redis.conf配置

# Redis configuration file example
# Redis示例配置文件
# 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:
# 注意单位问题：当需要设置内存大小的时候，可以使用类似1k、5GB、4M这样的常见格式：
#
# 1k => 1000 bytes
# 1kb => 1024 bytes
# 1m => 1000000 bytes
# 1mb => 1024*1024 bytes
# 1g => 1000000000 bytes
# 1gb => 1024*1024*1024 bytes
#
# units are case insensitive so 1GB 1Gb 1gB are all the same.
# 单位是大小写不敏感的，所以1GB 1Gb 1gB的写法都是完全一样的
################################## INCLUDES ###################################
# Include one or more other config files here.  This is useful if you
# have a standard template that goes to all Redis servers but also need
# to customize a few per-server settings.  Include files can include
# other files, so use this wisely.
#
# Notice option "include" won‘t be rewritten by command "CONFIG REWRITE"
# from admin or Redis Sentinel. Since Redis always uses the last processed
# line as value of a configuration directive, you‘d better put includes
# at the beginning of this file to avoid overwriting config change at runtime.
#
# If instead you are interested in using includes to override configuration
# options, it is better to use include as the last line.
# 包含一个或多个其他配置文件。
# 这在你有标准配置模板但是每个redis服务器又需要个性设置的时候很有用。
# 包含文件特性允许你引人其他配置文件，所以好好利用吧。
#
# 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.
# Redis默认是不作为守护进程来运行的。你可以把这个设置为"yes"让它作为守护进程来运行。
# 注意，当作为守护进程的时候，Redis会把进程ID写到 /var/run/redis.pid
daemonize no
# When running daemonized, Redis writes a pid file in /var/run/redis.pid by
# default. You can specify a custom pid file location here.
# 当以守护进程方式运行的时候，Redis会把进程ID默认写到 /var/run/redis.pid。你可以在这里修改路径
pidfile /var/run/redis.pid
# Accept connections on the specified port, default is 6379.
# If port 0 is specified Redis will not listen on a TCP socket.
# 接受连接的特定端口，默认是6379。
# 如果端口设置为0，Redis就不会监听TCP套接字。
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-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.
# 如果你想的话，你可以绑定单一接口；如果这里没单独设置，那么所有接口的连接都会被监听
# Examples:
#
# bind 192.168.1.100 10.0.0.1
# bind 127.0.0.1
# Specify the path for the Unix socket that will be used to listen for
# incoming connections. There is no default, so Redis will not listen
# on a unix socket when not specified.
# 指定用来监听连接的unxi套接字的路径。这个没有默认值，所以如果你不指定的话，Redis就不会通过unix套接字来监听
# unixsocket /tmp/redis.sock
# unixsocketperm 700
# Close the connection after a client is idle for N seconds (0 to disable)
# 一个客户端空闲多少秒后关闭连接。(0代表禁用，永不关闭)
timeout 0
# TCP keepalive.
#
# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
# of communication. This is useful for two reasons:
#
# 1) Detect dead peers.
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# On Linux, the specified value (in seconds) is the period used to send ACKs.
