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Redis入门--1.安装Redis讲解

xmjava 2021年02月13日 大数据 240 0

 redis是什么?

是完全开源免费的,用c语言编写的,是一个单线程,高性能的(key/value)内存数据库,基于内存运行并支持持久化的nosql数据库

redis能干嘛? 

主要是用来做缓存,但不仅仅只能做缓存,比如:redis的计数器生成分布式唯一主键,redis实现分布式锁,队列,会话缓存

redis的安装(用的百度云服务器,centos7.5版本)

下面是Redis5.0.5 Linux版本的下载地址

http://download.redis.io/releases/redis-5.0.5.tar.gz

我安装在以下路径下

cd /usr/local/java

解压Redis

 tar zxvf redis-5.0.5.tar.gz

删除安装包

 rm -rf redis-5.0.5.tar.gz 

重命名为redis

mv redis-5.0.5/ redis

进入文件目录

cd redis/

 

上面的redis.conf文件就是Redis的核心配置文件

 

编译redis

make

出现以下报错

 

这是因为redis是c语言写的,需要安装gcc编译器

 yum install gcc-c++

安装好gcc之后执行一下make distclean 因为前面make的时候它编译了一些东西  要先把他们清掉

 make distclean

重新编译

make

编译完成后安装redis

make install

默认安装在/usr/local/bin路径下

 

make install 默认安装到/usr/local/bin 目录下) 使用:如果需要指定安装路径,需要添加 PREFIX 参数,命令如下

 make PREFIX=/usr/local/redis/ install 

  

 好,安装成功,在根目录创建redisConf文件夹,并存放redis.conf核心配置文件的备份

 cp redis.conf /redisConf/

 

进入redis解压目录,编辑配置文件redis.conf

 vim redis.conf

 

 

bind 配置  指定可以连接本实例Redis的ip

bind 127.0.0.1

这里要注意不能使用外网ip,必须使用内网ip才能启动redis

比如我用的百度云服务器ip是

180.76.58.137

那我这里不能填这个ip,因为他是外网ip,会无法启动redis,我们可以使用命令来查看该服务器的内网ip,如图

 上图中的两个ip地址均可以填入.我测试过都能正常启动redis

 如果注释(删掉)或填写0.0.0.0 , 则任意IP都可以连接,一般写本机ip就可以了,

如果需要使用windows客户端访问虚拟机安装的redis可以配置 0.0.0.0,配合如下配置,可以使用windows客户端访问虚拟机安装的redis

protected-mode保护模式配置:禁止外网访问redis ,默认yes

它启用的条件有两个,第一是没有使用bind,第二是没有设置访问密码。也就是说,如果你配置了bind,那不管你怎么配置,都算不启用

如果启用了,比如注释掉了bind 127.0.0.1,再访问redis的时候是无法连接的

protected-mode yes

 

port 配置 指定Redis的端口,默认6379

port 6379

 

daemonize配置 是否以守护进程启动 默认no

当状态为no是,按Ctrl+c就会退出redis,所以我们改成yes,即在后台运行

daemonize yes

 

配置完成,保存退出.使用默认安装目录/usr/local/bin来启动redis

 /usr/local/bin/redis-server ./redis.conf 

 

查看redis进程是否启动

ps -ef|grep redis

 

添加放行端口

firewall-cmd --zone=public --add-port=6379/tcp --permanent

 

重启防火墙

firewall-cmd --reload 
或firewall-cmd --complete-reload 
两者的区别就是第一个无需断开连接,就是firewalld特性之一动态 
添加规则,第二个需要断开连接,类似重启服务

 

查看已开放端口:

firewall-cmd --list-all

 

 

用Windows客户端连接redis

 

 好,安装redis成功.

 

最后附上一份中文注释的redis配置文件内容

# Redis configuration file example. 
# 
# Note that in order to read the configuration file, Redis must be 
# started with the file path as first argument: 
# 
# ./redis-server /path/to/redis.conf 
 
# Note on units: when memory size is needed, it is possible to specify 
# it in the usual form of 1k 5GB 4M and so forth: 
# 配置大小单位,开头定义了一些基本的度量单位,只支持bytes,不支持bit 对大小写不敏感 
# 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. 
 
