# Redis configuration file example # Note on units: when memory size is needed, it is possible to specifiy# it in the usual form of 1k 5GB 4M and so forth:## 1k => 1000 bytes# 1kb => 1024 bytes# 1m => 1000000 bytes# 1mb => 1024*1024 bytes# 1g => 1000000000 bytes# 1gb => 1024*1024*1024 bytes## units are case insensitive so 1GB 1Gb 1gB are all the same. # By default Redis does not run as a daemon. Use ‘yes‘ if you need it.# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.daemonize no  Redis默认不是以守护进程的方式运行，可以通过该配置项修改，使用yes启用守护进程 # When running daemonized, Redis writes a pid file in /var/run/redis.pid by# default. You can specify a custom pid file location here.pidfile /var/run/redis.pid当Redis以守护进程方式运行时，Redis默认会把pid写入/var/run/redis.pid文件，可以通过pidfile指定# Accept connections on the specified port, default is 6379.# If port 0 is specified Redis will not listen on a TCP socket.port 6379指定Redis监听端口，默认端口为6379# If you want you can bind a single interface, if the bind option is not# specified all the interfaces will listen for incoming connections.## bind 127.0.0.1绑定的主机地址# 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 755 # Close the connection after a client is idle for N seconds (0 to disable)timeout 0当 客户端闲置多长时间后关闭连接，如果指定为0，表示关闭该功能# Set server verbosity to ‘debug‘# it can be one of:# debug (a lot of information, useful for development/testing)# verbose (many rarely useful info, but not a mess like the debug level)# notice (moderately verbose, what you want in production probably)# warning (only very important / critical messages are logged)loglevel verbose指定日志记录级别，Redis总共支持四个级别：debug、verbose、notice、warning，默认为verbose# Specify the log file name. Also ‘stdout‘ 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/nulllogfile stdout日志记录方式，默认为标准输出，如果配置Redis为守护进程方式运行，而这里又配置为日志记录方式为标准输出，则日志将会发送给/dev/null# To enable logging to the system logger, just set ‘syslog-enabled‘ to yes,# and optionally update the other syslog parameters to suit your needs.# syslog-enabled no # Specify the syslog identity.# syslog-ident redis # Specify the syslog facility.  Must be USER or between LOCAL0-LOCAL7.# syslog-facility local0 # Set the number of databases. The default database is DB 0, you can select# a different one on a per-connection basis using SELECT <dbid> where# dbid is a number between 0 and ‘databases‘-1databases 16设置数据库的数量，默认数据库为0，可以使用SELECT <dbid>命令在连接上指定数据库id################################ 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 at all commenting all the "save" lines. save 900 1save 300 10save 60 10000分别表示900秒（15分钟）内有1个更改，300秒（5分钟）内有10个更改以及60秒内有10000个更改。指定在多长时间内，有多少次更新操作，就将数据同步到数据文件，可以多个条件配合# Compress string objects using LZF when dump .rdb databases?# For default that‘s set to ‘yes‘ as it‘s almost always a win.# If you want to save some CPU in the saving child set it to ‘no‘ but# the dataset will likely be bigger if you have compressible values or keys.rdbcompression yes指定存储至本地数据库时是否压缩数据，默认为yes，Redis采用LZF压缩，如果为了节省CPU时间，可以关闭该选项，但会导致数据库文件变的巨大# The filename where to dump the DBdbfilename dump.rdb指定本地数据库文件名，默认值为dump.rdb# The working directory.## The DB will be written inside this directory, with the filename specified# above using the ‘dbfilename‘ configuration directive.# # Also the Append Only File will be created inside this directory.# # Note that you must specify a directory here, not a file name.dir ./指定本地数据库存放目录################################# 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.## slaveof <masterip> <masterport>slaveof <masterip> <masterport> 设置当本机为slav服务时，设置master服务的IP地址及端口，在Redis启动时，它会自动从master进行数据同步# If the master is password protected (using the "requirepass" configuration# directive below) it is possible to tell the slave to authenticate before# starting the replication synchronization process, otherwise the master will# refuse the slave request.## masterauth <master-password>masterauth <master-password> 当master服务设置了密码保护时，slav服务连接master的密码# When a slave lost the 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 data data, or the#    data set may just be empty if this is the first synchronization.## 2) if slave-serve-stale data is set to ‘no‘ the slave will reply with#    an error "SYNC with master in progress" to all the kind of commands#    but to INFO and SLAVEOF.#slave-serve-stale-data yes # Slaves send PINGs to server in a predefined interval. It‘s possible to change# this interval with the repl_ping_slave_period option. The default value is 10# seconds.## repl-ping-slave-period 10 # The following option sets a timeout for both Bulk transfer I/O timeout and# master data or ping response timeout. The default value is 60 seconds.## It is important to make sure that this value is greater than the value# specified for repl-ping-slave-period otherwise a timeout will be detected# every time there is low traffic between the master and the slave.## repl-timeout 60 ################################## SECURITY ################################### # Require clients to issue AUTH <PASSWORD> before processing any other# commands.  This might be useful in environments in which you do not trust# others with access to the host running redis-server.