redis-5.0.4配置文件详解

目录

redis.conf

Redis configuration file example关注点:  

INCLUDES关注点:

 MODULES关注点:

NETWORK 关注点:

GENERAL 关注点:

SNAPSHOTTING  关注点：

REPLICATION 关注点：

SECURITY 关注点：

CLIENTS 关注点：

MEMORY MANAGEMENT关注点：

 LAZY FREEING 关注点：

APPEND ONLY MODE关注点：

LUA SCRIPTING关注点：

REDIS CLUSTER关注点：

CLUSTER DOCKER/NAT support关注点：

SLOW LOG关注点：

LATENCY MONITOR关注点：

EVENT NOTIFICATION关注点：

ADVANCED CONFIG关注点：

ACTIVE DEFRAGMENTATION关注点：

---

redis.conf

# 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.

Redis configuration file example关注点:  

1.redis的启动命令   ./redis-server /path/to/redis.conf         

2.当配置中需要配置内存大小时，可以使用 1k, 5GB, 4M 等类似的格式，其转换方式

 

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

INCLUDES关注点:

在此处包括一个或多个其他配置文件。如果你有一个标准的模板，它指向所有Redis服务器，但也需要自定义一些每服务器设置。包含文件可以包含其他文件，所以要明智地使用

注意选项“include”不会被命令“CONFIG REWRITE”重写来自管理员或Redis哨兵。因为Redis总是使用最后处理的行作为配置指令的值，最好将includes在该文件的开头，以避免在运行时覆盖配置更改

如果您对使用includes重写配置感兴趣选项，最好使用include作为最后一行。(没看懂,所以直接贴的百度翻译,在实践中也真的没有用到过这里...)

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

 MODULES关注点:

启动时加载模块。如果服务器无法加载模块它将中止。可以使用多个loadmodule指令。(同上...)

 

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

NETWORK 关注点:

1.bind 127.0.0.1 

指定redis只接收来自于该IP地址的请求，如果不进行设置，那么将处理所有请求(比如你在虚拟机里面安装redis设置成127.0.0.1,外部宿主机是无法访问的.我们自己玩的时候可以设置成0.0.0.0)

2. protected-mode yes 

 只有bind的ip可以访问你的redis

 protected-mode no 

任何都可以访问你的redis

3.port 6379   

访问redis的端口                 

如果指定了端口0,Redis将不会监听TCP套接字

4.tcp-backlog 511   

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。(https://www.cnblogs.com/z-books/p/7279218.html)

5.timeout 0     

 设置客户端连接时的超时时间，单位为秒。当客户端在这段时间内没有发出任何指令，那么关闭该连接
 0是关闭此设置

6.tcp-keepalive 300

表示服务器周期性的检测客户端健康状态,默认300秒

 

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

GENERAL 关注点:

1.daemonize no

默认是不允许后台运行的    可以改为yes就可以后台运行了

2.supervised no

可以通过upstart和systemd管理Redis守护进程
选项：
   supervised no - 没有监督互动
   supervised upstart - 通过将Redis置于SIGSTOP模式来启动信号
   supervised systemd - signal systemd将READY = 1写入$ NOTIFY_SOCKET
   supervised auto - 检测upstart或systemd方法基于 UPSTART_JOB或NOTIFY_SOCKET环境变量(https://www.cnblogs.com/pqchao/p/6558688.html)

3.pidfile /var/run/redis_6379.pid

pid文件的存储位置

4.loglevel notice

设置的日志级别(debug、verbose、notice、warning) 记录日志详细程度递减

5.logfile ""

日志文件的存储位置(是一个文件，文件不存在的情况下会自动创建，但是目录必须存在，不会自动创建) 

6.syslog-enabled no

要启用系统日志记录，只需将“syslog enabled”设置为yes，还可以选择更新其他syslog参数以满足您的需要。

7.databases 16
可用数据库数，默认值为16，默认使用的数据库为0，数据库范围在0-（database-1）之间

8.always-show-logo yes

是否显示logo(无聊的配置项。。。)

################################ SNAPSHOTTING  ################################
#
# Save the DB on disk:
#
#   save  
#
#   Will save the DB if both the given number of seconds and the given
#   number of write operations against the DB occurred.
#
#   In the example below the behaviour will be to save:
#   after 900 sec (15 min) if at least 1 key changed
#   after 300 sec (5 min) if at least 10 keys changed
#   after 60 sec if at least 10000 keys changed
#
#   Note: you can disable saving 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 ./

