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Redis学习笔记(四)——redis配置文件详解


一、前言

之前几篇文章给大家介绍了Redis的安装及基本操作命令,初步介绍了Redis的基本配置,讲解较浅,所以这次专门写一篇关于Redis的配置文件详解文章。

二、 配置文件详解

  • Redis配置文件默认是安装目录下的redis.conf,如果不想破坏原出厂默认配置,可以将配置文件copy一份到其他目录(建议),本次以5.0.5版本为例。

2.1 总览

先总览一下配置文件的构成

# 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:
#
# 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 ###################################
...
################################## MODULES #####################################
...
################################## NETWORK #####################################
...
################################# GENERAL #####################################
...
################################ SNAPSHOTTING  ################################
...
################################# REPLICATION #################################
...
################################## SECURITY ###################################
...
################################### CLIENTS ####################################
...
############################## MEMORY MANAGEMENT ################################
...
############################# LAZY FREEING ####################################
...
############################## APPEND ONLY MODE ###############################
...
################################ LUA SCRIPTING  ###############################
...
################################ REDIS CLUSTER  ###############################
...
########################## CLUSTER DOCKER/NAT support  ########################
...
################################## SLOW LOG ###################################
...
################################ LATENCY MONITOR ##############################
...
############################# EVENT NOTIFICATION ##############################
...
############################### ADVANCED CONFIG ###############################
...
########################### ACTIVE DEFRAGMENTATION #######################
...

配置文件主要包含以上20个区域(具体内容省略号展示),接下来将对每一块的配置区域进行详解。

2.2 配置区域块详解

2.2.1 开头

# 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:
#
# 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.

该区域主要介绍了两部分内容

  • Redis启动应该指定配置文件,格式如下

    ./redis-server 配置文件地址
    
  • 内存大小说明:

    • 单位不区分大小写
    • 注意1k1kb的区别

2.2.2 核心配置

2.2.2.1 INCLUDES

外部引用配置文件的配置

################################## 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

翻译一下就是:

  • 可以定制一套可用于所有Redis服务器的标准配置模板,通过在此处引用,同时在下面自定义自己的配置(Redis始终使用最后的处理作为配置指令的值

  • 如果想要使用include覆盖配置选项,则最好使用include作为最后一行。

  • 写法

    include /path/to/base.conf
    include /path/to/other.conf
    

2.2.2.2 MODULES

模块配置

################################## 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
  • Redis 4.0之后引入的配置
  • 可以自定义扩展 redis 的模块,比如可以自定义数据结构类型等
  • 具体参考以下官方介绍文档

2.2.2.3 NETWORK

网络连接配置

################################## 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 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.
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 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.
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
  • bind:绑定redis服务器网卡IP
    • 默认为127.0.0.1
    • 如果配置IP地址,表示只接收来自于该IP地址的请求
    • 如果不配置,则表示接受所有来自于可用网络接口的连接
  • protected-mode:是否开启保护模式
    • 默认开启
    • 如果配置里面没有配置bind和密码,开启该参数,Redis会拒绝外部访问,只允许内容访问
    • 如果配置了bind和密码,建议关闭
  • port:端口号,默认为6379(开启单个Redis时不建议修改)
  • tcp-backlog:TCP连接中已完成队列(完成三次握手之后)的长度
    • 默认为511
  • timeout:客户端空闲超时时间,超过此时间服务器将会断开连接
    • 默认为0,代表服务端不会主动断开连接
    • 大于等于0
  • tcp-keepalive: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
    • 默认300,单位为秒
    • 如果设置为0,则不会周期性的检测

2.2.2.4 GENERAL

通用配置区域

################################# 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 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.
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_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)
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
  • daemonize:是否在后台执行
    • 默认为no
    • yes表示将以守护进程的方式启动,即后台启动
  • supervised:是否配置upstart或者systemd来管理Redis服务器
    • 默认为no:没有监督互动
    • upstart :通过将Redis置于SIGSTOP模式来启动信号
    • systemd :通过将READY = 1写入$ NOTIFY_SOCKET来产生信号
    • auto :基于UPSTART_JOB或NOTIFY_SOCKET环境变量来选择upstart或systemd
  • pidfile:redis的进程文件
    • 默认为/var/run/redis_6379.pid
    • 当redis作为守护进程运行的时候,它会把 pid 默认写到配置指定的文件里面
  • loglevel:日志等级
    • notice(默认):适当的日志级别,适合生产环境
    • debug:记录大量日志信息,适用于开发、测试阶段
    • verbose:许多有用的信息,但是没有debug级别信息多
    • warning:仅有部分重要、关键信息才会被记录
  • logfile:指定了记录日志的文件
    • 默认配置为空字符串,表示日志会打印到标准输出设备/dev/null
  • syslog-enabled:是否开启记录syslog功能,默认关闭
  • syslog-ident:syslog的标识符,默认为redis
  • syslog-facility:日志的来源、设备
  • databases:数据库的数目
    • 默认为16,默认的数据库为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
  • always-show-logo:启动日志中是否显示redis logo,默认显示

