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
194 # Note: you can disable saving completely by commenting out all "save" lines. 195 # 196 # It is also possible to remove all the previously configured save 197 # points by adding a save directive with a single empty string argument 198 # like in the following example: 199 # 200 # save "" 202 save 900 1 203 save 300 10 204 save 60 10000
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
200 # save "" 202 save 900 1 203 save 120 10 204 save 60 10000
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：
