平淡的流年

1. yum install gcc gcc-c++ wget

2. 官网下载一个redis 路径不贴了

3. make && make PREFIX=/usr/local/redis install (随意)

安装完成。。

sh /usr/local/redis/utils/install_server.sh  执行脚本  设置好端口、日志以及进程pid路径等。 相关redis.conf的配置详细参数  在下面

配置好启动

/usr/local/redis/src/redis-server /etc/redis/redis_7396.conf

但是这边遇到一个问题，由于我是用redis用户登录的，所以启动redis后，执行redis的用户是root用户。我感觉这个很不安全，一旦登录，会被提权。

redis.conf又没有和mysql一样  设置group 或 user 的配置

找了很多文档，都是新建一个用户  并且用这个用户去执行上面的启动命令。

但是我新建的用户都是 /usr/sbin/nologin 是没有登录权限的。所以焦头烂额，这可能是洁癖

groupadd redis

useradd -g redis -s /usr/sbin/nologin redis

最后用 sudo -u redis /usr/local/redis/src/redis-server /etc/redis/redis_7396.conf

实现用redis用户执行redis  当然文件夹以及相关日志等这些属于redis的 都需要更改权限

chown -R redis:redis 路径 修改

以下是redis.conf  的详解

 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 ###################################

 

# 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

 

#额外载入配置文件，如果需要的话，可以开启此配置

 

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

 

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

#绑定redis服务器网卡IP，默认为127.0.0.1,即本地回环地址。这样的话，访问redis服务只能通过本机的客户端连接，而无法通过远程连接。如果bind选项为空的话，那会接受所有来自于可用网络接口的连接。如上配置，绑定一个127.0.0.1的本机地址和192.168.1.100的外网地址。

 

# 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

#保护模式，默认是开启状态，只允许本地客户端连接，可以设置密码或添加bind来连接

 

# 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

#监听端口号，默认为6379，如果设置为0，redis将不在socket上监听任何客户端连接

 

# 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

#TCP监听的最大容量，在高并发的环境下，你需要把这个值调高以避免客户端连接缓慢的问题。Linux内核会把这个值缩小成/proc/sys/net/core/somaxconn对应的值，要提升并发量需要修改这两个值才能达到目的

 

# 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

#指定redis监听的unix socket路径，默认不启用，unixsocketper指定文件的权限

 

# Close the connection after a client is idle for N seconds (0 to disable)

timeout 0

#指定在一个client空闲多少秒之后关闭连接（0表示永不关闭）

# 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

#单位是秒，表示将周期性的使用SO_KEEPALIVE检测客户端是否还处于健康状态，避免服务器一直阻塞，官方给出的建议值是300s，如果设置为0，则不会周期性的检测

 

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

#默认情况下redis不是作为守护进程运行的，如果你想让它在后台运行，你就把它改成yes.当redis作为守护进程运行的时候，它会写一个pid到/var/run/redis.pid文件里面

 

# 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

#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

 

# 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

#配置PID文件路径，当redis作为守护线程运行时，它会把pid默认写到/var/run/redis_6379.pid里面

 

# 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

#定义日志级别。

#  可以是下面的这些值：

#  debug（记录大量日志信息，适用于开发、测试阶段）

#  verbose（较多日志信息）

#  notice（适量日志信息，使用于生产环境）

#  warning（仅有部分重要、关键信息才会被记录）

 

# 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 ""

#日志文件的位置，当指定为空字符串时，为标准输出，如果redis已守护进程模式运行，那么日志将会输出到/dev/null

 

# 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

#要想把日志记录为系统日志，就把它改成yes，也可以可选择性的更新其他的syslog参数以达到你的要求

 

# Specify the syslog identity.

# syslog-ident redis

#设置系统日志的ID

 

# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.