2.2.2.5 SNAPSHOTTING

持久化配置(RDB方式)

################################ 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.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 ./
  • save:配置触发 Redis的持久化条件
    • 配置格式:save <指定时间间隔> <执行指定次数更新操作>
      • 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
    • 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 ""
  • stop-writes-on-bgsave-error:当RDB持久化出现错误后,是否依然进行继续进行工作,默认值为yes
  • rdbcompression:配置存储至本地数据库时是否压缩数据
    • 默认为yes,redis会采用LZF算法进行压缩。
    • 设置为no可以减少CPU的消耗(不明显),但是持久化后的快照会比较大,所以建议开启
  • rdbchecksum:是否校验rdb文件
    • 默认是yes,redis会使用CRC64算法来进行数据校验,但是会有10%的性能消耗
    • 如果对性能有要求的话,可以设置为no
  • dbfilename:设置快照的文件名,默认是 dump.rdb
  • dir:设置快照文件的存放路径
    • 改配置为目录,非文件,它会使用dbfilename作为文件名

2.2.2.6 REPLICATION

复制配置

################################# 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
  • replicaof :配置master的ip和端口
  • masterauth:配置master密码(如果master设置了密码)
  • replica-serve-stale-data: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
    • yes(默认):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
    • 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
  • replica-read-only:配置Redis的Slave实例是否只读
    • 默认为yes:表示只读
    • no:允许写(不建议)
  • 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
    • 目前redis复制提供两种方式,disk和socket
      • disk:disk方式是master创建一个新的进程把rdb文件保存到磁盘,再把磁盘上的rdb文件传递给slave;当一个rdb保存的过程中,多个slave都能共享这个rdb文件
      • socket(默认):socket是master创建一个新的进程,直接把rdb文件以socket的方式发给slave
      • 在磁盘速度缓慢,网速快的情况下推荐用socket方式
  • repl-diskless-sync-delay:diskless复制的延迟时间
    • 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。
  • repl-ping-replica-period:slave根据指定的时间间隔向服务器发送ping请求
  • repl-timeout:复制连接超时时间
    • master和slave都有超时时间的设置。
      • master检测到slave上次发送的时间超过repl-timeout,即认为slave离线,清除该slave信息。
      • slave检测到上次和master交互的时间超过repl-timeout,则认为master离线。
    • 需要注意的是repl-timeout需要设置一个比repl-ping-slave-period更大的值,不然会经常检测到超时
  • repl-disable-tcp-nodelay:是否禁止复制tcp链接的tcp nodelay参数
    • 默认是no,即使用tcp nodelay。
    • 如果设置了yes来禁止tcp nodelay设置,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
    • 默认我们推荐更小的延迟,但是在数据量传输很大的场景下,建议选择yes
  • repl-backlog-size:复制缓冲区大小
    • 默认1m
    • 这是一个环形复制缓冲区,用来保存最新复制的命令。这样在slave离线的时候,不需要完全复制master的数据,如果可以执行部分同步,只需要把缓冲区的部分数据复制给slave,就能恢复正常复制状态
    • 缓冲区的大小越大,slave离线的时间可以更长,复制缓冲区只有在有slave连接的时候才分配内存
    • 没有slave的一段时间,内存会被释放出来
  • repl-backlog-ttl:master没有slave一段时间会释放复制缓冲区的内存,repl-backlog-ttl用来设置该时间长度。默认为3600,单位为秒。
  • replica-priority:当master不可用,Sentinel会根据slave的优先级选举一个master。最低的优先级的slave,当选master。而配置成0,永远不会被选举。
  • min-replicas-to-write:redis提供了可以让master停止写入的方式,如果配置了min-replicas-to-write,健康的slave的个数小于N,mater就禁止写入。master最少得有多少个健康的slave存活才能执行写命令。这个配置虽然不能保证N个slave都一定能接收到master的写操作,但是能避免没有足够健康的slave的时候,master不能写入来避免数据丢失。设置为0是关闭该功能。
  • min-replicas-max-lag:延迟小于min-replicas-max-lag秒的slave才认为是健康的slave

