redis-04配置文件

1.daemonize no

# By default Redis does not run as a daemon. Use 'yes' if youneed it.
# Note that Redis will write a pid file in /var/run/redis.pidwhen daemonized.
#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

2.pidfile /var/run/redis.pid
# When running daemonized, Redis writes a pid file in/var/run/redis.pid by
# default. You can specify a custom pid file locationhere.
#当 Redis 以守护进程的方式运行的时候，Redis 默认会把 pid文件放在/var/run/redis.pid
#可配置到其他地址，当运行多个 redis 服务时，需要指定不同的 pid 文件和端口

3.port 6379
# Accept connections on the specified port, default is6379.
# If port 0 is specified Redis will not listen on a TCPsocket.
#端口

4.bind 127.0.0.1
# If you want you can bind a single interface, if the bindoption is not
# specified all the interfaces will listen for incomingconnections.
#指定Redis可接收请求的IP地址,不设置将处理所有请求,建议生产环境中设置
# bind 127.0.0.1

5.timeout
# Close the connection after a client is idle for N seconds (0to disable)
#客户端连接的超时时间,单位为秒,在这段时间内没有数据交互，会关闭连接。默认为0，代表永不断开
timeout 0

6.loglevel
# Set server verbosity to 'debug'
# it can be one of:
# debug (a lot of information, useful fordevelopment/testing)
# verbose (many rarely useful info, but not a mess like thedebug level)
# notice (moderately verbose, what you want in productionprobably)
# warning (only very important / critical messages arelogged)
# 日志记录等级，4个可选值

debug：在开发，调试阶段很有用，大量的日志

verbose：在debug的基础上，减少连接信息以及内部信息

notice：建议在生产使用

warning：只打印重要、关键的信息
loglevel notice

7.logfile
# Specify the log file name. Also 'stdout' can be used toforce
# Redis to log on the standard output. Note that if you usestandard
# output for logging but daemonize, logs will be sent to/dev/null
#配置 log 文件地址,默认打印在命令行终端的窗口上，也可设为/dev/null屏蔽日志、
logfile stdout

8.databases
# Set the number of databases. The default database is DB 0,you can select
# a different one on a per-connection basis using SELECTwhere
# dbid is a number between 0 and 'databases'-1
#设置数据库的个数,默认16个，可以使用 SELECT 命令来切换数据库。
databases 16

9.save
# Save the DB on disk:
#   Will save the DB if both the given numberof seconds and the given
#   number of write operations against the DBoccurred.
#   In the example below the behaviour willbe to save:
#   after 900 sec (15 min) if at least 1 keychanged
#   after 300 sec (5 min) if at least 10 keyschanged
#   after 60 sec if at least 10000 keyschanged
#   Note: you can disable saving at allcommenting all the "save" lines.
#设置RDB进行数据库镜像持久化的频率。 保存数据到disk的策略
#900秒之内有1个keys发生变化时
#30秒之内有10个keys发生变化时
#60秒之内有10000个keys发生变化时
save 900 1
save 300 10
save 60 10000

10.rdbcompression
# Compress string objects using LZF when dump .rdbdatabases?
# For default that's set to 'yes' as it's almost always awin.
# 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 compressiblevalues or keys.
#在进行RDB镜像备份时,是否进行压缩
rdbcompression yes

11.dbfilename
# The filename where to dump the DB
#镜像备份文件的文件名-RDB持久化数据保存的文件名称
dbfilename dump.rdb

12.dir
# The working directory.
# The DB will be written inside this directory, with thefilename specified
# above using the 'dbfilename' configuration directive.
# Also the Append Only File will be created inside thisdirectory.
# Note that you must specify a directory here, not a filename.
#数据库镜像备份的文件放置的路径-RDB持久化数据保存的文件路径
#路径跟文件名分开配置是因为 Redis 备份时，先会将当前数据库的状态写入到一个临时文件
#等备份完成时，再把该临时文件替换为上面所指定的文件
#而临时文件和上面所配置的备份文件都会放在这个指定的路径当中
#默认值为 ./
dir /var/lib/redis/

13.rdbchecksum yes

是否进行校验和，是否对rdb文件使用CRC64校验和,默认为"yes"，那么每个rdb文件内容的末尾都会追加CRC校验和，利于第三方校验工具检测文件完整性，读取和写入时候，会损失10%性能

