Redis配置文件简介
这里呢，主要讲的是redis.conf（版本是基于redis-5.0.0）
我们需要注意的是，奇数的版本，是测试版本，偶数的版本，是稳定的版本。
1.开头说明
################################## INCLUDES ################################### # Include one or more other config files here. This is useful if you # have a standard template that goes to all Redis servers but also need # to customize a few per-server settings. Include files can include # other files, so use this wisely. # # Notice option "include" won't be rewritten by command "CONFIG REWRITE" # from admin or Redis Sentinel. Since Redis always uses the last processed # line as value of a configuration directive, you'd better put includes # at the beginning of this file to avoid overwriting config change at runtime. # # If instead you are interested in using includes to override configuration # options, it is better to use include as the last line. # # include /path/to/local.conf # include /path/to/other.conf
这里没什么好说的，需要注意的是后面需要使用内存大小时，可以指定单位，通常是以 k,gb,m的形式出现，并且单位不区分大小写。
2.INCLUDES
################################## INCLUDES ################################### # Include one or more other config files here. This is useful if you # have a standard template that goes to all Redis servers but also need # to customize a few per-server settings. Include files can include # other files, so use this wisely. # # Notice option "include" won't be rewritten by command "CONFIG REWRITE" # from admin or Redis Sentinel. Since Redis always uses the last processed # line as value of a configuration directive, you'd better put includes # at the beginning of this file to avoid overwriting config change at runtime. # # If instead you are interested in using includes to override configuration # options, it is better to use include as the last line. # # include /path/to/local.conf # include /path/to/other.conf
我们知道Redis只有一个配置文件，如果多个人进行开发维护，那么就需要多个这样的配置文件，这时候多个配置文件就可以在此通过 include /path/to/local.conf 配置进来，而原本的 redis.conf 配置文件就作为一个总闸。
ps:如果用过struts2 开发的同学，在项目组中多人开发的情况下，通常会有多个struts2.xml 文件，这时候也会通过类时的配置引入进来。
另外需要注意的时，如果将此配置写在redis.conf 文件的开头，那么后面的配置会覆盖引入文件的配置，如果想以引入文件的配置为主，那么需要将 include 配置写在 redis.conf 文件的末尾。
3.MODULES
################################## MODULES ##################################### # Load modules at startup. If the server is not able to load modules # it will abort. It is possible to use multiple loadmodule directives. # # loadmodule /path/to/my_module.so # loadmodule /path/to/other_module.so
redis3.0的爆炸功能是新增了集群，而redis4.0就是在3.0的基础上新增了许多功能，其中这里的 自定义模块配置就是其中之一。通过这里的 loadmodule 配置将引入自定义模块来新增一些功能。
4.NETWORK
################################## NETWORK ##################################### # By default, if no "bind" configuration directive is specified, Redis listens # for connections from all the network interfaces available on the server. # It is possible to listen to just one or multiple selected interfaces using # the "bind" configuration directive, followed by one or more IP addresses. # # Examples: # # bind 192.168.1.100 10.0.0.1 # bind 127.0.0.1 ::1 # # ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the # internet, binding to all the interfaces is dangerous and will expose the # instance to everybody on the internet. So by default we uncomment the # following bind directive, that will force Redis to listen only into # the IPv4 loopback interface address (this means Redis will be able to # accept connections only from clients running into the same computer it # is running). # # IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES # JUST COMMENT THE FOLLOWING LINE. # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ bind 0.0.0.0 # Protected mode is a layer of security protection, in order to avoid that # Redis instances left open on the internet are accessed and exploited. # # When protected mode is on and if: # # 1) The server is not binding explicitly to a set of addresses using the # "bind" directive. # 2) No password is configured. # # The server only accepts connections from clients connecting from the # IPv4 and IPv6 loopback addresses 127.0.0.1 and ::1, and from Unix domain # sockets. # # By default protected mode is enabled. You should disable it only if # you are sure you want clients from other hosts to connect to Redis # even if no authentication is configured, nor a specific set of interfaces # are explicitly listed using the "bind" directive. protected-mode yes # Accept connections on the specified port, default is 6379 (IANA #815344). # If port 0 is specified Redis will not listen on a TCP socket. port 6380 # TCP listen() backlog. # # In high requests-per-second environments you need an high backlog in order # to avoid slow clients connections issues. Note that the Linux kernel # will silently truncate it to the value of /proc/sys/net/core/somaxconn so # make sure to raise both the value of somaxconn and tcp_max_syn_backlog # in order to get the desired effect. tcp-backlog 511 # Unix socket. # # 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 700 # Close the connection after a client is idle for N seconds (0 to disable) timeout 0 # TCP keepalive. # # If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence # of communication. This is useful for two reasons: # # 1) Detect dead peers. # 2) Take the connection alive from the point of view of network # equipment in the middle. # # On Linux, the specified value (in seconds) is the period used to send ACKs. # Note that to close the connection the double of the time is needed. # On other kernels the period depends on the kernel configuration. # # A reasonable value for this option is 300 seconds, which is the new # Redis default starting with Redis 3.2.1. tcp-keepalive 300
ps:这里的配置较长，我只截取了一部分，下同。
