redis配置文件redis.conf參數說明

# By default Redis does not run as a daemon. Use 'yes' if you need it.

# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.

#Redis默認不是以守護進程的方式運行，能夠經過該配置項修改，使用yes啓用守護進程

daemonize no

# When running daemonized, Redis writes a pid file in /var/run/redis.pid by

# default. You can specify a custom pid file location here.

#當 Redis 以守護進程的方式運行的時候，Redis 默認會把 pid 文件放在/var/run/redis.pid

#可配置到其餘地址，當運行多個 redis 服務時，須要指定不一樣的 pid 文件和端口

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.

#端口

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.

#指定Redis可接收請求的IP地址,不設置將處理全部請求,建議生產環境中設置

# bind 127.0.0.1

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

#客戶端鏈接的超時時間,單位爲秒,超時後會關閉鏈接

timeout 0

# 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)

# 日誌記錄等級，4個可選值

loglevel notice

# 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

#配置 log 文件地址,默認打印在命令行終端的窗口上，也可設爲/dev/null屏蔽日誌、

logfile stdout

# Set the number of databases. The default database is DB 0, you can select

# a different one on a per-connection basis using SELECT where

# dbid is a number between 0 and 'databases'-1

#設置數據庫的個數,可使用 SELECT 命令來切換數據庫。

databases 16

#

# Save the DB on disk:

#

#    save

#

#    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.

#設置 Redis 進行數據庫鏡像的頻率。 保存數據到disk的策略

#900秒以內有1個keys發生變化時

#30秒以內有10個keys發生變化時

#60秒以內有10000個keys發生變化時

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.

#在進行鏡像備份時,是否進行壓縮

rdbcompression yes

# The filename where to dump the DB

#鏡像備份文件的文件名

dbfilename dump.rdb

# The working directory.

#

# The DB will be written inside this directory, with the filename specified

# above using the 'dbfilename' configuration directive.

# 

# Also the Append Only File will be created inside this directory.

# 

# Note that you must specify a directory here, not a file name.

#數據庫鏡像備份的文件放置的路徑

#路徑跟文件名分開配置是由於 Redis 備份時，先會將當前數據庫的狀態寫入到一個臨時文件

#等備份完成時，再把該臨時文件替換爲上面所指定的文件

#而臨時文件和上面所配置的備份文件都會放在這個指定的路徑當中

#默認值爲 ./

dir /var/lib/redis/

# 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.

#設置該數據庫爲其餘數據庫的從數據庫

#slaveof <masterip> <masterport> 當本機爲從服務時，設置主服務的IP及端口

# slaveof

# 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.

#指定與主數據庫鏈接時須要的密碼驗證

#masterauth <master-password> 當本機爲從服務時，設置主服務的鏈接密碼

# masterauth

# 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.

#當slave丟失與master的鏈接時，或slave仍然在於master進行數據同步時（未與master保持一致）

#slave可有兩種方式來響應客戶端請求：

#1)若是 slave-serve-stale-data 設置成 'yes'(默認)，slave仍 會響應客戶端請求,此時可能會有問題

#2)若是 slave-serve-stale-data 設置成 'no'，slave會返回"SYNC with master in progress"錯誤信息，但 INFO 和SLAVEOF命令除外。

slave-serve-stale-data yes

# Require clients to issue AUTH 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.

#設置客戶端鏈接後進行任何其餘指定前須要使用的密碼

#redis速度至關快，一個外部用戶在一秒鐘進行150K次密碼嘗試，需指定強大的密碼來防止暴力破解

# requirepass foobared

# 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'.

#限制同時鏈接的客戶數量。

#當鏈接數超過這個值時，redis 將再也不接收其餘鏈接請求，客戶端嘗試鏈接時將收到 error 信息

# 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

# accordingly to the eviction policy selected (see maxmemmory-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

# an 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').

#設置redis可以使用的最大內存。

#達到最大內存設置後，Redis會先嚐試清除已到期或即將到期的Key（ 設置過expire信息的key）

#在刪除時,按照過時時間進行刪除，最先將要被過時的key將最早被刪除

#若是 已到期或即將到期的key刪光，仍進行set操做，那麼將返回錯誤

#此時redis將再也不接收寫請求,只接收get請求。

#maxmemory的設置比較適合於把redis看成於相似memcached 的緩存來使用

# maxmemory <bytes>

# 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.

#redis  默認每次更新操做後會在後臺異步的把數據庫鏡像備份到磁盤，但該備份很是耗時，且備份不宜太頻繁

#redis 同步數據文件是按上面save條件來同步的

#若是發生諸如拉閘限電、拔插頭等情況,那麼將形成比較大範圍的數據丟失

#因此redis提供了另一種更加高效的數據庫備份及災難恢復方式

#開啓append only 模式後,redis 將每一次寫操做請求都追加到appendonly.aof 文件中

#redis從新啓動時,會從該文件恢復出以前的狀態。

#但可能會形成 appendonly.aof 文件過大，因此redis支持BGREWRITEAOF 指令，對appendonly.aof從新整理

appendonly no

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

##更新日誌文件名，默認值爲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".

