一、概述
平时我们工作中除了基本的Redis命令外，我们对于Redis的一些基础配置也是需要有一定了解的，上期中给大家介绍了Units、Includes、Network等方面的相关的内容，今天会带大家针对Redis的配置文件剩余部分进行了解。
Reids配置文件是位于安装目录下的redis.conf，如果没有找到的话，可以从源码文件夹中copy，一般我们不会对原始文件进行修改，而是copy一份。
cp redis.conf myredis.conf让Redis以制定配置文件启动的话，我们可以执行以下语句
./redis-server /path/to/redis.conf
二、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.我们可以看到，由于Redis速度很快，每秒可以尝试一百万个密码进行攻击。这意味着你应该使用很强的密码，否则很容易被破解。当然一般情况下，我们不会真的把安全策略做在Redis这一层。
在默认配置文件中，安全这块的配置也都是被注释掉的。
如果我们需要添加代码，我们可以连接上Redis后执行以下命令：???????
127.0.0.1:6379> CONFIG GET requirepass
1) "requirepass"
2) ""
127.0.0.1:6379> CONFIG SET requirepass "123456"
OK
127.0.0.1:6379>之后我们再连上Redis，如果需要执行命令的话，需要先进行授权???????
~ redis-cli
127.0.0.1:6379> ping
(error) NOAUTH Authentication required.
127.0.0.1:6379> AUTH 123456
OK
127.0.0.1:6379> ping
PONG
127.0.0.1:6379>
三、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>设置Redis可以使用的最大内存数，单位是bytes。一旦达到内存使用上限，redis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无法移除内存中的数据，那么当我们执行SET、LPUSH等写操作时，将会返回错误信息，但是对于GET这类的读操作则不会有影响。???????
# 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当内存达到上限时，Redis释放内存的策略主要有以下几种：
volatile-lru：在设置了过期时间的key中使用LRU算法随机进行移除
allkeys-lru：使用LRU算法移除key
volatile-lfu：在设置了过期时间的key中使用LFU算法随机进行移除
allkeys-lfu：使用LFU算法移除key
volatile-random：在设置了过期时间的key中随机进行移除
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，只是返回错误信息
由于默认策略是noeviction，但我们生产环境中一般不会选择此项配置，各位小伙伴也可以看下自己公司Redis此项配置。
四、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设置Redis最大的客户端进行连接数。默认情况下为10000个客户端。当没有更多的可供的连接数时，redis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” 错误。
五、REPLICATION
主从相关配置，我们在之后的章节中进行介绍。
六、APPEND ONLY MODE
aof相关配置，我们在之后的章节中进行介绍。
七、总结
今天给大家介绍了一下redis的常用配置，如果大家还有别的什么问题，可以在评论中留言。