# syslog-facility local0

#指定系统日志设置，必须是 USER 或者是 LOCAL0-LOCAL7 之间的值

 

# Set the number of databases. The default database is DB 0, you can select

# a different one on a per-connection basis using SELECT <dbid> where

# dbid is a number between 0 and 'databases'-1

databases 16

#设置数据库的数目。默认的数据库是DB 0 ，可以在每个连接上使用select  <dbid> 命令选择一个不同的数据库，dbid是一个介于0到databases - 1 之间的数值。

 

# By default Redis shows an ASCII art logo only when started to log to the

# standard output and if the standard output is a TTY. Basically this means

# that normally a logo is displayed only in interactive sessions.

#

# However it is possible to force the pre-4.0 behavior and always show a

# ASCII art logo in startup logs by setting the following option to yes.

always-show-logo yes

 

################################ SNAPSHOTTING  ################################

#

# Save the DB on disk:

#

#   save <seconds> <changes>

#

#   Will save the DB if both the given number of seconds and the given

#   number of write operations against the DB occurred.

#

#   In the example below the behaviour will be to save:

#   after 900 sec (15 min) if at least 1 key changed

#   after 300 sec (5 min) if at least 10 keys changed

#   after 60 sec if at least 10000 keys changed

#

#   Note: you can disable saving completely by commenting out all "save" lines.

#

#   It is also possible to remove all the previously configured save

#   points by adding a save directive with a single empty string argument

#   like in the following example:

#

#   save ""

 

save 900 1

save 300 10

save 60 10000

#存 DB 到磁盘：

#    格式：save <间隔时间（秒）> <写入次数>

#    根据给定的时间间隔和写入次数将数据保存到磁盘

#    下面的例子的意思是：

#    900 秒内如果至少有 1 个 key 的值变化，则保存

#    300 秒内如果至少有 10 个 key 的值变化，则保存

#    60 秒内如果至少有 10000 个 key 的值变化，则保存　

#    注意：你可以注释掉所有的 save 行来停用保存功能。

#    也可以直接一个空字符串来实现停用：

#    save ""

 

# 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

#  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。

 

# 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

#  对于存储到磁盘中的快照，可以设置是否进行压缩存储。

#  如果是的话，redis会采用LZF算法进行压缩。如果你不想消耗CPU来进行压缩的话，

#  可以设置为关闭此功能，但是存储在磁盘上的快照会比较大。

 

# 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

#  在存储快照后，我们还可以让redis使用CRC64算法来进行数据校验，但是这样做会增加大约10%的性能消耗，

#  如果希望获取到最大的性能提升，可以关闭此功能。

 

# The filename where to dump the DB

dbfilename dump.rdb

# 设置快照的文件名

 

# 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 ./

#  设置快照文件的存放路径，这个配置项一定是个目录，而不能是文件名

 

################################# 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>

#主从复制，使用replicaof来让一个redis实例成为另一个redis实例的副本，默认关闭

#注意这个只需要在replica上配置

 

# 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>

#如果master需要密码认证，就在这里设置，默认不设置

 

# 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

#当一个 replica与 master 失去联系，或者复制正在进行的时候，

#  replica可能会有两种表现：

#  1) 如果为 yes ，replica仍然会应答客户端请求，但返回的数据可能是过时，

#     或者数据可能是空的在第一次同步的时候

#  2)如果copy -serve- stal- data设置为“否”，那么这个副本将会回复

#    在所有命令中出现“与master同步”的错误

#    但是对于INFO, replicaOF, AUTH, PING, SHUTDOWN, REPLCONF, ROLE, CONFIG，

#    订阅，取消订阅，PSUBSCRIBE, PUNSUBSCRIBE, PUBLISH, PUBSUB，

#    命令，POST, HOST:延时。

 

# 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

#  你可以配置一个 slave 实体是否接受写入操作。

#  通过写入操作来存储一些短暂的数据对于一个 replica实例来说可能是有用的，

#  因为相对从 master 重新同步数而言，据数据写入到 replica会更容易被删除。

#  但是如果客户端因为一个错误的配置写入，也可能会导致一些问题。

#  从 redis 2.6 版起，默认 slaves 都是只读的。

 

# 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

#  主从数据复制是否使用无硬盘复制功能。

#  新的从站和重连后不能继续备份的从站，需要做所谓的“完全备份”，即将一个RDB文件从主站传送到从站。

#  这个传送有以下两种方式：

#  1）硬盘备份：redis主站创建一个新的进程，用于把RDB文件写到硬盘上。过一会儿，其父进程递增地将文件传送给从站。

#  2）无硬盘备份：redis主站创建一个新的进程，子进程直接把RDB文件写到从站的套接字，不需要用到硬盘。

#  在硬盘备份的情况下，主站的子进程生成RDB文件。一旦生成，多个从站可以立即排成队列使用主站的RDB文件。

#  在无硬盘备份的情况下，一次RDB传送开始，新的从站到达后，需要等待现在的传送结束，才能开启新的传送。

#  如果使用无硬盘备份，主站会在开始传送之间等待一段时间（可配置，以秒为单位），希望等待多个子站到达后并行传送。

#  在硬盘低速而网络高速（高带宽）情况下，无硬盘备份更好。

 