################################## 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. 
# 引入其他文件 
# include /path/to/local.conf 
# include /path/to/other.conf 
 
################################## 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 
 
################################## 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. 
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
# 绑定Ip 指定可以连接本实例Redis的ip 如果注释(删掉)则任意IP都可以连接,一般写本机ip就可以了 
bind 127.0.0.1 
 
# 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. 
#禁止外网访问redis,如果启用了,即使注释掉了bind 127.0.0.1,再访问redisd时候还是无法连接的 
#它启用的条件有两个,第一是没有使用bind,第二是没有设置访问密码。 
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. 
#指定Redis的端口 
port 6379 
 
# 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. 
# 此参数确定了TCP连接中已完成队列(完成三次握手之后)的长度,  
# 当然此值必须不大于Linux系统定义的/proc/sys/net/core/somaxconn值,默认是511, 
# 而Linux的默认参数值是128。当系统并发量大并且客户端速度缓慢的时候,可以将这二个参数一起参考设定。 
# 在高并发环境下你需要一个高backlog值来避免慢客户端连接问题 
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) 
# 当客户端闲置多长时间后关闭连接,如果指定为0,表示关闭该功能 
timeout 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. 
# 设置多长时间检测死连接 单位为秒,如果设置为0,则不会进行Keepalive检测 
tcp-keepalive 300 
 
################################# 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. 
# 是否以守护进程启动 
daemonize no 
 
# 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. 
#可以通过upstart和systemd管理Redis守护进程,这个参数是和具体的操作系统相关的。 
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. 
#当Redis以守护进程方式运行时,Redis默认会把pid写入/var/run/redis.pid文件,可以通过pidfile指定 
pidfile /var/run/redis_6379.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) 
#设置日志的级别 debug、verbose、notice、warning,默认为verbose 
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 
#日志文件的位置,当指定为空字符串时,为标准输出,如果redis已守护进程模式运行,那么日志将会输出到 /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 
# 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。 
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 
 
################################ 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 "" 
# 指定在多长时间内,有多少次更新操作,就将数据同步到数据文件,可以多个条件配合 
# 这里表示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 
# 如果想禁用RDB持久化的策略,只要不设置任何save指令,或者给save传入一个空字符串参数也可以 
save 900 1 
save 300 10 
save 60 1 
 
# 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. 
# 默认情况下,如果 redis 最后一次的后台保存失败,redis 将停止接受写操作,这样以一种强硬的方式让用户知道数据不能正确的持久化到磁盘,  
# 否则就会没人注意到灾难的发生。 如果后台保存进程重新启动工作了,redis 也将自动的允许写操作。 
# 如果配置成no,表示你不在乎数据不一致或者有其他的手段发现和控制 
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. 
# 对于存储到磁盘中的快照(rdb),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 
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. 
# 在存储快照后,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 
rdbchecksum yes 
 
# The filename where to dump the DB 
#rdb文件的名字。 
dbfilename dump.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. 
# dbfilename文件存放目录。必须是一个目录,aof文件也会保存到该目录下。 
dir ./ 
 
################################# 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. 
#设置当本机为slave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 
# 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. 
#当master服务设置了密码保护时,slave服务连接master的密码 
# 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. 
#当一个slave与master失去联系时,或者复制正在进行的时候,slave应对请求的行为:  
#如果为 yes(默认值) ,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 
#如果为 no ,在你执行除了 info 和 salveof 之外的其他命令时,slave 都将返回一个 "SYNC with master in progress" 的错误。 
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. 
#设置slave是否是只读的。从2.6版起,slave默认是只读的。 
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. 
# 主从数据复制是否使用无硬盘复制功能。 
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. 
# 指定slave定期ping master的周期,默认10秒钟。 
# 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. 
#设置主库批量数据传输时间或者ping回复时间间隔,默认值是60秒 。 
# 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. 
#指定向slave同步数据时,是否禁用socket的NO_DELAY选项。 
#若配置为“yes”,则禁用NO_DELAY,则TCP协议栈会合并小包统一发送,这样可以减少主从节点间的包数量并节省带宽,但会增加数据同步到 slave的时间。 
#若配置为“no”,表明启用NO_DELAY,则TCP协议栈不会延迟小包的发送时机,这样数据同步的延时会减少,但需要更大的带宽。  
#通常情况下,应该配置为no以降低同步延时,但在主从节点间网络负载已经很高的情况下,可以配置为yes。 
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. 
# 设置主从复制backlog容量大小。这个 backlog 是一个用来在 slaves 被断开连接时存放 slave 数据的 buffer, 
# 所以当一个 slave 想要重新连接,通常不希望全部重新同步,只是部分同步就够了,仅仅传递 slave 在断开连接时丢失的这部分数据。 
# 这个值越大,salve 可以断开连接的时间就越长。 
# 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. 
#配置当master和slave失去联系多少秒之后,清空backlog释放空间。当配置成0时,表示永远不清空。 
# 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. 
#当 master 不能正常工作的时候,Redis Sentinel 会从 slaves 中选出一个新的 master,这个值越小,就越会被优先选中,但是如果是 0 , 那是意味着这个 slave 不可能被选中。 默认优先级为 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 
 
