Redis配置文件（2）SNAPSHOTTING快照/APPEND ONLY MODE追加

redis.conf文件

1.Save

a. 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，
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。

182 # Save the DB on disk:

184 #   save <seconds> <changes>

186 #   Will save the DB if both the given number of seconds and the given

187 #   number of write operations against the DB occurred.

189 #   In the example below the behaviour will be to save:

190 #   after 900 sec (15 min) if at least 1 key changed

191 #   after 300 sec (5 min) if at least 10 keys changed

192 #   after 60 sec if at least 10000 keys changed

b.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

 #   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:
 #
200 #   save ""
 save
 save
 save  

set key value1

save
此时立马执行，形成最新的dump文件

stop-writes-on-bgsave-error

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

# 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

yes：出错了就立即停止

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?
# 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

dbfilename

默认生成的rdb文件名

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

dir

# Note that you must specify a directory here, not a file name.
dir ./

实战测试：

修改配置文件

 #   save ""
 save
203 save 120 10
 save  

两分钟10次操作

之后会生成一个dump.rdb文件，具体生成文件的默认名请修改：dbfilename

进行复制（备份）

模拟事故：

此时直接删除所有的数据

此时再次重新登陆则是会显示为空，即是存在dump.rdb文件

在管不redis时，迅速斩断，保存文件dump.rdb

此时删除之前的dump.rdb文件，并且把之前的dump_cp.rdb备份文件复制一份命名为dump.rdb

此时又可以进行之前的keys的值获取

 APPEND ONLY MODE追加

appendonly：默认开关状态，可以同时和RDB一起开着

# 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
默认是关着的

appendfilename：默认的文件名

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

appendfsync

# 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.
always：同步持久话每次发生数据变更立即记录到磁盘，性能比较差但是数据完整性好
everysec：出场默认的推荐的，异步操作，每秒记录，如果一秒内宕机，有数据丢失

# More details please check the following article:
# http://antirez.com/post/redis-persistence-demystified.html
# If unsure, use "everysec".
# appendfsync always
appendfsync everysec

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。

# 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

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

# 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

实战测试：

aof测试

首先开启aof测试

# Please check http://redis.io/topics/persistence for more information.
appendonly yes

此时已经生成文件，aof自动开启

创造性的意外事件

查看appendonly.aof

发现已经记下了我们写的命令

记录了我们执行的每一条命令

重新启动

里面的内容为空

删除appendonly.aof

的最后一句

此时重新启动

获取到我们之前的内容

假设出现下面的情况：

appendonly.aof文件出错：可能是网络，断电.......

此时RDB和AOF文件都在

此时启动Redis

 在dump.rdb文件完整的情况下，appendonly.aof文件出错，说明后者的优先级大于前者

那么此时的处理方式是：

redis-check-aof --fix appendonly.aof

再次重新启动：