2.2.2.7 SECURITY

安全配置

################################## SECURITY ###################################

# Require clients to issue AUTH <PASSWORD> before processing any other
# commands.  This might be useful in environments in which you do not trust
# others with access to the host running redis-server.
#
# This should stay commented out for backward compatibility and because most
# people do not need auth (e.g. they run their own servers).
#
# Warning: since Redis is pretty fast an outside user can try up to
# 150k passwords per second against a good box. This means that you should
# use a very strong password otherwise it will be very easy to break.
#
# requirepass foobared

# 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.
  • requirepass:设置用户使用AUTH命令来认证密码
    • 为了保持向后的兼容性,可以注释该命令,因为大部分用户也不需要认证。
    • 使用requirepass的时候需要注意,因为redis太快了,每秒可以认证15w次密码,简单的密码很容易被攻破,所以最好使用一个更复杂的密码
  • 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)等,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,禁用写法rename-command FLUSHALL "";也可以保留命令但是不能轻易使用,即重命名命令,例:rename-command FLUSHALL abcdefg,这样服务器重启后就会使用这些新命令,否则就会报错unknown command

2.2.2.8 CLIENTS

客户端配置

################################### 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
  • 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
    • 如果设置 maxclients为0 ,表示不作限制。
    • 最小建议设置到32
    • 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

2.2.2.9 MEMORY MANAGEMENT

内存管理配置

############################## 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
  • maxmemory:redis配置的最大内存容量
    • 当内存满了,需要配合maxmemory-policy策略进行处理。
    • 注意slave的输出缓冲区是不计算在maxmemory内的。所以为了防止主机内存使用完,建议设置的maxmemory需要更小一些
  • maxmemory-policy:当内存使用达到最大值时,redis使用的清楚策略
    • 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(默认):不移除任何key,只是返回一个写错误
  • maxmemory-samples:lru检测的样本数,使用lru或者ttl淘汰算法,从需要淘汰的列表中随机选择sample个key,选出闲置时间最长的key移除
  • replica-ignore-maxmemory:是否开启salve的最大内存

2.2.2.10 LAZY FREEING

延迟释放配置

  • 当删除键的时候,redis提供异步延时释放key内存的功能,把key释放操作放在bio(Background I/O)单独的子线程处理中,减少删除big key对redis主线程的阻塞。有效地避免删除big key带来的性能和可用性问题
  • 在redis4.0前,没有lazy free功能;DBA只能通过取巧的方法,类似scan big key,每次删除100个元素;但在面对“被动”删除键的场景,这种取巧的删除就无能为力。例如:我们生产Redis Cluster大集群,业务缓慢地写入一个带有TTL的2000多万个字段的Hash键,当这个键过期时,redis开始被动清理它时,导致redis被阻塞20多秒,当前分片主节点因20多秒不能处理请求,并发生主库故障切换
############################# 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

2.2.2.11 APPEND ONLY MODE

持久化配置(AOF方式)

