docker介绍和简单使用

docker介绍

docker

为什么会有docker出现?

一款产品从开发到上线,从操作系统到运行环境,再到应用配置,作为开发+运维直接的协作我们需要关心很多东西,这也是互联网公司不得 不面对问题,特别是各种版本迭代之后,不同版本的兼容,都是对运维人员考验

软件可以带环境安装,也就是说安装的时候把原始环境一模一样的复制过来,开发人员利用Docker可以消除协作编码时的'不能跑通'的问题.

Docker 理念

一处构建,处处都能够运行

docker能干什么?

让开发者不必安装和配置复杂的数据库，也无需在不兼容语言工具链版本之间切换时担心。应用容器化之后，其复杂性就被转移到能够轻松构建、共享和运行的容器中。当有新同事安排到新的代码库时，无需再费时费力地安装软件和解释设置过程。以 Dockerfile 文件形式发布的代码使用起来非常简单：首先安装 Docker 和编辑器，然后拉取作为 Docker 镜像打包在一起的依赖资源，短短数分钟，就能够构建和调试应用了。

官网:

中文官网:http://www.docker-cn.com/

docker-hub官网:http://hub.docker.com

docker命令

docker version #查看docker版本
docker info    #查看docker信息
docker --help  #查看docker指令的使用方法

镜像

镜像概念

• 是一种轻量级,可执行的独立软件包,用于打包软件运行环境和基于运行环境开发的软件,简单理解为类
• union文件系统是一种分层,轻量级并且高性能的文件系统,它支持对文件系统的修改作为一次提交来一层层的叠加,同时可以将不同目录挂在到同一个虚拟系统下.Union文件系统是docker镜像的基础.镜像可以通过分层来进行集成,基于基础镜像,可以制作各种具体的应用镜像
• 一次同时加载多个文件系统,在外面看起来,只能看到一个文件系统,联合加载会把各层系统叠加起来,这样最总文件系统会包含所有底层的文件和目录

最大的好处就是共享资源:

比如:有多个镜像都从相同的base镜像构建而来,那么宿主机只需要在磁盘上保存一份base镜像,同时内存中也只需要加载一份base镜像,就可以为所有容器服务了.而且镜像的每一层都是可以被共享的

镜像命令

查看镜像

docker images  #查看本机上的镜像
                      -a #列出本机所有的镜像(包含映象层)
                      -q #显示镜像ID
                      --digests #显示镜像摘要
                      --no-trunc #显示完整镜像信息

查找镜像

docker search 镜像名
#docker search -s 30 mysql 
#查找超过30个收藏的mysql镜像

拉镜像到本地

docker pull 镜像
#docker pull mysql

删除镜像

#删除单个镜像
docker rmi -f 镜像名/镜像id

#删除多个
docker -rmi -f 镜像1 镜像2

#全部删除
docker -rmi -f $(docker imags -qa

容器

容器是用镜像创建的运行实例 它可以被启动,停止,删除,每个容器都是可以相互隔离保证安全的平台,可以把容器看做一个简易版的linux坏境

容器镜像是轻量的、可执行的独立软件包，包含软件运行所需的所有内容：代码、运行时环境、系统工具、系统库和设置。容器化软件适用于基于 Linux 和 Windows 的应用，在任何环境中都能够始终如一地运行。容器赋予了软件独立性，使其免受外在环境差异（例如，开发和预演环境的差异）的影响，从而有助于减少团队间在相同基础设施上运行不同软件时的冲突。

• 轻量

  • 在一台机器上运行的多个 Docker 容器可以共享这台机器的操作系统内核；它们能够迅速启动，只需占用很少的计算和内存资源。镜像是通过文件系统层进行构造的，并共享一些公共文件。这样就能尽量降低磁盘用量，并能更快地下载镜像。

• 标准

  • Docker 容器基于开放式标准，能够在所有主流 Linux 版本、Microsoft Windows 以及包括 VM、裸机服务器和云在内的任何基础设施上运行。
• 安全
  • Docker 赋予应用的隔离性不仅限于彼此隔离，还独立于底层的基础设施。Docker 默认提供最强的隔离，因此应用出现问题，也只是单个容器的问题，而不会波及到整台机器。

容器对于虚拟机有什么优点?