# Note that to close the connection the double of the time is needed.
# On other kernels the period depends on the kernel configuration.
#
# A reasonable value for this option is 60 seconds.
tcp-keepalive 0
# 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)
# 设置服务器调试等级。
# 可能值：
# debug （很多信息，对开发/测试有用）
# verbose （很多精简的有用信息，但是不像debug等级那么多）
# notice （适量的信息，基本上是你生产环境中需要的程度）
# warning （只有很重要/严重的信息会记录下来）
loglevel notice
# Specify the log file name. Also the empty string can be used to force
# Redis to log on the standard output. Note that if you use standard
# output for logging but daemonize, logs will be sent to /dev/null
# 指明日志文件名。也可以使用"stdout"来强制让Redis把日志信息写到标准输出上。
# 注意：如果Redis以守护进程方式运行，而你设置日志显示到标准输出的话，那么日志会发送到 /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.
# 要使用系统日志记录器很简单，只要设置 "syslog-enabled" 为 "yes" 就可以了。
# 然后根据需要设置其他一些syslog参数就可以了。
# syslog-enabled no
# Specify the syslog identity.
# 指明syslog身份
# syslog-ident redis
# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
# 指明syslog的设备。必须是一个用户或者是 LOCAL0 ~ LOCAL7 之一。
# syslog-facility local0
# Set the number of databases. The default database is DB 0, you can select
# a different one on a per-connection basis using SELECT <dbid> where
# dbid is a number between 0 and ‘databases‘-1
# 设置数据库个数。默认数据库是 DB 0，你可以通过SELECT <dbid> WHERE dbid（0～‘databases‘ - 1）来为每个连接使用不同的数据库。
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:
#
# 把数据库存到磁盘上:
#
#   save <seconds> <changes>
#   
#   会在指定秒数和数据变化次数之后把数据库写到磁盘上。
#
#   下面的例子将会进行把数据写入磁盘的操作:
#   900秒（15分钟）之后，且至少1次变更
#   300秒（5分钟）之后，且至少10次变更
#   60秒之后，且至少10000次变更
#
#   注意：你要想不写磁盘的话就把所有 "save" 设置注释掉就行了。
#
#   save ""
save 900 1
save 300 10
save 60 10000
# By default Redis will stop accepting writes if RDB snapshots are enabled
# (at least one save point) and the latest background save failed.
# This will make the user aware (in a hard way) that data is not persisting
# on disk properly, otherwise chances are that no one will notice and some
# disaster will happen.
#
# If the background saving process will start working again Redis will
# automatically allow writes again.
#
# However if you have setup your proper monitoring of the Redis server
# and persistence, you may want to disable this feature so that Redis will
# continue to work as usual even if there are problems with disk,
# permissions, and so forth.
stop-writes-on-bgsave-error yes
# Compress string objects using LZF when dump .rdb databases?
# For default that‘s set to ‘yes‘ as it‘s almost always a win.
# If you want to save some CPU in the saving child set it to ‘no‘ but
# the dataset will likely be bigger if you have compressible values or keys.
# 当导出到 .rdb 数据库时是否用LZF压缩字符串对象。
# 默认设置为 "yes"，所以几乎总是生效的。
# 如果你想节省CPU的话你可以把这个设置为 "no"，但是如果你有可压缩的key的话，那数据文件就会更大了。
rdbcompression yes
# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
# This makes the format more resistant to corruption but there is a performance
# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
# for maximum performances.
#
# RDB files created with checksum disabled have a checksum of zero that will
# tell the loading code to skip the check.
rdbchecksum yes
# The filename where to dump the DB
# 数据库的文件名
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.
