Redis配置文件詳解

# Redis configuration file example.

################################## 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.
#
# 假如說你有一個可用於全部的 redis server 的標準配置模板，
# 但針對某些 server 又須要一些個性化的設置，
# 你可使用 include 來包含一些其餘的配置文件，這對你來講是很是有用的。
#
# 可是要注意哦，include 是不能被 config rewrite 命令改寫的
# 因爲 redis 老是以最後的加工線做爲一個配置指令值，因此你最好是把 include 放在這個文件的最前面，
# 以免在運行時覆蓋配置的改變，相反，你就把它放在後面
# include /path/to/local.conf
# include /path/to/other.conf

################################ 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.
# 默認狀況下 redis 不是做爲守護進程運行的，若是你想讓它在後臺運行，你就把它改爲 yes。
# 當redis做爲守護進程運行的時候，它會寫一個 pid 到 /var/run/redis.pid 文件裏面。
daemonize yes

# When running daemonized, Redis writes a pid file in /var/run/redis.pid by
# default. You can specify a custom pid file location here.
# 當 Redis 以守護進程的方式運行的時候，Redis 默認會把 pid 文件放在/var/run/redis.pid
# 可配置到其餘地址，當運行多個 redis 服務時，須要指定不一樣的 pid 文件和端口
# 指定存儲Redis進程號的文件路徑
pidfile /usr/local/redis/redis.pid

# Accept connections on the specified port, default is 6379.
# If port 0 is specified Redis will not listen on a TCP socket.
# 端口，默認端口是6379，生產環境中建議更改端口號，安全性更高
# 若是你設爲 0 ，redis 將不在 socket 上監放任何客戶端鏈接。
port 6379

# TCP listen() backlog.
#
# In high requests-per-second environments you need an high backlog in order
# to avoid slow clients connections issues. Note that the Linux kernel
# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
# in order to get the desired effect.
# TCP 監聽的最大容納數量
# 此參數肯定了TCP鏈接中已完成隊列(完成三次握手以後)的長度，
# 當系統併發量大而且客戶端速度緩慢的時候，你須要把這個值調高以免客戶端鏈接緩慢的問題。
# Linux 內核會一言不發的把這個值縮小成 /proc/sys/net/core/somaxconn 對應的值128，默認是511，而Linux的默認參數值是128，因此能夠將這二個參數一塊兒參考設定，你以便達到你的預期。
# 實際在啓動redis時，會有WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
tcp-backlog 511

# By default Redis listens for connections from all the network interfaces
# available on the server. It is possible to listen to just one or multiple
# interfaces using the "bind" configuration directive, followed by one or
# more IP addresses.
#
# Examples:
#
# bind 192.168.1.100 10.0.0.1
# 有時候爲了安全起見，redis通常都是監聽127.0.0.1 可是有時候又有同網段能鏈接的需求，固然能夠綁定0.0.0.0 用iptables來控制訪問權限，或者設置redis訪問密碼來保證數據安全

# 不設置將處理全部請求,建議生產環境中設置，有個誤區：bind是用來限制外網IP訪問的，其實不是，限制外網ip訪問能夠經過iptables；
如：-A INPUT -s 10.10.1.0/24 -p tcp -m state --state NEW -m tcp --dport 9966 -j ACCEPT ；
# 實際上，bind ip 綁定的是redis所在服務器網卡的ip，固然127.0.0.1也是能夠的
#若是綁定一個外網ip，就會報錯：Creating Server TCP listening socket xxx.xxx.xxx.xxx:6379: bind: Cannot assign requested address

# bind 127.0.0.1
bind 127.0.0.1 10.10.1.3

# 假設綁定是以上ip，使用 netstat -anp|grep 9966 會發現，這兩個ip被bind，其中10.10.1.3是服務器網卡的ip
# tcp        0      0 10.10.1.3:6379         0.0.0.0:*                   LISTEN      11188/redis-server  
# tcp        0      0 127.0.0.1:6379         0.0.0.0:*                   LISTEN      11188/redis-server 

