Redis的配置文件格式类似于java的properties文件，是一个一个的键值对，但是redis的键值对之间是用空格分隔的。同样以#号开头的行为注释行
# By default Redis does not run as a daemon. Use 'yes' if you need it. # Note that Redis will write a pid file in /var/run/redis.pid when daemonized. #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 daemonize no # When running daemonized,Redis writes a pid file in /var/run/redis.pid by # default. You can specify a custom pid file location here. #当 Redis 以守护进程的方式运行的时候，Redis 默认会把 pid 文件放在/var/run/redis.pid #可配置到其他地址，当运行多个 redis 服务时，需要指定不同的 pid 文件和端口 pidfile /var/run/redis.pid # Accept connections on the specified port,default is 6379. # If port 0 is specified Redis will not listen on a TCP socket. #端口 port 6379 # If you want you can bind a single interface,if the bind option is not # specified all the interfaces will listen for incoming connections. #指定Redis可接收请求的IP地址,不设置将处理所有请求,建议生产环境中设置 # bind 127.0.0.1 # Close the connection after a client is idle for N seconds (0 to disable) #客户端连接的超时时间,单位为秒,超时后会关闭连接 timeout 0 # Set server verbosity to 'debug' # it can be one of: # debug (a lot of information,useful for development/testing) # 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) #日志记录等级，4个可选值 loglevel notice # Specify the log file name. Also 'stdout' can be used to force # Redis to log on the standard output. Note that if you use standard # output for logging but daemonize,logs will be sent to /dev/null #配置 log 文件地址,默认打印在命令行终端的窗口上，也可设为/dev/null屏蔽日志、 logfile stdout # Set the number of databases. The default database is DB 0,you can select # a different one on a per-connection basis using SELECT where # dbid is a number between 0 and 'databases'-1 #设置数据库的个数,可以使用 SELECT 命令来切换数据库。 databases 16 # # 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 at all commenting all the "save" lines. #设置 Redis 进行数据库镜像的频率。保存数据到disk的策略 #900秒之内有1个keys发生变化时 #30秒之内有10个keys发生变化时 #60秒之内有10000个keys发生变化时 save 900 1 save 300 10 save 60 10000 # 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. #在进行镜像备份时,是否进行压缩 rdbcompression yes # The filename where to dump the DB #镜像备份文件的文件名 dbfilename dump.rdb # The working directory. # # The DB will be written inside this directory,with the filename specified # above using the 'dbfilename' configuration directive. # # Also the Append Only File will be created inside this directory. # # Note that you must specify a directory here,not a file name. #数据库镜像备份的文件放置的路径 #路径跟文件名分开配置是因为 Redis 备份时，先会将当前数据库的状态写入到一个临时文件 #等备份完成时，再把该临时文件替换为上面所指定的文件 #而临时文件和上面所配置的备份文件都会放在这个指定的路径当中 #默认值为 ./ dir /var/lib/redis/ # Master-Slave replication. Use slaveof to make a Redis instance a copy of # another Redis server. Note that the configuration is local to the slave # 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. #设置该数据库为其他数据库的从数据库 #slaveof 当本机为从服务时，设置主服务的IP及端口 # slaveof # If the master is password protected (using the "requirepass" configuration # directive below) it is possible to tell the slave to authenticate before # starting the replication synchronization process,otherwise the master will # refuse the slave request. #指定与主数据库连接时需要的密码验证 #masterauth 当本机为从服务时，设置主服务的连接密码 # masterauth # 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: # # 1) 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. # # 2) 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. #当slave丢失与master的连接时，或slave仍然在于master进行数据同步时（未与master保持一致） #slave可有两种方式来响应客户端请求： #1)如果 slave-serve-stale-data 设置成 'yes'(默认)，slave仍会响应客户端请求,此时可能会有问题 #2)如果 slave-serve-stale-data 设置成 'no'，slave会返回"SYNC with master in progress"错误信息，但 INFO 和SLAVEOF命令除外。 