# 工作目录
#
# 数据库会写到这个目录下，文件名就是上面的 "dbfilename" 的值。
# 
# 累加文件也放这里。
# 
# 注意你这里指定的必须是目录，不是文件名。
dir ./
################################# REPLICATION #################################
# Master-Slave replication. Use slaveof to make a Redis instance a copy of
# another Redis server. A few things to understand ASAP about Redis replication.
#
# 1) Redis replication is asynchronous, but you can configure a master to
#    stop accepting writes if it appears to be not connected with at least
#    a given number of slaves.
# 2) Redis slaves are able to perform a partial resynchronization with the
#    master if the replication link is lost for a relatively small amount of
#    time. You may want to configure the replication backlog size (see the next
#    sections of this file) with a sensible value depending on your needs.
# 3) Replication is automatic and does not need user intervention. After a
#    network partition slaves automatically try to reconnect to masters
#    and resynchronize with them.
#
# 主从同步。通过 slaveof 配置来实现Redis实例的备份。
# 注意，这里是本地从远端复制数据。也就是说，本地可以有不同的数据库文件、绑定不同的IP、监听不同的端口。
#
# 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.
# 如果master设置了密码（通过下面的 "requirepass" 选项来配置），那么slave在开始同步之前必须进行身份验证，否则它的同步请求会被拒绝。
#
# masterauth <master-password>
# When a slave loses its connection with the master, or when the replication
# is still in progress, the slave can act in two different ways:
#
# 1) if slave-serve-stale-data is set to ‘yes‘ (the default) the slave will
#    still reply to client requests, possibly with out of date data, or the
#    data set may just be empty if this is the first synchronization.
#
# 2) if slave-serve-stale-data is set to ‘no‘ the slave will reply with
#    an error "SYNC with master in progress" to all the kind of commands
#    but to INFO and SLAVEOF.
# 当一个slave失去和master的连接，或者同步正在进行中，slave的行为有两种可能：
#
# 1) 如果 slave-serve-stale-data 设置为 "yes" (默认值)，slave会继续响应客户端请求，可能是正常数据，也可能是还没获得值的空数据。
# 2) 如果 slave-serve-stale-data 设置为 "no"，slave会回复"正在从master同步（SYNC with master in progress）"来处理各种请求，除了 INFO 和 SLAVEOF 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.
slave-read-only yes
# Replication SYNC strategy: disk or socket.
#
# -------------------------------------------------------
# WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
# -------------------------------------------------------
#
# New slaves and reconnecting slaves that are not able to continue the replication
# process just receiving differences, need to do what is called a "full
# synchronization". An RDB file is transmitted from the master to the slaves.
# The transmission can happen in two different ways:
#
# 1) Disk-backed: The Redis master creates a new process that writes the RDB
#                 file on disk. Later the file is transferred by the parent
#                 process to the slaves incrementally.
# 2) Diskless: The Redis master creates a new process that directly writes the
#              RDB file to slave sockets, without touching the disk at all.
#
# With disk-backed replication, while the RDB file is generated, more slaves
# can be queued and served with the RDB file as soon as the current child producing
# the RDB file finishes its work. With diskless replication instead once
# the transfer starts, new slaves arriving will be queued and a new transfer
# will start when the current one terminates.
#
# When diskless replication is used, the master waits a configurable amount of
# time (in seconds) before starting the transfer in the hope that multiple slaves
# will arrive and the transfer can be parallelized.
#
# With slow disks and fast (large bandwidth) networks, diskless replication
# works better.
repl-diskless-sync no
# When diskless replication is enabled, it is possible to configure the delay
# the server waits in order to spawn the child that trnasfers the RDB via socket
# to the slaves.
#
# This is important since once the transfer starts, it is not possible to serve
# new slaves arriving, that will be queued for the next RDB transfer, so the server
# waits a delay in order to let more slaves arrive.
#
# The delay is specified in seconds, and by default is 5 seconds. To disable
# it entirely just set it to 0 seconds and the transfer will start ASAP.
repl-diskless-sync-delay 5
# Slaves send PINGs to server in a predefined interval. It‘s possible to change
# this interval with the repl_ping_slave_period option. The default value is 10
# seconds.
# slave根据指定的时间间隔向服务器发送ping请求。
# 时间间隔可以通过 repl_ping_slave_period 来设置。
# 默认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.
# 下面的选项设置了大块数据I/O、向master请求数据和ping响应的过期时间。
# 默认值60秒。
#
# 一个很重要的事情是：确保这个值比 repl-ping-slave-period 大，否则master和slave之间的传输过期时间比预想的要短。
#
# 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.
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.
#
# 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.
#
# 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.
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.
# 要求客户端在处理任何命令时都要验证身份和密码。
# 这在你信不过来访者时很有用。
#
# 为了向后兼容的话，这段应该注释掉。而且大多数人不需要身份验证（例如：它们运行在自己的服务器上。）
# 
# 警告：因为Redis太快了，所以居心不良的人可以每秒尝试150k的密码来试图破解密码。
# 这意味着你需要一个高强度的密码，否则破解太容易了。
#
# 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
# 命令重命名
#
# 在共享环境下，可以为危险命令改变名字。比如，你可以为 CONFIG 改个其他不太容易猜到的名字，这样你自己仍然可以使用，而别人却没法做坏事了。
#
# 例如:
#
# rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
#
# 甚至也可以通过给命令赋值一个空字符串来完全禁用这条命令：
#
# 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.
#请注意，改变指令所记录到的名字
#AOF文件或者发送到从站可能会引起问题。
################################### 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‘.