# 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)
#前段時間，因爲線上redis服務器的內存使用率達到了機器總內存的50%以上，致使內存數據的dump持久化一直失敗。擴展到多臺redis後，應用系統訪問redis時，
#在業務量較少時，時不時會出現如下異常，當業務量較大，redis訪問頻率很高時，卻不會發生這個異常，一時以爲很詭異
#redis.clients.jedis.exceptions.JedisConnectionException:It seems like server has closed the connection.
#看提示，應該是服務端主動關閉了鏈接。查看了新上線的redis服務器的配置，有這麼一項：timeout 120
#客戶端和Redis服務端的鏈接超時時間，默認是0，表示服務端永不主動關閉鏈接。
#而op人員把服務器端的超時時間設置爲了120秒。這就解釋了發生這個異常的緣由。客戶端使用了一個鏈接池管理訪問redis的全部鏈接，這些鏈接是長鏈接，當業務量較小時，
#客戶端部分鏈接使用率較低，當兩次使用之間的間隔超過120秒時，redis服務端就主動關閉了這個鏈接，而等客戶端下次再使用這個鏈接對象時，發現服務端已經關閉了鏈接，進而報錯。
#解決方案有兩種：

　　1. 在redis-cli下直接修改redis 的配置，把timeout改回爲0，無需重啓redis便可直接生效。

　　2. 修改應用系統代碼，設置鏈接的最大空閒時長（超出此時長將斷開空閒鏈接）小於120秒。

　　出於改動成本考慮，採用了第一種方案，修改後，報錯再也不出現。

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 60 seconds.

# tcp 心跳包。
#
# 若是設置爲非零，則在與客戶端缺少通信的時候使用 SO_KEEPALIVE 發送 tcp acks 給客戶端。
# 這個之全部有用，主要由兩個緣由：
#
# 1) 防止死的 peers
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# 推薦一個合理的值就是60秒
tcp-keepalive 60

# 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)
# 日誌記錄等級，4個可選值debug,verbose,notice,warning
# 能夠是下面的這些值：
# debug (適用於開發或測試階段)
# verbose (many rarely useful info, but not a mess like the debug level)
# notice (適用於生產環境)
# warning (僅僅一些重要的消息被記錄)
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
#配置 log 文件地址,默認打印在命令行終端的窗口上，也可設爲/dev/null屏蔽日誌。該地址若是配置的是相對路徑，相對於dir配置的路徑.通常推薦配置絕對路徑
logfile "./redis6379.log"

 

# To enable logging to the system logger, just set 'syslog-enabled' to yes,
# and optionally update the other syslog parameters to suit your needs.
# 要想把日誌記錄到系統日誌，就把它改爲 yes，
# 也能夠可選擇性的更新其餘的syslog 參數以達到你的要求
# syslog-enabled no

# Specify the syslog identity.
# 設置 syslog 的 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
# 可用的數據庫數，默認值爲16，默認數據庫爲0，數據庫範圍在0-（database-1）之間
databases 16

################################ 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 ""
# 在 900 秒內最少有 1 個 key 被改動，或者 300 秒內最少有 10 個 key 被改動，又或者 60 秒內最少有 1000 個 key 被改動，以上三個條件隨便知足一個，就觸發一次保存操做。

#    if(在60秒以內有10000個keys發生變化時){
#      進行鏡像備份
#    }else if(在300秒以內有10個keys發生了變化){
#      進行鏡像備份
#    }else if(在900秒以內有1個keys發生了變化){
#      進行鏡像備份
#    }

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.
# 默認狀況下，若是 redis 最後一次的後臺保存失敗，redis 將中止接受寫操做，
# 這樣以一種強硬的方式讓用戶知道數據不能正確的持久化到磁盤，
# 不然就會沒人注意到災難的發生。
#
# 若是後臺保存進程從新啓動工做了，redis 也將自動的容許寫操做。
#
# 然而你要是安裝了靠譜的監控，你可能不但願 redis 這樣作，那你就改爲 no 好
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.
# 在進行備份時,是否進行壓縮
# 是否在 dump .rdb 數據庫的時候使用 LZF 壓縮字符串
# 默認都設爲 yes
# 若是你但願保存子進程節省點 cpu ，你就設置它爲 no ，
# 不過這個數據集可能就會比較大
rdbcompression yes

# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
# This makes the format more resistant to corruption but there is a performance
# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
# for maximum performances.
#
# RDB files created with checksum disabled have a checksum of zero that will
# tell the loading code to skip the check.    
# 讀取和寫入的時候是否支持CRC64校驗，默認是開啓的
rdbchecksum yes

# The filename where to dump the DB
# 備份文件的文件名
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.
# 數據庫備份的文件放置的路徑
# 路徑跟文件名分開配置是由於 Redis 備份時，先會將當前數據庫的狀態寫入到一個臨時文件
# 等備份完成時，再把該臨時文件替換爲上面所指定的文件
# 而臨時文件和上面所配置的備份文件都會放在這個指定的路徑當中
# 默認值爲 ./，該相對路徑是根據你啓動redis-server的路徑有關，好比./src/redis-server,那麼./就表明和src同級目錄，最好用絕對路徑。
dir /usr/local/redis/data6379

################################# REPLICATION - 主從複製 #################################

# 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.
#
# 設置該數據庫爲其餘數據庫的從數據庫
# slaveof <masterip> <masterport> 當本機爲從服務時，設置主服務的IP及端口
# 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.
#
# 指定與主數據庫鏈接時須要的密碼驗證
# masterauth <master-password> 當本機爲從服務時，設置訪問master服務器的密碼
# 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slave服務器和master服務器失去鏈接後，或者當數據正在複製傳輸的時候，若是此參數值設置「yes」，slave服務器能夠繼續接受客戶端的請求，不然，
#會返回給請求的客戶端以下信息「SYNC with master in progress」,除了INFO，SLAVEOF這兩個命令
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.
# 是否容許slave服務器節點只提供讀服務
slave-read-only yes

# 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.
#
# Slaves 在一個預約義的時間間隔內發送 ping 命令到 server 。
# 你能夠改變這個時間間隔。默認爲 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.
#
# 設置主從複製過時時間
# 這個值必定要比 repl-ping-slave-period 大
# 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.
# 指定向slave同步數據時，是否禁用socket的NO_DELAY選 項。若配置爲「yes」，則禁用NO_DELAY，則TCP協議棧會合並小包統一發送，這樣能夠減小主從節點間的包數量並節省帶寬，但會增長數據同步到 slave的時間。
#若配置爲「no」，代表啓用NO_DELAY，則TCP協議棧不會延遲小包的發送時機，這樣數據同步的延時會減小，但須要更大的帶寬。 一般狀況下，應該配置爲no以下降同步延時，但在主從節點間網絡負載已經很高的狀況下，能夠配置爲yes。
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.
#
# 設置主從複製容量大小。這個 backlog 是一個用來在 slaves 被斷開鏈接時
# 存放 slave 數據的 buffer，因此當一個 slave 想要從新鏈接，一般不但願所有從新同步，
# 只是部分同步就夠了，僅僅傳遞 slave 在斷開鏈接時丟失的這部分數據。

# The biggest the replication backlog, the longer the time the slave can be
# disconnected and later be able to perform a partial resynchronization.
# 這個值越大，salve 能夠斷開鏈接的時間就越長。

# 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.
#
# A value of 0 means to never release the backlog.
#
# 在某些時候，master 再也不鏈接 slaves，backlog 將被釋放。
# 若是設置爲 0 ，意味着毫不釋放 backlog 。
# repl-backlog-ttl 3600

# The slave priority is an integer number published by Redis in the INFO output.
# It is used by Redis Sentinel in order to select a slave to promote into a
# master if the master is no longer working correctly.
#
# A slave with a low priority number is considered better for promotion, so
# for instance if there are three slaves with priority 10, 100, 25 Sentinel will
# pick the one with priority 10, that is the lowest.
#
# 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.
# 指定slave的優先級。在不僅1個slave存在的部署環境下，當master宕機時，Redis
# Sentinel會將priority值最小的slave提高爲master。
# 這個值越小，就越會被優先選中，須要注意的是，
# 若該配置項爲0，則對應的slave永遠不會自動提高爲master。
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:
#
# 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.

