Redis設定檔解讀

Redis設定檔解讀

Redis設定檔參數說明: 

1. Redis預設不是以守護進程的方式運行，可以通過該配置項修改，使用yes啟用守護進程

daemonize no

2. 當Redis以守護進程方式運行時，Redis預設會把pid寫入/var/run/redis.pid檔案，可以通過pidfile指定

pidfile /var/run/redis.pid

3. 指定Redis監聽連接埠，預設連接埠為6379，作者在自己的一篇博文中解釋了為什麼選用6379作為預設連接埠，因為6379在手機按鍵上MERZ對應的號碼，而MERZ取自意大利歌女Alessia Merz的名字

port 6379

4. 綁定的主機地址

bind 127.0.0.1

5.當 用戶端閑置多長時間後關閉串連，如果指定為0，表示關閉該功能

timeout 300

6. 指定日誌記錄層級，Redis總共支援四個層級：debug、verbose、notice、warning，預設為verbose

loglevel verbose

7. 日誌記錄方式，預設為標準輸出，如果配置Redis為守護進程方式運行，而這裡又配置為日誌記錄方式為標準輸出，則日誌將會發送給/dev/null

logfile stdout

8. 設定資料庫的數量，預設資料庫為0，可以使用SELECT <dbid>命令在串連上指定資料庫id

databases 16

9. 指定在多長時間內，有多少次更新操作，就將資料同步到資料檔案，可以多個條件配合

save <seconds> <changes>

Redis預設設定檔中提供了三個條件：

save 900 1

save 300 10

save 60 10000

分別表示900秒（15分鐘）內有1個更改，300秒（5分鐘）內有10個更改以及60秒內有10000個更改。

 

10. 指定儲存至本機資料庫時是否壓縮資料，預設為yes，Redis採用LZF壓縮，如果為了節省CPU時間，可以關閉該選項，但會導致資料庫檔案變的巨大

rdbcompression yes

11. 指定本機資料庫檔案名稱，預設值為dump.rdb

dbfilename dump.rdb

12. 指定本機資料庫存放目錄

dir ./

13. 設定當本機為slav服務時，設定master服務的IP地址及連接埠，在Redis啟動時，它會自動從master進行資料同步

slaveof <masterip> <masterport>

14. 當master服務設定了密碼保護時，slav服務串連master的密碼

masterauth <master-password>

15. 設定Redis串連密碼，如果配置了串連密碼，用戶端在串連Redis時需要通過AUTH <password>命令提供密碼，預設關閉

requirepass foobared

16. 設定同一時間最大用戶端串連數，預設無限制，Redis可以同時開啟的用戶端串連數為Redis進程可以開啟的最大檔案描述符數，如果設定 maxclients 0，表示不作限制。當用戶端串連數到達限制時，Redis會關閉新的串連並向用戶端返回max number of clients reached錯誤資訊

maxclients 128

17. 指定Redis最大記憶體限制，Redis在啟動時會把資料載入到記憶體中，達到最大記憶體後，Redis會先嘗試清除已到期或即將到期的Key，當此方法處理 後，仍然到達最大記憶體設定，將無法再進行寫入操作，但仍然可以進行讀取操作。Redis新的vm機制，會把Key存放記憶體，Value會存放在swap區

maxmemory <bytes>

18. 指定是否在每次更新操作後進行日誌記錄，Redis在預設情況下是非同步把資料寫入磁碟，如果不開啟，可能會在斷電時導致一段時間內的資料丟失。因為 redis本身同步資料檔案是按上面save條件來同步的，所以有的資料會在一段時間內只存在於記憶體中。預設為no

appendonly no

19. 指定更新記錄檔名，預設為appendonly.aof

appendfilename appendonly.aof

20. 指定更新日誌條件，共有3個可選值：
no：表示等作業系統進行資料緩衝同步到磁碟（快）
always：表示每次更新操作後手動調用fsync()將資料寫到磁碟（慢，安全）
everysec：表示每秒同步一次（折衷，預設值）

appendfsync everysec

 

