Redis配置文件redis.conf详解

一、Redis配置文件redis.conf详解

 # Note on units: when memory size is needed, it is possible to specifiy
 # it in the usual form of 1k 5GB 4M and so forth:
 #
 # 1k =>  bytes
 # 1kb =>  bytes
 # 1m =>  bytes
 # 1mb => * bytes
 # 1g =>  bytes
 # 1gb => ** bytes
 #
 # units are case insensitive so 1GB 1Gb 1gB are all the same.

 # Redis默认不是以守护进程的方式运行，可以通过该配置项修改，使用yes启用守护进程
 # 启用守护进程后，Redis会把pid写到一个pidfile中，在/var/run/redis.pid
 daemonize no

 # 当Redis以守护进程方式运行时，Redis默认会把pid写入/var/run/redis.pid文件，可以通过pidfile指定
 pidfile /var/run/redis.pid

 # 指定Redis监听端口，默认端口为6379
 # 如果指定0端口，表示Redis不监听TCP连接
 port 

 # 绑定的主机地址
 # 你可以绑定单一接口，如果没有绑定，所有接口都会监听到来的连接
 # bind 127.0.0.1

 # Specify the path for the unix socket that will be used to listen for
 # incoming connections. There is no default, so Redis will not listen
 # on a unix socket when not specified.
 #
 # unixsocket /tmp/redis.sock
 # unixsocketperm 

 # 当客户端闲置多长时间后关闭连接，如果指定为0，表示关闭该功能
 timeout 

 # 指定日志记录级别，Redis总共支持四个级别：debug、verbose、notice、warning，默认为verbose
 # debug (很多信息, 对开发／测试比较有用)
 # verbose (many rarely useful info, but not a mess like the debug level)
 # notice (moderately verbose, what you want in production probably)
 # warning (only very important / critical messages are logged)
 loglevel verbose

 # 日志记录方式，默认为标准输出，如果配置为redis为守护进程方式运行，而这里又配置为标准输出，则日志将会发送给/dev/null
 logfile stdout

 # To enable logging to the system logger, just set 'syslog-enabled' to yes,
 # and optionally update the other syslog parameters to suit your needs.
 # syslog-enabled no

 # Specify the syslog identity.
 # syslog-ident redis

 # Specify the syslog facility.  Must be USER or between LOCAL0-LOCAL7.
 # syslog-facility local0

 # 设置数据库的数量，默认数据库为0，可以使用select <dbid>命令在连接上指定数据库id
 # dbid是从0到‘databases’-1的数目
 databases 

 ################################ SNAPSHOTTING  #################################
 # 指定在多长时间内，有多少次更新操作，就将数据同步到数据文件，可以多个条件配合
 # Save the DB on disk:
 #
 #   save <seconds> <changes>
 #
 #   Will save the DB if both the given number of seconds and the given
 #   number of write operations against the DB occurred.
 #
 #   满足以下条件将会同步数据:
 #   900秒（15分钟）内有1个更改
 #   300秒（5分钟）内有10个更改
 #   60秒内有10000个更改
 #   Note: 可以把所有“save”行注释掉，这样就取消同步操作了

 save
 save
 save  

 # 指定存储至本地数据库时是否压缩数据，默认为yes，Redis采用LZF压缩，如果为了节省CPU时间，可以关闭该选项，但会导致数据库文件变的巨大
 rdbcompression yes

 # 指定本地数据库文件名，默认值为dump.rdb
 dbfilename dump.rdb

 # 工作目录.
 # 指定本地数据库存放目录，文件名由上一个dbfilename配置项指定
 #
 # Also the Append Only File will be created inside this directory.
 #
 # 注意，这里只能指定一个目录，不能指定文件名
 dir ./

 ################################# REPLICATION #################################

 # 主从复制。使用slaveof从 Redis服务器复制一个Redis实例。注意，该配置仅限于当前slave有效
 # so for example it is possible to configure the slave to save the DB with a
 # different interval, or to listen to another port, and so on.
 # 设置当本机为slav服务时，设置master服务的ip地址及端口，在Redis启动时，它会自动从master进行数据同步
 # slaveof <masterip> <masterport>