①、bind:绑定redis服务器网卡IP，默认为127.0.0.1,即本地回环地址。这样的话，访问redis服务只能通过本机的客户端连接，而无法通过远程连接。如果bind选项为空的话，那会接受所有来自于可用网络接口的连接。
②、port：指定redis运行的端口，默认是6379。由于Redis是单线程模型，因此单机开多个Redis进程的时候会修改端口。
③、timeout：设置客户端连接时的超时时间，单位为秒。当客户端在这段时间内没有发出任何指令，那么关闭该连接。默认值为0，表示不关闭。
④、tcp-keepalive ：单位是秒，表示将周期性的使用SO_KEEPALIVE检测客户端是否还处于健康状态，避免服务器一直阻塞，官方给出的建议值是300s，如果设置为0，则不会周期性的检测。
5.GENERAL
################################# GENERAL ##################################### # 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 yes # If you run Redis from upstart or systemd, Redis can interact with your # supervision tree. Options: # supervised no - no supervision interaction # supervised upstart - signal upstart by putting Redis into SIGSTOP mode # supervised systemd - signal systemd by writing READY=1 to $NOTIFY_SOCKET # supervised auto - detect upstart or systemd method based on # UPSTART_JOB or NOTIFY_SOCKET environment variables # Note: these supervision methods only signal "process is ready." # They do not enable continuous liveness pings back to your supervisor. supervised no # If a pid file is specified, Redis writes it where specified at startup # and removes it at exit. # # When the server runs non daemonized, no pid file is created if none is # specified in the configuration. When the server is daemonized, the pid file # is used even if not specified, defaulting to "/var/run/redis.pid". # # Creating a pid file is best effort: if Redis is not able to create it # nothing bad happens, the server will start and run normally. pidfile /var/run/redis_6380.pid # Specify the server verbosity level. # This 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 notice # Specify the log file name. Also the empty string 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 "" # 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 # By default Redis shows an ASCII art logo only when started to log to the # standard output and if the standard output is a TTY. Basically this means # that normally a logo is displayed only in interactive sessions. # # However it is possible to force the pre-4.0 behavior and always show a # ASCII art logo in startup logs by setting the following option to yes. always-show-logo yes
具体配置详解：
①、daemonize:设置为yes表示指定Redis以守护进程的方式启动（后台启动）。默认值为 no
②、pidfile:配置PID文件路径，当redis作为守护进程运行的时候，它会把 pid 默认写到 /var/redis/run/redis_6379.pid 文件里面
③、loglevel ：定义日志级别。默认值为notice，有如下4种取值：
debug（记录大量日志信息，适用于开发、测试阶段）
verbose（较多日志信息）
notice（适量日志信息，使用于生产环境）
warning（仅有部分重要、关键信息才会被记录）
④、logfile ：配置log文件地址,默认打印在命令行终端的窗口上
⑤、databases：设置数据库的数目。默认的数据库是DB 0 ，可以在每个连接上使用select <dbid> 命令选择一个不同的数据库，dbid是一个介于0到databases - 1 之间的数值。默认值是 16，也就是说默认Redis有16个数据库。
6.SNAPSHOTTING
################################ 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 completely by commenting out all "save" lines. # # It is also possible to remove all the previously configured save # points by adding a save directive with a single empty string argument # like in the following example: # # save "" save 900 1 save 300 10 save 60 10000 # By default Redis will stop accepting writes if RDB snapshots are enabled # (at least one save point) and the latest background save failed. # This will make the user aware (in a hard way) that data is not persisting # on disk properly, otherwise chances are that no one will notice and some # disaster will happen. # # If the background saving process will start working again Redis will # automatically allow writes again. # # However if you have setup your proper monitoring of the Redis server # and persistence, you may want to disable this feature so that Redis will # continue to work as usual even if there are problems with disk, # permissions, and so forth. stop-writes-on-bgsave-error yes # 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 # Since version 5 of RDB a CRC64 checksum is placed at the end of the file. # This makes the format more resistant to corruption but there is a performance # hit to pay (around 10%) when saving and loading RDB files, so you can disable it # for maximum performances. # # RDB files created with checksum disabled have a checksum of zero that will # tell the loading code to skip the check. rdbchecksum yes # The filename where to dump the DB dbfilename dump_6380.rdb # The working directory. # # The DB will be written inside this directory, with the filename specified # above using the 'dbfilename' configuration directive. # # The Append Only File will also be created inside this directory. # # Note that you must specify a directory here, not a file name. dir ./
这里的配置主要用来做持久化操作。
①、save：这里是用来配置触发 Redis的持久化条件，也就是什么时候将内存中的数据保存到硬盘。默认如下配置：
save 900 1：表示900 秒内如果至少有 1 个 key 的值变化，则保存 save 300 10：表示300 秒内如果至少有 10 个 key 的值变化，则保存 save 60 10000：表示60 秒内如果至少有 10000 个 key 的值变化，则保存
当然如果你只是用Redis的缓存功能，不需要持久化，那么你可以注释掉所有的 save 行来停用保存功能。可以直接一个空字符串来实现停用：save ""
②、stop-writes-on-bgsave-error ：默认值为yes。当启用了RDB且最后一次后台保存数据失败，Redis是否停止接收数据。这会让用户意识到数据没有正确持久化到磁盘上，否则没有人会注意到灾难（disaster）发生了。如果Redis重启了，那么又可以重新开始接收数据了
③、rdbcompression ；默认值是yes。对于存储到磁盘中的快照，可以设置是否进行压缩存储。如果是的话，redis会采用LZF算法进行压缩。如果你不想消耗CPU来进行压缩的话，可以设置为关闭此功能，但是存储在磁盘上的快照会比较大。
④、rdbchecksum ：默认值是yes。在存储快照后，我们还可以让redis使用CRC64算法来进行数据校验，但是这样做会增加大约10%的性能消耗，如果希望获取到最大的性能提升，可以关闭此功能。
⑤、dbfilename ：设置快照的文件名，默认是 dump.rdb
⑥、dir：设置快照文件的存放路径，这个配置项一定是个目录，而不能是文件名。使用上面的 dbfilename 作为保存的文件名。
7.REPLICATION