SNAPSHOTTING  关注点：

1.save    

save 900 1
save 300 10
save 60 10000

指出在多长时间内，有多少次更新操作，就将数据同步到数据文件rdb。
相当于条件触发抓取快照，这个可以多个条件配合
比如默认配置文件中的设置，就设置了三个条件
save 900 1  900秒内至少有1个key被改变
save 300 300秒内至少有300个key被改变
save 60 10000  60秒内至少有10000个key被改变

2.stop-writes-on-bgsave-error yes

  如果用户开启了RDB快照功能，那么在redis持久化数据到磁盘时如果出现失败，默认情况下，redis会停止接受所有的写请求。
  这样做的好处在于可以让用户很明确的知道内存中的数据和磁盘上的数据已经存在不一致了。
  如果redis不顾这种不一致，一意孤行的继续接收写请求，就可能会引起一些灾难性的后果。
  如果下一次RDB持久化成功，redis会自动恢复接受写请求。
  如果不在乎这种数据不一致或者有其他的手段发现和控制这种不一致的话，可以关闭这个功能，
  以便在快照写入失败时，也能确保redis继续接受新的写请求。(https://www.cnblogs.com/pqchao/p/6558688.html)

3.rdbcompression yes

存储至本地数据库时（持久化到rdb文件）是否压缩数据，默认为yes

4.rdbchecksum yes

持久化快照时，是否进行算法校验，开启后大概会降低10%左右性能消耗。

5.dbfilename dump.rdb

快照的文件名

6.dir ./

快照的本地持久化位置(注意此处是一个文件夹而不是一个文件)  

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

# 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 

# 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

REPLICATION 关注点：

1.replicaof   

配置主从模式redis   主节点ip  端口号

2.masterauth

如果主节点设置了密码的话，必须在开启此处配置，否则主节点拒绝访问

3.replica-serve-stale-data yes

当从节点slave失去与主节点master或者正在进行同步操作时，设置为yes 从节点会继续响应客户端请求。

设置为no 则不会响应客户端请求，而是返回"SYNC with master in progress" 

4.replica-read-only yes

是否开启副本只读  yes时，从节点只能读取数据，不能写入   默认此配置

5.repl-diskless-sync no

磁盘同步方式，也就是RDB文件从主服务器传输到副本的方式。传输可以通过两种不同的方式进行：磁盘复制和无磁盘复制

对于慢速磁盘和快速（大带宽）网络，无磁盘复制工作得更好。

默认 no  磁盘复制

6.repl-diskless-sync-delay 5

启用无盘复制后，可以配置服务器等待的延迟，以便生成通过套接字将RDB传输到副本的子项。延迟时间内可以等待更多的副本同时开始复制。延迟以秒为单位指定，默认情况下为5秒。要完全禁用它，只需将其设置为0秒，传输将尽快开始。

7.repl-ping-replica-period 10

从节点会定时向主节点发送ping请求，默认10秒

8.repl-timeout 60

确保该值大于repl-ping-replica-period，否则每次主副本和复制副本之间的通信量较低时都会检测到超时。一般不设超时时间

9.repl-disable-tcp-nodelay no

以下解释来自百度翻译>>>>>>>>>>>>>>>>>>>>>>>>>>>>

如果选择“是”，Redis将使用较少的TCP数据包和较少的带宽向副本发送数据。
但这可能会增加数据在副本端出现的延迟，对于使用默认配置的Linux内核，延迟可达40毫秒。

如果选择“否”，数据出现在副本端的延迟将减少，但复制将使用更多带宽。

默认情况下，我们会针对低延迟进行优化，但在流量非常大的情况下，
或者当主副本和副本之间的跳数很多时，将其设置为“是”可能是一个好主意。

10.repl-backlog-size 1mb

设置副本backlog 大小。acklog是一个缓冲区，当副本断开连接一段时间后，它会累积副本数据，因此当副本想要重新连接时，通常不需要完全重新同步，但是部分重新同步就足够了，只需传递副本在断开连接时丢失的数据部分。只有当至少连接了一个副本时，才会分配backlog。

11.repl-backlog-ttl 3600

在主服务器有一段时间没有连接副本后，将释放backlog。下面的选项配置从最后一个副本断开连接开始释放backlog缓冲区所需的秒数。值为0意味着永远不会释放backlog。

12.replica-priority 100

副本优先级，优先级别越低越有可能有限升级为主副本。但是设置为0的话将永远不会升级为主副本。默认为100.