################################## 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. 
# 设置Redis连接密码,如果配置了连接密码,客户端在连接Redis时需要通过AUTH <password>命令提供密码,默认关闭 
# requirepass foobared 
 
# Command renaming. 
# 
# It is 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. 
 
################################### 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'. 
#设置同一时间最大客户端连接数,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 
# maxclients 10000 
 
############################## 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'). 
# 指定Redis最大内存限制,Redis在启动时会把数据加载到内存中,达到最大内存后,Redis会先尝试清除已到期或即将到期的Key, 
# 当此方法处理后,仍然到达最大内存设置,将无法再进行写入操作,但仍然可以进行读取操作。 
# Redis新的vm机制,会把Key存放内存,Value会存放在swap区 
# maxmemory <bytes> 
 
# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory 
# is reached. You can select among five 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 syc 
# 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: 
#当内存使用达到最大值时,redis使用的清除策略。有以下几种可以选择(明明有6种,官方配置文件里却说有5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key  
# 5)volatile-ttl   移除即将过期的key(minor TTL)  
# 6)noeviction  不移除任何key,只是返回一个写错误 。默认选项 
 
# 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. 
# 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测。redis默认选择5个样本进行检测,你可以通过maxmemory-samples进行设置样本数。 
# 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 
 
############################# 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 
 
############################## 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. 
# 是否启用aof持久化方式 。否在每次更新操作后进行日志记录,Redis在默认情况下是异步的把数据写入磁盘,如果不开启,可能会在断电时导致一段时间内的数据丢失。 
# 因为 redis本身同步数据文件是按上面save条件来同步的,所以有的数据会在一段时间内只存在于内存中。默认为no 
appendonly no 
 
# The name of the append only file (default: "appendonly.aof") 
# 指定更新日志(aof)文件名,默认为appendonly.aof 
appendfilename "appendonly.aof" 
 
# The fsync() call tells the Operating System to actually write data on disk 
# instead 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". 
#指定更新日志条件,共有3个可选值:  
# no:表示等操作系统进行数据缓存同步到磁盘(快,持久化没保证)  
# always:同步持久化,每次发生数据变更时,立即记录到磁盘(慢,安全)  
# everysec:表示每秒同步一次(默认值,很快,但可能会丢失一秒以内的数据) 
# 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. 
# 指定是否在后台aof文件rewrite期间调用fsync,默认为no,表示要调用fsync(无论后台是否有子进程在刷盘)。 
# Redis在后台写RDB文件或重写AOF文件期间会存在大量磁盘IO,此时,在某些linux系统中,调用fsync可能会阻塞。 
#如果应用系统无法忍受延迟,而可以容忍少量的数据丢失,则设置为yes。如果应用系统无法忍受数据丢失,则设置为no。 
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. 
#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AOF文件大小的增长率大于该配置项时自动开启重写。 
auto-aof-rewrite-percentage 100 
#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AOF文件大小大于该配置项时自动开启重写 
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. 
#redis在启动时可以加载被截断的AOF文件,而不需要先执行redis-check-aof 工具。 
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. 
#是否开启混合持久化 
aof-use-rdb-preamble yes 
 
