redis参数说明

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1. 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

daemonize no

2. 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

pidfile /var/run/redis.pid

3. 指定Redis监听端口，默认端口为6379，作者在自己的一篇博文中解释了为什么选用6379作为默认端口，因为6379在手机按键上MERZ对应的号码，而MERZ取自意大利歌女Alessia Merz的名字

port 6379

4. 绑定的主机地址

bind 127.0.0.1

5.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

timeout 300

6. 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

loglevel verbose

7. 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

logfile stdout

8. 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

databases 16

9. 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

save <seconds> <changes>

Redis默认配置文件中提供了三个条件：

save 900 1

    save 300 10

    save 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。

10. 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

rdbcompression yes

11. 指定本地数据库文件名，默认值为dump.rdb

dbfilename dump.rdb

12. 指定本地数据库存放目录

dir ./

13. 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

slaveof <masterip> <masterport>

14. 当master服务设置了密码保护时，slav服务连接master的密码

masterauth <master-password>

15. 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

requirepass foobared

16. 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

maxclients 128

17. 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 <bytes>

18. 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

appendonly no

19. 指定更新日志文件名，默认为appendonly.aof

appendfilename appendonly.aof

20. 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）

appendfsync everysec

21. 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 no

22. 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-swap-file /tmp/redis.swap

23. 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

vm-max-memory 0

24. Redis 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

vm-page-size 32

25. 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。

vm-pages 134217728

26. 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

vm-max-threads 4

27. 设置在向客户端应答时，是否把较小的包合并为一个包发送，默认为开启

glueoutputbuf yes

28. 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

hash-max-zipmap-entries 64

    hash-max-zipmap-value 512

29. 指定是否激活重置哈希，默认为开启（后面在介绍Redis的哈希算法时具体介绍）

activerehashing yes

30. 指定包含其它的配置文件，可以在同一主机上多个Redis实例之间使用同一份配置文件，而同时各个实例又拥有自己的特定配置文件

include /path/to/local.conf

# 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 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.

pidfile /usr/local/redis/run/redis.pid

 

# Accept connections on the specified port, default is 6379

port 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 192.168.20.12

 

# Close the connection after a client is idle for N seconds (0 to disable)

timeout 300

 

# 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

 

# 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/null

#logfile stdout

logfile ./logs/redis.log

 

# 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

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 at all commenting all the "save" lines.

 

save 900 1

save 300 10

save 60 10000

 

# 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

 

# The filename where to dump the DB

dbfilename 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 ./data/

 

################################# 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>

 

# 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>

 

################################## 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

 

################################### 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 128

 

# 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>

 

############################## 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 yes

 

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

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 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 always

appendfsync everysec

# appendfsync no

 

################################ VIRTUAL MEMORY ###############################

 

# 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

# 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

 

# 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

 

# 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 32

 

# 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

 

# 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

 

############################### ADVANCED CONFIG ###############################

 

# Glue small output buffers together in order to send small replies in a

# single TCP packet. Uses a bit more CPU but most of the times it is a win

# in terms of number of queries per second. Use 'yes' if unsure.

glueoutputbuf yes

 

# 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 64

hash-max-zipmap-value 512

 

# 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

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