14.stop-writes-on-bgsave-error yes
当持久化出现错误时，是否依然继续进行工作，是否终止所有的客户端write请求。默认设置"yes"表示终止，一旦snapshot数据保存故障，那么此server为只读服务。如果为"no"，那么此次snapshot将失败，但下一次snapshot不会受到影响，不过如果出现故障,数据只能恢复到"最近一个成功点"

15.slaveof
# Master-Slave replication. Use slaveof to make a Redisinstance a copy of
# another Redis server. Note that the configuration is localto the slave
# so for example it is possible to configure the slave to savethe DB with a
# different interval, or to listen to another port, and soon.
#设置该数据库为其他数据库的从数据库
#slaveof <masterip><masterport>当本机为从服务时，设置主服务的IP及端口
# slaveof 主机ip 主机port

16.masterauth
# If the master is password protected (using the "requirepass"configuration
# directive below) it is possible to tell the slave toauthenticate before
# starting the replication synchronization process, otherwisethe master will
# refuse the slave request.
#指定与主数据库连接时需要的密码验证
#masterauth <master-password>当本机为从服务时，设置主服务的连接密码
# masterauth

17.slave-serve-stale-data
# When a slave lost the connection with the master, or whenthe replication
# is still in progress, the slave can act in two differentways:
# 1) if slave-serve-stale-data is set to 'yes' (the default)the slave will
#     still reply to clientrequests, possibly with out of data data, or the
#     data set may just beempty if this is the first synchronization.
# 2) if slave-serve-stale data is set to 'no' the slave willreply with
#     an error "SYNC withmaster in progress" to all the kind of commands
#     but to INFO andSLAVEOF.
#当slave丢失与master的连接时，或slave仍然在于master进行数据同步时（未与master保持一致）
#slave可有两种方式来响应客户端请求：
#1)如果 slave-serve-stale-data 设置成 'yes'(默认)，slave仍 会响应客户端请求,此时可能会有数据不同步的问题
#2)如果 slave-serve-stale-data 设置成 'no'，slave会返回"SYNC withmaster in progress"错误信息，但 INFO 和SLAVEOF命令除外。
slave-serve-stale-data yes

18.slave-read-only yes

slave是否为"只读"，不解释设置"yes"

19.epl-ping-slave-period 10

slave向指定的master发送ping消息的时间间隔(秒)，默认为10

20.repl-timeout 60

slave与master通讯中,最大空闲时间,默认60秒.超时将导致连接关闭

21.repl-disable-tcp-nodelay no
slave与master的连接,是否禁用TCP nodelay选项。"yes"表示禁用,那么socket通讯中数据将会以packet方式发送(packet大小受到socket buffer限制)。
可以提高socket通讯的效率(tcp交互次数),但是小数据将会被buffer,不会被立即发送,对于接受者可能存在延迟。"no"表示开启tcp nodelay选项,任何数据都会被立即发送,及时性较好,但是效率较低，建议设为no

22.slave-priority 100
适用哨兵模块，需要额外的哨兵配置文件支持。slave的权重值,默认100.当master失效后,Sentinel将会从slave列表中找到权重值最低(>0)的slave,并提升为master。如果权重值为0,表示此slave为"观察者",不参与master选举

23.requirepass
# Require clients to issue AUTH before processing anyother
# commands.   This might be useful inenvironments in which you do not trust
# others with access to the host running redis-server.
# This should stay commented out for backward compatibilityand because most
# people do not need auth (e.g. they run their ownservers).
# Warning: since Redis is pretty fast an outside user can tryup to
# 150k passwords per second against a good box. This meansthat you should
# use a very strong password otherwise it will be very easy tobreak.
#设置Redis密码
# requirepass foobared

24.maxclients
# Set the max number of connected clients at the same time. Bydefault there
# is no limit, and it's up to the number of file descriptorsthe Redis process
# is able to open. The special value '0' means nolimits.
# Once the limit is reached Redis will close all the newconnections sending
# an error 'max number of clients reached'.
#限制同时连接的客户数量-最大连接数
#当连接数超过这个值时，redis 将不再接收其他连接请求，客户端尝试连接时将收到 error 信息
# maxclients 128