# 设置最多同时连接客户端数量。
# 默认没有限制，这个关系到Redis进程能够打开的文件描述符数量。
# 特殊值"0"表示没有限制。
# 一旦达到这个限制，Redis会关闭所有新连接并发送错误"达到最大用户数上限（max number of clients reached）"
#
# 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‘).
# 不要用比设置的上限更多的内存。一旦内存使用达到上限，Redis会根据选定的回收策略（参见：maxmemmory-policy）删除key。
#
# 如果因为删除策略问题Redis无法删除key，或者策略设置为 "noeviction"，Redis会回复需要更多内存的错误信息给命令。
# 例如，SET,LPUSH等等。但是会继续合理响应只读命令，比如：GET。
#
# 在使用Redis作为LRU缓存，或者为实例设置了硬性内存限制的时候（使用 "noeviction" 策略）的时候，这个选项还是满有用的。
#
# 警告：当一堆slave连上达到内存上限的实例的时候，响应slave需要的输出缓存所需内存不计算在使用内存当中。
# 这样当请求一个删除掉的key的时候就不会触发网络问题／重新同步的事件，然后slave就会收到一堆删除指令，直到数据库空了为止。
#
# 简而言之，如果你有slave连上一个master的话，那建议你把master内存限制设小点儿，确保有足够的系统内存用作输出缓存。
# （如果策略设置为"noeviction"的话就不无所谓了）
#
# 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
# 内存策略：如果达到内存限制了，Redis如何删除key。你可以在下面五个策略里面选：
# 
# volatile-lru -> 根据LRU算法生成的过期时间来删除。
# allkeys-lru -> 根据LRU算法删除任何key。
# volatile-random -> 根据过期设置来随机删除key。
# allkeys->random -> 无差别随机删。
# volatile-ttl -> 根据最近过期时间来删除（辅以TTL）
# noeviction -> 谁也不删，直接在写操作时返回错误。
# 
# 注意：对所有策略来说，如果Redis找不到合适的可以删除的key都会在写操作时返回一个错误。
#
#       这里涉及的命令：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 volatile-lru
# LRU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can select as well the sample
# size to check. For instance for default Redis will check three keys and
# pick the one that was used less recently, you can change the sample size
# using the following configuration directive.
# LRU和最小TTL算法的实现都不是很精确，但是很接近（为了省内存），所以你可以用样例做测试。
# 例如：默认Redis会检查三个key然后取最旧的那个，你可以通过下面的配置项来设置样本的个数。
#
# maxmemory-samples 3
############################## 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.