################################ 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. 
#一个Lua脚本最长的执行时间,单位为毫秒,如果为0或负数表示无限执行时间 
lua-time-limit 5000 
 
################################ 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: 
# 是否开启cluster集群模式 如果配置yes则开启集群功能,此redis实例作为集群的一个节点,否则,它是一个普通的单一的redis实例。 
# 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. 
#虽然此配置的名字叫"集群配置文件",但是此配置文件不能人工编辑,它是集群节点自动维护的文件, 
#主要用于记录集群中有哪些节点、他们的状态以及一些持久化参数等,方便在重启时恢复这些状态。通常是在收到请求之后这个文件就会被更新。 
# 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. 
#这是集群中的节点能够失联的最大时间,超过这个时间,该节点就会被认为故障。如果主节点超过这个时间还是不可达,则用它的从节点将启动故障迁移,升级成主节点。 
# 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. 
#如果设置成0,则无论从节点与主节点失联多久,从节点都会尝试升级成主节点。 
#如果设置成正数,则cluster-node-timeout乘以cluster-slave-validity-factor得到的时间,是从节点与主节点失联后, 
#此从节点数据有效的最长时间,超过这个时间,从节点不会启动故障迁移。 
#假设cluster-node-timeout=5,cluster-slave-validity-factor=10,则如果从节点跟主节点失联超过50秒,此从节点不能成为主节点。 
#注意,如果此参数配置为非0,将可能出现由于某主节点失联却没有从节点能顶上的情况,从而导致集群不能正常工作, 
#在这种情况下,只有等到原来的主节点重新回归到集群,集群才恢复运作。 
# 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. 
#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。 
#不建议设置为0 
#想禁用可以设置一个非常大的值 
#如果小于0则启动失败 
# 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. 
# 表示当负责一个插槽的主库下线且没有相应的从库进行故障恢复时,是否整个集群不可用? 
# 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 
 
################################## 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 128 
 
################################ LATENCY MONITOR ############################## 
 
# The Redis latency monitoring subsystem samples different operations 
# at runtime in order to collect data related to possible sources of 
# latency of a Redis instance. 
# 
# Via the LATENCY command this information is available to the user that can 
# print graphs and obtain reports. 
# 
# The system only logs operations that were performed in a time equal or 
# greater than the amount of milliseconds specified via the 
# latency-monitor-threshold configuration directive. When its value is set 
# to zero, the latency monitor is turned off. 
# 
# By default latency monitoring is disabled since it is mostly not needed 
# if you don't have latency issues, and collecting data has a performance 
# impact, that while very small, can be measured under big load. Latency 
# monitoring can easily be enabled at runtime using the command 
# "CONFIG SET latency-monitor-threshold <milliseconds>" if needed. 
latency-monitor-threshold 0 
 
############################# EVENT NOTIFICATION ############################## 
 
# Redis can notify Pub/Sub clients about events happening in the key space. 
# This feature is documented at http://redis.io/topics/notifications 
# 
# For instance if keyspace events notification is enabled, and a client 
# performs a DEL operation on key "foo" stored in the Database 0, two 
# messages will be published via Pub/Sub: 
# 
# PUBLISH [email protected]__:foo del 
# PUBLISH [email protected]__:del foo 
# 
# It is possible to select the events that Redis will notify among a set 
# of classes. Every class is identified by a single character: 
# 
# K Keyspace events, published with __keyspace@<db>__ prefix. 
# E Keyevent events, published with __keyevent@<db>__ prefix. 
# g Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ... 
# $ String commands 
# l List commands 
# s Set commands 
# h Hash commands 
# z Sorted set commands 
# x Expired events (events generated every time a key expires) 
# e Evicted events (events generated when a key is evicted for maxmemory) 
# A Alias for g$lshzxe, so that the "AKE" string means all the events. 
# 
# The "notify-keyspace-events" takes as argument a string that is composed 
# of zero or multiple characters. The empty string means that notifications 
# are disabled. 
# 
# Example: to enable list and generic events, from the point of view of the 
# event name, use: 
# 
# notify-keyspace-events Elg 
# 
# Example 2: to get the stream of the expired keys subscribing to channel 
# name [email protected]__:expired use: 
# 
# notify-keyspace-events Ex 
# 
# By default all notifications are disabled because most users don't need 
# this feature and the feature has some overhead. Note that if you don't 
# specify at least one of K or E, no events will be delivered. 
notify-keyspace-events "" 
 
