第四章、解析配置文件 redis.conf

Redis学习

redis.conf 文件位置：find / -name redis.conf
/usr/local/redis-3.2.1/
一般单独 copy 出该文件单独执行启动实例。

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一、units 单位

# Redis configuration file example.
#
# Note that in order to read the configuration file, Redis must be
# started with the file path as first argument:
#
# ./redis-server /path/to/redis.conf

# Note on units: when memory size is needed, it is possible to specify
# 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.


配置大小单位,开头定义了一些基本的度量单位,不支持bit
对大小写不敏感

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二 、INCLUDES 包含

# Include one or more other config files here.  This is useful if you
# have a standard template that goes to all Redis servers but also need
# to customize a few per-server settings.  Include files can include
# other files, so use this wisely.
#
# Notice option "include" won't be rewritten by command "CONFIG REWRITE"
# from admin or Redis Sentinel. Since Redis always uses the last processed
# line as value of a configuration directive, you'd better put includes
# at the beginning of this file to avoid overwriting config change at runtime.
#
# If instead you are interested in using includes to override configuration
# options, it is better to use include as the last line.
#
# include /path/to/local.conf
# include /path/to/other.conf

类似 html 中可以引入多个脚本文件，此处可引入多个 redis 配置文件，进行包含。

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三、GENERAL 通用【重要】

参数配置：

• Daemonize：是否守护进程运行。
• Pidfile：进程文件
• Port：redis 端口
• Syslog-enabled：是否把日志输出到 syslog 中。
• Loglevel：日志级别
• Logfile：
• Syslog-ident：指定 syslog 里的日志标志。
• Syslog-facility：指定syslog设备，值可以是 USER 或 LOCAL0-LOCAL7。
• Databases：数据库个数。

# 是否以守护进行
daemonize no

# 进程管道 id 文件,如果没有指定,则在这个路径下
pidfile /var/run/redis_6379.pid
# Specify the server verbosity level.
# This 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)

# 日志级别
loglevel notice
# Specify the server verbosity level.
# This 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)

# 日志名字
loglevel notice
# To enable logging to the system logger, just set 'syslog-enabled' to yes,
# and optionally update the other syslog parameters to suit your needs.

# 是否把日志输出到 syslog 中
# syslog-enabled no
# Specify the syslog identity.

# 指定 syslog 里的日志表示
# syslog-ident redis

# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
# syslog-facility local0
# Specify the syslog identity.
# syslog-ident redis

# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
# 指定syslog设备,值可以是user或者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'-1

# 默认有16个数据库
databases 16

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四、SNAPSHOTTING 快照

• save：save 秒钟 写操作次数。
• RDB 是整个内存的压缩过的 Snapshot，RDB 的数据结构，可以配置复合的快照触发条件。
• 如果想禁用 RDB 持久化的策略，只要不设置任何 save 指令，或者给 save 传入一个空字符串参数也可以。
• Stop-writes-on-bgsave-error：
• rdbcompression：
• rdbchecksum：
• dbfilename：
• dir：

################################ 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 completely by commenting out all "save" lines.
#
#   It is also possible to remove all the previously configured save
#   points by adding a save directive with a single empty string argument
#   like in the following example:

# flushall 和 shutdown 会立即出发 save 命令,进行备份
# 禁用 RDB 持久化策略,只要不设置任何 save 指令(在 redis 的命令窗口中使用 save 命令)或者使用下面的 save "" 也可以( save 传入一个空字符串参数也可以)
#   save ""
# 下面三个条件符合其一就触发备份
# 900 秒内有一个 key 改变过就备份
save 900 1
# 300秒内有10个key改变过就备份
save 300 10
# 60秒内有10000个key改变就触发备份
save 60 10000


# By default Redis will stop accepting writes if RDB snapshots are enabled
# (at least one save point) and the latest background save failed.
# This will make the user aware (in a hard way) that data is not persisting
# on disk properly, otherwise chances are that no one will notice and some
# disaster will happen.
#
# If the background saving process will start working again Redis will
# automatically allow writes again.
#
# However if you have setup your proper monitoring of the Redis server
# and persistence, you may want to disable this feature so that Redis will
# continue to work as usual even if there are problems with disk,
# permissions, and so forth.