# 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

#  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。

 

# 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

#从redis会周期性的向主redis发出PING包，你可以通过repl_ping_slave_period指令来控制其周期，默认是10秒。

 

# 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

# 接下来的选项为以下内容设置备份的超时时间：

#  1）从从站的角度，同步期间的批量传输的I/O

#  2）从站角度认为的主站超时（数据，ping）

#  3）主站角度认为的从站超时（REPLCONF ACK pings)

#  确认这些值比定义的repl-ping-slave-period要大，否则每次主站和从站之间通信低速时都会被检测为超时。

 

# 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

#  同步之后是否禁用从站上的TCP_NODELAY

#  如果你选择yes，redis会使用较少量的TCP包和带宽向从站发送数据。但这会导致在从站增加一点数据的延时。

#  Linux内核默认配置情况下最多40毫秒的延时。

#  如果选择no，从站的数据延时不会那么多，但备份需要的带宽相对较多。

#  默认情况下我们将潜在因素优化，但在高负载情况下或者在主从站都跳的情况下，把它切换为yes是个好主意。

 

# 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

#  设置备份的工作储备大小。工作储备是一个缓冲区，当从站断开一段时间的情况时，它替从站接收存储数据，

#  因此当从站重连时，通常不需要完全备份，只需要一个部分同步就可以，即把从站断开时错过的一部分数据接收。

#  工作储备越大，从站可以断开并稍后执行部分同步的断开时间就越长。

#  只要有一个从站连接，就会立刻分配一个工作储备。

 

# 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

#  主站有一段时间没有与从站连接，对应的工作储备就会自动释放。

#  这个选项用于配置释放前等待的秒数，秒数从断开的那一刻开始计算，值为0表示不释放。

 

# 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

#  从站优先级是可以从redis的INFO命令输出中查到的一个整数。当主站不能正常工作时

#  redis sentinel使用它来选择一个从站并将它提升为主站。

#  低优先级的从站被认为更适合于提升，因此如果有三个从站优先级分别是10，

#  100，25，sentinel会选择优先级为10的从站，因为它的优先级最低。

#  然而优先级值为0的从站不能执行主站的角色，因此优先级为0的从站永远不会被redis sentinel提升。

#  默认优先级是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

#  主站可以停止接受写请求，当与它连接的从站少于N个，滞后少于M秒，N个从站必须是在线状态。

#  延迟的秒数必须<=所定义的值，延迟秒数是从最后一次收到的来自从站的ping开始计算。ping通常是每秒一次。

#  这一选项并不保证N个备份都会接受写请求，但是会限制在指定秒数内由于从站数量不够导致的写操作丢失的情况。

#  如果想要至少3个从站且延迟少于10秒，如上配置即可

 

#

# 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

# Redis master能够以不同的方式列出所连接slave的地址和端口。

# 例如，“INFO replication”部分提供此信息，除了其他工具之外，Redis Sentinel还使用该信息来发现slave实例。

# 此信息可用的另一个地方在masterser的“ROLE”命令的输出中。

# 通常由slave报告的列出的IP和地址,通过以下方式获得：

# IP：通过检查slave与master连接使用的套接字的对等体地址自动检测地址。

# 端口：端口在复制握手期间由slavet通信，并且通常是slave正在使用列出连接的端口。

# 然而，当使用端口转发或网络地址转换（NAT）时，slave实际上可以通过(不同的IP和端口对)来到达。 slave可以使用以下两个选项，以便向master报告一组特定的IP和端口，

# 以便INFO和ROLE将报告这些值。

# 如果你需要仅覆盖端口或IP地址，则没必要使用这两个选项。

 

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

#设置Redis连接密码

 

# 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 ""

#  将命令重命名，为了安全考虑，可以将某些重要的、危险的命令重命名。

#  当你把某个命令重命名成空字符串的时候就等于取消了这个命令。

#

# Please note that changing the name of commands that are logged into the

# AOF file or transmitted to replicas may cause problems.

 