• docker有着比虚拟机更少的抽象层.由于docker不需要Hypevisor实现硬件资源虚拟化,在运行docker容器上的程序直接使用都是实际物理机的硬件资源,因此在cpu和内存的利用率上docker将会在效率上有明显优势
• docker利用的是宿主机内核,不需要guest os.因此当新建一个容器时,docker不需要和虚拟机一样重新加载一个操作系统内核.避免加载操作系统内核比较浪费时间的过程.所以docker开启时秒级的,而虚拟机时分钟级别的.

容器命令

启动容器

docker run    [option] 镜像id
        --name #为容器定义一个新的名字
        -d          #后台运行,返回容器id,开启守护容器式
        -i            #以交互模式运行容器,通常与-t同时使用
        -t            #为容器分配一个伪终端
        -p            #指定端口映射
                        #hostport : containerPort
        -P             #随机分配端口

示例:

docker run -it -p 12345:3306 --name mymysql  mysql/镜像id 

查看容器

docker ps [option]
    -a        #列出当前所有正在运行的容器+历史上运行过的
    -l        #显示最新创建的容器
    -n        #显示最近n个创建的容器
    -q        #静默模式,只显示容器编号
    --no-trunc    #不截断输出

启动容器

docker start 镜像名/镜像ID

退出容器

exit #容器停止并且退出
ctrl+p+q #容器不停止退出

停止容器

docker stop 容器id/容器名   #停止容器
docker kill     ~         #强制停止容器
docker rm       ~          #删除单个容器  删除多个参照镜像

查看容器日志

docker logs -f -t --tail 容器id
#-t 加入时间戳
#-f 跟随最新的日志打印
# --tail 显示最后多少条

容器交互

docker exec -it 容器id/镜像名 bashShell
例子:
docker exec -it 容器id /bin/bash

docker attach 容器id/镜像名 #直接进入容器命令终端,不会启动新的进程

docker exec #是在容器中打开新的终端,并且可以打开新的进程

 容器提交

容器卷

docker 理念

将运用与运行的环境打包形成容器运行,运行可以伴随着容器,但是我们队数据的要求是希望持久化的

容器之间希望有可能共享数据

容器卷的设计目的就是数据的持久化,完全独立于容器的生存周期,因此docker不会再容器删除时发删除其挂在的数据卷

特点

• 数据卷可在容器之间共享或重用数据
• 卷中的更改可以直接生效
• 数据卷中的更改不会包含在镜像的更新中
• 数据卷的生命周期一直持续到没有容器使用它位置

命令添加容器卷

docker run -it -v /宿主机绝对路径目录:/容器内目录   镜像名

简单例子:

创建了关联文件夹以后,里面的数据进行共享

无论在目录下哪个文件编写内容都可以进行同步

即使关闭了容器,编写了内容,再开启容器,那么数据也是可以进行同步的

例子2:

容器卷权限

docker run -it -v /宿主机绝对路劲:/容器目录:ro 镜像名

#ro read only

Dockerfile

dockerfile 简单实例

Dockerfile是什么?

       Docker images  --à DockerFile 是对镜像源码级的描述

例子:

用dockerfile添加数据卷

•  根目录下新建mydocker文件夹并进入
• 可在dockerfile中使用volume指令来给镜像添加一个或者多个容器卷
• file构建
• build后生成镜像 获得一个新的镜像
• run 容器

mkdir mydocker
cd mydocker/
vim dockerfile
    

dockerfile文件:

FROM centos
VOLUME [ "/dataVolumeContainer1","/dataVolumeContainer2" ]
CMD echo "success"
CMD /bin/bash

#根据dockerfile创建一个新的镜像
docker build -f /mydocker/dockerfile -t mycentos

#查看新建的镜像
docker images 

有了新的镜像之后我们就可以运行容器实例且自带容器卷

我们来看centos的dockerfile

dockerfile的解析过程

1. 每条保留字指令都必须为大写字母且后面要跟随至少一个参数
2. 指令按照从上到下,顺序执行
3. #表示注释
4. 每条指令都会创建一个新的镜像层,并对镜像进行提交