25.maxmemory
# Don't use more memory than the specified amount ofbytes.
# When the memory limit is reached Redis will try to removekeys
# accordingly to the eviction policy selected (seemaxmemmory-policy).
# If Redis can't remove keys according to the policy, or ifthe policy is
# set to 'noeviction', Redis will start to reply with errorsto commands
# that would use more memory, like SET, LPUSH, and so on, andwill continue
# to reply to read-only commands like GET.
# This option is usually useful when using Redis as an LRUcache, or to set
# an hard memory limit for an instance (using the 'noeviction'policy).
# WARNING: If you have slaves attached to an instance withmaxmemory on,
# the size of the output buffers needed to feed the slaves aresubtracted
# from the used memory count, so that network problems /resyncs will
# not trigger a loop where keys are evicted, and in turn theoutput
# buffer of slaves is full with DELs of keys evictedtriggering the deletion
# of more keys, and so forth until the database is completelyemptied.
# In short... if you have slaves attached it is suggested thatyou set a lower
# limit for maxmemory so that there is some free RAM on thesystem for slave
# output buffers (but this is not needed if the policy is'noeviction').
#设置redis能够使用的最大内存。
#达到最大内存设置后，Redis会先尝试清除已到期或即将到期的Key
#在删除时,按照过期时间进行删除，最早将要被过期的key将最先被删除
#如果已到期或即将到期的key删光，仍进行set操作，那么将返回错误
#此时redis将不再接收写请求,只接收get请求。
#maxmemory的设置比较适合于把redis当作于类似memcached 的缓存来使用
#maxmemory <bytes>

26.maxmemory-policy volatile-lru
内存不足"时,数据清除策略,默认为"volatile-lru"。
volatile-lru

->对"过期集合"中的数据采取LRU(近期最少使用)算法.如果对key使用"expire"指令指定了过期时间,那么此key将会被添加到"过期集合"中。将已经过期/LRU的数据优先移除.如果"过期集合"中全部移除仍不能满足内存需求,将OOM.
allkeys-lru ->对所有的数据,采用LRU算法
volatile-random ->对"过期集合"中的数据采取"随即选取"算法,并移除选中的K-V,直到"内存足够"为止. 如果如果"过期集合"中全部移除全部移除仍不能满足,将OOM
allkeys-random ->对所有的数据,采取"随机选取"算法,并移除选中的K-V,直到"内存足够"为止
volatile-ttl ->对"过期集合"中的数据采取TTL算法(最小存活时间),移除即将过期的数据.
noeviction ->不做任何干扰操作,直接返回OOM异常
另外，如果数据的过期不会对"应用系统"带来异常,且系统中write操作比较密集,建议采取"allkeys-lru"

27.maxmemory-samples 3

默认值3，上面LRU和最小TTL策略并非严谨的策略，而是大约估算的方式，因此可以选择取样值以便检查

28.appendonly
# By default Redis asynchronously dumps the dataset on disk.If you can live
# with the idea that the latest records will be lost ifsomething like a crash
# happens this is the preferred way to run Redis. If insteadyou care a lot
# about your data and don't want to that a single record canget lost you should
# enable the append only mode: when this mode is enabled Rediswill append
# every write operation received in the file appendonly.aof.This file will
# be read on startup in order to rebuild the full dataset inmemory.
# Note that you can have both the async dumps and the appendonly file if you
# like (you have to comment the "save" statements above todisable the dumps).
# Still if append only mode is enabled Redis will load thedata from the
# log file at startup ignoring the dump.rdb file.
# IMPORTANT: Check the BGREWRITEAOF to check how to rewritethe append
# log file in background when it gets too big.
#redis  默认每次更新操作后会在后台异步的把数据库镜像备份到磁盘，但该备份非常耗时，且备份不宜太频繁
#redis 同步数据文件是按上面save条件来同步的
#如果发生诸如拉闸限电、拔插头等状况,那么将造成比较大范围的数据丢失
#所以redis提供了另外一种更加高效的数据库备份及灾难恢复方式
#开启append only 模式后,redis 将每一次写操作请求(记录的是写操作命令)都追加到appendonly.aof 文件中
#redis重新启动时,会从该文件恢复出之前的状态。
#但可能会造成 appendonly.aof 文件过大，所以redis支持BGREWRITEAOF指令，对appendonly.aof重新整理