13. min-replicas-to-write N
      min-replicas-max-lag M

如果连接的副本少于N个，且延迟小于或等于M秒，则主服务器可以停止接受写入。

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

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

SECURITY 关注点：

1.requirepass foobared

设置redis登录密码。警告：由于Redis非常快，外部用户可以尝试每秒15万个密码。这意味着你应该使用一个非常强的密码，否则很容易破解。所以说，设置密码基本没什么必要。

2.rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52

命令重命名。也可以通过将命令重命名为空字符串来禁用命令：rename-command CONFIG ""

请注意，更改登录到AOF文件或传输到副本的命令的名称可能会导致问题。

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

 

CLIENTS 关注点：

1.maxclients 10000

设置redis客户端最大连接数。一旦达到限制，redis将关闭所有新连接，并发送错误。

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

# 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

MEMORY MANAGEMENT关注点：

1.maxmemory

设置内存使用限制。简而言之。。。如果附加了副本，建议您设置一个较低的maxmemory的限制，以便系统上有一些可用的RAM用于复制输出缓冲区（但如果策略为“noeviction”，则不需要此缓冲区）。

2.maxmemory-policy noeviction

内存达到限制后的清除策略，共有五种（默认maxmemory-policy noeviction）：

volatile-lru -> 使用lru在设置了过期时间的数据中清除最久没有使用的数据
allkeys-lru -> 使用lru在所有数据中清除最久没有使用的数据
volatile-lfu -> 使用lfu在设置了过期时间的数据中清除使用频率最低的数据
allkeys-lfu -> 使用lfu在所有数据中清除使用评率最低的数据
volatile-random -> 在设置了过期时间的数据中随机清除数据
allkeys-random -> 在所有数据中随机清除数据
volatile-ttl -> 从设置了过期时间的数据中删除即将过期的数据
noeviction -> 不清除任何数据，在达到限制后返回错误

lru就是最近使用。lfu就是使用频率。注意：使用上述任何策略，当没有合适的密钥可收回时，Redis将在写操作时返回错误。

3.maxmemory-samples 5

LRU、LFU和最小TTL算法不是精确算法，而是近似算法（为了节省内存），因此可以调整速度或精度。默认情况下，Redis将检查五个键并选择最近使用较少的键，您可以使用以下配置指令更改样本大小。默认值5产生足够好的结果。10接近非常真实的LRU，但花费更多的CPU。3更快，但不太准确。

4.replica-ignore-maxmemory yes

以下来自百度翻译>>>>>>>>>>>>>>>>>>>>>>>>>>>

从Redis 5开始，默认情况下，复制副本将忽略其maxmemory设置（除非在故障转移后升级为master或手动）
。这意味着密钥的收回将由主服务器处理，将DEL命令作为主服务器端的密钥收回发送到副本。

此行为确保主副本和副本保持一致，并且通常是您所希望的，但是，如果您的副本是可写的，
或者您希望副本具有不同的内存设置，并且您确定对副本执行的所有写入都是等幂的，
则可以更改此默认值（但请确保了解您正在执行的操作）。

请注意，由于默认情况下副本不会退出，因此它可能会使用比通过maxmemory设置的内存更多的内存
（副本上可能有某些缓冲区更大，或者数据结构有时可能占用更多内存等等）。
因此，请确保监视复制副本，并确保它们有足够的内存，在主副本达到配置的maxmemory设置之前，
不会出现真正的内存不足情况。

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

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

 LAZY FREEING 关注点：

1.lazyfree-lazy-eviction no
lazyfree-lazy-expire no
lazyfree-lazy-server-del no
replica-lazy-flush no
这一块是redis阻塞删除和非阻塞删除的设置。我理解的不深。老样子>>>>>>>>>>>>>>>>>>>>>

Redis有两个原语用于删除键。一个称为DEL，是对对象的阻塞删除。这意味着服务器停止处理新命令，
 以便以同步方式回收与对象关联的所有内存。如果删除的键与一个小对象相关联，
 则执行DEL命令所需的时间非常短，与Redis中的大多数其他O（1）或O（log_N）命令相当。
 但是，如果密钥与包含数百万个元素的聚合值关联，则服务器可以阻塞很长时间（甚至几秒钟）以完成操作。