############################### ADVANCED CONFIG ############################### 
 
# Hashes are encoded using a memory efficient data structure when they have a 
# small number of entries, and the biggest entry does not exceed a given 
# threshold. These thresholds can be configured using the following directives. 
hash-max-ziplist-entries 512 
hash-max-ziplist-value 64 
 
# Lists are also encoded in a special way to save a lot of space. 
# The number of entries allowed per internal list node can be specified 
# as a fixed maximum size or a maximum number of elements. 
# For a fixed maximum size, use -5 through -1, meaning: 
# -5: max size: 64 Kb <-- not recommended for normal workloads 
# -4: max size: 32 Kb <-- not recommended 
# -3: max size: 16 Kb <-- probably not recommended 
# -2: max size: 8 Kb <-- good 
# -1: max size: 4 Kb <-- good 
# Positive numbers mean store up to _exactly_ that number of elements 
# per list node. 
# The highest performing option is usually -2 (8 Kb size) or -1 (4 Kb size), 
# but if your use case is unique, adjust the settings as necessary. 
list-max-ziplist-size -2 
 
# Lists may also be compressed. 
# Compress depth is the number of quicklist ziplist nodes from *each* side of 
# the list to *exclude* from compression. The head and tail of the list 
# are always uncompressed for fast push/pop operations. Settings are: 
# 0: disable all list compression 
# 1: depth 1 means "don't start compressing until after 1 node into the list, 
# going from either the head or tail" 
# So: [head]->node->node->...->node->[tail] 
# [head], [tail] will always be uncompressed; inner nodes will compress. 
# 2: [head]->[next]->node->node->...->node->[prev]->[tail] 
# 2 here means: don't compress head or head->next or tail->prev or tail, 
# but compress all nodes between them. 
# 3: [head]->[next]->[next]->node->node->...->node->[prev]->[prev]->[tail] 
# etc. 
list-compress-depth 0 
 
# Sets have a special encoding in just one case: when a set is composed 
# of just strings that happen 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 
 
# HyperLogLog sparse representation bytes limit. The limit includes the 
# 16 bytes header. When an HyperLogLog using the sparse representation crosses 
# this limit, it is converted into the dense representation. 
# 
# A value greater than 16000 is totally useless, since at that point the 
# dense representation is more memory efficient. 
# 
# The suggested value is ~ 3000 in order to have the benefits of 
# the space efficient encoding without slowing down too much PFADD, 
# which is O(N) with the sparse encoding. The value can be raised to 
# ~ 10000 when CPU is not a concern, but space is, and the data set is 
# composed of many HyperLogLogs with cardinality in the 0 - 15000 range. 
hll-sparse-max-bytes 3000 
 
# Streams macro node max size / items. The stream data structure is a radix 
# tree of big nodes that encode multiple items inside. Using this configuration 
# it is possible to configure how big a single node can be in bytes, and the 
# maximum number of items it may contain before switching to a new node when 
# appending new stream entries. If any of the following settings are set to 
# zero, the limit is ignored, so for instance it is possible to set just a 
# max entires limit by setting max-bytes to 0 and max-entries to the desired 
# value. 
stream-node-max-bytes 4096 
stream-node-max-entries 100 
 
# 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 a hash table 
# that is rehashing, 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 
# actively rehash 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 from 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 
 