################################# REPLICATION ################################# # Master-Replica replication. Use replicaof to make a Redis instance a copy of # another Redis server. A few things to understand ASAP about Redis replication. # # +------------------+ +---------------+ # | Master | ---> | Replica | # | (receive writes) | | (exact copy) | # +------------------+ +---------------+ # # 1) Redis replication is asynchronous, but you can configure a master to # stop accepting writes if it appears to be not connected with at least # a given number of replicas. # 2) Redis replicas are able to perform a partial resynchronization with the # master if the replication link is lost for a relatively small amount of # time. You may want to configure the replication backlog size (see the next # sections of this file) with a sensible value depending on your needs. # 3) Replication is automatic and does not need user intervention. After a # network partition replicas automatically try to reconnect to masters # and resynchronize with them. # # replicaof <masterip> <masterport> # If the master is password protected (using the "requirepass" configuration # directive below) it is possible to tell the replica to authenticate before # starting the replication synchronization process, otherwise the master will # refuse the replica request. # # masterauth <master-password> # When a replica loses its connection with the master, or when the replication # is still in progress, the replica can act in two different ways: # # 1) if replica-serve-stale-data is set to 'yes' (the default) the replica will # still reply to client requests, possibly with out of date data, or the # data set may just be empty if this is the first synchronization. # # 2) if replica-serve-stale-data is set to 'no' the replica will reply with # an error "SYNC with master in progress" to all the kind of commands # but to INFO, replicaOF, AUTH, PING, SHUTDOWN, REPLCONF, ROLE, CONFIG, # SUBSCRIBE, UNSUBSCRIBE, PSUBSCRIBE, PUNSUBSCRIBE, PUBLISH, PUBSUB, # COMMAND, POST, HOST: and LATENCY. # replica-serve-stale-data yes # You can configure a replica instance to accept writes or not. Writing against # a replica instance may be useful to store some ephemeral data (because data # written on a replica will be easily deleted after resync with the master) but # may also cause problems if clients are writing to it because of a # misconfiguration. # # Since Redis 2.6 by default replicas are read-only. # # Note: read only replicas are not designed to be exposed to untrusted clients # on the internet. It's just a protection layer against misuse of the instance. # Still a read only replica exports by default all the administrative commands # such as CONFIG, DEBUG, and so forth. To a limited extent you can improve # security of read only replicas using 'rename-command' to shadow all the # administrative / dangerous commands. replica-read-only yes # Replication SYNC strategy: disk or socket. # # ------------------------------------------------------- # WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY # ------------------------------------------------------- # # New replicas and reconnecting replicas that are not able to continue the replication # process just receiving differences, need to do what is called a "full # synchronization". An RDB file is transmitted from the master to the replicas. # The transmission can happen in two different ways: # # 1) Disk-backed: The Redis master creates a new process that writes the RDB # file on disk. Later the file is transferred by the parent # process to the replicas incrementally. # 2) Diskless: The Redis master creates a new process that directly writes the # RDB file to replica sockets, without touching the disk at all. # # With disk-backed replication, while the RDB file is generated, more replicas # can be queued and served with the RDB file as soon as the current child producing # the RDB file finishes its work. With diskless replication instead once # the transfer starts, new replicas arriving will be queued and a new transfer # will start when the current one terminates. # # When diskless replication is used, the master waits a configurable amount of # time (in seconds) before starting the transfer in the hope that multiple replicas # will arrive and the transfer can be parallelized. # # With slow disks and fast (large bandwidth) networks, diskless replication # works better. repl-diskless-sync no # When diskless replication is enabled, it is possible to configure the delay # the server waits in order to spawn the child that transfers the RDB via socket # to the replicas. # # This is important since once the transfer starts, it is not possible to serve # new replicas arriving, that will be queued for the next RDB transfer, so the server # waits a delay in order to let more replicas arrive. # # The delay is specified in seconds, and by default is 5 seconds. To disable # it entirely just set it to 0 seconds and the transfer will start ASAP. repl-diskless-sync-delay 5 # Replicas send PINGs to server in a predefined interval. It's possible to change # this interval with the repl_ping_replica_period option. The default value is 10 # seconds. # # repl-ping-replica-period 10 # The following option sets the replication timeout for: # # 1) Bulk transfer I/O during SYNC, from the point of view of replica. # 2) Master timeout from the point of view of replicas (data, pings). # 3) Replica timeout from the point of view of masters (REPLCONF ACK pings). # # It is important to make sure that this value is greater than the value # specified for repl-ping-replica-period otherwise a timeout will be detected # every time there is low traffic between the master and the replica. # # repl-timeout 60 # Disable TCP_NODELAY on the replica socket after SYNC? # # If you select "yes" Redis will use a smaller number of TCP packets and # less bandwidth to send data to replicas. But this can add a delay for # the data to appear on the replica side, up to 40 milliseconds with # Linux kernels using a default configuration. # # If you select "no" the delay for data to appear on the replica