌長度。當一個新的命令被寫進日誌的時候，最老的那個記錄會被刪掉，這個長度沒有限制。
 #  只要有足夠的記憶體就行，你可以通過 SLOWLOG RESET 來釋放記憶體
 slowlog-max-len 128

 #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     # LATENCY MONITOR      #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #     #

 # The Redis latency monitoring subsystem samples different operations
 # at runtime in order to collect data related to possible sources of
 # latency of a Redis instance.
 #
 # Via the LATENCY command this information is available to the user that can
 # print graphs and obtain reports.
 #
 # The system only logs operations that were performed in a time equal or
 # greater than the amount of milliseconds specified via the
 # latency-monitor-threshold configuration directive. When its value is set
 # to zero, the latency monitor is turned off.
 #
 # By default latency monitoring is disabled since it is mostly not needed
 # if you don`t have latency issues, and collecting data has a performance
 # impact, that while very small, can be measured under big load. Latency
 # monitoring can easily be enabled at runtime using the command
 # "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.
 # 延遲監控功能是用來監控redis中執行比較緩慢的一些操作，用LATENCY列印redis例項在跑命令時的耗時圖表。
 #   只記錄大於等於下邊設定的值的操作，0的話，就是關閉監視。
 #   預設延遲監控功能是關閉的，如果你需要開啟，也可以通過CONFIG SET命令動態設定。
 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.
 # 鍵空間通知使得客戶端可以通過訂閱頻道或模式，來接收那些以某種方式改動了 Redis 資料集的事件。因為開啟鍵空間通知功能需要消耗一些 CPU ，所以在預設配置下，該功能處於關閉狀態。
 #  notify-keyspace-events 的引數可以是以下字元的任意組合，它指定了伺服器該傳送哪些型別的通知：
 #   K 鍵空間通知，所有通知以 __keyspace@__ 為字首
 #   E 鍵事件通知，所有通知以 __keyevent@__ 為字首
 #   g DEL 、 EXPIRE 、 RENAME 等型別無關的通用命令的通知
 #   $ 字串命令的通知
 #   l 列表命令的通知
 #   s 集合命令的通知
 #   h 雜湊命令的通知
 #   z 有序集合命令的通知
 #   x 過期事件：每當有過期鍵被刪除時傳送
 #   e 驅逐(evict)事件：每當有鍵因為 maxmemory 政策而被刪除時傳送
 #   A 引數 g$lshzxe 的別名
 #  輸入的引數中至少要有一個 K 或者 E，否則的話，不管其餘的引數是什麼，都不會有任何 通知被分發。
 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型別的資料結構在編碼上可以使用ziplist和hashtable。
 #  ziplist的特點就是檔案儲存(以及記憶體儲存)所需的空間較小,在內容較小時,效能和hashtable幾乎一樣。
 #  因此redis對hash型別預設採取ziplist。如果hash中條目的條目個數或者value長度達到閥值,將會被重構為hashtable。
 #  這個引數指的是ziplist中允許儲存的最大條目個數，，預設為512，建議為128
 hash-max-ziplist-entries 128

 # ziplist中允許條目value值最大位元組數，預設為64，建議為1024
 hash-max-ziplist-value 512

 # 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.
 # 當取正值的時候，表示按照資料項個數來限定每個quicklist節點上的ziplist長度。比如，當這個引數配置成5的時候，表示每個quicklist節點的ziplist最多包含5個資料項。
 # 當取負值的時候，表示按照佔用位元組數來限定每個quicklist節點上的ziplist長度。這時，它只能取-1到-5這五個值，每個值含義如下：
 #     -5: 每個quicklist節點上的ziplist大小不能超過64 Kb。（注：1kb => 1024 bytes）
 #     -4: 每個quicklist節點上的ziplist大小不能超過32 Kb。
 #     -3: 每個quicklist節點上的ziplist大小不能超過16 Kb。
 #     -2: 每個quicklist節點上的ziplist大小不能超過8 Kb。（-2是Redis給出的預設值）
 #     -1: 每個quicklist節點上的ziplist大小不能超過4 Kb。
 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.
 # 這個參數列示一個quicklist兩端不被壓縮的節點個數。
 # 注：這裡的節點個數是指quicklist雙向連結串列的節點個數，而不是指ziplist裡面的資料項個數。
 # 實際上，一個quicklist節點上的ziplist，如果被壓縮，就是整體被壓縮的。
 # 引數list-compress-depth的取值含義如下：
 #     0: 是個特殊值，表示都不壓縮。這是Redis的預設值。
 #     1: 表示quicklist兩端各有1個節點不壓縮，中間的節點壓縮。
 #     2: 表示quicklist兩端各有2個節點不壓縮，中間的節點壓縮。
 #     3: 表示quicklist兩端各有3個節點不壓縮，中間的節點壓縮。
 #     依此類推…
 # 由於0是個特殊值，很容易看出quicklist的頭節點和尾節點總是不被壓縮的，以便於在表的兩端進行快速存取。
 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.
 #資料量小於等於set-max-intset-entries用intset，大於set-max-intset-entries用set
 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:
 # 資料量小於等於zset-max-ziplist-entries用ziplist，大於zset-max-ziplist-entries用zset
 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.
 # value大小小於等於hll-sparse-max-bytes使用稀疏資料結構（sparse）
 #   大於hll-sparse-max-bytes使用稠密的資料結構（dense），一個比16000大的value是幾乎沒用的，
 #   建議的value大概為3000。如果對CPU要求不高，對空間要求較高的，建議設定到10000左右
 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.
 #   Redis將在每100毫秒時使用1毫秒的CPU時間來對redis的hash表進行重新hash，可以降低記憶體的使用。
 #   當你的使用場景中，有非常嚴格的實時性需要，不能夠接受Redis時不時的對請求有2毫秒的延遲的話，把這項配置為no。
 #   如果沒有這麼嚴格的實時性要求，可以設定為yes，以便能夠儘可能快的釋放記憶體
 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.
 #  對客戶端輸出緩衝進行限制可以強迫那些不從伺服器讀取資料的客戶端斷開連線，用來強制關閉傳輸緩慢的客戶端。
 #  對於normal client，第一個0表示取消hard limit，第二個0和第三個0表示取消soft limit，normal client預設取消限制，
 #  因為如果沒有尋問，他們是不會接收資料的
 client-output-buffer-limit normal 0 0 0
 
 #  對於slave client和MONITER client，如果client-output-buffer一旦超過256mb，
 #  又或者超過64mb持續60秒，那麼伺服器就會立即斷開客戶端連線。
 client-output-buffer-limit slave 256mb 64mb 60
 
 #  對於pubsub client，如果client-output-buffer一旦超過32mb，又或者超過8mb持續60秒，那麼伺服器就會立即斷開客戶端連線。
 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.
 #   在aof重寫的時候，如果開啟了aof-rewrite-incremental-fsync開關，系統會每32MB執行一次fsync。
 #   這對於把檔案寫入磁碟是有幫助的，可以避免過大的延遲峰值
 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 熱點key 發現機制的 概率因子和衰減因子
 # 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