出于上述原因，Redis还提供了UNLINK（non-blocking DEL）等非阻塞删除原语以及FLUSHALL和FLUSHDB命令的异步选项，
以便在后台回收内存。这些命令在固定时间内执行。另一个线程将尽可能快地增量释放背景中的对象。

FLUSHALL和FLUSHDB的DEL、UNLINK和ASYNC选项都是用户控制的，这取决于应用程序的设计，
以了解何时使用它们是一个好主意。然而，Redis服务器有时不得不删除密钥或刷新整个数据库，这是其他操作的副作用。

具体来说，在以下情况下，Redis独立于用户调用删除对象：

1)在逐出时，由于maxmemory和maxmemory策略配置，为了在不超过指定内存限制的情况下为新数据腾出空间。

2)因为过期：必须从内存中删除具有相关生存时间的密钥（请参阅expire命令）。

3)由于命令的副作用，它将数据存储在可能已经存在的密钥上。例如，当旧的密钥内容被另一个密钥内容替换时，
    RENAME命令可能会删除它。类似的SunNoSt店或Stand带有Stand选项可以删除现有密钥。
    SET命令本身删除指定键的任何旧内容，以便用指定的字符串替换它

4)在复制过程中，当复制副本与其主服务器执行完全重新同步时，将删除整个数据库的内容，以便加载刚刚传输的RDB文件。

在上述所有情况下，默认情况是以阻塞的方式删除对象，就像调用DEL一样。但是，
 您可以使用以下配置指令，具体配置每种情况，以非阻塞方式释放内存，如调用UNLINK：

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.

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

APPEND ONLY MODE关注点：

1.appendonly no

是否开启AOF持久化。yes开启。no不开启。AOF和RDB可以同时开启。如果在启动时启用了AOF，Redis将加载AOF，即具有更好的持久性保证的文件。

2.appendfilename "appendonly.aof"

持久化文件的名字

3.# appendfsync always
      appendfsync everysec
   # appendfsync no

fsync（）调用告诉操作系统实际在磁盘上写入数据，而不是在输出缓冲区中等待更多数据。一些操作系统将真正刷新磁盘上的数据，一些其他操作系统将尝试尽快这样做。

Redis支持三种不同的模式：

no：不要fsync，只要让操作系统在需要的时候刷新数据就行了。更快。

 always：每次写入仅追加日志后fsync。慢点，最安全。

 everysec：每秒钟只同步一次。折中方案。

 默认的 "everysec" 通常来说能在速度和数据安全性之间取得比较好的平衡。

4.no-appendfsync-on-rewrite no

如果您有延迟问题，请将其设置为“yes”。否则，从耐久性的角度来看，这是最安全的选择。

5.auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb

关于自动重写AOF文件。将此基础大小与当前大小进行比较。如果当前大小是大于指定的百分比时，将触发重写。此外您需要为要重写的AOF文件指定最小大小，这对于避免重写AOF文件很有用，即使达到了百分比增长，但仍然很小。

auto-aof-rewrite-percentage 设置为0的时候将禁用此功能。

6.aof-load-truncated yes

此处指的是当redis启动时发现aof文件错误的话如何处理。当aof-load-truncated yes 时会加载没有被损坏的aof文件。

aof-load-truncated no 时redis会拒绝启动，用户需要在重新启动服务器之前使用“redis check AOF”实用程序修复AOF文件。

7.aof-use-rdb-preamble yes

此处说的是redis的混合加载，开启之后既能保证数据完整性又同时保证了加载数据文件的速度。加载Redis时，会识别出AOF文件以“Redis”字符串开头并加载前缀RDB文件，然后继续加载AOF尾部。

################################ 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 SCRIPTING关注点：

1.lua-time-limit 5000

lua脚本的最大运行时间。将其设置为0或负值，以便在没有警告的情况下无限执行

################################ REDIS CLUSTER  ###############################
#
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# WARNING EXPERIMENTAL: Redis Cluster is considered to be stable code, however
# in order to mark it as "mature" we need to wait for a non trivial percentage
# of users to deploy it in production.
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#
# Normal Redis instances can't be part of a Redis Cluster; only nodes that are
# started as cluster nodes can. In order to start a Redis instance as a
# cluster node enable the cluster support uncommenting the following:
#
# cluster-enabled yes