## This should stay commented out for backward compatibility and because most# people do not need auth (e.g. they run their own servers).# # Warning: since Redis is pretty fast an outside user can try up to# 150k passwords per second against a good box. This means that you should# use a very strong password otherwise it will be very easy to break.## requirepass foobared requirepass foobared 设置Redis连接密码，如果配置了连接密码，客户端在连接Redis时需要通过AUTH <password>命令提供密码，默认关闭# Command renaming.## It is possilbe to change the name of dangerous commands in a shared# environment. For instance the CONFIG command may be renamed into something# of hard to guess so that it will be still available for internal-use# tools but not available for general clients.## Example:## rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52## It is also possilbe to completely kill a command renaming it into# an empty string:## rename-command CONFIG "" ################################### LIMITS #################################### # Set the max number of connected clients at the same time. By default there# is no limit, and it‘s up to the number of file descriptors the Redis process# is able to open. The special value ‘0‘ means no limits.# Once the limit is reached Redis will close all the new connections sending# an error ‘max number of clients reached‘.## maxclients 128maxclients 128 设置同一时间最大客户端连接数，默认无限制，Redis可以同时打开的客户端连接数为Redis进程可以打开的最大文件描述符数，如果设置 maxclients 0，表示不作限制。当客户端连接数到达限制时，Redis会关闭新的连接并向客户端返回max number of clients reached错误信息# Don‘t use more memory than the specified amount of bytes.# When the memory limit is reached Redis will try to remove keys with an# EXPIRE set. It will try to start freeing keys that are going to expire# in little time and preserve keys with a longer time to live.# Redis will also try to remove objects from free lists if possible.## If all this fails, Redis will start to reply with errors to commands# that will use more memory, like SET, LPUSH, and so on, and will continue# to reply to most read-only commands like GET.## WARNING: maxmemory can be a good idea mainly if you want to use Redis as a# ‘state‘ server or cache, not as a real DB. When Redis is used as a real# database the memory usage will grow over the weeks, it will be obvious if# it is going to use too much memory in the long run, and you‘ll have the time# to upgrade. With maxmemory after the limit is reached you‘ll start to get# errors for write operations, and this may even lead to DB inconsistency.## maxmemory <bytes> maxmemory <bytes>指定Redis最大内存限制，Redis在启动时会把数据加载到内存中，达到最大内存后，Redis会先尝试清除已到期或即将到期的Key，当此方法处理 后，仍然到达最大内存设置，将无法再进行写入操作，但仍然可以进行读取操作。Redis新的vm机制，会把Key存放内存，Value会存放在swap区# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory# is reached? You can select among five behavior:# # 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 all the kind of 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:## 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.## maxmemory-samples 3 ############################## APPEND ONLY MODE ############################### # By default Redis asynchronously dumps the dataset on disk. If you can live# with the idea that the latest records will be lost if something like a crash# happens this is the preferred way to run Redis. If instead you care a lot# about your data and don‘t want to that a single record can get lost you should# enable the append only mode: when this mode is enabled Redis will append# every write operation received in the file appendonly.aof. This file will# be read on startup in order to rebuild the full dataset in memory.## Note that you can have both the async dumps and the append only file if you# like (you have to comment the "save" statements above to disable the dumps).# Still if append only mode is enabled Redis will load the data from the# log file at startup ignoring the dump.rdb file.## IMPORTANT: Check the BGREWRITEAOF to check how to rewrite the append# log file in background when it gets too big. appendonly noappendonly no指定是否在每次更新操作后进行日志记录，Redis在默认情况下是异步的把数据写入磁盘，如果不开启，可能会在断电时导致一段时间内的数据丢失。因为 redis本身同步数据文件是按上面save条件来同步的，所以有的数据会在一段时间内只存在于内存中。默认为no# The name of the append only file (default: "appendonly.aof")# appendfilename appendonly.aof appendfilename appendonly.aof指定更新日志文件名，默认为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 if one second passed since the last fsync. Compromise.## The default is "everysec" 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 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.## If unsure, use "everysec". # appendfsync alwaysappendfsync everysec# appendfsync no指定更新日志条件，共有3个可选值：no：表示等操作系统进行数据缓存同步到磁盘（快）always：表示每次更新操作后手动调用fsync()将数据写到磁盘（慢，安全）everysec：表示每秒同步一次（折衷，默认值）# 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", that in pratical terms means that it is# possible to lost 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.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 will growth by the specified percentage.# # This is how it works: Redis remembers the size of the AOF file after the# latest rewrite (or if no rewrite 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 precentage of zero in order to disable the automatic AOF# rewrite feature. auto-aof-rewrite-percentage 100auto-aof-rewrite-min-size 64mb ################################## 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.