side will # be reduced but more bandwidth will be used for replication. # # By default we optimize for low latency, but in very high traffic conditions # or when the master and replicas are many hops away, turning this to "yes" may # be a good idea. repl-disable-tcp-nodelay no # Set the replication backlog size. The backlog is a buffer that accumulates # replica data when replicas are disconnected for some time, so that when a replica # wants to reconnect again, often a full resync is not needed, but a partial # resync is enough, just passing the portion of data the replica missed while # disconnected. # # The bigger the replication backlog, the longer the time the replica can be # disconnected and later be able to perform a partial resynchronization. # # The backlog is only allocated once there is at least a replica connected. # # repl-backlog-size 1mb # After a master has no longer connected replicas for some time, the backlog # will be freed. The following option configures the amount of seconds that # need to elapse, starting from the time the last replica disconnected, for # the backlog buffer to be freed. # # Note that replicas never free the backlog for timeout, since they may be # promoted to masters later, and should be able to correctly "partially # resynchronize" with the replicas: hence they should always accumulate backlog. # # A value of 0 means to never release the backlog. # # repl-backlog-ttl 3600 # The replica priority is an integer number published by Redis in the INFO output. # It is used by Redis Sentinel in order to select a replica to promote into a # master if the master is no longer working correctly. # # A replica with a low priority number is considered better for promotion, so # for instance if there are three replicas with priority 10, 100, 25 Sentinel will # pick the one with priority 10, that is the lowest. # # However a special priority of 0 marks the replica as not able to perform the # role of master, so a replica with priority of 0 will never be selected by # Redis Sentinel for promotion. # # By default the priority is 100. replica-priority 100 # It is possible for a master to stop accepting writes if there are less than # N replicas connected, having a lag less or equal than M seconds. # # The N replicas need to be in "online" state. # # The lag in seconds, that must be <= the specified value, is calculated from # the last ping received from the replica, that is usually sent every second. # # This option does not GUARANTEE that N replicas will accept the write, but # will limit the window of exposure for lost writes in case not enough replicas # are available, to the specified number of seconds. # # For example to require at least 3 replicas with a lag <= 10 seconds use: # # min-replicas-to-write 3 # min-replicas-max-lag 10 # # Setting one or the other to 0 disables the feature. # # By default min-replicas-to-write is set to 0 (feature disabled) and # min-replicas-max-lag is set to 10. # A Redis master is able to list the address and port of the attached # replicas in different ways. For example the "INFO replication" section # offers this information, which is used, among other tools, by # Redis Sentinel in order to discover replica instances. # Another place where this info is available is in the output of the # "ROLE" command of a master. # # The listed IP and address normally reported by a replica is obtained # in the following way: # # IP: The address is auto detected by checking the peer address # of the socket used by the replica to connect with the master. # # Port: The port is communicated by the replica during the replication # handshake, and is normally the port that the replica is using to # listen for connections. # # However when port forwarding or Network Address Translation (NAT) is # used, the replica may be actually reachable via different IP and port # pairs. The following two options can be used by a replica in order to # report to its master a specific set of IP and port, so that both INFO # and ROLE will report those values. # # There is no need to use both the options if you need to override just # the port or the IP address. # # replica-announce-ip 5.5.5.5 # replica-announce-port 1234
①、slave-serve-stale-data：默认值为yes。当一个 slave 与 master 失去联系，或者复制正在进行的时候，slave 可能会有两种表现：
1) 如果为 yes ，slave 仍然会应答客户端请求，但返回的数据可能是过时，或者数据可能是空的在第一次同步的时候
2) 如果为 no ，在你执行除了 info he salveof 之外的其他命令时，slave 都将返回一个 "SYNC with master in progress" 的错误
②、slave-read-only：配置Redis的Slave实例是否接受写操作，即Slave是否为只读Redis。默认值为yes。
③、repl-diskless-sync：主从数据复制是否使用无硬盘复制功能。默认值为no。
④、repl-diskless-sync-delay：当启用无硬盘备份，服务器等待一段时间后才会通过套接字向从站传送RDB文件，这个等待时间是可配置的。 这一点很重要，因为一旦传送开始，就不可能再为一个新到达的从站服务。从站则要排队等待下一次RDB传送。因此服务器等待一段 时间以期更多的从站到达。延迟时间以秒为单位，默认为5秒。要关掉这一功能，只需将它设置为0秒，传送会立即启动。默认值为5。
⑤、repl-disable-tcp-nodelay：同步之后是否禁用从站上的TCP_NODELAY 如果你选择yes，redis会使用较少量的TCP包和带宽向从站发送数据。但这会导致在从站增加一点数据的延时。 Linux内核默认配置情况下最多40毫秒的延时。如果选择no，从站的数据延时不会那么多，但备份需要的带宽相对较多。默认情况下我们将潜在因素优化，但在高负载情况下或者在主从站都跳的情况下，把它切换为yes是个好主意。默认值为no。
8.SECURITY
################################## 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 123456 # Command renaming. # # It is possible to change the name of dangerous commands in a shared # environment. For instance the CONFIG command may be renamed into something # hard to guess so that it will still be available for internal-use tools # but not available for general clients. # # Example: # # rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52 # # It is also possible to completely kill a command by renaming it into # an empty string: # # rename-command CONFIG "" # # Please note that changing the name of commands that are logged into the # AOF file or transmitted to replicas may cause problems.