#简单来说就是开启AOF，默认是no
appendonly no

29.appendfilename
# The name of the append only file (default:"appendonly.aof")
##AOF保存操作记录的文件名，默认值为appendonly.aof
# appendfilename appendonly.aof

30.appendfsync
# The fsync() call tells the Operating System to actuallywrite data on disk
# instead to wait for more data in the output buffer. Some OSwill really flush
# data on disk, some other OS will just try to do itASAP.
# Redis supports three different modes:
# no: don't fsync, just let the OS flush the data when itwants. Faster.
# always: fsync after every write to the append only log .Slow, Safest.
# everysec: fsync only if one second passed since the lastfsync. Compromise.
# The default is "everysec" that's usually the rightcompromise between
# speed and data safety. It's up to you to understand if youcan relax this to
# "no" that will will let the operating system flush theoutput buffer when
# it wants, for better performances (but if you can live withthe idea of
# some data loss consider the default persistence mode that'ssnapshotting),
# or on the contrary, use "always" that's very slow but a bitsafer than
# everysec.
# If unsure, use "everysec".
#设置对 appendonly.aof 文件进行同步的频率-AOF持久化策略
#always 表示每次有写操作都进行同步,everysec 表示对写操作进行累积,每秒同步一次。
#no表示等操作系统进行数据缓存同步到磁盘， 都进行同步

#everysec 表示每秒同步一次
# appendfsync always :
appendfsync everysec
# appendfsync no

31.no-appendfsync-on-rewrite no
在aof rewrite期间,是否对aof新记录的append暂缓使用文件同步策略,主要考虑磁盘IO开支和请求阻塞时间。默认为no,表示"不暂缓",新的aof记录仍然会被立即同步

32 auto-aof-rewrite-percentage 100
当Aof log增长超过指定比例时，重写log file， 设置为0表示不自动重写Aof 日志，重写是为了使aof体积保持最小，而确保保存最完整的数据。

33 auto-aof-rewrite-min-size 64mb
触发aof rewrite的最小文件尺寸

34.vm-enabled
# Virtual Memory allows Redis to work with datasets biggerthan the actual
# amount of RAM needed to hold the whole dataset inmemory.
# In order to do so very used keys are taken in memory whilethe other keys
# are swapped into a swap file, similarly to what operatingsystems do
# with memory pages.
# To enable VM just set 'vm-enabled' to yes, and set thefollowing three
# VM parameters accordingly to your needs.
#是否开启虚拟内存支持。
#redis 是一个内存数据库，当内存满时,无法接收新的写请求,所以在redis2.0后,提供了虚拟内存的支持
#但需要注意的，redis 所有的key都会放在内存中，在内存不够时,只把value 值放入交换区
#虽使用虚拟内存，但性能基本不受影响，需要注意的是要把vm-max-memory设置到足够来放下所有的key
vm-enabled no
# vm-enabled yes

35.vm-swap-file
# 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 sureto use a swap
# file for every redis process you are running. Redis willcomplain if the
# swap file is already in use.
# The best kind of storage for the Redis swap file (that'saccessed at random)
# is a Solid State Disk (SSD).
# *** WARNING *** if you are using a shared hosting thedefault of putting
# the swap file under /tmp is not secure. Create a dir withaccess granted
# only to Redis user and configure Redis to create the swapfile there.
#设置虚拟内存的交换文件路径，不可多个Redis实例共享
vm-swap-file /tmp/redis.swap

36.vm-max-memory
# vm-max-memory configures the VM to use at max the specifiedamount 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 swapfile.
# 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 inbytes, but it's
# better to leave some margin. For instance specify an amountof RAM
# that's more or less between 60 and 80% of your freeRAM.
#设置开启虚拟内存后,redis将使用的最大物理内存大小。
#默认为0，redis将把他所有能放到交换文件的都放到交换文件中，以尽量少的使用物理内存
#即当vm-max-memory设置为0的时候,其实是所有value都存在于磁盘
#在生产环境下,需要根据实际情况设置该值,最好不要使用默认的 0
vm-max-memory 0