总结:

• 从应用角度看,dockerfile,docker镜像和docker容器分别代表软件的三个不同的阶段,
• Dockerfile是软件的原材料
• docker镜像是软件的交付品
• docker容器则可以认为是软件的运行态

dockerfile需要定义一进城需要的一切东西,dockerfile设计的内容包括执行代码或者是文件,环境,变量,依赖包,运行时的环境,动态链接库,操作系统的发行版,服务京城和内核进城

docker镜像,在dockerfile定义一个文件以后,docker build 会产生一个docker镜像,当运行docker镜像时,会真正开始提供服务

dockerfile保留字

FROM #基础镜像,当前新镜像时基于哪个镜像的

MAINTAINER #镜像维护者的姓名和邮箱地址

RUN #容器构建时需要运行的命令

EXPOSE #当前容器对外暴露的端口

ENV # 用来在构建镜像过程中设置环境变量

ADD #将宿主机目录下的文件拷贝进镜像且ADD命令会自动处理url和解压tar压缩包

COPY #将从构建上下文目录中<源目录>的文件/目录复制到一个新的镜像内的<目标路径>位置 
        #用法 COPY src dest 或者 COPY ["src","dest"]

VOLUME #容器数据卷,用于数据的保存和持久化

CMD #dockerfile可以有多个CMD命令,但只有最后一个生效 CMD会被docker run之后的参数替换

ENTRYPOINT #和CMD一样 指定一个容器启动时要运行的命令但是可以追加命令

ONBUILD #当构建一个被继承的dockerfile时运行命令,父镜像在被子镜像继承后父镜像的onbuild被触发

例子1:

构建一个自带vim和net-tool的centos镜像

dockerfile文件内容:

FROM centos

MAINTAINER chen<540112587@qq.com>

ENV mypth /tmp
WORKDIR $mypth

RUN yum -y install vim
RUN yum -y install net-tools

EXPOSE 80
CMD echo $mypth
CMD echo "success"
CMD /bin/bash

例子2:

CMD和ENTRYPOINT的区别

dockerfile:
返回ip值
FROM centos
RUN yum install –y curl
CMD [  “curl”,”-s”,”http://ip.cn”  ]

根据dockerfile创建镜像

Docker run myip 执行myip镜像 
如果执行 docker run myip –i 那么-i会覆盖[]里面的内容
变成 CMD –i那么久会报错

FROM centos
RUN yum install –y curl
ENTRYPOINT [  “curl”,”-s”,”http://ip.cn”  ]

当我们用ENTRYPOINT 的时候是追加的状态
那么运行 docker run myip2
实际上是执行了 curl –s –i http://ip.cn (-i是查看请求头)

例子3

自定制tomcat

 

安装mysql和redis

例子:4 

运行mysql

docker pull mysql:5.6

创建容器且配置数据卷 和mysql密码
docker run -p 12345:3306 --name mysql -v /cxmuse/mysql/conf:/etc/mysql/conf.d 
-v /cxmuse/mysql/logs:/logs -v/cxmuse/mysql/data:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=123456 -d mysql:5.6
###############################
进入mysql
docker exec -it  容器id  /bin/bash
mysql -uroot –p
123456

Win10 连接docker的mysql

ifconfig

用docker做数据库的备份

 

例子5

用docker 使用redis

docker pull redis:3.2

启动redis容器
docker run -p 6379:6379 -v /cxmuse/myredis/data:/data 
-v /cxmuse/myredis/conf/redis.conf:/usr/local/etc/redis/redis.conf -d redis:3.2 redis-server /usr/local/etc/redis/redis.conf --appendonly yes

配置文件写入redis.conf文件(不是文件夹)

# Redis配置文件样例

# Note on units: when memory size is needed, it is possible to specifiy
# 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默认不是以守护进程的方式运行，可以通过该配置项修改，使用yes启用守护进程
# 启用守护进程后，Redis会把pid写到一个pidfile中，在/var/run/redis.pid
daemonize no