#設置對 appendonly.aof 文件進行同步的頻率

#always 表示每次有寫操做都進行同步,everysec 表示對寫操做進行累積,每秒同步一次。

#no表示等操做系統進行數據緩存同步到磁盤， 都進行同步,everysec 表示對寫操做進行累積,每秒同步一次

# appendfsync always

appendfsync everysec

# appendfsync no

# 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.

#是否開啓虛擬內存支持。

#redis 是一個內存數據庫，當內存滿時,沒法接收新的寫請求,因此在redis2.0後,提供了虛擬內存的支持

#但須要注意的，redis 全部的key都會放在內存中，在內存不夠時,只把value 值放入交換區

#雖使用虛擬內存，但性能基本不受影響，須要注意的是要把vm-max-memory設置到足夠來放下全部的key

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.

#設置虛擬內存的交換文件路徑，不可多個Redis實例共享

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.

#設置開啓虛擬內存後,redis將使用的最大物理內存大小。

#默認爲0，redis將把他全部能放到交換文件的都放到交換文件中，以儘可能少的使用物理內存

#即當vm-max-memory設置爲0的時候,實際上是全部value都存在於磁盤

#在生產環境下,須要根據實際狀況設置該值,最好不要使用默認的 0

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 :)

#設置虛擬內存的頁大小

若是 value 值比較大,如要在 value 中放置博客、新聞之類的全部文章內容，就設大一點

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.

#設置交換文件的總的 page 數量

#注意page table信息是放在物理內存中，每8個page 就會佔據RAM中的 1 個 byte

#總的虛擬內存大小 = vm-page-size * vm-pages

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.

#設置 VM IO 同時使用的線程數量。

vm-max-threads 4

# 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.

#redis 2.0後引入了 hash 數據結構。 

#hash 中包含超過指定元素個數而且最大的元素當沒有超過臨界時，hash 將以zipmap 來存儲

# zipmap又稱爲 small hash，可大大減小內存的使用

hash-max-zipmap-entries 512

hash-max-zipmap-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.

#是否重置Hash表

#設置成yes後redis將每100毫秒使用1毫秒CPU時間來對redis的hash表從新hash，可下降內存的使用

#當使用場景有較爲嚴格的實時性需求,不能接受Redis時不時的對請求有2毫秒的延遲的話，把這項配置爲no。

#若是沒有這麼嚴格的實時性要求,能夠設置爲 yes,以便可以儘量快的釋放內存

activerehashing yes

Redis官方文檔對VM的使用提出了一些建議:

• 當key很小而value很大時,使用VM的效果會比較好.由於這樣節約的內存比較大
• 當key不小時,能夠考慮使用一些很是方法將很大的key變成很大的value,如可將key,value組合成一個新的value
• 最好使用linux ext3 等對稀疏文件支持比較好的文件系統保存你的swap文件
• vm-max-threads參數可設置訪問swap文件的線程數，最好不要超過機器的核數；設置爲0則全部對swap文件的操做都是串行的，可能會形成比較長時間的延遲,可是對數據完整性有很好的保證

redis數據存儲

redis的存儲分爲內存存儲、磁盤存儲和log文件三部分，配置文件中有三個參數對其進行配置。

• save seconds updates，save配置，指出在多長時間內，有多少次更新操做，就將數據同步到數據文件。可多個條件配合，默認配置了三個條件。
• appendonly yes/no ，appendonly配置，指出是否在每次更新操做後進行日誌記錄，若是不開啓，可能會在斷電時致使一段時間內的數據丟失。由於redis自己同步數據文件是按上面的save條件來同步的，因此有的數據會在一段時間內只存在於內存中。
• appendfsync no/always/everysec ，appendfsync配置，no表示等操做系統進行數據緩存同步到磁盤，always表示每次更新操做後手動調用fsync()將數據寫到磁盤，everysec表示每秒同步一次。