   

################################## 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.
#
# 設置鏈接redis的密碼
# redis速度至關快，一個外部用戶在一秒鐘進行150K次密碼嘗試，需指定強大的密碼來防止暴力破解
requirepass set_enough_strong_passwd

# Command renaming.
#
# It is possible to change the name of dangerous commands in a shared
# environment. For instance the CONFIG command may be renamed into something
# hard to guess so that it will still be available for internal-use tools
# but not available for general clients.
#
# Example:
#
# rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
#
# It is also possible to completely kill a command by renaming it into
# an empty string:
#
# rename-command CONFIG ""
#
# Please note that changing the name of commands that are logged into the
# AOF file or transmitted to slaves may cause problems.
# 重命名一些高危命令，用來禁止高危命令
rename-command FLUSHALL ZYzv6FOBdwflW2nX
rename-command CONFIG aI7zwm1GDzMMrEi
rename-command EVAL S9UHPKEpSvUJMM
rename-command FLUSHDB D60FPVDJuip7gy6l

################################### 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'.
#
# 限制同時鏈接的客戶數量,默認是10000
# 當鏈接數超過這個值時，redis 將再也不接收其餘鏈接請求，客戶端嘗試鏈接時將收到 error 信息
# maxclients 10000

# 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').
#
# 設置redis可以使用的最大內存。
# 達到最大內存設置後，Redis會先嚐試清除已到期或即將到期的Key（設置過expire信息的key）
# 在刪除時,按照過時時間進行刪除，最先將要被過時的key將最早被刪除
# 若是已到期或即將到期的key刪光，仍進行set操做，那麼將返回錯誤
# 此時redis將再也不接收寫請求,只接收get請求。
# maxmemory的設置比較適合於把redis看成於相似memcached 的緩存來使用
# 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

# 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

############################## 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.

# redis 默認每次更新操做後會在後臺異步的把數據庫鏡像備份到磁盤，但該備份很是耗時，且備份不宜太頻繁
# redis 同步數據文件是按上面save條件來同步的
# 若是發生諸如拉閘限電、拔插頭等情況,那麼將形成比較大範圍的數據丟失
# 因此redis提供了另一種更加高效的數據庫備份及災難恢復方式
# 開啓append only 模式後,redis 將每一次寫操做請求都追加到appendonly.aof 文件中
# redis從新啓動時,會從該文件恢復出以前的狀態。
# 但可能會形成 appendonly.aof 文件過大，因此redis支持BGREWRITEAOF 指令，對appendonly.aof從新整理,默認是不開啓的。

appendonly no

# The name of the append only file (default: "appendonly.aof")
# 默認爲appendonly.aof。
appendfilename "appendonly.aof"

# The fsync() call tells the Operating System to actually write data on disk
# instead of waiting for more data in the output buffer. Some OS will really flush
# data on disk, some other OS will just try to do it ASAP.
#
# Redis supports three different modes:
#
# no: don't fsync, just let the OS flush the data when it wants. Faster.
# always: fsync after every write to the append only log. Slow, Safest.
# everysec: fsync only one time every second. Compromise.
#
# The default is "everysec", as that's usually the right compromise between
# speed and data safety. It's up to you to understand if you can relax this to
# "no" that will let the operating system flush the output buffer when
# it wants, for better performances (but if you can live with the idea of
# some data loss consider the default persistence mode that's snapshotting),
# or on the contrary, use "always" that's very slow but a bit safer than
# everysec.
#
# More details please check the following article:
# http://antirez.com/post/redis-persistence-demystified.html
#
# If unsure, use "everysec".