# The client output buffer limits can be used to force disconnection of clients 
# that are not reading data from the server fast enough for some reason (a 
# common reason is that a Pub/Sub client can't consume messages as fast as the 
# publisher can produce them). 
# 
# The limit can be set differently for the three different classes of clients: 
# 
# normal -> normal clients including MONITOR clients 
# replica -> replica clients 
# pubsub -> clients subscribed to at least one pubsub channel or pattern 
# 
# The syntax of every client-output-buffer-limit directive is the following: 
# 
# client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds> 
# 
# A client is immediately disconnected once the hard limit is reached, or if 
# the soft limit is reached and remains reached for the specified number of 
# seconds (continuously). 
# So for instance if the hard limit is 32 megabytes and the soft limit is 
# 16 megabytes / 10 seconds, the client will get disconnected immediately 
# if the size of the output buffers reach 32 megabytes, but will also get 
# disconnected if the client reaches 16 megabytes and continuously overcomes 
# the limit for 10 seconds. 
# 
# By default normal clients are not limited because they don't receive data 
# without asking (in a push way), but just after a request, so only 
# asynchronous clients may create a scenario where data is requested faster 
# than it can read. 
# 
# Instead there is a default limit for pubsub and replica clients, since 
# subscribers and replicas receive data in a push fashion. 
# 
# Both the hard or the soft limit can be disabled by setting them to zero. 
client-output-buffer-limit normal 0 0 0 
client-output-buffer-limit replica 256mb 64mb 60 
client-output-buffer-limit pubsub 32mb 8mb 60 
 
# Client query buffers accumulate new commands. They are limited to a fixed 
# amount by default in order to avoid that a protocol desynchronization (for 
# instance due to a bug in the client) will lead to unbound memory usage in 
# the query buffer. However you can configure it here if you have very special 
# needs, such us huge multi/exec requests or alike. 
# 
# client-query-buffer-limit 1gb 
 
# In the Redis protocol, bulk requests, that are, elements representing single 
# strings, are normally limited ot 512 mb. However you can change this limit 
# here. 
# 
# proto-max-bulk-len 512mb 
 
# Redis calls an internal function to perform many background tasks, like 
# closing connections of clients in timeout, purging expired keys that are 
# never requested, and so forth. 
# 
# Not all tasks are performed with the same frequency, but Redis checks for 
# tasks to perform according to the specified "hz" value. 
# 
# By default "hz" is set to 10. Raising the value will use more CPU when 
# Redis is idle, but at the same time will make Redis more responsive when 
# there are many keys expiring at the same time, and timeouts may be 
# handled with more precision. 
# 
# The range is between 1 and 500, however a value over 100 is usually not 
# a good idea. Most users should use the default of 10 and raise this up to 
# 100 only in environments where very low latency is required. 
hz 10 
 
# Normally it is useful to have an HZ value which is proportional to the 
# number of clients connected. This is useful in order, for instance, to 
# avoid too many clients are processed for each background task invocation 
# in order to avoid latency spikes. 
# 
# Since the default HZ value by default is conservatively set to 10, Redis 
# offers, and enables by default, the ability to use an adaptive HZ value 
# which will temporary raise when there are many connected clients. 
# 
# When dynamic HZ is enabled, the actual configured HZ will be used as 
# as a baseline, but multiples of the configured HZ value will be actually 
# used as needed once more clients are connected. In this way an idle 
# instance will use very little CPU time while a busy instance will be 
# more responsive. 
dynamic-hz yes 
 
# When a child rewrites the AOF file, if the following option is enabled 
# the file will be fsync-ed every 32 MB of data generated. This is useful 
# in order to commit the file to the disk more incrementally and avoid 
# big latency spikes. 
aof-rewrite-incremental-fsync yes 
 
# When redis saves RDB file, if the following option is enabled 
# the file will be fsync-ed every 32 MB of data generated. This is useful 
# in order to commit the file to the disk more incrementally and avoid 
# big latency spikes. 
rdb-save-incremental-fsync yes 
 
