Redis应用（二）——redis.conf配置文件详解

朱雀 2022-08-07 08:42 123阅读 0赞

# Redis configuration file example
     
    # 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 => 1000 bytes
    # 1kb => 1024 bytes
    # 1m => 1000000 bytes
    # 1mb => 1024*1024 bytes
    # 1g => 1000000000 bytes
    # 1gb => 1024*1024*1024 bytes
    #
    # units are case insensitive so 1GB 1Gb 1gB are all the same.
     
    # 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.
    daemonize no  
    #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
     
    # When running daemonized, Redis writes a pid file in /var/run/redis.pid by
    # default. You can specify a custom pid file location here.
    pidfile /var/run/redis.pid
    #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
    # Accept connections on the specified port, default is 6379.
    # If port 0 is specified Redis will not listen on a TCP socket.
    port 6379
    #指定Redis监听端口，默认端口为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.
    #
    # bind 127.0.0.1
    #绑定的主机地址
    # 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 755
     
    # Close the connection after a client is idle for N seconds (0 to disable)
    timeout 0
    #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
    # 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)
    loglevel verbose
    #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
    # 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
    logfile stdout
    #日志记录方式，默认为标准输出，如果配置Redis为守护进程方式运行，而这里又配置为日志记录方式为标准输出，则日志将会发送给/dev/null
    # 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
     
    # Set the number of databases. The default database is DB 0, you can select
    # a different one on a per-connection basis using SELECT <dbid> where
    # dbid is a number between 0 and 'databases'-1
    databases 16
    #设置开启数据库的数量，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
    ################################ SNAPSHOTTING  #################################
    #
    # 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.
    #
    #   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.
     
    save 900 1
    save 300 10
    save 60 10000
    #save * * 保存快照的频率，第一个*表示多长时间（单位秒），第二个*表示执行多少次更新操作，上述三行代码分别表示900秒（15分钟）内有1个更改，300秒（5分钟）内有10个更改以及60秒内有10000个更改。
    #指定在一定时间内执行一定数量的更新操作时，就将数据同步到数据快照文件，可以多个条件配合
    # 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.
    rdbcompression yes
    #指定存储至数据快照文件时是否压缩数据，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
    # The filename where to dump the DB
    dbfilename dump.rdb
    #指定数据快照文件名（只是文件名，不包括目录），默认值为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.
    dir ./
    #数据快照的保存目录（这个是目录）
    ################################# REPLICATION #################################
     
    # 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.
    #
    # slaveof <masterip> <masterport>
    #slaveof <masterip> <masterport> 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
    # 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.
    #
    # masterauth <master-password>
    #masterauth <master-password> 当master服务设置了密码保护时，slav服务连接master的密码
    # 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.
    #
    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 10
    # seconds.
    #
    # repl-ping-slave-period 10
     
    # The following option sets a timeout for both Bulk transfer I/O timeout and
    # master data or ping response timeout. The default value is 60 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 60
     
    ################################## SECURITY ###################################
     
    # Require clients to issue AUTH <PASSWORD> 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.
    #
    # requirepass foobared
    #requirepass foobared 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
    # 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 ####################################
     
    # 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'.
    #
    # maxclients 128
    # maxclients 128 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 0，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
    # 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.
    #
    # maxmemory <bytes>
    # maxmemory <bytes>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 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 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；如果开启将会提高数据抗风险能力，但影响效率。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
    #指定更新日志的时机，共有3个可选值：
    #no：不调用fsync()，等待操作系统进行数据缓存同步到磁盘（快）
    #always：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 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(2) 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 30 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 100
    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 1000000 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 10000
     
    # 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 1024
     
    ################################ 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.
    #
    # To enable VM just set 'vm-enabled' to yes, and set the following three
    # VM parameters accordingly to your needs.
     
    vm-enabled no
    #指定是否启用虚拟内存机制，默认值为no，简单的介绍一下，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（在后面的文章我会仔细分析Redis的VM机制）
    # 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.
    vm-swap-file /tmp/redis.swap
    #虚拟内存文件路径，默认值为/tmp/redis.swap，不可多个Redis实例共享
    # 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.
    vm-max-memory 0
    #将所有大于vm-max-memory的数据存入虚拟内存,无论vm-max-memory设置多小,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
    # 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 :)
    vm-page-size 32
    #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，作者建议如果存储很多小对象，page大小最好设置为32或者64bytes；如果存储很大大对象，则可以使用更大的page，如果不 确定，就使用默认值
    # 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.
    vm-pages 134217728
    #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）是在放在内存中的，在磁盘上每8个pages将消耗1byte的内存。
    # 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.
    vm-max-threads 4
    #设置访问swap文件的线程数,最好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
    ############################### 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.
    hash-max-zipmap-entries 512
    hash-max-zipmap-value 64
    #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
    # 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 512
    list-max-ziplist-value 64
     
    # Sets have a special encoding in just one case: when a set is composed
    # of just strings that happens to be integers in radix 10 in the range
    # of 64 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 512
     
    # 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 128
    zset-max-ziplist-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.
    activerehashing yes
     
    ################################## INCLUDES ###################################
     
    # Include one or more other config files here.  This is useful if you
    # have a standard template that goes to all redis server but also need
    # to customize a few per-server settings.  Include files can include
    # other files, so use this wisely.
    #
    # include /path/to/local.conf
    # include /path/to/other.conf
    #指定包含其它的配置文件，可以在同一主机上多个Redis实例之间使用同一份配置文件，而同时各个实例又拥有自己的特定配置文件