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the key with the nearest expire time (minor TTL) # noeviction -> don't expire at all, just return an error on write operations # # Note: with all the kind of policies, Redis will return an error on write # operations, when there are not suitable keys for eviction. # # At the date of writing this 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 volatile-lru # LRU and minimal TTL algorithms are not precise algorithms but approximated # algorithms (in order to save memory), so you can select as well the sample # size to check. For instance for default Redis will check three keys and # pick the one that was used less recently, you can change the sample size # using the following configuration directive. # # maxmemory-samples 3 ############################## APPEND ONLY MODE ############################### # By default Redis asynchronously dumps the dataset on disk. If you can live # with the idea that the latest records will be lost if something like a crash # happens this is the preferred way to run Redis. If instead you care a lot # about your data and don't want to that a single record can get lost you should # enable the append only mode: when this mode is enabled Redis will append # every write operation received in the file appendonly.aof. This file will # be read on startup in order to rebuild the full dataset in memory. # # Note that you can have both the async dumps and the append only file if you # like (you have to comment the "save" statements above to disable the dumps). # Still if append only mode is enabled Redis will load the data from the # log file at startup ignoring the dump.rdb file. # # IMPORTANT: Check the BGREWRITEAOF to check how to rewrite the append # log file in background when it gets too big. appendonly no appendonly no指定是否在每次更新操作后进行日志记录，Redis在默认情况下是异步的把数据写入磁盘，如果不开启，可能会在断电时导致一段时间内的数据丢失。因为 redis本身同步数据文件是按上面save条件来同步的，所以有的数据会在一段时间内只存在于内存中。默认为no # The name of the append only file (default: "appendonly.aof") # appendfilename appendonly.aof appendfilename appendonly.aof指定更新日志文件名，默认为appendonly.aof # The fsync() call tells the Operating System to actually write data on disk # instead to wait for more data in the output buffer. Some OS will really flush # data on disk, some other OS will just try to do it ASAP. # # Redis supports three different modes: # # 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 if one second passed since the last fsync. Compromise. # # The default is "everysec" that's usually the right compromise between # speed and data safety. It's up to you to understand if you can relax this to # "no" that will will let the operating system flush the output buffer when # it wants, for better performances (but if you can live with the idea of # some data loss consider the default persistence mode that's snapshotting), # or on the contrary, use "always" that's very slow but a bit safer than # everysec. # # If unsure, use "everysec". # appendfsync always appendfsync everysec # appendfsync no 指定更新日志条件，共有3个可选值： no：表示等操作
系统进行数据缓存同步到磁盘（快） always：表示每次更新操作后手动调用fsync()将数据写到磁盘（慢，安全） everysec：表示每秒同步一次（折衷，默认值） # When the AOF fsync policy is set to always or everysec, and a background # saving process (a background save or AOF log background rewri |