配置文件解析

Mr.Liu大约 19 分钟

Unit

# 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，只支持bytes，不支持bit
对大小写不敏感

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

# Unix socket.
#
# Specify the path for the Unix socket that will be used to listen for
# incoming connections. There is no default, so Redis will not listen
# on a unix socket when not specified.
#
# unixsocket /var/run/redis/redis-server.sock
# unixsocketperm 700

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

bind

# By default, if no "bind" configuration directive is specified, Redis listens
# for connections from all the network interfaces available on the server.
# It is possible to listen to just one or multiple selected interfaces using
# the "bind" configuration directive, followed by one or more IP addresses.
#
# Examples:
#
# bind 192.168.1.100 10.0.0.1
# bind 127.0.0.1 ::1
bind 127.0.0.1 ::1

tcp-keepalive

# 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

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

loglevel

# 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

logfile

# 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 /var/log/redis/redis-server.log

syslog-enabled

# 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

# Specify the syslog identity.
# syslog-ident redis

syslog-facility

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

databases

# 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

################################ 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:
#
#   save ""

save 900 1
save 300 10
save 60 10000

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

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，默认:

是1分钟内改了1万次，

或5分钟内改了10次，

或15分钟内改了1次。

如果想禁用RDB持久化的策略，只要不设置任何save指令(可以在redis中调用**save命令主动备份**)，或者给save传入一个空字符串参数也可以。

# 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

如果配置成no，表示你不在乎数据不一致或者有其他的手段发现和控制

# 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

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。

# 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

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。

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

RDB持久化文件名

# 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 /var/lib/redis

redis服务的工作路径，也是备份文件的存储路径。

如果不确定redis服务运行路径，可以使用如下操作，确定redis运行路径

root@XTZJ-20220305QE:/var/lib/redis# which redis-server
/usr/bin/redis-server

root@XTZJ-20220305QE:/var/lib/redis# whereis redis-server
redis-server: /usr/bin/redis-server /usr/share/man/man1/redis-server.1.gz

# 如果命令 which 和 whereis 都找不到安装目录，可使用以下办法
root@XTZJ-20220305QE:/var/lib/redis# ps -ef|grep redis  # 得到了进程号 xxxx
root       307    11  0 22:46 pts/0    00:00:00 sudo vi /etc/redis/redis.conf
root       308   307  0 22:46 pts/0    00:00:00 vi /etc/redis/redis.conf
root      1359   601  0 23:10 ?        00:00:00 redis-server 127.0.0.1:6379
lsf       1363  1040  0 23:10 pts/2    00:00:00 redis-cli
root      1367  1028  0 23:14 pts/1    00:00:00 grep --color=auto redis

root@XTZJ-20220305QE:/var/lib/redis# ls -l /proc/1359/cwd # 然后 ls -l /proc/xxxx/cwd
lrwxrwxrwx 1 root root 0 Apr  4 23:15 /proc/1359/cwd -> /var/lib/redis

APPEND ONLY MODE追加

# 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 yes

默认是no，yes就打开持久化

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

appendfilename "appendonly.aof"

AOF持久化文件名

# 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

Always: 同步持久化每次发生数据变更会被立即记录到磁盘性能较差但数据完整性比较好
Everysec: 出厂默认推荐，异步操作，每秒记录如果一秒内宕机，有数据丢失，
No

# 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

No-appendfsync-on-rewrite：重写时是否可以运用Appendfsync，用默认no即可，保证数据安全性。

bgrewriteaof机制，在一个子进程中进行aof的重写，从而不阻塞主进程对其余命令的处理，同时解决了aof文件过大问题。

现在问题出现了，同时在执行bgrewriteaof操作和主进程写aof文件的操作，两者都会操作磁盘，而bgrewriteaof往往会涉及大量磁盘操作，这样就会造成主进程在写aof文件的时候出现阻塞的情形，现在no-appendfsync-on-rewrite参数出场了。如果该参数设置为no，是最安全的方式，不会丢失数据，但是要忍受阻塞的问题。如果设置为yes呢？这就相当于将appendfsync设置为no，这说明并没有执行磁盘操作，只是写入了缓冲区，因此这样并不会造成阻塞（因为没有竞争磁盘），但是如果这个时候redis挂掉，就会丢失数据。丢失多少数据呢？在linux的操作系统的默认设置下，最多会丢失30s的数据。

因此，如果应用系统无法忍受延迟，而可以容忍少量的数据丢失，则设置为yes。如果应用系统无法忍受数据丢失，则设置为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.