 # 当master服务设置了密码保护时，slav服务连接master的密码
 # 下文的“requirepass”配置项可以指定密码
 # masterauth <master-password>

 # When a slave lost the connection with the master, or when the replication
 # is still in progress, the slave can act in two different ways:
 #
 # ) if slave-serve-stale-data is set to 'yes' (the default) the slave will
 #    still reply to client requests, possibly with out of data data, or the
 #    data set may just be empty if this is the first synchronization.
 #
 # ) if slave-serve-stale data is set to 'no' the slave will reply with
 #    an error "SYNC with master in progress" to all the kind of commands
 #    but to INFO and SLAVEOF.
 #
 slave-serve-stale-data yes

 # Slaves send PINGs to server in a predefined interval. It's possible to change
 # this interval with the repl_ping_slave_period option. The default value is
 # seconds.
 #
 # repl-ping-slave-period 

 # The following option sets a timeout for both Bulk transfer I/O timeout and
 # master data or ping response timeout. The default value is  seconds.
 #
 # It is important to make sure that this value is greater than the value
 # specified for repl-ping-slave-period otherwise a timeout will be detected
 # every time there is low traffic between the master and the slave.
 #
 # repl-timeout 

 ################################## SECURITY ###################################

 # Warning: since Redis is pretty fast an outside user can try up to
 # 150k passwords per second against a good box. This means that you should
 # use a very strong password otherwise it will be very easy to break.
 # 设置Redis连接密码，如果配置了连接密码，客户端在连接Redis时需要通过auth <password>命令提供密码，默认关闭
 # requirepass foobared

 # Command renaming.
 #
 # It is possilbe to change the name of dangerous commands in a shared
 # environment. For instance the CONFIG command may be renamed into something
 # of hard to guess so that it will be still available for internal-use
 # tools but not available for general clients.
 #
 # Example:
 #
 # rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
 #
 # It is also possilbe to completely kill a command renaming it into
 # an empty string:
 #
 # rename-command CONFIG ""

 ################################### LIMITS ####################################

 # 设置同一时间最大客户端连接数，默认无限制，Redis可以同时打开的客户端连接数为Redis进程可以打开的最大文件描述符数，
 # 如果设置maxclients ，表示不作限制。当客户端连接数到达限制时，Redis会关闭新的连接并向客户端返回max Number of clients reached错误信息
 # maxclients 

 # Don't use more memory than the specified amount of bytes.
 # When the memory limit is reached Redis will try to remove keys with an
 # EXPIRE set. It will try to start freeing keys that are going to expire
 # in little time and preserve keys with a longer time to live.
 # Redis will also try to remove objects from free lists if possible.
 #
 # If all this fails, Redis will start to reply with errors to commands
 # that will use more memory, like SET, LPUSH, and so on, and will continue
 # to reply to most read-only commands like GET.
 #
 # WARNING: maxmemory can be a good idea mainly if you want to use Redis as a
 # 'state' server or cache, not as a real DB. When Redis is used as a real
 # database the memory usage will grow over the weeks, it will be obvious if
 # it is going to use too much memory in the long run, and you'll have the time
 # to upgrade. With maxmemory after the limit is reached you'll start to get
 # errors for write operations, and this may even lead to DB inconsistency.
 # 指定Redis最大内存限制，Redis在启动时会把数据加载到内存中，达到最大内存后，Redis会先尝试清除已到期或即将到期的Key，
 # 当此方法处理后，仍然到达最大内存设置，将无法再进行写入操作，但仍然可以进行读取操作。
 # Redis新的vm机制，会把Key存放内存，Value会存放在swap区
 # maxmemory <bytes>

 # MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
 # is reached? You can select among five behavior:
 #
 # volatile-lru -> remove the key with an expire set using an LRU algorithm
 # allkeys-lru -> remove any key accordingly to the LRU algorithm
 # volatile-random -> remove a random key with an expire set
 # allkeys->random -> remove a random key, any key
 # volatile-ttl -> remove 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 

 ############################## APPEND ONLY MODE ###############################

 #
 # 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.
 # 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
 # IMPORTANT: Check the BGREWRITEAOF to check how to rewrite the append
 # log file in background when it gets too big.