slave-serve-stale-data yes # Require clients to issue AUTH before processing any other # commands. This might be useful in environments in which you do not trust # others with access to the host running redis-server. # # This should stay commented out for backward compatibility and because most # people do not need auth (e.g. they run their own servers). # # 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. #设置客户端连接后进行任何其他指定前需要使用的密码 #redis速度相当快，一个外部用户在一秒钟进行150K次密码尝试，需指定强大的密码来防止暴力破解 # requirepass foobared # Set the max number of connected clients at the same time. By default there # is no limit,and it's up to the number of file descriptors the Redis process # is able to open. The special value '0' means no limits. # Once the limit is reached Redis will close all the new connections sending # an error 'max number of clients reached'. #限制同时连接的客户数量。 #当连接数超过这个值时，redis 将不再接收其他连接请求，客户端尝试连接时将收到 error 信息 # maxclients 128 # Don't use more memory than the specified amount of bytes. # When the memory limit is reached Redis will try to remove keys # accordingly to the eviction policy selected (see maxmemmory-policy). # # If Redis can't remove keys according to the policy,or if the policy is # set to 'noeviction',Redis will start to reply with errors to commands # that would use more memory,like SET,LPUSH,and so on,and will continue # to reply to read-only commands like GET. # # This option is usually useful when using Redis as an LRU cache,or to set # an hard memory limit for an instance (using the 'noeviction' policy). # # WARNING: If you have slaves attached to an instance with maxmemory on,# the size of the output buffers needed to feed the slaves are subtracted # from the used memory count,so that network problems / resyncs will # not trigger a loop where keys are evicted,and in turn the output # buffer of slaves is full with DELs of keys evicted triggering the deletion # of more keys,and so forth until the database is completely emptied. # # In short... if you have slaves attached it is suggested that you set a lower # limit for maxmemory so that there is some free RAM on the system for slave # output buffers (but this is not needed if the policy is 'noeviction'). #设置redis能够使用的最大内存。 #达到最大内存设置后，Redis会先尝试清除已到期或即将到期的Key（设置过expire信息的key） #在删除时,按照过期时间进行删除，最早将要被过期的key将最先被删除 #如果已到期或即将到期的key删光，仍进行set操作，那么将返回错误 #此时redis将不再接收写请求,只接收get请求。 #maxmemory的设置比较适合于把redis当作于类似memcached 的缓存来使用 # maxmemory # 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. #redis 默认每次更新操作后会在后台异步的把数据库镜像备份到磁盘，但该备份非常耗时，且备份不宜太频繁 #redis 同步数据文件是按上面save条件来同步的 #如果发生诸如拉闸限电、拔插头等状况,那么将造成比较大范围的数据丢失 #所以redis提供了另外一种更加高效的数据库备份及灾难恢复方式 #开启append only 模式后,redis 将每一次写操作请求都追加到appendonly.aof 文件中 #redis重新启动时,会从该文件恢复出之前的状态。 #但可能会造成 appendonly.aof 文件过大，所以redis支持BGREWRITEAOF 指令，对appendonly.aof重新整理 appendonly no # The name of the append only file (default: "appendonly.aof") ##更新日志文件名，默认值为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. # # 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". #设置对 appendonly.aof 文件进行同步的频率 #always 表示每次有写操作都进行同步,everysec 表示对写操作进行累积,每秒同步一次。 #no表示等操作系统进行数据缓存同步到磁盘，都进行同步,每秒同步一次 # appendfsync always appendfsync everysec # appendfsync no # 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. # # To enable VM just set 'vm-enabled' to yes,and set the following three # VM parameters accordingly to your needs. #是否开启虚拟内存支持。 #redis 是一个内存数据库，当内存满时,无法接收新的写请求,所以在redis2.0后,提供了虚拟内存的支持 #但需要注意的，redis 所有的key都会放在内存中，在内存不够时,只把value 值放入交换区 #虽使用虚拟内存，但性能基本不受影响，需要注意的是要把vm-max-memory设置到足够来放下所有的key 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. # # The best kind of storage for the Redis swap file (that's accessed at random) # is a Solid State Disk (SSD). # # *** 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. #设置虚拟内存的交换文件路径，不可多个Redis实例共享 vm-swap-file /tmp/redis.swap # vm-max-memory configures the VM to use at max the specified amount of # RAM. Everything that deos not fit will be swapped on disk *if* possible,that # is,if there is still enough contiguous space in the swap file. # # With vm-max-memory 0 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. #设置开启虚拟内存后,redis将使用的最大物理内存大小。 #默认为0，redis将把他所有能放到交换文件的都放到交换文件中，以尽量少的使用物理内存 #即当vm-max-memory设置为0的时候,其实是所有value都存在于磁盘 #在生产环境下,需要根据实际情况设置该值,最好不要使用默认的 0 vm-max-memory 0 # Redis swap files is split into pages. An object can be saved using multiple # contiguous pages,but pages can't be shared between different objects. # So if your page is too big,small objects swapped out on disk will waste # a lot of space. If you page is too small,there is less space in the swap # file (assuming you configured the same number of total swap file pages). # # If you use a lot of small objects,use a page size of 64 or 32 bytes. # If you use a lot of big objects,use a bigger page size. # If unsure,use the default :) #设置虚拟内存的页大小 如果 value 值比较大,如要在 value 中放置博客、新闻之类的所有文章内容，就设大一点 vm-page-size 32 # Number of total memory pages in the swap file. # Given that the page table (a bitmap of free/used pages) is taken in memory,# every 8 pages on disk will consume 1 byte of RAM. # # The total swap size is vm-page-size * vm-pages # # With the default of 32-bytes memory pages and 134217728 pages Redis will # use a 4 GB swap file,that will use 16 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. #设置交换文件的总的 page 数量 #注意page table信息是放在物理内存中，每8个page 就会占据RAM中的 1 个 byte #总的虚拟内存大小 = vm-page-size * vm-pages vm-pages 134217728 # 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. # # The special value of 0 turn off threaded I/O and enables the blocking # Virtual Memory implementation. #设置 VM IO 同时使用的线程数量。 vm-max-threads 4 # 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. #redis 2.0后引入了 hash 数据结构。 #hash 中包含超过指定元素个数并且最大的元素当没有超过临界时，hash 将以zipmap来存储 #zipmap又称为 small hash，可大大减少内存的使用 hash-max-zipmap-entries 512 hash-max-zipmap-value 64 # Active rehashing uses 1 millisecond every 100 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 10 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 2 milliseconds delay. # # use "activerehashing yes" if you don't have such hard requirements but # want to free memory asap when possible. #是否重置Hash表 #设置成yes后redis将每100毫秒使用1毫秒CPU时间来对redis的hash表重新hash，可降低内存的使用 #当使用场景有较为严格的实时性需求,不能接受Redis时不时的对请求有2毫秒的延迟的话，把这项配置为no。 #如果没有这么严格的实时性要求,可以设置为 yes,以便能够尽可能快的释放内存 activerehashing yes
Redis官方文档对VM的使用提出了一些建议:
当key很小而value很大时,使用VM的效果会比较好.因为这样节约的内存比较大,当key不小时,可以考虑使用一些非常方法将很大的key变成很大的value,如可将key,value组合成一个新的value,最好使用linux ext3 等对稀疏文件支持比较好的文件系统保存你的swap文件,vm-max-threads参数可设置访问swap文件的线程数，最好不要超过机器的核数；设置为0则所有对swap文件的操作都是串行的，可能会造成比较长时间的延迟,但是对数据完整性有很好的保证
redis数据存储
redis的存储分为内存存储、磁盘存储和log文件三部分，配置文件中有三个参数对其进行配置。
save seconds updates，save配置，指出在多长时间内，有多少次更新操作，就将数据同步到数据文件。可多个条件配合，默认配置了三个条件。
appendonly yes/no ，appendonly配置，指出是否在每次更新操作后进行日志记录，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的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。
appendfsync no/always/everysec ，appendfsync配置，no表示等操作系统进行数据缓存同步到磁盘，always表示每次更新操作后手动调用fsync()将数据写到磁盘，everysec表示每秒同步一次。
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