Ubuntu安装Redis过程完整笔记

# Redis configuration file example  
  
# 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:  
# 内存大小的配置，下面是内存大小配置的转换方式  
#  
# 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.  
# 内存大小的配置，不区分大小写  
  
################################## INCLUDES ###################################  
  
# Include one or more other config files here.  This is useful if you  
# have a standard template that goes to all Redis server 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  
# 当配置多个redis时，可能大部分配置一样，而对于不同的redis，只有少部分配置需要定制  
# 就可以配置一个公共的模板配置。  
# 对于具体的reids，只需设置少量的配置，并用include把模板配置包含进来即可。  
#  
# 值得注意的是，对于同一个配置项，redis只对最后一行的有效  
# 所以为避免模板配置覆盖当前配置，应在配置文件第一行使用include  
# 当然，如果模板配置的优先级比较高，就在配置文件最后一行使用include  
  
################################ 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.  
# yes为使用守护进程，此时redis的进程ID会被写进 pidfile的配置中  
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.  
# 当redis以守护进程的方式启动时，redis的进程ID将会写在这个文件中  
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.  
# redis 启动的端口。【应该知道redis是服务端吧】  
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.  
# 最大链接缓冲池的大小，这里应该是指的未完成链接请求的数量  
#（测试值为1时，仍可以有多个链接）  
# 但该值与listen函数中的backlog意义应该是相同的，源码中该值就是被用在了listen函数中  
# 该值同时受/proc/sys/net/core/somaxconn 和 tcp_max_syn_backlog（/etc/sysctl.conf中配置）的限制  
# tcp_max_syn_backlog 指的是未完成链接的数量  
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.  
# 绑定ip，指定ip可以连接到redis  
#  
# 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.  
#  
# 这个应该就是以文件形式创建的socket  
# unixsocket /tmp/redis.sock  
# unixsocketperm 755  
  
# Close the connection after a client is idle for N seconds (0 to disable)  
# 超时断链机制，如果一个链接在N秒内没有任何操作，则断开该链接  
# N为0时，该机制失效  
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.  
# 就像心跳检测一样，检查链接是否保持正常，同时也可以保持正常链接的通信  
# 建议值为60  
#  
# 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)  
# 日志级别  
loglevel notice  
  
# Specify the log file name. Also the empty string can be used to force  
# Redis to log on the standard output. Note that if you use standard  
# output for logging but daemonize, logs will be sent to /dev/null  
# 日志存放路径，默认是输出到标准输出，但当以守护进程方式启动时，默认输出到/dev/null(传说中的linux黑洞)  
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.  
# yes 表示将日志写到系统日志中  
# syslog-enabled no  
  
# Specify the syslog identity.  
# 当syslog-enabled为yes时，指定系统日志的标示为 redis  
# syslog-ident redis  
  
# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.  
# 指定系统日志的设备  
# 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  
# redis的数据库格式，默认16个(0~15)，默认使用第0个。  
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.  
# 快照，即将数据写到硬盘上，在<seconds>秒内，至少有<changes>次写入数据库操作  
# 则会将数据写入硬盘一次。  
# 将save行注释掉则永远不会写入硬盘  
# save "" 表示删除所有的快照点  
#  
#   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 at all commenting all the "save" lines.  
#  
#   It is also possible to remove all the previously configured save  
#   points by adding a save directive with a single empty string argument  
#   like in the following example:  
#  
#   save ""  
  
save 900 1  
save 300 10  
save 60 10000  
  
# By default Redis will stop accepting writes if RDB snapshots are enabled  
# (at least one save point) and the latest background save failed.  
# This will make the user aware (in a hard way) that data is not persisting  
# on disk properly, otherwise chances are that no one will notice and some  
# disaster will happen.  
#  
# If the background saving process will start working again Redis will  
# automatically allow writes again.  
#  
# However if you have setup your proper monitoring of the Redis server  
# and persistence, you may want to disable this feature so that Redis will  
# continue to work as usual even if there are problems with disk,  
# permissions, and so forth.  
# 当做快照失败的时候，redis会停止继续向其写入数据，保证第一时间发现redis快照出现问题  
# 当然，通过下面配置为 no，即使redis快照失败，也能继续向redis写入数据  
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.  
# 快照的时候，是否用LZF压缩，使用压缩会占一定的cpu，但不使用压缩，快照会很大  
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.  
# 数据校验，快照末尾会存放一个校验值，保证数据的准确性  
# 但数据校验会使性能下降约10%，默认开启校验  
rdbchecksum yes  
  