############################## 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
  • appendonly:是否开启AOF持久化
    • 默认为no,表示不开启aof
    • redis默认使用rdb方式来持久化,但是如果在save的过程中redis突然宕机,会导致几分钟的数据的丢失。
    • AOF(Append Only File):Redis会把每次写入的数据的操作命令都写入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。
  • appendfilename:aof文件名,默认是"appendonly.aof"
  • appendfsync:aof持久化策略的配置
    • everysec(默认):表示每秒执行一次fsync,可能会导致丢失这1s数据
    • always:表示每次写入都执行fsync,以保证数据同步到磁盘
    • no:不执行fsync,由操作系统保证数据同步到磁盘,速度最快
  • no-appendfsync-on-rewrite:rewrite期间对新写操作是否持久化同步
    • 默认为no,即做持久化同步,对于持久化特性来说这是更安全的选择,但是在aof重写或者写入rdb文件的时候,会执行大量IO,尤其对于everysec和always的aof模式来说,执行fsync会造成阻塞过长时间
    • 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,即如果有子进程在进行保存操作,那么Redis就处于"不可同步"的状态。
    • 如果对延迟要求很高的应用,这个字段可以设置为yes(Linux的默认fsync策略是30秒。可能丢失30秒数据)
  • auto-aof-rewrite-percentage:aof自动重写配置,即当目前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。
    • 默认为100,,即当前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。
  • auto-aof-rewrite-min-size: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
  • aof-load-truncated
    • 默认为yes
    • 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。
  • aof-use-rdb-preamble:是否开启混合持久化
    • 默认开启
    • redis保证RDB转储跟AOF重写不会同时进行
    • 当redis启动时,即便RDB和AOF持久化同时启用且AOF,RDB文件都存在,则redis总是会先加载AOF文件,这是因为AOF文件被认为能够更好的保证数据一致性
    • 当加载AOF文件时,如果启用了混合持久化,那么redis将首先检查AOF文件的前缀,如果前缀字符是REDIS,那么该AOF文件就是混合格式的,redis服务器会先加载RDB部分,然后再加载AOF部分

2.2.3 其余配置

2.2.3.1 LUA SCRIPTING

LUA脚本配置

################################ 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
  • lua-time-limit:一个lua脚本执行的最大时间,单位为ms。默认值为5000

2.2.3.2 REDIS CLUSTER

集群配置

################################ REDIS CLUSTER  ###############################

# 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
  • cluster-enabled:集群开关,默认是不开启
  • 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。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
  • cluster-node-timeout:节点互连超时的阀值,单位毫秒数
  • cluster-replica-validity-factor: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:
      • 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
  • cluster-migration-barrier: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
  • 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。
  • cluster-replica-no-failover:设置为yes时,此选项可防止replicas在master发生故障时尝试对其主服务器进行故障转移。

2.2.3.3 CLUSTER DOCKER/NAT support

Docker集群配置

########################## 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
  • cluster-announce-ip:集群公告ip
  • cluster-announce-port:集群公告端口
  • cluster-announce-bus-port:集群公告总线端口

2.2.3.4 SLOW LOG

慢查询日志配置:用来记录redis运行中执行比较慢的命令耗时,当命令的执行超过了指定时间,就记录在slow log中,slog log保存在内存中,所以没有IO操作

################################## 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
  • slowlog-log-slower-than
    • 执行时间比slowlog-log-slower-than大的请求记录到slowlog里面,单位是微秒,所以1000000就是1秒。
    • 负数时间会禁用慢查询日志,
    • 0则会强制记录所有命令
  • slowlog-max-len:慢查询日志长度
    • 当一个新的命令被写进日志的时候,最老的那个记录会被删掉。
    • 这个长度没有限制,只要有足够的内存就行。
    • 可以通过SLOWLOG RESET来释放内存

2.2.3.5 LATENCY MONITOR

延时监控配置:用来监控redis中执行比较缓慢的一些操作,用LATENCY打印redis实例在跑命令时的耗时图表

################################ 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
  • latency-monitor-threshold:记录执行时间大于或等于预定时间(毫秒)的操作
    • 默认为0:表示不记录,即关闭监控
    • 可以通过CONFIG SET命令动态设置

2.2.3.6 EVENT NOTIFICATION

事件通知配置:客户端可以通过订阅频道或模式,来接收那些以某种方式改动了 Redis 数据集的事件

############################# 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 __keyspace@0__:foo del
# PUBLISH __keyevent@0__: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 __keyevent@0__: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 ""
  • notify-keyspace-events:默认为“”,表示关闭(因为开启键空间通知功能需要消耗一些 CPU ,所以在默认配置下,该功能处于关闭状态)。

