redis.conf简单介绍

redis启动的时候，就会通过配置文件来启动。

units对大小写不敏感

# 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.

可以把其他配置文件导入进来（python 的 import）

################################## INCLUDES ###################################
# include /path/to/local.conf
# include /path/to/other.conf

网络

################################## NETWORK #####################################
bind 127.0.0.1
protected-mode yes
port 6379

通用

################################# GENERAL #####################################
# 以守护进程方式后台运行，默认是no，需要手动开启，不开启的话，一退出进程就结束了
daemonize yes
# 如果以后台的方式运行，我们就需要指定一个pid文件
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) 生产环境使用
# warning (only very important / critical messages are logged)

# >>>>>>>>>>>>>>日志级别
loglevel notice
# 日志的文件名，如果为空的话，就转化为标准输出
logfile ""
# 数据库的数量，默认是16个
databases 16
# 启动redis时显示的log，默认为yes
always-show-logo yes

快照

################################ SNAPSHOTTING  ################################
save 900 1		# 如果900秒内至少1个key发生变化（新增、修改和删除），则重写rdb文件；
save 300 10		# 如果每300秒内至少10个key发生变化（新增、修改和删除），则重写rdb文件；
save 60 10000	        # 如果每60秒内至少10000个key发生变化（新增、修改和删除），则重写rdb文件。

# >>>>> 我们之后学习持久化，会自己定义数据

# 持久化发生错误之后，是否还继续工作
stop-writes-on-bgsave-error yes
# 是否压缩rdb文件，需要消耗一些cpu资源
rdbcompression yes
# 保存rdb文件的时候，进行文件检查，校验和
rdbchecksum yes
# rdb文件保存目录
dir ./

持久化，在规定的时间内，执行了多少次操作，则会持久化到文件(.rdb或.aof文件)

redis是内存数据库，如果没有持久化，数据断电即失。

################################# REPLICATION #################################
# >>>>>>>>>>>>> 复制，后面学习主从复制的时候，再来了解

安全

################################## SECURITY ###################################
# requirepass foobared 需要密码

密码默认为空，可以通过命令行的方式进行设置

127.0.0.1:6379> config get requirepass
1) "requirepass"
2) ""
127.0.0.1:6379> config set requirepass "123456"	# 设置密码
OK
127.0.0.1:6379> config get requirepass
1) "requirepass"
2) "123456"
127.0.0.1:6379> auth 123456						# 登录
OK

客户端限制

################################### CLIENTS ####################################
# Set the max number of connected clients at the same time. 

# 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

内存

############################## MEMORY MANAGEMENT ################################
# Set a memory usage limit to the specified amount of bytes.

# 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).

# maxmemory <bytes>

# Note: with any of the above policies, Redis will return an error on write
#       operations, when there are no suitable keys for eviction.

# The default is:
#
# maxmemory-policy noeviction

# 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

# replica-ignore-maxmemory yes

redis回收过期的keys有两种方式，一种是访问时发现这些keys已经过期，并且在后台被称为“活动的过期keys”。
第二种是缓慢的，交互式的扫描keys空间，以查找要回收的过期keys，以便可以释放已过期且短时间之内不会
再访问的keys。
# Redis reclaims expired keys in two ways: upon access when those keys are
# found to be expired, and also in background, in what is called the
# "active expire key". The key space is slowly and interactively scanned
# looking for expired keys to reclaim, so that it is possible to free memory
# of keys that are expired and will never be accessed again in a short time.

默认的过期周期的设置将避免超过10%的过期keys在内存中，并且将尽量避免消费超过总内存的25%，
以及避免增加系统延迟。
# The default effort of the expire cycle will try to avoid having more than
# ten percent of expired keys still in memory, and will try to avoid consuming
# more than 25% of total memory and to add latency to the system. 

effort每增加1，就会增加10%，系统就会消耗更多的CPU资源，并会减少仍然存在于系统中的过期密钥的数量。
所以必须在内存，cpu和延迟之间做权衡。
# However it is possible to increase the expire "effort" that is normally set to
# "1", to a greater value, up to the value "10". At its maximum value the
# system will use more CPU, longer cycles (and technically may introduce
# more latency), and will tollerate less already expired keys still present
# in the system. It's a tradeoff betweeen memory, CPU and latecy.

# active-expire-effort 1

总结：

# maxmemory <bytes>		# redis配置的最大内存容量
# maxmemory-policy noeviction	# 内存达到上限之后的处理策略

LRU表示最近最少使用
# LRU means Least Recently Used
LFU表示最少使用
# LFU means Least Frequently Used

LRU，LFU和volatile-ttl均使用近似随机算法实现。

maxmemory-policy策略

策略	官方	白话
volatile-lru	在设置了过期时间的键中采用LRU算法删除键，直到腾出足够内存为止。	只对设置了过期时间的 keys进行LRU
allkeys-lru	在所有键中采用LRU算法删除键，直到腾出足够内存为止。	删除LRU算法的keys
volatile-random	在设置了过期时间的键中随机删除键，直到腾出足够内存为止。	随机删除即将过期的keys
allkeys-random	在所有键中采用随机删除键，直到腾出足够内存为止。	随机删除keys，无论是否过期
volatile-ttl	在设置了过期时间的键空间中，具有更早过期时间的key优先移除。	删除即将过期的keys
noeviction	当内存使用达到阈值的时候，所有引起申请内存的命令会报错。	永不过期，返回错误
volatile-lfu	在设置了过期时间的键中采用LFU算法删除键，直到腾出足够内存为止。	只对设置了过期时间的 keys进行LFU
allkeys-lfu	在所有键中采用LFU算法删除键，直到腾出足够内存为止。	删除LFU算法的keys

AOF配置，默认是不开启的，默认使用RDB持久化方式。

############################## 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).

appendonly no
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.

# If unsure, use "everysec".

# appendfsync always	# 每次修改都会修改fsync()
appendfsync everysec	# 每秒执行一次 fsync()
# appendfsync no	# 不执行fsync()，这时候操作系统自己同步数据，速度最快！