• redis配置文件详解


    (1)安装依赖包
    yum install -y gcc*
    yum install -y tcl
    (2)安装redis
    http://download.redis.io/releases/redis-3.2.3.tar.gz
    tar xzf redis-3.2.3.tar.gz
    cd redis-3.2.3
    mv redis-3.2.3 redis
    mv  redis /usr/local/
    make
    make test
    make install
     
    # 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 <masterip> <masterport> 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 <master-password> 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 <bytes>
     
    # 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,everysec 表示对写操作进行累积,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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  • 原文地址:https://www.cnblogs.com/liqing1009/p/5896174.html
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