# The filename where to dump the DB  
# 快照的名字  
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.  
#   
# 快照存放的目录  
# linux root下测试，会发现该进程会在当前目录下创建一个dump.rdb  
# 但快照却放在了根目录/下，重启的时候，是不会从快照中恢复数据的  
# 当把根目录下的dump.rdb文件拷贝到当前目录的时候，再次启动，就会从快照中恢复数据  
# 而且以后的快照也都在当前目录的dump.rdb中做操作  
#  
# 值得一提的是，快照是异步方式的，如果在还未达到快照的时候，修改了数据，而且redis发生问题crash了  
# 那么中间的修改数据是不会被保存到dump.rdb快照中的  
# 解决办法就是用Append Only Mode的同步模式(下面将会有该配置项)  
# 将会把每个操作写到Append Only File中，该文件也存放于当前配置的目录  
# 建议使用绝对路径！！！  
#   
dir ./  
  
################################# REPLICATION #################################  
  
# Master-Slave replication. Use slaveof to make a Redis instance a copy of  
# another Redis server. Note that the configuration is local to the slave  
# so for example it is possible to configure the slave to save the DB with a  
# different interval, or to listen to another port, and so on.  
#  
# 主从复制，类似于双机备份。  
# 配置需指定主机的ip 和port  
# 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.  
#  
# 如果主机redis需要密码，则指定密码  
# 密码配置在下面安全配置中  
# 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.  
#  
# 当从机与主机断开时，即同步出现问题的时候，从机有两种处理方式  
# yes, 继续响应客户端请求，但可能有脏数据（过期数据、空数据等）  
# no，对客户端的请求统一回复为“SYNC with master in progress”，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只读选项，设置从机只读（默认）。  
# 即使设置可写，当下一次从主机上同步数据，仍然会删除当前从机上写入的数据  
# 【待测试】：主机与从机互为slave会出现什么情况？  
# 【预期三种结果】：1. 提示报错 2. 主从服务器数据不可控 3. 一切正常  
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.  
#  
# 从服务器向主服务器发送心跳包，默认10发送一次  
# 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.  
#  
# 超时响应时间，值必须比repl-ping-slave-period大  
# 批量数据传输超时、ping超时  
# 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.  
# 主从同步是否延迟  
# yes 有延迟，约40毫秒（linux kernel的默认配置），使用较少的数据包，较小的带宽  
# no 无延迟（减少延迟），但需要更大的带宽  
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 biggest 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.  
#  
# 默认情况下，当slave重连的时候，会进行全量数据同步  
# 但实际上slave只需要部分同步即可，这个选项设置部分同步的大小  
# 设置值越大，同步的时间就越长  
# 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.  
#  
# 主机的后台日志释放时间，即当没有slave连接时，过多久释放后台日志  
# 0表示不释放  
# repl-backlog-ttl 3600  
  
# The slave priority is an integer number published by Redis in the INFO output.  
# It is used by Redis Sentinel in order to select a slave to promote into a  
# master if the master is no longer working correctly.  
#  
# A slave with a low priority number is considered better for promotion, so  
# for instance if there are three slaves with priority 10, 100, 25 Sentinel will  
# pick the one with priority 10, that is the lowest.  
#  
# However a special priority of 0 marks the slave as not able to perform the  
# role of master, so a slave with priority of 0 will never be selected by  
# Redis Sentinel for promotion.  
#  
# By default the priority is 100.  
# 当主机crash的时候，在从机中选择一台作为主机，数字越小，优先级越高  
# 0 表示永远不作为主机，默认值是100  
slave-priority 100  
  
