Redis配置檔案-redis.conf-3.2.0
阿新 • • 發佈：2019-01-06
# 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 ###################################
# 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
#額外載入配置檔案，如果需要的話，可以開啟此配置
################################## 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.
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# bind 127.0.0.1
#繫結redis伺服器網絡卡IP，預設為127.0.0.1,即本地迴環地址。這樣的話，訪問redis服務只能通過本機的客戶端連線，而無法通過遠端連線。如果bind選項為空的話，那會接受所有來自於可用網路介面的連線。如上配置，繫結一個127.0.0.1的本機地址和192.168.1.100的外網地址。
# 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
#保護模式，預設是開啟狀態，只允許本地客戶端連線，可以設定密碼或新增bind來連線
# 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 6379
#監聽埠號，預設為6379，如果設定為0，redis將不在socket上監聽任何客戶端連線
# 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
#TCP監聽的最大容量，在高併發的環境下，你需要把這個值調高以避免客戶端連線緩慢的問題。Linux核心會把這個值縮小成/proc/sys/net/core/somaxconn對應的值，要提升併發量需要修改這兩個值才能達到目的
# 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
#指定redis監聽的unix socket路徑，預設不啟用，unixsocketper指定檔案的許可權
# Close the connection after a client is idle for N seconds (0 to disable)
timeout 0
#指定在一個client空閒多少秒之後關閉連線（0表示永不關閉）
# 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 60 seconds.
tcp-keepalive 0
#單位是秒，表示將週期性的使用SO_KEEPALIVE檢測客戶端是否還處於健康狀態，避免伺服器一直阻塞，官方給出的建議值是300s，如果設定為0，則不會週期性的檢測
################################# 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 no
#預設情況下redis不是作為守護程序執行的，如果你想讓它在後臺執行，你就把它改成yes.當redis作為守護程序執行的時候，它會寫一個pid到/var/run/redis.pid檔案裡面
# 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 $NOTIFY_SOCKET
# supervised auto - detect upstart or systemd method based on
# UPSTART_JOB or NOTIFY_SOCKET environment variables
# Note: these supervision methods only signal "process is ready."
# They do not enable continuous liveness pings back to your supervisor.
supervised no
#可以通過upstart和systemd管理Redis守護程序
#選項：
# supervised no - 沒有監督互動
# supervised upstart - 通過將Redis置於SIGSTOP模式來啟動訊號
# supervised systemd - signal systemd將READY = 1寫入$ NOTIFY_SOCKET
# supervised auto - 檢測upstart或systemd方法基於 UPSTART_JOB或NOTIFY_SOCKET環境變數
# 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.pid
#配置PID檔案路徑，當redis作為守護執行緒執行時，它會把pid預設寫到/var/run/redis.pid裡面
# 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
#定義日誌級別。
# 可以是下面的這些值：
# debug（記錄大量日誌資訊，適用於開發、測試階段）
# verbose（較多日誌資訊）
# notice（適量日誌資訊，使用於生產環境）
# warning（僅有部分重要、關鍵資訊才會被記錄）
# 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 ""
#日誌檔案的位置，當指定為空字串時，為標準輸出，如果redis已守護程序模式執行，那麼日誌將會輸出到/dev/null
# 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
#要想把日誌記錄為系統日誌，就把它改成yes，也可以可選擇性的更新其他的syslog引數以達到你的要求
# Specify the syslog identity.
# syslog-ident redis
#設定系統日誌的ID
# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
# syslog-facility local0
#指定系統日誌設定，必須是 USER 或者是 LOCAL0-LOCAL7 之間的值
# 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
#設定資料庫的數目。預設的資料庫是DB 0 ，可以在每個連線上使用select <dbid> 命令選擇一個不同的資料庫，dbid是一個介於0到databases - 1 之間的數值。
################################ SNAPSHOTTING 快照################################
#
# 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 # 觸發自動儲存快照
# 存 DB 到磁碟：
# 格式：save <間隔時間（秒）> <寫入次數>
# 根據給定的時間間隔和寫入次數將資料儲存到磁碟
# 下面的例子的意思是：
# 900 秒內如果至少有 1 個 key 的值變化，則儲存
# 300 秒內如果至少有 10 個 key 的值變化，則儲存
# 60 秒內如果至少有 10000 個 key 的值變化，則儲存
# 注意：你可以註釋掉所有的 save 行來停用儲存功能。
# 也可以直接一個空字串來實現停用：
# save ""
# 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 #設定在儲存快照出錯時，是否停止redis命令的寫入
# 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。
# 這樣做的好處在於可以讓使用者很明確的知道記憶體中的資料和磁碟上的資料已經存在不一致了。
# 如果redis不顧這種不一致，一意孤行的繼續接收寫請求，就可能會引起一些災難性的後果。
# 如果下一次RDB持久化成功，redis會自動恢復接受寫請求。
# 如果不在乎這種資料不一致或者有其他的手段發現和控制這種不一致的話，可以關閉這個功能，
# 以便在快照寫入失敗時，也能確保redis繼續接受新的寫請求。
# 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 #是否在匯出.rdb資料庫檔案的時候採用LZF壓縮
# 對於儲存到磁碟中的快照，可以設定是否進行壓縮儲存。
# 如果是的話，redis會採用LZF演算法進行壓縮。如果你不想消耗CPU來進行壓縮的話，
# 可以設定為關閉此功能，但是儲存在磁碟上的快照會比較大。
# 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 #是否開啟CRC64校驗
# 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，
# 如果希望獲取到最大的效能提升，可以關閉此功能
# The filename where to dump the DB
dbfilename dump.rdb #匯出資料庫的檔名稱
# 設定快照的檔名
# 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 ./ #匯出的資料庫所在的目錄
# 設定快照檔案的存放路徑，這個配置項一定是個目錄，而不能是檔名
################################# 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.
