Redis AOF log persistence

AOF working principle  

When you use Redis Do something , Will write what you do to a text file .

To configure ：

appendonly This is aof Log function Whether to open yes

We are using AOF How to improve write speed and data persistence , Create a balanced plan , Here you can use

appendfsync    always ： Every time 1 All commands are synchronized to AOF Security , Slow speed

                         no        :    Write to the operating system , Because the operating system determines the buffer size , Write uniformly AOF, Low synchronization frequency , Fast .

                       eveysec :    compromise proposal , Write once a second

no-appendfsync-on-rewrite  yes: # Exporting rdb During snapshot , Do you want to stop syncing aof

auto-aof-rewrite-percentage 100 #aof The size of the file is larger than the last time it was rewritten , growth rate 100% when , rewrite

auto-aof-rewrite-min-size 64mb #aof file , At least more than 64M when , rewrite (bgrewriteaof  Rewrite the command )

Interview frequently asked ：

notes : stay dump rdb In the process ,aof If you stop synchronizing , Will you lose ?

answer : Can't , All operations are cached in memory queues , dump After completion , Unified operation .

notes : aof What does rewriting mean ?

answer : aof Rewriting refers to putting data in memory , Reverse into command , Write to .aof In the Journal To solve the problem aof The problem of too large log .

ask : If rdb file , and aof Files exist , Who will be the first to recover data ?

answer : rdb rdb Recover data quickly

ask : 2 Whether the two can be used at the same time ?

answer : Sure , And it's recommended

ask : When you recover rdb and aof Which recovers faster

answer : rdb fast , Because it is a memory mapping of data , Load directly into memory , and aof Is the command , It needs to be carried out item by item