# 默认情况下，Redis是异步的把数据导出到磁盘上。这种情况下，当Redis挂掉的时候，最新的数据就丢了。
# 如果不希望丢掉任何一条数据的话就该用纯累加模式：一旦开启这个模式，Redis会把每次写入的数据在接收后都写入 appendonly.aof 文件。
# 每次启动时Redis都会把这个文件的数据读入内存里。
#
# 注意，异步导出的数据库文件和纯累加文件可以并存（你得把上面所有"save"设置都注释掉，关掉导出机制）。
# 如果纯累加模式开启了，那么Redis会在启动时载入日志文件而忽略导出的 dump.rdb 文件。
#
# 重要：查看 BGREWRITEAOF 来了解当累加日志文件太大了之后，怎么在后台重新处理这个日志文件。
appendonly no
# The name of the append only file (default: "appendonly.aof")
# 纯累加文件名字（默认："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".
# fsync() 请求操作系统马上把数据写到磁盘上，不要再等了。
# 有些操作系统会真的把数据马上刷到磁盘上；有些则要磨蹭一下，但是会尽快去做。
#
# Redis支持三种不同的模式：
#
# no：不要立刻刷，只有在操作系统需要刷的时候再刷。比较快。
# always：每次写操作都立刻写入到aof文件。慢，但是最安全。
# everysec：每秒写一次。折衷方案。
#
# 默认的 "everysec" 通常来说能在速度和数据安全性之间取得比较好的平衡。
# 如果你真的理解了这个意味着什么，那么设置"no"可以获得更好的性能表现（如果丢数据的话，则只能拿到一个不是很新的快照）；
# 或者相反的，你选择 "always" 来牺牲速度确保数据安全、完整。
#
# 如果拿不准，就用 "everysec"
# appendfsync always
appendfsync everysec
# appendfsync no
# When the AOF fsync policy is set to always or everysec, and a background
# saving process (a background save or AOF log background rewriting) is
# performing a lot of I/O against the disk, in some Linux configurations
# Redis may block too long on the fsync() call. Note that there is no fix for
# this currently, as even performing fsync in a different thread will block
# our synchronous write(2) call.
#
# In order to mitigate this problem it‘s possible to use the following option
# that will prevent fsync() from being called in the main process while a
# BGSAVE or BGREWRITEAOF is in progress.
#
# This means that while another child is saving, the durability of Redis is
# the same as "appendfsync none". In practical terms, this means that it is
# possible to lose up to 30 seconds of log in the worst scenario (with the
# default Linux settings).
#
# If you have latency problems turn this to "yes". Otherwise leave it as
# "no" that is the safest pick from the point of view of durability.
# 如果AOF的同步策略设置成 "always" 或者 "everysec"，那么后台的存储进程（后台存储或写入AOF日志）会产生很多磁盘I/O开销。
# 某些Linux的配置下会使Redis因为 fsync() 而阻塞很久。
# 注意，目前对这个情况还没有完美修正，甚至不同线程的 fsync() 会阻塞我们的 write(2) 请求。
#
# 为了缓解这个问题，可以用下面这个选项。它可以在 BGSAVE 或 BGREWRITEAOF 处理时阻止 fsync()。
# 
# 这就意味着如果有子进程在进行保存操作，那么Redis就处于"不可同步"的状态。
# 这实际上是说，在最差的情况下可能会丢掉30秒钟的日志数据。（默认Linux设定）
# 
# 如果你有延迟的问题那就把这个设为 "yes"，否则就保持 "no"，这是保存持久数据的最安全的方式。
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.
# 自动重写AOF文件
#
# 如果AOF日志文件大到指定百分比，Redis能够通过 BGREWRITEAOF 自动重写AOF日志文件。
# 
# 工作原理：Redis记住上次重写时AOF日志的大小（或者重启后没有写操作的话，那就直接用此时的AOF文件），
#           基准尺寸和当前尺寸做比较。如果当前尺寸超过指定比例，就会触发重写操作。
#
# 你还需要指定被重写日志的最小尺寸，这样避免了达到约定百分比但尺寸仍然很小的情况还要重写。
#
# 指定百分比为0会禁用AOF自动重写特性。
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb
# An AOF file may be found to be truncated at the end during the Redis
# startup process, when the AOF data gets loaded back into memory.
# This may happen when the system where Redis is running
# crashes, especially when an ext4 filesystem is mounted without the
# data=ordered option (however this can‘t happen when Redis itself
# crashes or aborts but the operating system still works correctly).
#
# Redis can either exit with an error when this happens, or load as much
# data as possible (the default now) and start if the AOF file is found
# to be truncated at the end. The following option controls this behavior.
#
# If aof-load-truncated is set to yes, a truncated AOF file is loaded and
# the Redis server starts emitting a log to inform the user of the event.
# Otherwise if the option is set to no, the server aborts with an error
# and refuses to start. When the option is set to no, the user requires
# to fix the AOF file using the "redis-check-aof" utility before to restart
# the server.
#
# Note that if the AOF file will be found to be corrupted in the middle
# the server will still exit with an error. This option only applies when
# Redis will try to read more data from the AOF file but not enough bytes
# will be found.
aof-load-truncated yes
################################ LUA SCRIPTING  ###############################
# Max execution time of a Lua script in milliseconds.
#
# If the maximum execution time is reached Redis will log that a script is
# still in execution after the maximum allowed time and will start to
# reply to queries with an error.
#
# When a long running script exceeds the maximum execution time only the
# SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
# used to stop a script that did not yet called write commands. The second
# is the only way to shut down the server in the case a write command was
# already issued by the script but the user doesn‘t want to wait for the natural
# termination of the script.
#
# Set it to 0 or a negative value for unlimited execution without warnings.
lua-time-limit 5000
################################## 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.
