Redis的配置文件redis.conf的解析

来源于：尚硅谷谷周阳

文章目录

配置文件位置
常见配置
Units单位
INCLUDES包含
GENERAL通用
- deamonize
- port
- tcp-backlog
- timeout
- tcp-keepalive 300
- loglevel
- syslog-enabled
- syslog-ident
- syslog-facility
- databases
SECURITY安全
LIMITS限制
- maxclients
- maxmemory
- maxmemory-policy
- maxmemory-samples
SNAPSHOTTING 快照
- save seconds changes
- dbfilename dump.rdb
- save ""
- stop-writes-on-bgsave-error
- rdbcompression
- rdbchecksum
- dir
APPEND ONLY MODE 写日志
- appendonly
- appendfilename
- appendfsync
- auto-aof-rewrite-percentage 100
no-appendfsync-on-rewrite
主从复制的配置

配置文件位置

安装包在文件夹opt中解压。原厂配置文件位置如下：

保留原厂配置文件（备份），拷贝一份到了/myRedis/redis.conf

启动时通过这个配置文件启动
修改

常见配置

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verboseloglevel 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/nulllogfile 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iddatabases 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 1save 300 10save 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.rdbdbfilename 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noappendonly no
19. 指定更新日志文件名，默认为appendonly.aofappendfilename 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 everysec21. 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0vm-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4vm-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 64hash-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

Units单位

INCLUDES包含

GENERAL通用

deamonize

# 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

deamon n.守护线程
daemonize是用来指定redis是否要用守护线程的方式启动。

当我们采用yes时，redis会在后台运行，此时redis将一直运行，除非手动kill该进程。同时将进程pid号写入至redis.conf选项pidfile设置的文件中，默认会生成在/var/run/redis.pid，也可以通过pidfile来指定pid文件生成的位置

# If a pid file is specified, Redis writes it where specified at startup
# and removes it at exit.
#
# When the server runs non daemonized, no pid file is created if none is
# specified in the configuration. When the server is daemonized, the pid file
# is used even if not specified, defaulting to "/var/run/redis.pid".
#
# Creating a pid file is best effort: if Redis is not able to create it
# nothing bad happens, the server will start and run normally.
pidfile /var/run/redis_6379.pid

而采用no时，当前界面将进入redis的命令行界面，exit强制退出或者关闭连接工具(putty,xshell等)都会导致redis进程退出。

port

默认端口6379

# Accept connections on the specified port, default is 6379 (IANA #815344).
# If port 0 is specified Redis will not listen on a TCP socket.
port 6379

tcp-backlog

默认 tcp-backlog 511

# TCP listen() backlog.
#
# In high requests-per-second environments you need a high backlog in order
# to avoid slow clients connection 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

timeout

空闲多少秒后关闭连接

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

tcp-keepalive 300

单位为秒，如果设置为0，则不会进行Keepalive检测，Redis 6.0默认300

# 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) Force network equipment in the middle to consider the connection to be
#    alive.
#
# 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

loglevel

loglevel 日志级别四种级别：debug 、verbose、notice 、warning
logfile “” 日志文件名

# 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)
loglevel notice# Specify the log file name. Also the empty string 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 ""

syslog-enabled

是否把日志输出到syslog中

# To enable logging to the system logger, just set 'syslog-enabled' to yes,
# and optionally update the other syslog parameters to suit your needs.
# syslog-enabled no

syslog-ident

指定syslog里的日志标志

# Specify the syslog identity.
# syslog-ident redis

syslog-facility

指定syslog设备，值可以是USER或LOCAL0-LOCAL7

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

databases

默认16个库，切换库用select，默认使用使用0库

# 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

SECURITY安全

安全这里都默认注释掉了，为了效率，这块安全暂不开启，交给Linux

################################## SECURITY #################################### Warning: since Redis is pretty fast, an outside user can try up to
# 1 million passwords per second against a modern box. This means that you
# should use very strong passwords, otherwise they will be very easy to break.
# Note that because the password is really a shared secret between the client
# and the server, and should not be memorized by any human, the password
# can be easily a long string from /dev/urandom or whatever, so by using a
# long and unguessable password no brute force attack will be possible.# Redis ACL users are defined in the following format:
#
#   user <username> ... acl rules ...
#
# For example:
#
#   user worker +@list +@connection ~jobs:* on >ffa9203c493aa99
#
# The special username "default" is used for new connections. If this user
# has the "nopass" rule, then new connections will be immediately authenticated
# as the "default" user without the need of any password provided via the
# AUTH command. Otherwise if the "default" user is not flagged with "nopass"
# the connections will start in not authenticated state, and will require
# AUTH (or the HELLO command AUTH option) in order to be authenticated and
# start to work.
#
# The ACL rules that describe what a user can do are the following:
#
#  on           Enable the user: it is possible to authenticate as this user.
#  off          Disable the user: it's no longer possible to authenticate
#               with this user, however the already authenticated connections
#               will still work.
#  +<command>   Allow the execution of that command
#  -<command>   Disallow the execution of that command

