Redis持久化快照的方法与原理

################################ SNAPSHOTTING ################################ # # Save the DB on disk: # # save   # # 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 #900秒内至少有1个key被更改就执行快照 save 300 10 #300内描述至少有10个key被更改就执行快照 save 60 10000 #60秒内至少有10000个key被更改就执行快照 # 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 #拍摄快照失败是否继续执行写命令 # 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 #是否对快照文件进行压缩 # 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 #是否进行数据校验 # The filename where to dump the DB dbfilename dump.rdb #快照文件存储的名称 # 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 /opt/redis-5.0.3#快照文件存储的位置

[root@root redis-5.0.3]# src/redis-cli 127.0.0.1:6379> ping PONG 127.0.0.1:6379> set name aaa OK 127.0.0.1:6379> set age 18 OK 127.0.0.1:6379> incr age (integer) 19 127.0.0.1:6379> shutdown not connected> exit

[root@root redis-5.0.3]# src/redis-server redis.conf 1211:C 13 Feb 2019 01:27:22.668 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo 1211:C 13 Feb 2019 01:27:22.668 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=1211, just started 1211:C 13 Feb 2019 01:27:22.668 # Configuration loaded [root@root redis-5.0.3]# src/redis-cli 127.0.0.1:6379> ping PONG 127.0.0.1:6379> get name "aaa" 127.0.0.1:6379> get age "19" 127.0.0.1:6379> keys * 1) "name" 2) "age"

[root@root redis-5.0.3]# src/redis-server redis.conf 1218:C 13 Feb 2019 01:29:01.336 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo 1218:C 13 Feb 2019 01:29:01.336 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=1218, just started 1218:C 13 Feb 2019 01:29:01.336 # Configuration loaded [root@root redis-5.0.3]# src/redis-cli 127.0.0.1:6379> ping PONG 127.0.0.1:6379> keys * (empty list or set)

127.0.0.1:6379> ping PONG 127.0.0.1:6379> keys * (empty list or set) 127.0.0.1:6379> set name zhangsan OK 127.0.0.1:6379> set age 20 OK 127.0.0.1:6379> bgsave Background saving started

save ""

appendonly yes appendfilename "appendonly.aof" # If unsure, use "everysec". # appendfsync always appendfsync everysec # appendfsync no no-appendfsync-on-rewrite no auto-aof-rewrite-percentage 100 auto-aof-rewrite-min-size 64mb

save "" #save 900 1 #save 300 10 #save 60 10000