# 如何配置成 no,表示不在乎数据不一致或者其他的手段发现和控制
stop-writes-on-bgsave-error yes


# 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.
# 对于存储到磁盘中的快照,可以设置是否进行压缩存储.
# 如果是的话,redis 会采用 LZF 算法进行压缩.
# 如果不想消耗CPU进行要锁,可以设置为关闭此功能
rdbcompression yes


# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
# This makes the format more resistant to corruption but there is a performance
# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
# for maximum performances.
#
# RDB files created with checksum disabled have a checksum of zero that will
# tell the loading code to skip the check.
# 在存储快照后,还可以让 redis 使用 CRC64 算法来进行数据检验
# 这样做会增加 10% 的性能消耗,
# 如果想获得最大的性能提升,则可以关闭此功能
rdbchecksum yes


# The filename where to dump the DB
# 保存时的文件名称,断电重启时读取的文件名称
dbfilename dump.rdb


# The working directory.
#
# The DB will be written inside this directory, with the filename specified
# above using the 'dbfilename' configuration directive.
#
# The Append Only File will also be created inside this directory.
#
# Note that you must specify a directory here, not a file name.
# 工作目录
dir ./

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五、REPLICATION 复制

六、SECURITY 安全

• 访问密码的查看、设置和取消

# 获取登录密码
config get requirepass
127.0.0.1:8686> config get requirepass
1) "requirepass"
2) "51310400"

# 查询启动时所在的目录
config get dir
127.0.0.1:8686> config get dir
1) "dir"
2) "/alidata/redis-5.0.3/db"

# 设置 redis 密码
config set requirepass 123456

# 登录 redis
[root@izm5e2q95pbpe1hh0kkwoiz /]# redis-cli -p 8686
127.0.0.1:8686> ping
(error) NOAUTH Authentication required.
127.0.0.1:8686> auth 51310400
OK
127.0.0.1:8686> ping
PONG

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七、LIMITS 限制【重要】

内存淘汰策略:

• LRU 算法(最近最少使用算法)。
• TTL 算法(移除那些 ttl 值最小的 key,即那些最近要过期的 key)。
  参数配置：
• Maxclients：
• Maxmemory：
• Maxmemory-policy：
• maxmemory-samples：

Maxclients

## 设置redis同时可以与多少个客户端进行连接。默认情况下为10000个客户端。当你
## 无法设置进程文件句柄限制时，redis会设置为当前的文件句柄限制值减去32，因为
## redis会为自身内部处理逻辑留一些句柄出来。如果达到了此限制，redis则会拒绝新的## 连接请求，并且向这些连接请求方发出“max number of clients reached”以作回应。

## maxmemory 最大内存：设置 redis 可以使用的内存量。一旦到达内存使用上限，redis 将会试图移## 除内部数据，移除规则可以通过 maxmemory-policy 来指定。如果 redis 无法根据移除## 规则来移除内存中的数据，或者设置了“不允许移除”，
## 那么 redi s则会针对那些需要申请内存的指令返回错误信息，比如SET、LPUSH等
# maxmemory <bytes>

## 达到最大内存时清除策略：
## （1）volatile-lru：使用LRU算法移除key，只对设置了过期时间的键
## （2）allkeys-lru：使用LRU算法移除key
## （3）volatile-random：在过期集合中移除随机的key，只对设置了过期时间的键
## （4）allkeys-random：移除随机的key
## （5）volatile-ttl：移除那些TTL值最小的key，即那些最近要过期的key
## （6）noeviction：不进行移除。针对写操作，只是返回错误信息

# maxmemory-policy: how Redis will select what to remove when maxmemory
# is reached. You can select among five behaviors:
#
## 使用 LRU 算法移除 key,只对设置了过期时间的键.LRU最近最少使用算法
# volatile-lru -> Evict using approximated LRU among the keys with an expire set.

## 使用 LRU 算法移除 key
# allkeys-lru -> Evict any key using approximated LRU.
# volatile-lfu -> Evict using approximated LFU among the keys with an expire set.
# allkeys-lfu -> Evict any key using approximated LFU.

## 在过期集合中移除随机的 key,只对设置了过期时间的键
# volatile-random -> Remove a random key among the ones with an expire set.

## 移除随机的 key
# allkeys-random -> Remove a random key, any key.

## 移除那些 ttl 值最小的 key,即那些最近要过期的 key
# volatile-ttl -> Remove the key with the nearest expire time (minor TTL)

## 不进行移除.针对写操作,只是返回错误信息   
# noeviction -> Don't evict anything, just return an error on write operations.
#
# LRU means Least Recently Used
# LFU means Least Frequently Used
#
# Both LRU, LFU and volatile-ttl are implemented using approximated
# randomized algorithms.
#
# Note: with any of the above policies, Redis will return an error on write
#       operations, when there are no suitable keys for eviction.
#
#       At the date of writing these 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:
# 默认配置是不清除,但是配置没有开启
# maxmemory-policy noeviction
# LRU, LFU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can tune it for speed or
# accuracy. For default Redis will check five keys and pick the one that was
# used less recently, you can change the sample size using the following
# configuration directive.
#
# The default of 5 produces good enough results. 10 Approximates very closely
# true LRU but costs more CPU. 3 is faster but not very accurate.
# 设置样本数量,LRU 算法和最小 TTL 算法都并非是精确的算法,而是估算值,醉意可以设置样本的大小.redis 默认会检查这么多个 key 并选择其中 LRU 的那个
# maxmemory-samples 5