37.vm-page-size
# Redis swap files is split into pages. An object can be savedusing multiple
# contiguous pages, but pages can't be shared betweendifferent objects.
# So if your page is too big, small objects swapped out ondisk will waste
# a lot of space. If you page is too small, there is lessspace in the swap
# file (assuming you configured the same number of total swapfile pages).
# If you use a lot of small objects, use a page size of 64 or32 bytes.
# If you use a lot of big objects, use a bigger pagesize.
# If unsure, use the default :)
#设置虚拟内存的页大小
如果 value 值比较大,如要在 value 中放置博客、新闻之类的所有文章内容，就设大一点
vm-page-size 32

38.vm-pages
# Number of total memory pages in the swap file.
# Given that the page table (a bitmap of free/used pages) istaken 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 134217728pages Redis will
# use a 4 GB swap file, that will use 16 MB of RAM for thepage table.
# It's better to use the smallest acceptable value for yourapplication,
# but the default is large in order to work in mostconditions.
#设置交换文件的总的 page 数量
#注意page table信息是放在物理内存中，每8个page 就会占据RAM中的 1 个 byte
#总的虚拟内存大小 = vm-page-size * vm-pages
vm-pages 134217728

39.vm-max-threads
# 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 thereverse, a bigger
# number of threads can help with big objects even if theycan't help with
# I/O itself as the physical device may not be able to couplewith many
# reads/writes operations at the same time.
# The special value of 0 turn off threaded I/O and enables theblocking
# Virtual Memory implementation.
#设置 VM IO 同时使用的线程数量。
vm-max-threads 4

40.hash-max-zipmap
# Hashes are encoded in a special way (much more memoryefficient) when they
# have at max a given numer of elements, and the biggestelement does not
# exceed a given threshold. You can configure this limits withthe following
# configuration directives.
#redis 2.0后引入了 hash 数据结构。
#hash 中包含超过指定元素个数并且最大的元素当没有超过临界时，hash 将以zipmap 来存储
# zipmap又称为 smallhash，可大大减少内存的使用
hash-max-zipmap-entries 512
hash-max-zipmap-value 64

41.activerehashing
# Active rehashing uses 1 millisecond every 100 millisecondsof CPU time in
# order to help rehashing the main Redis hash table (the onemapping top-level
# keys to values). The hash table implementation redis uses(see dict.c)
# performs a lazy rehashing: the more operation you run intoan hash table
# that is rhashing, the more rehashing "steps" are performed,so if the
# server is idle the rehashing is never complete and some morememory is used
# by the hash table.
# The default is to use this millisecond 10 times every secondin order to
# active rehashing the main dictionaries, freeing memory whenpossible.
# If unsure:
# use "activerehashing no" if you have hard latencyrequirements and it is
# not a good thing in your environment that Redis can replyform time to time
# to queries with 2 milliseconds delay.
# use "activerehashing yes" if you don't have such hardrequirements but
# want to free memory asap when possible.
#是否重置Hash表
#设置成yes后redis将每100毫秒使用1毫秒CPU时间来对redis的hash表重新hash，可降低内存的使用
#当使用场景有较为严格的实时性需求,不能接受Redis时不时的对请求有2毫秒的延迟的话，把这项配置为no。
#如果没有这么严格的实时性要求,可以设置为 yes,以便能够尽可能快的释放内存
activerehashing yes

42. tcp-keepalive 0

定时向client发送tcp_ack包来探测client是否存活的。默认为0表示禁用，官方建议值为60秒。

43.include

# include /path/to/local.conf
# include /path/to/other.conf

额外载入配置文件。

 44.tcp-backlog：511

此参数确定了TCP连接中已完成队列(完成三次握手之后)的长度， 当然此值必须不大于Linux系统定义的/proc/sys/net/core/somaxconn值，默认是511，而Linux的默认参数值是128。当系统并发量大并且客户端速度缓慢的时候，可以将这二个参数一起参考设定

45.supervised

可以通过upstart和systemd管理Redis守护进程
选项：
   supervised no - 没有监督互动
   supervised upstart - 通过将Redis置于SIGSTOP模式来启动信号
   supervised systemd - signal systemd将READY = 1写入$ NOTIFY_SOCKET
   supervised auto - 检测upstart或systemd方法基于 UPSTART_JOB或NOTIFY_SOCKET环境变量