21. 指定是否啟用虛擬記憶體機制，預設值為no，簡單的介紹一下，VM機制將資料分頁存放，由Redis將訪問量較少的頁即冷資料swap到磁碟上，訪問多的頁面由磁碟自動換出到記憶體中（在後面的文章我會仔細分析Redis的VM機制）

vm-enabled no

22. 虛擬記憶體檔案路徑，預設值為/tmp/redis.swap，不可多個Redis執行個體共用

vm-swap-file /tmp/redis.swap

23. 將所有大於vm-max-memory的資料存入虛擬記憶體,無論vm-max-memory設定多小,所有索引資料都是記憶體儲存的(Redis的索引資料 就是keys),也就是說,當vm-max-memory設定為0的時候,其實是所有value都存在於磁碟。預設值為0

vm-max-memory 0

24. Redis swap檔案分成了很多的page，一個對象可以儲存在多個page上面，但一個page上不能被多個對象共用，vm-page-size是要根據儲存的 資料大小來設定的，作者建議如果儲存很多小對象，page大小最好設定為32或者64bytes；如果儲存很大大對象，則可以使用更大的page，如果不 確定，就使用預設值

vm-page-size 32

25. 設定swap檔案中的page數量，由於頁表（一種表示頁面空閑或使用的bitmap）是在放在記憶體中的，，在磁碟上每8個pages將消耗1byte的記憶體。

vm-pages 134217728

26. 設定訪問swap檔案的線程數,最好不要超過機器的核心數,如果設定為0,那麼所有對swap檔案的操作都是串列的，可能會造成比較長時間的延遲。預設值為4

vm-max-threads 4

27. 設定在向用戶端應答時，是否把較小的包合并為一個包發送，預設為開啟

glueoutputbuf yes

28. 指定在超過一定的數量或者最大的元素超過某一臨界值時，採用一種特殊的雜湊演算法

hash-max-zipmap-entries 64

hash-max-zipmap-value 512

29. 指定是否啟用重設雜湊，預設為開啟（後面在介紹Redis的雜湊演算法時具體介紹）

activerehashing yes

30. 指定包含其它的設定檔，可以在同一主機上多個Redis執行個體之間使用同一份設定檔，而同時各個執行個體又擁有自己的特定設定檔

include /path/to/local.conf

 

------------------------------------------------------------------------------------------------------------------------------

完整設定檔：

# Redis configuration file example

 

# 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

 

# When run as a daemon, Redis write a pid file in /var/run/redis.pid by default.

# You can specify a custom pid file location here.

pidfile /var/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 connections.

#

# bind 127.0.0.1

 

# 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)

# notice (moderately verbose, what you want in production probably)

# warning (only very important / critical messages are logged)

loglevel debug

 

# Specify the log file name. Also 'stdout' can be used to force

# the demon 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

 

# 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 （快照）#################################

#

# 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

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

 

# For default save/load DB in/from the working directory

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

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.

#

# 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).

#

# 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 limts.

# 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（非同步） 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.log. 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.

#

# The name of the append only file is "appendonly.log"

#

# IMPORTANT: Check the BGREWRITEAOF to check how to rewrite the append

# log file in background when it gets too big.

 

appendonly no

 

# 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 "always" that's the safer of the options. It's up to you to

# understand if you can relax this to "everysec" that will fsync every second

# or to "no" that will let the operating system flush the output buffer when

# it want, for better performances (but if you can live with the idea of

# some data loss consider the default persistence mode that's snapshotting).

 

appendfsync always

# appendfsync everysec

# appendfsync no

 

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

 

# Use object sharing. Can save a lot of memory if you have many common

# string in your dataset, but performs lookups against the shared objects

# pool so it uses more CPU and can be a bit slower. Usually it's a good

# idea.

#

# When object sharing is enabled (shareobjects yes) you can use

# shareobjectspoolsize to control the size of the pool used in order to try

# object sharing. A bigger pool size will lead to better sharing capabilities.

# In general you want this value to be at least the double of the number of

# very common strings you have in your dataset.

#

# WARNING: object sharing is experimental, don't enable this feature

# in production before of Redis 1.0-stable. Still please try this feature in

# your development environment so that we can test it better.

# shareobjects no

# shareobjectspoolsize 1024

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