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八、APPEND ONLY MODE 追加

参数配置：

• appendonly:
• appendfilename：
• Appendfsync：

############################## APPEND ONLY MODE ###############################

# By default Redis asynchronously dumps the dataset on disk. This mode is
# good enough in many applications, but an issue with the Redis process or
# a power outage may result into a few minutes of writes lost (depending on
# the configured save points).
#
# The Append Only File is an alternative persistence mode that provides
# much better durability. For instance using the default data fsync policy
# (see later in the config file) Redis can lose just one second of writes in a
# dramatic event like a server power outage, or a single write if something
# wrong with the Redis process itself happens, but the operating system is
# still running correctly.
#
# AOF and RDB persistence can be enabled at the same time without problems.
# If the AOF is enabled on startup Redis will load the AOF, that is the file
# with the better durability guarantees.
#
# Please check http://redis.io/topics/persistence for more information.
# 默认是关闭状态
appendonly no

# The name of the append only file (default: "appendonly.aof")
# 备份文件的名字
appendfilename "appendonly.aof"

# The fsync() call tells the Operating System to actually write data on disk
# instead of waiting 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 one time every second. Compromise.
#
# The default is "everysec", as 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 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.
#
# More details please check the following article:
# http://antirez.com/post/redis-persistence-demystified.html
#
# If unsure, use "everysec".

# appendfsync always
# 备份时机
# always:同步持久化,每次发生数据变更会被立即就到磁盘,性能较差但数据记录完整性比较好
# ererysec:出厂默认配置,异步操作,每秒记录,如果一秒内宕机,有数据丢失
# no:不追加
appendfsync everysec

# 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". In practical terms, this means that it is
# possible to lose 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.
# 重写时是否可以运用appendfsync,用默认no即可,保证数据安全性
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 grows by the specified percentage.
#
# This is how it works: Redis remembers the size of the AOF file after the
# latest rewrite (if no rewrite has 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 percentage of zero in order to disable the automatic AOF
# rewrite feature.
# 设置重写的基准值,此时是上次重写体积的100%,也就是体积翻一倍
auto-aof-rewrite-percentage 100
# 设置重写的基准值,此时是重写时日志要大于 64MB
auto-aof-rewrite-min-size 64mb

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九、NETWORK

参数配置：

• Tcp-backlog：设置tcp的backlog，backlog其实是一个连接队列，backlog队列总和=未完成三次握手队列 + 已经完成三次握手队列。在高并发环境下你需要一个高 backlog 值来避免慢客户端连接问题。注意 Linux 内核会将这个值减小到 /proc/sys/net/core/somaxconn 的值，所以需要确认增大 somaxconn 和tcp_max_syn_backlog 两个值来达到想要的效果。
• Tcp-keepalive：单位为秒，如果设置为 0，则不会进行 Keepalive 检测，建议设置成 60

################################## NETWORK #####################################

# TCP listen() backlog.
#
# In high requests-per-second environments you need an high backlog in order
# to avoid slow clients connections issues. Note that the Linux kernel
# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
# in order to get the desired effect.
tcp-backlog 511

设置tcp的backlog,backlog其实是一个连接队列,backlog队列总和=未完成三次握手队列+已完成三次握手队列.
在高并发环境下你需要一个高的backlog值来避免慢客户端连接问题.
注意linux内核会将这个值减小到/proc/sys/net/core/somaxconn的值,所以需要确认增大somaxconn和tcp_max_syn_backlog两个值来达到想要的效果



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

超时时间设置,0为关闭




# TCP keepalive.
#
# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
# of communication. This is useful for two reasons:
#
# 1) Detect dead peers.
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# On Linux, the specified value (in seconds) is the period used to send ACKs.
# Note that to close the connection the double of the time is needed.
# On other kernels the period depends on the kernel configuration.
#
# A reasonable value for this option is 300 seconds, which is the new
# Redis default starting with Redis 3.2.1.
tcp-keepalive 300

单位为秒,如果设置为0,则不会进行keepalive检测,建议设置成60

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十、常见配置 redis.conf 介绍

参数说明
redis.conf 配置项说明如下：
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