 appendonly no

 # 指定更新日志文件名，默认为appendonly.aof
 # appendfilename 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.

 # 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）

 appendfsync everysec
 # appendfsync no

 # When the AOF fsync policy is set to always or everysec, and a background
 # saving process (a background save or AOF log background rewriting) is
 # performing a lot of I/O against the disk, in some Linux configurations
 # Redis may block too long on the fsync() call. Note that there is no fix for
 # this currently, as even performing fsync in a different thread will block
 # our synchronous write() call.
 #
 # In order to mitigate this problem it's possible to use the following option
 # that will prevent fsync() from being called in the main process while a
 # BGSAVE or BGREWRITEAOF is in progress.
 #
 # This means that while another child is saving the durability of Redis is
 # the same as "appendfsync none", that in pratical terms means that it is
 # possible to lost up to  seconds of log in the worst scenario (with the
 # default Linux settings).
 #
 # 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

 # Automatic rewrite of the append only file.
 # Redis is able to automatically rewrite the log file implicitly calling
 # BGREWRITEAOF when the AOF log size will growth by the specified percentage.
 #
 # This is how it works: Redis remembers the size of the AOF file after the
 # latest rewrite (or if no rewrite happened since the restart, the size of
 # the AOF at startup is used).
 #
 # 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 precentage of zero in order to disable the automatic AOF
 # rewrite feature.

 auto-aof-rewrite-percentage
 auto-aof-rewrite-min-size 64mb

 ################################## SLOW LOG ###################################

 # The Redis Slow Log is a system to log queries that exceeded a specified
 # execution time. The execution time does not include the I/O operations
 # like talking with the client, sending the reply and so forth,
 # but just the time needed to actually execute the command (this is the only
 # stage of command execution where the thread is blocked and can not serve
 # other requests in the meantime).
 #
 # You can configure the slow log with two parameters: one tells Redis
 # what is the execution time, in microseconds, to exceed in order for the
 # command to get logged, and the other parameter is the length of the
 # slow log. When a new command is logged the oldest one is removed from the
 # queue of logged commands.

 # The following time is expressed in microseconds, so  is equivalent
 # to one second. Note that a negative number disables the slow log, while
 # a value of zero forces the logging of every command.
 slowlog-log-slower-than 

 # There is no limit to this length. Just be aware that it will consume memory.
 # You can reclaim memory used by the slow log with SLOWLOG RESET.
 slowlog-max-len 

 ################################ VIRTUAL MEMORY ###############################

 ### WARNING! Virtual Memory is deprecated in Redis 2.4
 ### The use of Virtual Memory is strongly discouraged.

 ### WARNING! Virtual Memory is deprecated in Redis 2.4
 ### The use of Virtual Memory is strongly discouraged.

 # Virtual Memory allows Redis to work with datasets bigger than the actual
 # amount of RAM needed to hold the whole dataset in memory.
 # In order to do so very used keys are taken in memory while the other keys
 # are swapped into a swap file, similarly to what operating systems do
 # with memory pages.
 # 指定是否启用虚拟内存机制，默认值为no，
 # VM机制将数据分页存放，由Redis将访问量较少的页即冷数据swap到磁盘上，访问多的页面由磁盘自动换出到内存中
 # 把vm-enabled设置为yes，根据需要设置好接下来的三个VM参数，就可以启动VM了
 vm-enabled no
 # vm-enabled yes

 # This is the path of the Redis swap file. As you can guess, swap files
 # can't be shared by different Redis instances, so make sure to use a swap
 # file for every redis process you are running. Redis will complain if the
 # swap file is already in use.
 #
 # Redis交换文件最好的存储是SSD（固态硬盘）
 # 虚拟内存文件路径，默认值为/tmp/redis.swap，不可多个Redis实例共享
 # *** WARNING *** if you are using a shared hosting the default of putting
 # the swap file under /tmp is not secure. Create a dir with access granted
 # only to Redis user and configure Redis to create the swap file there.
 vm-swap-file /tmp/redis.swap