################################### CLIENTS ####################################

 

# Set the max number of connected clients at the same time. By default

# this limit is set to 10000 clients, however if the Redis server is not

# able to configure the process file limit to allow for the specified limit

# the max number of allowed clients is set to the current file limit

# minus 32 (as Redis reserves a few file descriptors for internal uses).

#

# Once the limit is reached Redis will close all the new connections sending

# an error 'max number of clients reached'.

#

# maxclients 10000

#  设置客户端最大并发连接数，默认无限制，Redis可以同时打开的客户端连接数为Redis进程可以打开的最大文件

#  描述符数-32（redis server自身会使用一些），如果设置 maxclients为0

#  表示不作限制。当客户端连接数到达限制时，Redis会关闭新的连接并向客户端返回max number of clients reached错误信息

 

############################## 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>

#  指定Redis最大内存限制，Redis在启动时会把数据加载到内存中，达到最大内存后，Redis会先尝试清除已到期或即将到期的Key

#  当此方法处理 后，仍然到达最大内存设置，将无法再进行写入操作，但仍然可以进行读取操作。Redis新的vm机制，

#  会把Key存放内存，Value会存放在swap区，格式：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

#  当内存使用达到最大值时，redis使用的清楚策略。有以下几种可以选择：

#  1）volatile-lru   利用LRU算法移除设置过过期时间的key (LRU:最近使用 Least Recently Used )

#  2）allkeys-lru   利用LRU算法移除任何key

#  3）volatile-random 移除设置过过期时间的随机key

#  4）allkeys-random  移除随机ke

#  5）volatile-ttl   移除即将过期的key(minor TTL)

#  6）noeviction  noeviction   不移除任何key，只是返回一个写错误 ，默认选项

 

# 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

#  LRU 和 minimal TTL 算法都不是精准的算法，但是相对精确的算法(为了节省内存)

#  随意你可以选择样本大小进行检，redis默认选择3个样本进行检测，你可以通过maxmemory-samples进行设置样本数

 

# Starting from Redis 5, by default a replica will ignore its maxmemory setting

# (unless it is promoted to master after a failover or manually). It means

# that the eviction of keys will be just handled by the master, sending the

# DEL commands to the replica as keys evict in the master side.

#

# This behavior ensures that masters and replicas stay consistent, and is usually

# what you want, however if your replica is writable, or you want the replica to have

# a different memory setting, and you are sure all the writes performed to the

# replica are idempotent, then you may change this default (but be sure to understand

# what you are doing).

#

# Note that since the replica by default does not evict, it may end using more

# memory than the one set via maxmemory (there are certain buffers that may

# be larger on the replica, or data structures may sometimes take more memory and so

# forth). So make sure you monitor your replicas and make sure they have enough

# memory to never hit a real out-of-memory condition before the master hits

# the configured maxmemory setting.

#

# replica-ignore-maxmemory yes

 

############################# LAZY FREEING ####################################

 