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

Auto-aof-rewrite-min-size：设置重写的基准值

Auto-aof-rewrite-percentage：设置重写的基准值

SECURITY安全

redis默认是用来做缓存的，部署在已经经过安全验证的Linux服务器上，一般不考虑安全问题。因此，redis中有关安全的配置全部注释掉。当然，非要在Redis中使用安全也可以。

127.0.0.1:6379> ping  # 本身执行命令是没有问题的
PONG
127.0.0.1:6379> config set requirepass "123456"  # 设置访问密码为123456
OK
127.0.0.1:6379> ping  # 执行命令，就提示验证失败
(error) NOAUTH Authentication required.
127.0.0.1:6379> auth 123456  # 设置密码后，需要在每次执行命令前，先验证密码，才能成功执行命令
OK
127.0.0.1:6379> ping
PONG
127.0.0.1:6379> config set requirepass ""  # 设置密码为空，执行命令不需要验证密码
OK
127.0.0.1:6379> config get requirepass  # 获取当前密码为空
1) "requirepass"
2) ""
127.0.0.1:6379> config get dir  # 获取当前redis服务的执行路径
1) "dir"
2) "D:\\software\\Redis\\5.0.10"

LIMITS限制

Maxclients

################################### 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'.
#
# maxclients 10000

Maxmemory

# 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').
#
# maxmemory <bytes>

Maxmemory-policy

# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
# is reached. You can select among five behaviors:
#
# volatile-lru -> Evict using approximated LRU among the keys with an expire set.
# 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.
# volatile-random -> Remove a random key among the ones with 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

volatile-lru:使用LRU算法移除key，只对设置了过期时间的键
allkeys-lru:使用LRU算法移除key
volatile-lfu:使用LFU算法移除key，只对设置了过期时间的键
allkeys-lfu:使用LFU算法移除key
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
allkeys-random:移除随机的key
volatile-ttl:移除那些TTL值最小的key，即那些最近要过期的key
noeviction:不进行移除。针对写操作，只是写满返回错误信息

常见的缓存算法

LRU (Least recently used) 最近最少使用，如果数据最近被访问过，那么将来被访问的几率也更高。
LFU (Least frequently used) 最不经常使用，如果一个数据在最近一段时间内使用次数很少，那么在将来一段时间内被使用的可能性也很小。
FIFO (Fist in first out) 先进先出，如果一个数据最先进入缓存中，则应该最早淘汰掉。

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

# 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

REPLICATION复制

 ################################# REPLICATION #################################

 # Master-Replica replication. Use replicaof to make a Redis instance a copy of
 # another Redis server. A few things to understand ASAP about Redis replication.
 #
 #   +------------------+      +---------------+
 #   |      Master      | ---> |    Replica    |
 #   | (receive writes) |      |  (exact copy) |
 #   +------------------+      +---------------+
 #
 # 1) Redis replication is asynchronous, but you can configure a master to
 #    stop accepting writes if it appears to be not connected with at least
 #    a given number of replicas.
 # 2) Redis replicas are able to perform a partial resynchronization with the
 #    master if the replication link is lost for a relatively small amount of
 #    time. You may want to configure the replication backlog size (see the next
 #    sections of this file) with a sensible value depending on your needs.
 # 3) Replication is automatic and does not need user intervention. After a
 #    network partition replicas automatically try to reconnect to masters
 #    and resynchronize with them.
 #
 # replicaof <masterip> <masterport>
 
 # 旧版 slaveof <masterip> <masterport>

常见配置redis.conf介绍

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
```
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
```
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
```
绑定的主机地址
```
bind 127.0.0.1
```
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
```
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
```
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
```
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
```
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。
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
```
指定本地数据库文件名，默认值为dump.rdb
```
dbfilename dump.rdb
```
指定本地数据库存政目录
```
dir ./
```
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
```
# 旧版命令：slaveof <masterip> <masterport>
replicaof <masterip> <masterport>
```
当master服务设置了密码保护时，slav服务连接master的密码
```
masterauth <master-password>
```
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
```
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
```
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>
```
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
```
指定更新日志文件名，默认为appendonly.aof
```
appendfilename appendonly.aof
```
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
```
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
```
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
```
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
```
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
```
设置swap文件中的page数量y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
```
设置访间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
```
设置在向客户端应管时，是否把较小的包合并为一个包发送，默认为开启
```
glueoutputbuf yes
```
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
```
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
```
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
```

配置文件解析

Unit

INCLUDE

GENERAL

daemonize

pidfile

port

tcp-backlog

timeout

bind

tcp-keepalive

loglevel

logfile

syslog-enabled

syslog-ident

syslog-facility

databases

SNAPSHOTTING快照

APPEND ONLY MODE追加

SECURITY安全

LIMITS限制

Maxclients

Maxmemory

Maxmemory-policy

Maxmemory-samples

REPLICATION复制

常见配置redis.conf介绍