 # With vm-max-memory  the system will swap everything it can. Not a good
 # default, just specify the max amount of RAM you can in bytes, but it's
 # better to leave some margin. For instance specify an amount of RAM
 # that's more or less between 60 and 80% of your free RAM.
 # 将所有大于vm-max-memory的数据存入虚拟内存，无论vm-max-memory设置多少，所有索引数据都是内存存储的（Redis的索引数据就是keys）
 # 也就是说当vm-max-memory设置为0的时候，其实是所有value都存在于磁盘。默认值为0
 vm-max-memory 

 # Redis swap文件分成了很多的page，一个对象可以保存在多个page上面，但一个page上不能被多个对象共享，vm-page-size是要根据存储的数据大小来设定的。
 # 建议如果存储很多小对象，page大小最后设置为32或64bytes；如果存储很大的对象，则可以使用更大的page，如果不确定，就使用默认值
 vm-page-size 

 # 设置swap文件中的page数量由于页表（一种表示页面空闲或使用的bitmap）是存放在内存中的，在磁盘上每8个pages将消耗1byte的内存
 # swap空间总容量为 vm-page-size * vm-pages
 #
 # With the default of -bytes memory pages and  pages Redis will
 # use a  GB swap file, that will use  MB of RAM for the page table.
 #
 # It's better to use the smallest acceptable value for your application,
 # but the default is large in order to work in most conditions.
 vm-pages 

 # Max number of VM I/O threads running at the same time.
 # This threads are used to read/write data from/to swap file, since they
 # also encode and decode objects from disk to memory or the reverse, a bigger
 # number of threads can help with big objects even if they can't help with
 # I/O itself as the physical device may not be able to couple with many
 # reads/writes operations at the same time.
 # 设置访问swap文件的I/O线程数，最后不要超过机器的核数，如果设置为0，那么所有对swap文件的操作都是串行的，可能会造成比较长时间的延迟，默认值为4
 vm-max-threads 

 ############################### ADVANCED CONFIG ###############################

 # Hashes are encoded in a special way (much more memory efficient) when they
 # have at max a given numer of elements, and the biggest element does not
 # exceed a given threshold. You can configure this limits with the following
 # configuration directives.
 # 指定在超过一定的数量或者最大的元素超过某一临界值时，采用一种特殊的哈希算法
 hash-max-zipmap-entries
 hash-max-zipmap-value 

 # Similarly to hashes, small lists are also encoded in a special way in order
 # to save a lot of space. The special representation is only used when
 # you are under the following limits:
 list-max-ziplist-entries
 list-max-ziplist-value 

 # Sets have a special encoding in just one case: when a set is composed
 # of just strings that happens to be integers in radix  in the range
 # of  bit signed integers.
 # The following configuration setting sets the limit in the size of the
 # set in order to use this special memory saving encoding.
 set-max-intset-entries 

 # Similarly to hashes and lists, sorted sets are also specially encoded in
 # order to save a lot of space. This encoding is only used when the length and
 # elements of a sorted set are below the following limits:
 zset-max-ziplist-entries
 zset-max-ziplist-value 

 # Active rehashing uses  millisecond every  milliseconds of CPU time in
 # order to help rehashing the main Redis hash table (the one mapping top-level
 # keys to values). The hash table implementation redis uses (see dict.c)
 # performs a lazy rehashing: the more operation you run into an hash table
 # that is rhashing, the more rehashing "steps" are performed, so if the
 # server is idle the rehashing is never complete and some more memory is used
 # by the hash table.
 #
 # The default is to use this millisecond  times every second in order to
 # active rehashing the main dictionaries, freeing memory when possible.
 #
 # If unsure:
 # use "activerehashing no" if you have hard latency requirements and it is
 # not a good thing in your environment that Redis can reply form time to time
 # to queries with  milliseconds delay.
 # 指定是否激活重置哈希，默认为开启
 activerehashing yes

 ################################## INCLUDES ###################################

 # 指定包含其他的配置文件，可以在同一主机上多个Redis实例之间使用同一份配置文件，而同时各实例又拥有自己的特定配置文件
 # include /path/to/local.conf
 # include /path/to/other.conf