# Every cluster node has a cluster configuration file. This file is not
# intended to be edited by hand. It is created and updated by Redis nodes.
# Every Redis Cluster node requires a different cluster configuration file.
# Make sure that instances running in the same system do not have
# overlapping cluster configuration file names.
#
# cluster-config-file nodes-6379.conf

# Cluster node timeout is the amount of milliseconds a node must be unreachable
# for it to be considered in failure state.
# Most other internal time limits are multiple of the node timeout.
#
# cluster-node-timeout 15000

# A replica of a failing master will avoid to start a failover if its data
# looks too old.
#
# There is no simple way for a replica to actually have an exact measure of
# its "data age", so the following two checks are performed:
#
# 1) If there are multiple replicas able to failover, they exchange messages
#    in order to try to give an advantage to the replica with the best
#    replication offset (more data from the master processed).
#    Replicas will try to get their rank by offset, and apply to the start
#    of the failover a delay proportional to their rank.
#
# 2) Every single replica computes the time of the last interaction with
#    its master. This can be the last ping or command received (if the master
#    is still in the "connected" state), or the time that elapsed since the
#    disconnection with the master (if the replication link is currently down).
#    If the last interaction is too old, the replica will not try to failover
#    at all.
#
# The point "2" can be tuned by user. Specifically a replica will not perform
# the failover if, since the last interaction with the master, the time
# elapsed is greater than:
#
#   (node-timeout * replica-validity-factor) + repl-ping-replica-period
#
# So for example if node-timeout is 30 seconds, and the replica-validity-factor
# is 10, and assuming a default repl-ping-replica-period of 10 seconds, the
# replica will not try to failover if it was not able to talk with the master
# for longer than 310 seconds.
#
# A large replica-validity-factor may allow replicas with too old data to failover
# a master, while a too small value may prevent the cluster from being able to
# elect a replica at all.
#
# For maximum availability, it is possible to set the replica-validity-factor
# to a value of 0, which means, that replicas will always try to failover the
# master regardless of the last time they interacted with the master.
# (However they'll always try to apply a delay proportional to their
# offset rank).
#
# Zero is the only value able to guarantee that when all the partitions heal
# the cluster will always be able to continue.
#
# cluster-replica-validity-factor 10

# Cluster replicas are able to migrate to orphaned masters, that are masters
# that are left without working replicas. This improves the cluster ability
# to resist to failures as otherwise an orphaned master can't be failed over
# in case of failure if it has no working replicas.
#
# Replicas migrate to orphaned masters only if there are still at least a
# given number of other working replicas for their old master. This number
# is the "migration barrier". A migration barrier of 1 means that a replica
# will migrate only if there is at least 1 other working replica for its master
# and so forth. It usually reflects the number of replicas you want for every
# master in your cluster.
#
# Default is 1 (replicas migrate only if their masters remain with at least
# one replica). To disable migration just set it to a very large value.
# A value of 0 can be set but is useful only for debugging and dangerous
# in production.
#
# cluster-migration-barrier 1

# By default Redis Cluster nodes stop accepting queries if they detect there
# is at least an hash slot uncovered (no available node is serving it).
# This way if the cluster is partially down (for example a range of hash slots
# are no longer covered) all the cluster becomes, eventually, unavailable.
# It automatically returns available as soon as all the slots are covered again.
#
# However sometimes you want the subset of the cluster which is working,
# to continue to accept queries for the part of the key space that is still
# covered. In order to do so, just set the cluster-require-full-coverage
# option to no.
#
# cluster-require-full-coverage yes

# This option, when set to yes, prevents replicas from trying to failover its
# master during master failures. However the master can still perform a
# manual failover, if forced to do so.
#
# This is useful in different scenarios, especially in the case of multiple
# data center operations, where we want one side to never be promoted if not
# in the case of a total DC failure.
#
# cluster-replica-no-failover no

# In order to setup your cluster make sure to read the documentation
# available at http://redis.io web site.

REDIS CLUSTER关注点：

1.cluster-enabled yes

是否作为集群启动

2.cluster-config-file nodes-6379.conf

每个群集节点都有一个群集配置文件。这个文件不是打算手工编辑。它是由Redis节点创建和更新的。每个Redis集群节点都需要不同的集群配置文件。请确保在同一系统中运行的实例没有重叠的集群配置文件名。一般我们只运行一个redis不需要改名字。