LIMITS限制

maxclients

默认最大数连接10000

################################### CLIENTS ##################################### Set the max number of connected clients at the same time. By default
# this limit is set to 10000 clients, however if the Redis server is not
# able to configure the process file limit to allow for the specified limit
# the max number of allowed clients is set to the current file limit
# minus 32 (as Redis reserves a few file descriptors for internal uses).
#
# Once the limit is reached Redis will close all the new connections sending
# an error 'max number of clients reached'.
#
# IMPORTANT: When Redis Cluster is used, the max number of connections is also
# shared with the cluster bus: every node in the cluster will use two
# connections, one incoming and another outgoing. It is important to size the
# limit accordingly in case of very large clusters.
#
# maxclients 10000

maxmemory

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redis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。

但是对于无内存申请的指令，仍然会正常响应，比如GET等。如果你的redis是主redis（说明你的redis有从redis），那么在设置内存使用上限时，需要在系统中留出一些内存空间给同步队列缓存，只有在你设置的是“不移除”的情况下，才不用考虑这个因素

############################## MEMORY MANAGEMENT ################################# Set a memory usage limit to the specified amount of bytes.
# When the memory limit is reached Redis will try to remove keys
# according to the eviction policy selected (see maxmemory-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 or LFU cache, or to
# set a hard memory limit for an instance (using the 'noeviction' policy).
#
# WARNING: If you have replicas attached to an instance with maxmemory on,
# the size of the output buffers needed to feed the replicas 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 replicas 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 replicas attached it is suggested that you set a lower
# limit for maxmemory so that there is some free RAM on the system for replica
# output buffers (but this is not needed if the policy is 'noeviction').
#
# maxmemory <bytes>

maxmemory-policy

eviction
英 [ɪˈvɪkʃn]
n.驱逐;驱赶
noeviction 默认永不移除
（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

LRU means Least Recently Used 选择最近最久未使用的予以淘汰
LFU means Least Frequently Used 最近最少使用使用的予以淘汰

# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
# is reached. You can select one from the following behaviors:
#
# volatile-lru -> Evict using approximated LRU, only keys with an expire set.
# allkeys-lru -> Evict any key using approximated LRU.
# volatile-lfu -> Evict using approximated LFU, only keys with an expire set.
# allkeys-lfu -> Evict any key using approximated LFU.
# volatile-random -> Remove a random key having an expire set.
# allkeys-random -> Remove a random key, any key.
# volatile-ttl -> Remove the key with the nearest expire time (minor TTL)
# 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:
#
# maxmemory-policy noeviction

maxmemory-samples

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，所以你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。默认选取5个

# 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. By default Redis will check five keys and pick the one that was
# used least 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.
#
# maxmemory-samples 5

SNAPSHOTTING 快照

save seconds changes

设置触发RDB的条件
save 900 1
save 300 10
save 60 10000
900s内有一次改变
300s内有10次改变
60s内有10000次改变
以上三个条件满足任一就可触发RDB
即：
1分钟改变了1万次
5分钟改变了10次
15分钟改变了1次
注意：FLASHALL操作后内存清空，此时如果立刻关机（SHUTDOWN）会触发RDB，但是由于内存清空，保存的新的rdb文件是空的，重启redis后恢复出来的也是空的。

################################ 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 behavior 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.
#save 900 1
save 300 10
save 60 10000

dbfilename dump.rdb

设置保存快照的文件

# The filename where to dump the DB
dbfilename dump.rdb

save “”

禁用RBD

#   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:
#
#   save ""

stop-writes-on-bgsave-error

如果save出错、停止写入

# 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.
stop-writes-on-bgsave-error yes

rdbcompression

rdbcompression：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。如果你不想消耗CPU来进行压缩的话，可以设置为关闭此功能


# Compress string objects using LZF when dump .rdb databases?
# By default compression is enabled 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

rdbchecksum

rdbchecksum：在存储快照后，还可以让redis使用CRC64算法来进行数据校验，但是这样做会增加大约
10%的性能消耗，如果希望获取到最大的性能提升，可以关闭此功能

# 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.
rdbchecksum yes

dir

# 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.
dir ./

APPEND ONLY MODE 写日志

appendonly

开启aof

appendfilename

默认aof日志文件名 appendonly.aof

############################## 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.appendonly no# The name of the append only file (default: "appendonly.aof")appendfilename "appendonly.aof"

appendfsync

记录写日志的频率
appendfsync always 同步持久化，每次发生数据变更立即记录到磁盘文件，性能较差但数据完整性好
appendfsync everysec 每秒异步操作（出厂默认），每秒记录，如果宕机有1秒的数据丢失
appendfsync no 从不

# 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
appendfsync everysec
# appendfsync no

auto-aof-rewrite-percentage 100

auto-aof-rewrite-percentage 100 设置重写的基准值
auto-aof-rewrite-min-size 64mb 设置重写的基准值
redis会记录上次重写的aof文件的大小，默认配置是当aof文件大小是上次重写后大小的一倍，且文件大于64M时触发。

# 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.auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb

no-appendfsync-on-rewrite

重写时是否可用appendfsync，用默认的no即可。保证数据安全性

# 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.no-appendfsync-on-rewrite no

主从复制的配置