# It is possible for a master to stop accepting writes if there are less than  
# N slaves connected, having a lag less or equal than M seconds.  
#  
# The N slaves need to be in "online" state.  
#  
# The lag in seconds, that must be <= the specified value, is calculated from  
# the last ping received from the slave, that is usually sent every second.  
#  
# This option does not GUARANTEES 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:  
#  
# 当slave数量小于min-slaves-to-write，且延迟小于等于min-slaves-max-lag时，  
# 主机停止写入操作  
# 0表示禁用  
# 默认min-slaves-to-write为0，即禁用。min-slaves-max-lag为10  
# 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.  
#  
# redis密码，默认不配置，即无密码  
# 这里注意，如果设置了密码，应该设置一个复杂度比较高的密码  
# 因为redis的速度很快，每秒可以尝试150k次的密码测试，很容易对其进行暴力破解（跑码）。  
# 疑问：这里为什么不设置一个针对主机的测试次数限制的，例如每10次，则禁止建立连接1个小时！  
# 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.  
#  
# 命令重命名，将命令重命名为另一个字符串标识  
# 如果命令为空串("")，则会彻底禁用该命令  
# 命令重命名，会对写AOF(Append of file)文件、slave从机造成一些问题  
# 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.  
  
################################### 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'.  
#  
# 这只redis的最大连接数目，默认设置为10000个客户端  
# 当超过限制时，将段开新的连接，并响应“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').  
#  
# redis的最大内存限制，如果达到最大内存，会按照下面的maxmemory-policy进行清除  
# 如果不能再清除或者maxmemory-policy为noeviction，则对于需要增加空间的操作，将会返回错误  
maxmemory <1024*1024*1024>  
  
# 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 accordingly 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 not suitable keys for eviction.  
#  
#       At the date of writing this 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:  
#  
# 内存删除策略，默认volatile-lru，利用LRU算法，删除过期的key  
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算法与最小TTL算法只是相对精确的算法，并不是绝对精确的算法  
# 为了更精确，可以设置样本个数  
# 比如设置3个样本，redis会选取三个key，并选择删除那个上次使用时间最远的  
# 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.  
# 将对redis所有的操作都保存到AOF文件中  
# 因为dump.rdb是异步的，在下次快照到达之前，如果出现crash等问题，会造成数据丢失  
# 而AOF文件时同步记录的，所以会完整的恢复数据  
  
appendonly no  
  
# The name of the append only file (default: "appendonly.aof")  
# AOF文件的名字  
  
appendfilename "appendonly.aof"  
  
# The fsync() call tells the Operating System to actually write data on disk  
# instead to wait 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".  
# redis的数据同步方式，三种  
# no，redis本身不做同步，由OS来做。redis的速度会很快  
# always，在每次写操作之后，redis都进行同步，即写入AOF文件。redis会变慢，但是数据更安全  
# everysec，折衷考虑，每秒同步一次数据。【默认】  
  
# 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.  
# redis的同步方式中，always和everysec，快照和写AOF可能会执行大量的硬盘I/O操作，  
# 而在一些Linux的配置中，redis会阻塞很久，而redis本身并没有很好的解决这一问题。  
# 为了缓和这一问题，redis提供no-appendfsync-on-rewrite选项，  
# 即当有另外一个进程在执行保存操作的时候，redis采用no的同步方式。  
# 最坏情况下会有延迟30秒的同步延迟。  
# 如果你觉得这样做会有潜在危险，则请将该选项改为yes。否则就保持默认值no（基于稳定性考虑）。  
  