# Redis慢查询日志可以记录超过指定时间的查询。运行时间不包括各种I/O时间。
# 例如：连接客户端，发送响应数据等。只计算命令运行的实际时间（这是唯一一种命令运行线程阻塞而无法同时为其他请求服务的场景）
# 
# 你可以为慢查询日志配置两个参数：一个是超标时间，单位为微妙，记录超过个时间的命令。
# 另一个是慢查询日志长度。当一个新的命令被写进日志的时候，最老的那个记录会被删掉。
#
# 下面的时间单位是微秒，所以1000000就是1秒。注意，负数时间会禁用慢查询日志，而0则会强制记录所有命令。
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.
# 这个长度没有限制。只要有足够的内存就行。你可以通过 SLOWLOG RESET 来释放内存。（译者注：日志居然是在内存里的Orz）
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 enalbed at runtime using the command
# "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.
latency-monitor-threshold 0
############################# Event notification ##############################
# Redis can notify Pub/Sub clients about events happening in the key space.
# This feature is documented at http://redis.io/topics/notifications
#
# For instance if keyspace events notification is enabled, and a client
# performs a DEL operation on key "foo" stored in the Database 0, two
# messages will be published via Pub/Sub:
#
# PUBLISH __keyspace@0__:foo del
# PUBLISH __keyevent@0__:del foo
#
# It is possible to select the events that Redis will notify among a set
# of classes. Every class is identified by a single character:
#
#  K     Keyspace events, published with __keyspace@<db>__ prefix.
#  E     Keyevent events, published with __keyevent@<db>__ prefix.
#  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
#  $     String commands
#  l     List commands
#  s     Set commands
#  h     Hash commands
#  z     Sorted set commands
#  x     Expired events (events generated every time a key expires)
#  e     Evicted events (events generated when a key is evicted for maxmemory)
#  A     Alias for g$lshzxe, so that the "AKE" string means all the events.
#
#  The "notify-keyspace-events" takes as argument a string that is composed
#  of zero or multiple characters. The empty string means that notifications
#  are disabled.
#
#  Example: to enable list and generic events, from the point of view of the
#           event name, use:
#
#  notify-keyspace-events Elg
#
#  Example 2: to get the stream of the expired keys subscribing to channel
#             name __keyevent@0__:expired use:
#
#  notify-keyspace-events Ex
#
#  By default all notifications are disabled because most users don‘t need
#  this feature and the feature has some overhead. Note that if you don‘t
#  specify at least one of K or E, no events will be delivered.
notify-keyspace-events ""
############################### ADVANCED CONFIG ###############################
# Hashes are encoded using a memory efficient data structure when they have a
# small number of entries, and the biggest entry does not exceed a given
# threshold. These thresholds can be configured using the following directives.
# 当有大量数据时，适合用哈希编码（需要更多的内存），元素数量上限不能超过给定限制。
# 你可以通过下面的选项来设定这些限制：
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:
# 与哈希相类似，数据元素较少的情况下，可以用另一种方式来编码从而节省大量空间。
# 这种方式只有在符合下面限制的时候才可以用：
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.
# 还有这样一种特殊编码的情况：数据全是64位无符号整型数字构成的字符串。
# 下面这个配置项就是用来限制这种情况下使用这种编码的最大上限的。
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:
# 与第一、第二种情况相似，有序序列也可以用一种特别的编码方式来处理，可节省大量空间。
# 这种编码只适合长度和元素都符合下面限制的有序序列：
zset-max-ziplist-entries 128
zset-max-ziplist-value 64
# HyperLogLog sparse representation bytes limit. The limit includes the
# 16 bytes header. When an HyperLogLog using the sparse representation crosses
# this limit, it is converted into the dense representation.
#
# A value greater than 16000 is totally useless, since at that point the
# dense representation is more memory efficient.
#
# The suggested value is ~ 3000 in order to have the benefits of
# the space efficient encoding without slowing down too much PFADD,
# which is O(N) with the sparse encoding. The value can be raised to
# ~ 10000 when CPU is not a concern, but space is, and the data set is
# composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
hll-sparse-max-bytes 3000
# Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
# order to help rehashing the main Redis hash table (the one mapping top-level
# keys to values). The hash table implementation Redis uses (see dict.c)
# performs a lazy rehashing: the more operation you run into a hash table
# that is rehashing, the more rehashing "steps" are performed, so if the
# server is idle the rehashing is never complete and some more memory is used
# by the hash table.
#
# The default is to use this millisecond 10 times every second in order to
# actively rehash the main dictionaries, freeing memory when possible.
#
# If unsure:
# use "activerehashing no" if you have hard latency requirements and it is
# not a good thing in your environment that Redis can reply from time to time
# to queries with 2 milliseconds delay.
#
# use "activerehashing yes" if you don‘t have such hard requirements but
# want to free memory asap when possible.
# 哈希刷新，每100个CPU毫秒会拿出1个毫秒来刷新Redis的主哈希表（顶级键值映射表）。
# redis所用的哈希表实现（见dict.c）采用延迟哈希刷新机制：你对一个哈希表操作越多，哈希刷新操作就越频繁；
# 反之，如果服务器非常不活跃那么也就是用点内存保存哈希表而已。
# 
# 默认是每秒钟进行10次哈希表刷新，用来刷新字典，然后尽快释放内存。
#
# 建议：
# 如果你对延迟比较在意的话就用 "activerehashing no"，每个请求延迟2毫秒不太好嘛。
# 如果你不太在意延迟而希望尽快释放内存的话就设置 "activerehashing yes"。
activerehashing yes
# The client output buffer limits can be used to force disconnection of clients
# that are not reading data from the server fast enough for some reason (a
# common reason is that a Pub/Sub client can‘t consume messages as fast as the
# publisher can produce them).
#
# The limit can be set differently for the three different classes of clients:
#
# normal -> normal clients including MONITOR clients
# slave  -> slave clients
# pubsub -> clients subscribed to at least one pubsub channel or pattern
#
# The syntax of every client-output-buffer-limit directive is the following:
#
# client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
#
# A client is immediately disconnected once the hard limit is reached, or if
# the soft limit is reached and remains reached for the specified number of
# seconds (continuously).
# So for instance if the hard limit is 32 megabytes and the soft limit is
# 16 megabytes / 10 seconds, the client will get disconnected immediately
# if the size of the output buffers reach 32 megabytes, but will also get
# disconnected if the client reaches 16 megabytes and continuously overcomes
# the limit for 10 seconds.
#
# By default normal clients are not limited because they don‘t receive data
# without asking (in a push way), but just after a request, so only
# asynchronous clients may create a scenario where data is requested faster
# than it can read.
#
# Instead there is a default limit for pubsub and slave clients, since
# subscribers and slaves receive data in a push fashion.
#
# Both the hard or the soft limit can be disabled by setting them to zero.
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
# Redis calls an internal function to perform many background tasks, like
# closing connections of clients in timeout, purging expired keys that are
# never requested, and so forth.
#
# Not all tasks are performed with the same frequency, but Redis checks for
# tasks to perform according to the specified "hz" value.
#
# By default "hz" is set to 10. Raising the value will use more CPU when
# Redis is idle, but at the same time will make Redis more responsive when
# there are many keys expiring at the same time, and timeouts may be
# handled with more precision.
#
# The range is between 1 and 500, however a value over 100 is usually not
# a good idea. Most users should use the default of 10 and raise this up to
# 100 only in environments where very low latency is required.
hz 10
# When a child rewrites the AOF file, if the following option is enabled
# the file will be fsync-ed every 32 MB of data generated. This is useful
# in order to commit the file to the disk more incrementally and avoid
# big latency spikes.
aof-rewrite-incremental-fsync yes