# 設置對 appendonly.aof 文件進行同步的頻率,有三種選擇always、everysec、no，默認是everysec表示每秒同步一次。
# always 表示每次有寫操做都進行同步,everysec 表示對寫操做進行累積,每秒同步一次。
# no表示等操做系統進行數據緩存同步到磁盤，都進行同步,everysec 表示對寫操做進行累積,每秒同步一次
# 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.
# 指定是否在後臺aof文件rewrite期間調用fsync，默認爲no，表示要調用fsync（不管後臺是否有子進程在刷盤）。Redis在後臺寫RDB文件或重寫afo文件期間會存在大量磁盤IO，此時，在某些linux系統中，調用fsync可能會阻塞。
no-appendfsync-on-rewrite yes

# 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.
# 指定Redis重寫aof文件的條件，默認爲100，表示與上次rewrite的aof文件大小相比，當前aof文件增加量超過上次afo文件大小的100%時，就會觸發background rewrite。若配置爲0，則會禁用自動rewrite
auto-aof-rewrite-percentage 100

# 指定觸發rewrite的aof文件大小。若aof文件小於該值，即便當前文件的增量比例達到auto-aof-rewrite-percentage的配置值，也不會觸發自動rewrite。即這兩個配置項同時知足時，纔會觸發rewrite。
auto-aof-rewrite-min-size 64mb

################################ 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.
# 一個Lua腳本最長的執行時間，單位爲毫秒，若是爲0或負數表示無限執行時間，默認爲5000
lua-time-limit 5000

############################### 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.
# 當hash中包含超過指定元素個數而且最大的元素沒有超過臨界時，
# hash將以一種特殊的編碼方式（大大減小內存使用）來存儲，這裏能夠設置這兩個臨界值
hash-max-ziplist-entries 512
hash-max-ziplist-value 64

# Similarly to hashes, small lists are also encoded in a special way in order
# to save a lot of space. The special representation is only used when
# you are under the following limits:
# list數據類型多少節點如下會採用去指針的緊湊存儲格式。
# list數據類型節點值大小小於多少字節會採用緊湊存儲格式。
list-max-ziplist-entries 512
list-max-ziplist-value 64

# Sets have a special encoding in just one case: when a set is composed
# of just strings that happen to be integers in radix 10 in the range
# of 64 bit signed integers.
# The following configuration setting sets the limit in the size of the
# set in order to use this special memory saving encoding.
# set數據類型內部數據若是所有是數值型，且包含多少節點如下會採用緊湊格式存儲。
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:

# zsort數據類型多少節點如下會採用去指針的緊湊存儲格式。
# zsort數據類型節點值大小小於多少字節會採用緊湊存儲格式。
zset-max-ziplist-entries 128
zset-max-ziplist-value 64

# 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表進行從新hash，能夠下降內存的使用
# 當你的使用場景中，有很是嚴格的實時性須要，不可以接受Redis時不時的對請求有2毫秒的延遲的話，把這項配置爲no。
# 若是沒有這麼嚴格的實時性要求，能夠設置爲yes，以便可以儘量快的釋放內存
activerehashing yes

# When a child rewrites the AOF file, if the following option is enabled
# the file will be fsync-ed every 32 MB of data generated. This is useful
# in order to commit the file to the disk more incrementally and avoid
# big latency spikes.
# aof rewrite過程當中,是否採起增量文件同步策略,默認爲「yes」。 rewrite過程當中,每32M數據進行一次文件同步,這樣能夠減小aof大文件寫入對磁盤的操做次數
aof-rewrite-incremental-fsync yes

 

# redis數據存儲
redis的存儲分爲內存存儲、磁盤存儲和log文件三部分，配置文件中有三個參數對其進行配置。
save seconds updates，save配置，指出在多長時間內，有多少次更新操做，就將數據同步到數據文件。可多個條件配合，默認配置了三個條件。
appendonly yes/no ，appendonly配置，指出是否在每次更新操做後進行日誌記錄，若是不開啓，可能會在斷電時致使一段時間內的數據丟失。由於redis自己同步數據文件是按上面的save條件來同步的，因此有的數據會在一段時間內只存在於內存中。
appendfsync no/always/everysec ，appendfsync配置，no表示等操做系統進行數據緩存同步到磁盤，always表示每次更新操做後手動調用fsync()將數據寫到磁盤，everysec表示每秒同步一次。