3.cluster-node-timeout 15000

节点连接超时时间

4.cluster-replica-validity-factor 10

如果数据太旧，集群中的不可用master的slave节点会避免成为备用master。如果slave和master失联时间超过:(node-timeout * slave-validity-factor) + repl-ping-slave-period则不会被提升为master。如node-timeout为30秒，slave-validity-factor为10, 默认default repl-ping-slave-period为10秒,失联时间超过310秒slave就不会成为master。较大的slave-validity-factor值可能允许包含过旧数据的slave成为master，同时较小的值可能会阻止集群选举出新master。为了达到最大限度的高可用性，可以设置为0，即slave不管和master失联多久都可以提升为master。(https://blog.csdn.net/weixin_41436549/article/details/83820214)

5.cluster-migration-barrier 1

副本迁移屏障。意思指每个副本迁移时保留给当前主副本的最小副本数。默认值为1（副本仅在其主副本至少保留一个副本时迁移）。要禁用迁移，只需将其设置为一个非常大的值。可以设置值0，但该值仅用于调试和生产中的危险。

6.cluster-require-full-coverage yes

设置为yes将会检测当前集群哈希槽是否全部可用，如果有部分不可用，那么集群的状态即为不可用。

设置为no时，当哈希槽部分可用，那么集群将会使用可用的哈希槽，集群状态仍为可用。

7.cluster-replica-no-failover no

此设置yes时，会阻止从节点在主节点故障时进行故障转移。但是仍然可以手动进行故障转移。

########################## 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 DOCKER/NAT support关注点：

1.# cluster-announce-ip 10.1.1.5
   # cluster-announce-port 6379
   # cluster-announce-bus-port 6380

主要讲的是集群的容器化支持。设置ip、端口、集群总线端口。(暂时看不太懂，慢慢填坑。。。)

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

SLOW LOG关注点：

1.slowlog-log-slower-than 10000

Redis Slow Log是一个系统到日志的查询，它超过了指定的执行时间的命令。您可以使用两个参数配置慢日志：一个参数告诉Redis要超过多少执行时间（微秒），以便记录命令；另一个参数是慢日志的长度。记录新命令时，最旧的命令将从记录的命令队列中删除。

2.slowlog-max-len 128

这个长度没有限制。请注意它会消耗内存。您可以使用SLOWLOG RESET回收慢日志使用的内存。

 

################################ 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 " if needed.
latency-monitor-threshold 0

LATENCY MONITOR关注点：

1.latency-monitor-threshold 0

系统只记录在等于或大于通过延迟监视器阈值配置指令。当其值设置为零时，延迟监视器将关闭。默认情况下，延迟监视是禁用的，因为如果没有延迟问题，则通常不需要它，而且收集数据会对性能产生影响，虽然影响很小，但可以在大负载下测量。如果需要，可以在运行时使用命令“CONFIG SET Latency monitor threshold”轻松启用延迟监视。

############################# 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@__ prefix.
#  E     Keyevent events, published with __keyevent@__ 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 ""

EVENT NOTIFICATION关注点：

1.notify-keyspace-events ""

事件通知设置。

 K     Keyspace events, published with __keyspace@__ prefix.
 E     Keyevent events, published with __keyevent@__ 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.
格式如下：

    notify-keyspace-events Elg

    notify-keyspace-events Ex

默认情况下，所有通知都被禁用，因为大多数用户不需要此功能，而且此功能有一些开销。
请注意，如果未指定K或E中的至少一个，则不会传递任何事件。

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

ADVANCED CONFIG关注点：

1.hash-max-ziplist-entries 512
   hash-max-ziplist-value 64

这个部分讲的是高级配置。以下来自度娘。

当哈希有少量的条目，并且最大的条目不超过给定的阈值时，使用内存高效的数据结构对其进行编码。可以使用以下指令配置这些阈值。

2.list-max-ziplist-size -2

列表也以一种特殊的方式进行编码，以节省大量空间。
可以指定每个内部列表节点允许的条目数
作为一个固定的最大大小或最大数量的元素。
对于固定的最大尺寸，使用-5至-1，意思是：
# -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
正数意味着每一个列表节点存储的元素数量要精确到这个数量。
最高性能的选项通常是-2（8kb大小）或-1（4kb大小），但是如果您的用例是唯一的，则根据需要调整设置。