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  
# 当AOF日志文件大小增长到指定百分比时，redis会自动隐式调用BGREWRITEAOF来重写AOF文件  
# redis会记录上次重写AOF文件之后的大小，  
# 如果当前文件大小增加了auto-aof-rewrite-percentage，则会触发重写AOF日志功能  
# 当然如果文件过小，比如小于auto-aof-rewrite-min-size这个大小，是不会触发重写AOF日志功能的  
# auto-aof-rewrite-percentage为0时，禁用重写功能  
  
auto-aof-rewrite-percentage 100  
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 exceed 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 commands was  
# already issue by the script but the user don'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脚本的最大执行时间（单位是毫秒），默认5000毫秒，即5秒  
# 如果LUA脚本执行超过这个限制，可以调用SCRIPT KILL和SHUTDOWN NOSAVE命令。  
# SCRIPT KILL可以终止脚本执行  
# SHUTDOWN NOSAVE关闭服务，防止LUA脚本的写操作发生  
# 该值为0或者负数，表示没有限制时间  
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.  
# 记录执行比较慢的命令  
# 执行比较慢仅仅是指命令的执行时间，不包括客户端的链接与响应等时间  
# slowlog-log-slower-than 设定这个慢的时间，单位是微妙，即1000000表示1秒，0表示所有命令都记录，负数表示不记录  
# slowlog-max-len表示记录的慢命令的个数，超过限制，则最早记录的命令会被移除  
# 命令的长度没有限制，但是会消耗内存，用SLOWLOG RESET来收回这些消耗的内存  
  
# 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.  
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.  
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.  
# 延迟监控器  
# redis延迟监控子系统在运行时，会抽样检测可能导致延迟的不同操作  
# 通过LATENCY命令可以打印相关信息和报告, 命令如下（摘自源文件注释）：  
# LATENCY SAMPLES: return time-latency samples for the specified event.  
# LATENCY LATEST: return the latest latency for all the events classes.  
# LATENCY DOCTOR: returns an human readable analysis of instance latency.  
# LATENCY GRAPH: provide an ASCII graph of the latency of the specified event.  
#   
# 系统只记录超过设定值的操作，单位是毫秒，0表示禁用该功能  
# 可以通过命令“CONFIG SET latency-monitor-threshold <milliseconds>” 直接设置而不需要重启redis  
  
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/keyspace-events  
#   
# 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  
#  by zero or multiple characters. The empty string means that notifications  
#  are disabled at all.  
#  
#  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.  
# 事件通知，当事件发生时，redis可以通知Pub/Sub客户端  
# 空串表示禁用事件通知  
# 注意：K和E至少要指定一个，否则不会有事件通知  
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hash数目比较少，并且最大元素没有超过给定值时，Hash使用比较有效的内存数据结构来存储。  
# 即ziplist的结构（压缩的双向链表），参考：http://blog.csdn.net/benbendy1984/article/details/7796956  
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配置同Hash  
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 happens 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.  
# Sets的元素如果全部是整数（10进制），且为64位有符号整数，则采用特殊的编码方式。  
# 其元素个数限制配置如下：  
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:  
# sorted set 同Hash和List  
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.  
# 关于HyperLogLog的介绍：http://www.redis.io/topics/data-types-intro#hyperloglogs  
# HyperLogLog稀疏表示限制设置，如果其值大于16000，则仍然采用稠密表示，因为这时稠密表示更能有效使用内存  
# 建议值为3000  
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  
# active rehashing 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 form 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.  
# 每100毫秒，redis将用1毫秒的时间对Hash表进行重新Hash。  
# 采用懒惰Hash方式：操作Hash越多，则重新Hash的可能越多，若根本就不操作Hash，则不会重新Hash  
# 默认每秒10次重新hash主字典，释放可能释放的内存  
# 重新hash会造成延迟，如果对延迟要求较高，则设为no，禁止重新hash。但可能会浪费很多内存  
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:  
#  
# 客户端输出缓冲区限制，当客户端从服务端的读取速度不够快时，则强制断开  
# 三种不同的客户端类型：normal、salve、pubsub，语法如下：  
# 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.  
# 当达到硬限制，或者达到软限制且持续了算限制秒数，则立即与客户端断开  
# 限制设为0表示禁止该功能  
# 普通用户默认不限制  
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 accordingly 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.  
# redis调用内部函数执行的后台任务的频率  
# 后台任务比如：清除过期数据、客户端超时链接等  
# 默认为10，取值范围1~500,  
# 对延迟要求很低的可以设置超过100以上  
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.  
# 当修改AOF文件时，该设置为yes，则每生成32MB的数据，就进行同步  
aof-rewrite-incremental-fsync yes