①、rename-command：命令重命名，对于一些危险命令例如：
flushdb（清空数据库）
flushall（清空所有记录）
config（客户端连接后可配置服务器）
keys（客户端连接后可查看所有存在的键）
作为服务端redis-server，常常需要禁用以上命令来使得服务器更加安全，禁用的具体做法是是：
- rename-command FLUSHALL ""
也可以保留命令但是不能轻易使用，重命名这个命令即可：
- rename-command FLUSHALL abcdefg
这样，重启服务器后则需要使用新命令来执行操作，否则服务器会报错unknown command。
9.CLIENTS
################################### CLIENTS #################################### # Set the max number of connected clients at the same time. By default # this limit is set to 10000 clients, however if the Redis server is not # able to configure the process file limit to allow for the specified limit # the max number of allowed clients is set to the current file limit # minus 32 (as Redis reserves a few file descriptors for internal uses). # # Once the limit is reached Redis will close all the new connections sending # an error 'max number of clients reached'. # # maxclients 10000
①、maxclients ：设置客户端最大并发连接数，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-32（redis server自身会使用一些），如果设置 maxclients为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
10.MEMORY MANAGEMENT
############################## MEMORY MANAGEMENT ################################ # Set a memory usage limit to the specified amount of bytes. # When the memory limit is reached Redis will try to remove keys # according to the eviction policy selected (see maxmemory-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 or LFU cache, or to # set a hard memory limit for an instance (using the 'noeviction' policy). # # WARNING: If you have replicas attached to an instance with maxmemory on, # the size of the output buffers needed to feed the replicas 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 replicas 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 replicas attached it is suggested that you set a lower # limit for maxmemory so that there is some free RAM on the system for replica # output buffers (but this is not needed if the policy is 'noeviction'). # # maxmemory <bytes> # MAXMEMORY POLICY: how Redis will select what to remove when maxmemory # is reached. You can select among five behaviors: # # volatile-lru -> Evict using approximated LRU among the keys with an expire set. # allkeys-lru -> Evict any key using approximated LRU. # volatile-lfu -> Evict using approximated LFU among the keys with an expire set. # allkeys-lfu -> Evict any key using approximated LFU. # volatile-random -> Remove a random key among the ones 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 evict anything, just return an error on write operations. # # LRU means Least Recently Used # LFU means Least Frequently Used # # Both LRU, LFU and volatile-ttl are implemented using approximated # randomized algorithms. # # Note: with any of the above policies, Redis will return an error on write # operations, when there are no suitable keys for eviction. # # At the date of writing these 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 noeviction # LRU, LFU and minimal TTL algorithms are not precise algorithms but approximated # algorithms (in order to save memory), so you can tune it for speed or # accuracy. For default Redis will check five keys and pick the one that was # used less recently, you can change the sample size using the following # configuration directive. # # The default of 5 produces good enough results. 10 Approximates very closely # true LRU but costs more CPU. 3 is faster but not very accurate. # # maxmemory-samples 5 # Starting from Redis 5, by default a replica will ignore its maxmemory setting # (unless it is promoted to master after a failover or manually). It means # that the eviction of keys will be just handled by the master, sending the # DEL commands to the replica as keys evict in the master side. # # This behavior ensures that masters and replicas stay consistent, and is usually # what you want, however if your replica is writable, or you want the replica to have # a different memory setting, and you are sure all the writes performed to the # replica are idempotent, then you may change this default (but be sure to understand # what you are doing). # # Note that since the replica by default does not evict, it may end using more # memory than the one set via maxmemory (there are certain buffers that may # be larger on the replica, or data structures may sometimes take more memory and so # forth). So make sure you monitor your replicas and make sure they have enough # memory to never hit a real out-of-memory condition before the master hits # the configured maxmemory setting. # # replica-ignore-maxmemory yes
①、maxmemory：设置客户端最大并发连接数，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-32（redis server自身会使用一些），如果设置 maxclients为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。
②、maxmemory-policy ：当内存使用达到最大值时，redis使用的清楚策略。有以下几种可以选择：
1）volatile-lru 利用LRU算法移除设置过过期时间的key (LRU:最近使用 Least Recently Used )
2）allkeys-lru 利用LRU算法移除任何key
3）volatile-random 移除设置过过期时间的随机key
4）allkeys-random 移除随机ke
5）volatile-ttl 移除即将过期的key(minor TTL)
6）noeviction noeviction 不移除任何key，只是返回一个写错误 ，默认选项
③、maxmemory-samples ：LRU 和 minimal TTL 算法都不是精准的算法，但是相对精确的算法(为了节省内存)。随意你可以选择样本大小进行检，redis默认选择3个样本进行检测，你可以通过maxmemory-samples进行设置样本数。
11.LAZY FREEING（待补充。。。）