2.2.3.7 ADVANCED CONFIG

内部数据结构配置

############################### 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
  • hash-max-ziplist-entries:数据量小于等于hash-max-ziplist-entries的用ziplist,大于hash-max-ziplist-entries用hash
  • hash-max-ziplist-value:value大小小于等于hash-max-ziplist-value的用ziplist,大于hash-max-ziplist-value用hash
  • list-max-ziplist-size:当取正值的时候,表示按照数据项个数来限定每个quicklist节点上的ziplist长度;当取负值的时候,表示按照占用字节数来限定每个quicklist节点上的ziplist长度
    • -5:最大大小:64 KB<--不建议用于正常工作负载
    • -4:最大大小:32 KB<--不推荐
    • -3:最大大小:16 KB<--可能不推荐
    • -2:最大大小:8kb<--良好
    • -1:最大大小:4kb<--良好
  • list-compress-depth:表示一个quicklist两端不被压缩的节点个数(这里的节点个数是指quicklist双向链表的节点个数,而不是指ziplist里面的数据项个数)
    • 0(默认值): 是个特殊值,表示都不压缩。
    • 1: 表示quicklist两端各有1个节点不压缩,中间的节点压缩。
    • 2: 表示quicklist两端各有2个节点不压缩,中间的节点压缩。
    • 3: 表示quicklist两端各有3个节点不压缩,中间的节点压缩。
  • set-max-intset-entries:数据量小于等于set-max-intset-entries用iniset,大于set-max-intset-entries用set
  • zset-max-ziplist-entries:数据量小于等于zset-max-ziplist-entries用ziplist,大于zset-max-ziplist-entries用zset
  • zset-max-ziplist-value:value大小小于等于zset-max-ziplist-value用ziplist,大于zset-max-ziplist-value用zset
  • hll-sparse-max-bytes:value大小小于等于hll-sparse-max-bytes使用稀疏数据结构(sparse),大于hll-sparse-max-bytes使用稠密的数据结构(dense)
  • stream-node-max-bytes:每个宏节点(Macro Node)能够占用的最大字节数
  • stream-node-max-entries:每个宏节点中可存储条目的最大数量
  • activerehashing:启用哈希刷新,每100个CPU毫秒会拿出1个毫秒来刷新Redis的主哈希表(顶级键值映射表)
    • 当你的使用场景中,有非常严格的实时性需要,不能够接受Redis时不时的对请求有2毫秒的延迟的话,把这项配置为no。
    • 如果没有这么严格的实时性要求,可以设置为yes,以便能够尽可能快的释放内存
  • client-output-buffer-limit:客户端的输出缓冲区的限制,可用于强制断开那些因为某种原因从服务器读取数据的速度不够快的客户端
    • normal 0 0 0:第一个0表示取消hard limit,第二个0和第三个0表示取消soft limit,normal client
    • replica 256mb 64mb 60:如果client-output-buffer一旦超过256mb,又或者超过64mb持续60秒,那么服务器就会立即断开客户端连接
    • 如果client-output-buffer一旦超过32mb,又或者超过8mb持续60秒,那么服务器就会立即断开客户端连接pubsub 32mb 8mb 60:
  • client-query-buffer-limit:客户端查询的缓存极限值大小
  • proto-max-bulk-len:在redis协议中,批量请求,即表示单个字符串,通常限制为512 MB,可修改
  • hz:redis执行任务的频率为1s除以hz
  • dynamic-hz:开启动态hz
    • 当启用动态赫兹时,实际配置的赫兹将用作作为基线,但实际配置的赫兹值的倍数在连接更多客户端后根据需要使用。这样一个闲置的实例将占用很少的CPU时间,而繁忙的实例将反应更灵敏
  • aof-rewrite-incremental-fsync:在aof重写的时候,如果打开了aof-rewrite-incremental-fsync开关,系统会每32MB执行一次fsync。这对于把文件写入磁盘是有帮助的,可以避免过大的延迟峰值
  • rdb-save-incremental-fsync:在rdb保存的时候,如果打开了rdb-save-incremental-fsync开关,系统会每32MB执行一次fsync
  • lfu-log-factor:计数器对数因子
  • lfu-decay-time:计数器衰减时间

2.2.3.8 ACTIVE DEFRAGMENTATION

碎片整理配置

########################### 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
  • activedefrag:是否启用主动碎片整理
  • active-defrag-ignore-bytes:启动活动碎片整理的最小碎片浪费量
  • active-defrag-threshold-lower:启动碎片整理的最小碎片百分比
  • active-defrag-threshold-upper:使用最大消耗时的最大碎片百分比
  • active-defrag-cycle-min:在CPU百分比中进行碎片整理的最小消耗
  • active-defrag-cycle-max:在CPU百分比中进行碎片整理的最大消耗
  • active-defrag-max-scan-fields:将从主字典扫描处理的最大set / hash / zset / list字段数

参考

Redis
NoSQL
  • 作者:贤子磊
  • 发表时间:2020-09-19 21:57
  • 版权声明:自由转载-非商用-非衍生-保持署名
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