#
# slaveof <masterip> <masterport>
#主從複製，使用slaveof來讓一個redis例項成為另一個redis例項的副本，預設關閉
#注意這個只需要在slave上配置
# 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.
#
# masterauth <master-password>
#如果master需要密碼認證，就在這裡設定，預設不設定
# 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.
#
slave-serve-stale-data yes
#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
# You can configure a slave instance to accept writes or not. Writing against
# a slave instance may be useful to store some ephemeral data (because data
# written on a slave will be easily deleted after resync with the master) but
# may also cause problems if clients are writing to it because of a
# misconfiguration.
#
# Since Redis 2.6 by default slaves are read-only.
#
# Note: read only slaves are not designed to be exposed to untrusted clients
# on the internet. It's just a protection layer against misuse of the instance.
# Still a read only slave exports by default all the administrative commands
# such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
# security of read only slaves using 'rename-command' to shadow all the
# administrative / dangerous commands.
slave-read-only yes
# 你可以配置一個 slave 實體是否接受寫入操作。
# 通過寫入操作來儲存一些短暫的資料對於一個 slave 例項來說可能是有用的，
# 因為相對從 master 重新同步數而言，據資料寫入到 slave 會更容易被刪除。
# 但是如果客戶端因為一個錯誤的配置寫入，也可能會導致一些問題。
# 從 redis 2.6 版起，預設 slaves 都是隻讀的。
# Replication SYNC strategy: disk or socket.
#
# -------------------------------------------------------
# WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
# -------------------------------------------------------
#
# New slaves and reconnecting slaves that are not able to continue the replication
# process just receiving differences, need to do what is called a "full
# synchronization". An RDB file is transmitted from the master to the slaves.
# The transmission can happen in two different ways:
#
# 1) Disk-backed: The Redis master creates a new process that writes the RDB
# file on disk. Later the file is transferred by the parent
# process to the slaves incrementally.
# 2) Diskless: The Redis master creates a new process that directly writes the
# RDB file to slave sockets, without touching the disk at all.
#
# With disk-backed replication, while the RDB file is generated, more slaves
# can be queued and served with the RDB file as soon as the current child producing
# the RDB file finishes its work. With diskless replication instead once
# the transfer starts, new slaves arriving will be queued and a new transfer
# will start when the current one terminates.
#
# When diskless replication is used, the master waits a configurable amount of
# time (in seconds) before starting the transfer in the hope that multiple slaves
# will arrive and the transfer can be parallelized.
#
# With slow disks and fast (large bandwidth) networks, diskless replication
# works better.
repl-diskless-sync no
# 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序，用於把RDB檔案寫到硬碟上。過一會兒，其父程序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序，子程序直接把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，主站的子程序生成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。
# When diskless replication is enabled, it is possible to configure the delay
# the server waits in order to spawn the child that transfers the RDB via socket
# to the slaves.
#
# This is important since once the transfer starts, it is not possible to serve
# new slaves arriving, that will be queued for the next RDB transfer, so the server
# waits a delay in order to let more slaves arrive.
#
# The delay is specified in seconds, and by default is 5 seconds. To disable
# it entirely just set it to 0 seconds and the transfer will start ASAP.
repl-diskless-sync-delay 5
# 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。
# 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.
#
# repl-ping-slave-period 10
#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。
# 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.
#
# repl-timeout 60
# 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。
# 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.
repl-disable-tcp-nodelay no
# 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。
# 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.
#
# repl-backlog-size 1mb
# 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。
# 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.
#
# A value of 0 means to never release the backlog.
#
# repl-backlog-ttl 3600
# 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。
# 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.
slave-priority 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
# 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:
#
# min-slaves-to-write 3
# min-slaves-max-lag 10
# 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
#
# 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.
################################## 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 foobared
#設定Redis連線密碼
# 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 ""
# 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。
#
# Please note that changing the name of commands that are logged into the
# AOF file or transmitted to slaves may cause problems.
################################### LIMITS ####################################
# 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
# 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程序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
# Don't use more memory than 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 cache, or to set
# a hard memory limit for an instance (using the 'noeviction' policy).
#
# WARNING: If you have slaves attached to an instance with maxmemory on,
# the size of the output buffers needed to feed the slaves are subtracted
# from the used memory count, so that network problems / resyncs will
# not trigger a loop where keys are evicted, and in turn the output
# buffer of slaves is full with DELs of keys evicted triggering the deletion
# of more keys, and so forth until the database is completely emptied.
#
# In short... if you have slaves attached it is suggested that you set a lower
# limit for maxmemory so that there is some free RAM on the system for slave
# output buffers (but this is not needed if the policy is 'noeviction').
#
# maxmemory <bytes>
# 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 POLICY: how Redis will select what to remove when maxmemory
# is reached. You can select among five behaviors:
#
# volatile-lru -> remove the key with an expire set using an LRU algorithm
# allkeys-lru -> remove any key according to the LRU algorithm
# volatile-random -> remove a random key with an expire set
# allkeys-random -> remove a random key, any key
# volatile-ttl -> remove the key with the nearest expire time (minor TTL)
# noeviction -> don't expire at all, just return an error on write operations
#
# 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
# 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
# LRU 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 a bit more CPU. 3 is very fast but not very accurate.
#
# maxmemory-samples 5
# 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
############################## 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 #是否開啟AOF功能
# 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如果中途宕機，
# 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。
# The name of the append only file (default: "appendonly.aof")
appendfilename "appendonly.aof" #AOF檔名稱
#aof檔名
# 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:
#