############################# LAZY FREEING #################################### # Redis has two primitives to delete keys. One is called DEL and is a blocking # deletion of the object. It means that the server stops processing new commands # in order to reclaim all the memory associated with an object in a synchronous # way. If the key deleted is associated with a small object, the time needed # in order to execute the DEL command is very small and comparable to most other # O(1) or O(log_N) commands in Redis. However if the key is associated with an # aggregated value containing millions of elements, the server can block for # a long time (even seconds) in order to complete the operation. # # For the above reasons Redis also offers non blocking deletion primitives # such as UNLINK (non blocking DEL) and the ASYNC option of FLUSHALL and # FLUSHDB commands, in order to reclaim memory in background. Those commands # are executed in constant time. Another thread will incrementally free the # object in the background as fast as possible. # # DEL, UNLINK and ASYNC option of FLUSHALL and FLUSHDB are user-controlled. # It's up to the design of the application to understand when it is a good # idea to use one or the other. However the Redis server sometimes has to # delete keys or flush the whole database as a side effect of other operations. # Specifically Redis deletes objects independently of a user call in the # following scenarios: # # 1) On eviction, because of the maxmemory and maxmemory policy configurations, # in order to make room for new data, without going over the specified # memory limit. # 2) Because of expire: when a key with an associated time to live (see the # EXPIRE command) must be deleted from memory. # 3) Because of a side effect of a command that stores data on a key that may # already exist. For example the RENAME command may delete the old key # content when it is replaced with another one. Similarly SUNIONSTORE # or SORT with STORE option may delete existing keys. The SET command # itself removes any old content of the specified key in order to replace # it with the specified string. # 4) During replication, when a replica performs a full resynchronization with # its master, the content of the whole database is removed in order to # load the RDB file just transferred. # # In all the above cases the default is to delete objects in a blocking way, # like if DEL was called. However you can configure each case specifically # in order to instead release memory in a non-blocking way like if UNLINK # was called, using the following configuration directives: lazyfree-lazy-eviction no lazyfree-lazy-expire no lazyfree-lazy-server-del no replica-lazy-flush no
12.APPEND ONLY MODE
############################## APPEND ONLY MODE ############################### # By default Redis asynchronously dumps the dataset on disk. This mode is # good enough in many applications, but an issue with the Redis process or # a power outage may result into a few minutes of writes lost (depending on # the configured save points). # # The Append Only File is an alternative persistence mode that provides # much better durability. For instance using the default data fsync policy # (see later in the config file) Redis can lose just one second of writes in a # dramatic event like a server power outage, or a single write if something # wrong with the Redis process itself happens, but the operating system is # still running correctly. # # AOF and RDB persistence can be enabled at the same time without problems. # If the AOF is enabled on startup Redis will load the AOF, that is the file # with the better durability guarantees. # # Please check http://redis.io/topics/persistence for more information. appendonly no # The name of the append only file (default: "appendonly.aof") appendfilename "appendonly.aof" # The fsync() call tells the Operating System to actually write data on disk # instead of waiting 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 one time every second. Compromise. # # The default is "everysec", as 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 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. # # More details please check the following article: # http://antirez.com/post/redis-persistence-demystified.html # # If unsure, use "everysec". # appendfsync always 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(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". In practical terms, this means that it is # possible to lose 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 grows by the specified percentage. # # This is how it works: Redis remembers the size of the AOF file after the # latest rewrite (if no rewrite has 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 percentage of zero in order to disable the automatic AOF # rewrite feature. auto-aof-rewrite-percentage 100 auto-aof-rewrite-min-size 64mb # An AOF file may be found to be truncated at the end during the Redis # startup process, when the AOF data gets loaded back into memory. # This may happen when the system where Redis is running # crashes, especially when an ext4 filesystem is mounted without the # data=ordered option (however this can't happen when Redis itself # crashes or aborts but the operating system still works correctly). # # Redis can either exit with an error when this happens, or load as much # data as possible (the default now) and start if the AOF file is found # to be truncated at the end. The following option controls this behavior. # # If aof-load-truncated is set to yes, a truncated AOF