# Redis has two primitives to delete keys. One is called DEL and is a blocking

# deletion of the object. It means that the server stops processing new commands

# in order to reclaim all the memory associated with an object in a synchronous

# way. If the key deleted is associated with a small object, the time needed

# in order to execute the DEL command is very small and comparable to most other

# O(1) or O(log_N) commands in Redis. However if the key is associated with an

# aggregated value containing millions of elements, the server can block for

# a long time (even seconds) in order to complete the operation.

#

# For the above reasons Redis also offers non blocking deletion primitives

# such as UNLINK (non blocking DEL) and the ASYNC option of FLUSHALL and

# FLUSHDB commands, in order to reclaim memory in background. Those commands

# are executed in constant time. Another thread will incrementally free the

# object in the background as fast as possible.

#

# DEL, UNLINK and ASYNC option of FLUSHALL and FLUSHDB are user-controlled.

# It's up to the design of the application to understand when it is a good

# idea to use one or the other. However the Redis server sometimes has to

# delete keys or flush the whole database as a side effect of other operations.

# Specifically Redis deletes objects independently of a user call in the

# following scenarios:

#

# 1) On eviction, because of the maxmemory and maxmemory policy configurations,

#    in order to make room for new data, without going over the specified

#    memory limit.

# 2) Because of expire: when a key with an associated time to live (see the

#    EXPIRE command) must be deleted from memory.

# 3) Because of a side effect of a command that stores data on a key that may

#    already exist. For example the RENAME command may delete the old key

#    content when it is replaced with another one. Similarly SUNIONSTORE

#    or SORT with STORE option may delete existing keys. The SET command

#    itself removes any old content of the specified key in order to replace

#    it with the specified string.

# 4) During replication, when a replica performs a full resynchronization with

#    its master, the content of the whole database is removed in order to

#    load the RDB file just transferred.

#

# In all the above cases the default is to delete objects in a blocking way,

# like if DEL was called. However you can configure each case specifically

# in order to instead release memory in a non-blocking way like if UNLINK

# was called, using the following configuration directives:

 

lazyfree-lazy-eviction no

lazyfree-lazy-expire no

lazyfree-lazy-server-del no

replica-lazy-flush no

 

############################## APPEND ONLY MODE ###############################

 

# By default Redis asynchronously dumps the dataset on disk. This mode is

# good enough in many applications, but an issue with the Redis process or

# a power outage may result into a few minutes of writes lost (depending on

# the configured save points).

#

# The Append Only File is an alternative persistence mode that provides

# much better durability. For instance using the default data fsync policy

# (see later in the config file) Redis can lose just one second of writes in a

# dramatic event like a server power outage, or a single write if something

# wrong with the Redis process itself happens, but the operating system is

# still running correctly.

#

# AOF and RDB persistence can be enabled at the same time without problems.

# If the AOF is enabled on startup Redis will load the AOF, that is the file

# with the better durability guarantees.

#

# Please check http://redis.io/topics/persistence for more information.

 

appendonly no

#  默认redis使用的是rdb方式持久化，这种方式在许多应用中已经足够用了。但是redis如果中途宕机，

#  会导致可能有几分钟的数据丢失，根据save来策略进行持久化，Append Only File是另一种持久化方式，

#  可以提供更好的持久化特性。Redis会把每次写入的数据在接收后都写入appendonly.aof文件，

#  每次启动时Redis都会先把这个文件的数据读入内存里，先忽略RDB文件。

 

# The name of the append only file (default: "appendonly.aof")

 

appendfilename "appendonly.aof"

#aof文件名

 

# 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

#  aof持久化策略的配置

#  no表示不执行fsync，由操作系统保证数据同步到磁盘，速度最快。

#  always表示每次写入都执行fsync，以保证数据同步到磁盘。

#  everysec表示每秒执行一次fsync，可能会导致丢失这1s数据

 

# 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

#   在aof重写或者写入rdb文件的时候，会执行大量IO，此时对于everysec和always的aof模式来说，

#   执行fsync会造成阻塞过长时间，no-appendfsync-on-rewrite字段设置为默认设置为no。

#   如果对延迟要求很高的应用，这个字段可以设置为yes，否则还是设置为no，这样对持久化特性来说这是更安全的选择。

#   设置为yes表示rewrite期间对新写操作不fsync,暂时存在内存中,等rewrite完成后再写入，默认为no，建议yes。

#   Linux的默认fsync策略是30秒。可能丢失30秒数据。

 

# 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

#  aof自动重写配置，当目前aof文件大小超过上一次重写的aof文件大小的百分之多少进行重写，

#  即当aof文件增长到一定大小的时候，Redis能够调用bgrewriteaof对日志文件进行重写。

#  当前AOF文件大小是上次日志重写得到AOF文件大小的二倍（设置为100）时，自动启动新的日志重写过程。

auto-aof-rewrite-min-size 64mb

设置允许重写的最小aof文件大小，避免了达到约定百分比但尺寸仍然很小的情况还要重写

 

# 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

#  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。

 

# 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

 

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

#  如果达到最大时间限制（毫秒），redis会记个log，然后返回error。当一个脚本超过了最大时限。

#  只有SCRIPT KILL和SHUTDOWN NOSAVE可以用。第一个可以杀没有调write命令的东西。

#  要是已经调用了write，只能用第二个命令杀

 

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

#集群开关，默认是不开启集群模式

 

# 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

# 集群配置文件的名称，每个节点都有一个集群相关的配置文件，持久化保存集群的信息。

# 这个文件并不需要手动配置，这个配置文件有Redis生成并更新，每个Redis集群节点需要一个单独的配置文件

# 请确保与实例运行的系统中配置

----平淡的流年

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