# Redis LFU eviction (see maxmemory setting) can be tuned. However it is a good 
# idea to start with the default settings and only change them after investigating 
# how to improve the performances and how the keys LFU change over time, which 
# is possible to inspect via the OBJECT FREQ command. 
# 
# There are two tunable parameters in the Redis LFU implementation: the 
# counter logarithm factor and the counter decay time. It is important to 
# understand what the two parameters mean before changing them. 
# 
# The LFU counter is just 8 bits per key, it's maximum value is 255, so Redis 
# uses a probabilistic increment with logarithmic behavior. Given the value 
# of the old counter, when a key is accessed, the counter is incremented in 
# this way: 
# 
# 1. A random number R between 0 and 1 is extracted. 
# 2. A probability P is calculated as 1/(old_value*lfu_log_factor+1). 
# 3. The counter is incremented only if R < P. 
# 
# The default lfu-log-factor is 10. This is a table of how the frequency 
# counter changes with a different number of accesses with different 
# logarithmic factors: 
# 
# +--------+------------+------------+------------+------------+------------+ 
# | factor | 100 hits | 1000 hits | 100K hits | 1M hits | 10M hits | 
# +--------+------------+------------+------------+------------+------------+ 
# | 0 | 104 | 255 | 255 | 255 | 255 | 
# +--------+------------+------------+------------+------------+------------+ 
# | 1 | 18 | 49 | 255 | 255 | 255 | 
# +--------+------------+------------+------------+------------+------------+ 
# | 10 | 10 | 18 | 142 | 255 | 255 | 
# +--------+------------+------------+------------+------------+------------+ 
# | 100 | 8 | 11 | 49 | 143 | 255 | 
# +--------+------------+------------+------------+------------+------------+ 
# 
# NOTE: The above table was obtained by running the following commands: 
# 
# redis-benchmark -n 1000000 incr foo 
# redis-cli object freq foo 
# 
# NOTE 2: The counter initial value is 5 in order to give new objects a chance 
# to accumulate hits. 
# 
# The counter decay time is the time, in minutes, that must elapse in order 
# for the key counter to be divided by two (or decremented if it has a value 
# less <= 10). 
# 
# The default value for the lfu-decay-time is 1. A Special value of 0 means to 
# decay the counter every time it happens to be scanned. 
# 
# lfu-log-factor 10 
# lfu-decay-time 1 
 
########################### ACTIVE DEFRAGMENTATION ####################### 
# 
# WARNING THIS FEATURE IS EXPERIMENTAL. However it was stress tested 
# even in production and manually tested by multiple engineers for some 
# time. 
# 
# What is active defragmentation? 
# ------------------------------- 
# 
# Active (online) defragmentation allows a Redis server to compact the 
# spaces left between small allocations and deallocations of data in memory, 
# thus allowing to reclaim back memory. 
# 
# Fragmentation is a natural process that happens with every allocator (but 
# less so with Jemalloc, fortunately) and certain workloads. Normally a server 
# restart is needed in order to lower the fragmentation, or at least to flush 
# away all the data and create it again. However thanks to this feature 
# implemented by Oran Agra for Redis 4.0 this process can happen at runtime 
# in an "hot" way, while the server is running. 
# 
# Basically when the fragmentation is over a certain level (see the 
# configuration options below) Redis will start to create new copies of the 
# values in contiguous memory regions by exploiting certain specific Jemalloc 
# features (in order to understand if an allocation is causing fragmentation 
# and to allocate it in a better place), and at the same time, will release the 
# old copies of the data. This process, repeated incrementally for all the keys 
# will cause the fragmentation to drop back to normal values. 
# 
# Important things to understand: 
# 
# 1. This feature is disabled by default, and only works if you compiled Redis 
# to use the copy of Jemalloc we ship with the source code of Redis. 
# This is the default with Linux builds. 
# 
# 2. You never need to enable this feature if you don't have fragmentation 
# issues. 
# 
# 3. Once you experience fragmentation, you can enable this feature when 
# needed with the command "CONFIG SET activedefrag yes". 
# 
# The configuration parameters are able to fine tune the behavior of the 
# defragmentation process. If you are not sure about what they mean it is 
# a good idea to leave the defaults untouched. 
 
# Enabled active defragmentation 
# activedefrag yes 
 
# Minimum amount of fragmentation waste to start active defrag 
# active-defrag-ignore-bytes 100mb 
 
# Minimum percentage of fragmentation to start active defrag 
# active-defrag-threshold-lower 10 
 
# Maximum percentage of fragmentation at which we use maximum effort 
# active-defrag-threshold-upper 100 
 
# Minimal effort for defrag in CPU percentage 
# active-defrag-cycle-min 5 
 
# Maximal effort for defrag in CPU percentage 
# active-defrag-cycle-max 75 
 
# Maximum number of set/hash/zset/list fields that will be processed from 
# the main dictionary scan 
# active-defrag-max-scan-fields 1000
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