file is loaded and # the Redis server starts emitting a log to inform the user of the event. # Otherwise if the option is set to no, the server aborts with an error # and refuses to start. When the option is set to no, the user requires # to fix the AOF file using the "redis-check-aof" utility before to restart # the server. # # Note that if the AOF file will be found to be corrupted in the middle # the server will still exit with an error. This option only applies when # Redis will try to read more data from the AOF file but not enough bytes # will be found. aof-load-truncated yes # When rewriting the AOF file, Redis is able to use an RDB preamble in the # AOF file for faster rewrites and recoveries. When this option is turned # on the rewritten AOF file is composed of two different stanzas: # # [RDB file][AOF tail] # # When loading Redis recognizes that the AOF file starts with the "REDIS" # string and loads the prefixed RDB file, and continues loading the AOF # tail. aof-use-rdb-preamble yes
①、appendonly：默认redis使用的是rdb方式持久化，这种方式在许多应用中已经足够用了。但是redis如果中途宕机，会导致可能有几分钟的数据丢失，根据save来策略进行持久化，Append Only File是另一种持久化方式， 可以提供更好的持久化特性。Redis会把每次写入的数据在接收后都写入appendonly.aof文件，每次启动时Redis都会先把这个文件的数据读入内存里，先忽略RDB文件。默认值为no。
②、appendfilename ：aof文件名，默认是"appendonly.aof"
③、appendfsync：aof持久化策略的配置；no表示不执行fsync，由操作系统保证数据同步到磁盘，速度最快；always表示每次写入都执行fsync，以保证数据同步到磁盘；everysec表示每秒执行一次fsync，可能会导致丢失这1s数据
④、no-appendfsync-on-rewrite：在aof重写或者写入rdb文件的时候，会执行大量IO，此时对于everysec和always的aof模式来说，执行fsync会造成阻塞过长时间，no-appendfsync-on-rewrite字段设置为默认设置为no。如果对延迟要求很高的应用，这个字段可以设置为yes，否则还是设置为no，这样对持久化特性来说这是更安全的选择。 设置为yes表示rewrite期间对新写操作不fsync,暂时存在内存中,等rewrite完成后再写入，默认为no，建议yes。Linux的默认fsync策略是30秒。可能丢失30秒数据。默认值为no。
⑤、auto-aof-rewrite-percentage：默认值为100。aof自动重写配置，当目前aof文件大小超过上一次重写的aof文件大小的百分之多少进行重写，即当aof文件增长到一定大小的时候，Redis能够调用bgrewriteaof对日志文件进行重写。当前AOF文件大小是上次日志重写得到AOF文件大小的二倍（设置为100）时，自动启动新的日志重写过程。
⑥、auto-aof-rewrite-min-size：64mb。设置允许重写的最小aof文件大小，避免了达到约定百分比但尺寸仍然很小的情况还要重写。
⑦、aof-load-truncated：aof文件可能在尾部是不完整的，当redis启动的时候，aof文件的数据被载入内存。重启可能发生在redis所在的主机操作系统宕机后，尤其在ext4文件系统没有加上data=ordered选项，出现这种现象 redis宕机或者异常终止不会造成尾部不完整现象，可以选择让redis退出，或者导入尽可能多的数据。如果选择的是yes，当截断的aof文件被导入的时候，会自动发布一个log给客户端然后load。如果是no，用户必须手动redis-check-aof修复AOF文件才可以。默认值为 yes。
13.LUA SCRIPTING
################################ LUA SCRIPTING ############################### # Max execution time of a Lua script in milliseconds. # # If the maximum execution time is reached Redis will log that a script is # still in execution after the maximum allowed time and will start to # reply to queries with an error. # # When a long running script exceeds the maximum execution time only the # SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be # used to stop a script that did not yet called write commands. The second # is the only way to shut down the server in the case a write command was # already issued by the script but the user doesn't want to wait for the natural # termination of the script. # # Set it to 0 or a negative value for unlimited execution without warnings. lua-time-limit 5000
①、lua-time-limit：一个lua脚本执行的最大时间，单位为ms。默认值为5000.
14.REDIS CLUSTER
################################ REDIS CLUSTER ############################### # # ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ # WARNING EXPERIMENTAL: Redis Cluster is considered to be stable code, however # in order to mark it as "mature" we need to wait for a non trivial percentage # of users to deploy it in production. # ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ # # Normal Redis instances can't be part of a Redis Cluster; only nodes that are # started as cluster nodes can. In order to start a Redis instance as a # cluster node enable the cluster support uncommenting the following: # # cluster-enabled yes # Every cluster node has a cluster configuration file. This file is not # intended to be edited by hand. It is created and updated by Redis nodes. # Every Redis Cluster node requires a different cluster configuration file. # Make sure that instances running in the same system do not have # overlapping cluster configuration file names. # # cluster-config-file nodes-6379.conf # Cluster node timeout is the amount of milliseconds a node must be unreachable # for it to be considered in failure state. # Most other internal time limits are multiple of the node timeout. # # cluster-node-timeout 15000 # A replica of a failing master will avoid to start a failover if its data # looks too old. # # There is no simple way for a replica to actually have an exact measure of # its "data age", so the following two checks are performed: # # 1) If there are multiple replicas able to failover, they exchange messages # in order to try to give an advantage to the replica with the best # replication offset (more data from the master processed). # Replicas will try to get their rank by offset, and apply to the start # of the failover a delay proportional to their rank. # # 2) Every single replica computes the time of the last interaction with # its master. This can be the last ping or command received (if the master # is still in the "connected" state), or the time that elapsed since the # disconnection with the master (if the replication link is currently down). # If the last interaction is too old, the replica will not try to failover # at all. # # The point "2" can be tuned by user. Specifically a replica will not perform # the failover if, since