3.list-compress-depth 0

Compress depth是从列表的*each*侧到*exclude*的快速列表ziplist节点数。列表的头和尾始终未压缩，以进行快速push/pop操作。设置为：

    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]

4.set-max-intset-entries 512

5.zset-max-ziplist-entries 128

   zset-max-ziplist-value 64

与hashes和lists类似，sorted sets 也经过特殊编码，以节省大量空间。此编码仅在排序集的长度和元素低于以下限制时使用

6.hll-sparse-max-bytes 3000

7.stream-node-max-bytes 4096
   stream-node-max-entries 100

8.activerehashing yes

10.client-output-buffer-limit normal 0 0 0
     client-output-buffer-limit replica 256mb 64mb 60
     client-output-buffer-limit pubsub 32mb 8mb 60

客户机输出缓冲区限制可用于强制断开由于某些原因没有足够快地从服务器读取数据的客户机的连接
（一个常见的原因是发布服务器/子客户机无法以发布服务器能够生成的速度使用消息）。对于三种不同类型的客户机，可以设置不同的限制：

每个客户机输出缓冲区限制指令的语法如下：client-output-buffer-limit

一旦达到硬限制，或达到软限制并保持达到指定秒数（连续）时，客户端将立即断开连接。
例如，如果硬限制是32兆字节，而软限制是
16兆字节/10秒，如果输出缓冲区的大小达到32兆字节，客户端将立即断开连接，
但如果客户端达到16兆字节并连续超过限制10秒，客户端也将断开连接。

默认情况下，普通客户机不受限制，因为它们不会在没有请求（以推送方式）的情况下接收数据，
而是在请求之后才接收数据，因此只有异步客户机可能会创建这样一个场景：
请求数据的速度比读取数据的速度快。

硬限制或软限制都可以通过将其设置为零来禁用。

11.client-query-buffer-limit 1gb

客户端查询缓冲区累积新命令。默认情况下，它们被限制在一个固定的数量，以避免协议取消同步
（例如，由于客户端的错误）将导致查询缓冲区中的未绑定内存使用。但是，如果您有非常特殊的需求，
比如我们巨大的multi/exec请求或类似的请求，您可以在这里配置它。

12.proto-max-bulk-len 512mb

在Redis协议中，批量请求（即表示单个字符串的元素）通常被限制为512mb。不过，您可以在这里更改此限制。

13.hz 10

redis执行后台任务的频率。并不是越高越好。默认10.

14.dynamic-hz yes

redis执行后台任务的动态频率。当启用动态赫兹时，实际配置的赫兹将用作基线，但一旦连接了更多的客户机，实际将根据需要使用配置的赫兹值的倍数。这样，一个空闲的实例只需要很少的CPU时间，而一个繁忙的实例则会有更高的响应速度。

15.aof-rewrite-incremental-fsync yes

当一个子对象重写a of文件时，如果启用了以下选项，则每生成32 MB的数据就会对
该文件进行fsync。这对于更增量地将文件提交到磁盘并避免较大的延迟峰值非常有用。

16.rdb-save-incremental-fsync yes

当redis保存RDB文件时，如果启用了以下选项，每生成32 MB数据，文件将被fsync-ed。 这很有用，以便以递增方式将文件提交到磁盘并避免大延迟峰值。

17.# 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

ACTIVE DEFRAGMENTATION关注点：

1.# activedefrag yes

此功能是实验性的。然而，在生产过程中进行了应力测试，并由多个工程师手动测试了一段时间。

启用活动碎片整理

2.active-defrag-ignore-bytes 100mb

启动活动碎片整理的最小碎片浪费量

3.active-defrag-threshold-lower 10

启动活动碎片整理的最小碎片百分比

4.active-defrag-threshold-upper 100

 

 使用最大消耗时的最大碎片百分比

5. active-defrag-cycle-min 5

以CPU百分比表示的最小碎片整理工作量

6.active-defrag-cycle-max 75

磁盘碎片整理的最大消耗

7.active-defrag-max-scan-fields 1000

从主字典扫描中处理的SET/HASH/ZSET/List字段的最大数目