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 1024 ################################ VIRTUAL MEMORY ############################### ### WARNING! Virtual Memory is deprecated in Redis 2.4### The use of Virtual Memory is strongly discouraged. ### WARNING! Virtual Memory is deprecated in Redis 2.4### The use of Virtual Memory is strongly discouraged. # Virtual Memory allows Redis to work with datasets bigger than the actual# amount of RAM needed to hold the whole dataset in memory.# In order to do so very used keys are taken in memory while the other keys# are swapped into a swap file, similarly to what operating systems do# with memory pages.## To enable VM just set ‘vm-enabled‘ to yes, and set the following three# VM parameters accordingly to your needs. vm-enabled no指定是否启用虚拟内存机制，默认值为no，简单的介绍一下，VM机制将数据分页存放，由Redis将访问量较少的页即冷数据swap到磁盘上，访问多的页面由磁盘自动换出到内存中（在后面的文章我会仔细分析Redis的VM机制）# vm-enabled yes # This is the path of the Redis swap file. As you can guess, swap files# can‘t be shared by different Redis instances, so make sure to use a swap# file for every redis process you are running. Redis will complain if the# swap file is already in use.## The best kind of storage for the Redis swap file (that‘s accessed at random) # is a Solid State Disk (SSD).## *** WARNING *** if you are using a shared hosting the default of putting# the swap file under /tmp is not secure. Create a dir with access granted# only to Redis user and configure Redis to create the swap file there.vm-swap-file /tmp/redis.swap虚拟内存文件路径，默认值为/tmp/redis.swap，不可多个Redis实例共享# vm-max-memory configures the VM to use at max the specified amount of# RAM. Everything that deos not fit will be swapped on disk *if* possible, that# is, if there is still enough contiguous space in the swap file.## With vm-max-memory 0 the system will swap everything it can. Not a good# default, just specify the max amount of RAM you can in bytes, but it‘s# better to leave some margin. For instance specify an amount of RAM# that‘s more or less between 60 and 80% of your free RAM.vm-max-memory 0将所有大于vm-max-memory的数据存入虚拟内存,无论vm-max-memory设置多小,所有索引数据都是内存存储的(Redis的索引数据 就是keys),也就是说,当vm-max-memory设置为0的时候,其实是所有value都存在于磁盘。默认值为0# Redis swap files is split into pages. An object can be saved using multiple# contiguous pages, but pages can‘t be shared between different objects.# So if your page is too big, small objects swapped out on disk will waste# a lot of space. If you page is too small, there is less space in the swap# file (assuming you configured the same number of total swap file pages).## If you use a lot of small objects, use a page size of 64 or 32 bytes.# If you use a lot of big objects, use a bigger page size.# If unsure, use the default :)vm-page-size 32Redis swap文件分成了很多的page，一个对象可以保存在多个page上面，但一个page上不能被多个对象共享，vm-page-size是要根据存储的 数据大小来设定的，作者建议如果存储很多小对象，page大小最好设置为32或者64bytes；如果存储很大大对象，则可以使用更大的page，如果不 确定，就使用默认值# Number of total memory pages in the swap file.# Given that the page table (a bitmap of free/used pages) is taken in memory,# every 8 pages on disk will consume 1 byte of RAM.## The total swap size is vm-page-size * vm-pages## With the default of 32-bytes memory pages and 134217728 pages Redis will# use a 4 GB swap file, that will use 16 MB of RAM for the page table.## It‘s better to use the smallest acceptable value for your application,# but the default is large in order to work in most conditions.vm-pages 134217728设置swap文件中的page数量，由于页表（一种表示页面空闲或使用的bitmap）是在放在内存中的，，在磁盘上每8个pages将消耗1byte的内存。# Max number of VM I/O threads running at the same time.# This threads are used to read/write data from/to swap file, since they# also encode and decode objects from disk to memory or the reverse, a bigger# number of threads can help with big objects even if they can‘t help with# I/O itself as the physical device may not be able to couple with many# reads/writes operations at the same time.## The special value of 0 turn off threaded I/O and enables the blocking# Virtual Memory implementation.vm-max-threads 4设置访问swap文件的线程数,最好不要超过机器的核数,如果设置为0,那么所有对swap文件的操作都是串行的，可能会造成比较长时间的延迟。默认值为4############################### ADVANCED CONFIG ############################### # Hashes are encoded in a special way (much more memory efficient) when they# have at max a given numer of elements, and the biggest element does not# exceed a given threshold. You can configure this limits with the following# configuration directives.hash-max-zipmap-entries 512hash-max-zipmap-value 64指定在超过一定的数量或者最大的元素超过某一临界值时，采用一种特殊的哈希算法# 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-max-ziplist-entries 512list-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.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:zset-max-ziplist-entries 128zset-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 an hash table# that is rhashing, 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.activerehashing yes ################################## 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.## include /path/to/local.conf# include /path/to/other.conf