the last interaction with the master, the time # elapsed is greater than: # # (node-timeout * replica-validity-factor) + repl-ping-replica-period # # So for example if node-timeout is 30 seconds, and the replica-validity-factor # is 10, and assuming a default repl-ping-replica-period of 10 seconds, the # replica will not try to failover if it was not able to talk with the master # for longer than 310 seconds. # # A large replica-validity-factor may allow replicas with too old data to failover # a master, while a too small value may prevent the cluster from being able to # elect a replica at all. # # For maximum availability, it is possible to set the replica-validity-factor # to a value of 0, which means, that replicas will always try to failover the # master regardless of the last time they interacted with the master. # (However they'll always try to apply a delay proportional to their # offset rank). # # Zero is the only value able to guarantee that when all the partitions heal # the cluster will always be able to continue. # # cluster-replica-validity-factor 10 # Cluster replicas are able to migrate to orphaned masters, that are masters # that are left without working replicas. This improves the cluster ability # to resist to failures as otherwise an orphaned master can't be failed over # in case of failure if it has no working replicas. # # Replicas migrate to orphaned masters only if there are still at least a # given number of other working replicas for their old master. This number # is the "migration barrier". A migration barrier of 1 means that a replica # will migrate only if there is at least 1 other working replica for its master # and so forth. It usually reflects the number of replicas you want for every # master in your cluster. # # Default is 1 (replicas migrate only if their masters remain with at least # one replica). To disable migration just set it to a very large value. # A value of 0 can be set but is useful only for debugging and dangerous # in production. # # cluster-migration-barrier 1 # By default Redis Cluster nodes stop accepting queries if they detect there # is at least an hash slot uncovered (no available node is serving it). # This way if the cluster is partially down (for example a range of hash slots # are no longer covered) all the cluster becomes, eventually, unavailable. # It automatically returns available as soon as all the slots are covered again. # # However sometimes you want the subset of the cluster which is working, # to continue to accept queries for the part of the key space that is still # covered. In order to do so, just set the cluster-require-full-coverage # option to no. # # cluster-require-full-coverage yes # This option, when set to yes, prevents replicas from trying to failover its # master during master failures. However the master can still perform a # manual failover, if forced to do so. # # This is useful in different scenarios, especially in the case of multiple # data center operations, where we want one side to never be promoted if not # in the case of a total DC failure. # # cluster-replica-no-failover no # In order to setup your cluster make sure to read the documentation # available at http://redis.io web site. ########################## CLUSTER DOCKER/NAT support ######################## # In certain deployments, Redis Cluster nodes address discovery fails, because # addresses are NAT-ted or because ports are forwarded (the typical case is # Docker and other containers). # # In order to make Redis Cluster working in such environments, a static # configuration where each node knows its public address is needed. The # following two options are used for this scope, and are: # # * cluster-announce-ip # * cluster-announce-port # * cluster-announce-bus-port # # Each instruct the node about its address, client port, and cluster message # bus port. The information is then published in the header of the bus packets # so that other nodes will be able to correctly map the address of the node # publishing the information. # # If the above options are not used, the normal Redis Cluster auto-detection # will be used instead. # # Note that when remapped, the bus port may not be at the fixed offset of # clients port + 10000, so you can specify any port and bus-port depending # on how they get remapped. If the bus-port is not set, a fixed offset of # 10000 will be used as usually. # # Example: # # cluster-announce-ip 10.1.1.5 # cluster-announce-port 6379 # cluster-announce-bus-port 6380
①、cluster-enabled：集群开关，默认是不开启集群模式。
②、cluster-config-file：集群配置文件的名称，每个节点都有一个集群相关的配置文件，持久化保存集群的信息。 这个文件并不需要手动配置，这个配置文件有Redis生成并更新，每个Redis集群节点需要一个单独的配置文件。请确保与实例运行的系统中配置文件名称不冲突。默认配置为nodes-6379.conf。
③、cluster-node-timeout ：可以配置值为15000。节点互连超时的阀值，集群节点超时毫秒数
④、cluster-slave-validity-factor ：可以配置值为10。在进行故障转移的时候，全部slave都会请求申请为master，但是有些slave可能与master断开连接一段时间了， 导致数据过于陈旧，这样的slave不应该被提升为master。该参数就是用来判断slave节点与master断线的时间是否过长。判断方法是：比较slave断开连接的时间和(node-timeout * slave-validity-factor) + repl-ping-slave-period 如果节点超时时间为三十秒, 并且slave-validity-factor为10,假设默认的repl-ping-slave-period是10秒，即如果超过310秒slave将不会尝试进行故障转移
⑤、cluster-migration-barrier ：可以配置值为1。master的slave数量大于该值，slave才能迁移到其他孤立master上，如这个参数若被设为2，那么只有当一个主节点拥有2 个可工作的从节点时，它的一个从节点会尝试迁移。
⑥、cluster-require-full-coverage：默认情况下，集群全部的slot有节点负责，集群状态才为ok，才能提供服务。 设置为no，可以在slot没有全部分配的时候提供服务。不建议打开该配置，这样会造成分区的时候，小分区的master一直在接受写请求，而造成很长时间数据不一致。