# 当Redis以守护进程方式运行时，Redis默认会把pid写入/var/run/redis.pid文件，可以通过pidfile指定
pidfile /var/run/redis.pid

# 指定Redis监听端口，默认端口为6379
# 如果指定0端口，表示Redis不监听TCP连接
port 6379

# 绑定的主机地址
# 你可以绑定单一接口，如果没有绑定，所有接口都会监听到来的连接
# bind 127.0.0.1

# 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 755

# 当客户端闲置多长时间后关闭连接，如果指定为0，表示关闭该功能
timeout 0

# 指定日志记录级别，Redis总共支持四个级别：debug、verbose、notice、warning，默认为verbose
# debug (很多信息, 对开发／测试比较有用)
# 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 verbose

# 日志记录方式，默认为标准输出，如果配置为redis为守护进程方式运行，而这里又配置为标准输出，则日志将会发送给/dev/null
logfile stdout

# 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

# 设置数据库的数量，默认数据库为0，可以使用select <dbid>命令在连接上指定数据库id
# dbid是从0到‘databases’-1的数目
databases 16

################################ SNAPSHOTTING  #################################
# 指定在多长时间内，有多少次更新操作，就将数据同步到数据文件，可以多个条件配合
# 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.
#
#   满足以下条件将会同步数据:
#   900秒（15分钟）内有1个更改
#   300秒（5分钟）内有10个更改
#   60秒内有10000个更改
#   Note: 可以把所有“save”行注释掉，这样就取消同步操作了

save 900 1
save 300 10
save 60 10000

# 指定存储至本地数据库时是否压缩数据，默认为yes，Redis采用LZF压缩，如果为了节省CPU时间，可以关闭该选项，但会导致数据库文件变的巨大
rdbcompression yes

# 指定本地数据库文件名，默认值为dump.rdb
dbfilename dump.rdb

# 工作目录.
# 指定本地数据库存放目录，文件名由上一个dbfilename配置项指定
# 
# Also the Append Only File will be created inside this directory.
# 
# 注意，这里只能指定一个目录，不能指定文件名
dir ./

################################# REPLICATION #################################

# 主从复制。使用slaveof从 Redis服务器复制一个Redis实例。注意，该配置仅限于当前slave有效
# so for example it is possible to configure the slave to save the DB with a
# different interval, or to listen to another port, and so on.
# 设置当本机为slav服务时，设置master服务的ip地址及端口，在Redis启动时，它会自动从master进行数据同步
# slaveof <masterip> <masterport>


# 当master服务设置了密码保护时，slav服务连接master的密码
# 下文的“requirepass”配置项可以指定密码
# masterauth <master-password>

# When a slave lost the connection with the master, or when the replication
# is still in progress, the slave can act in two different ways:
#
# 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will
#    still reply to client requests, possibly with out of data data, or the
#    data set may just be empty if this is the first synchronization.
#
# 2) if slave-serve-stale data is set to 'no' the slave will reply with
#    an error "SYNC with master in progress" to all the kind of commands
#    but to INFO and SLAVEOF.
#
slave-serve-stale-data yes

# Slaves send PINGs to server in a predefined interval. It's possible to change
# this interval with the repl_ping_slave_period option. The default value is 10
# seconds.
#
# repl-ping-slave-period 10

# The following option sets a timeout for both Bulk transfer I/O timeout and
# master data or ping response timeout. The default value is 60 seconds.
#
# It is important to make sure that this value is greater than the value
# specified for repl-ping-slave-period otherwise a timeout will be detected
# every time there is low traffic between the master and the slave.
#
# repl-timeout 60

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

# Warning: since Redis is pretty fast an outside user can try up to
# 150k passwords per second against a good box. This means that you should
# use a very strong password otherwise it will be very easy to break.
# 设置Redis连接密码，如果配置了连接密码，客户端在连接Redis时需要通过auth <password>命令提供密码，默认关闭
# requirepass foobared

# Command renaming.
#
# It is possilbe to change the name of dangerous commands in a shared
# environment. For instance the CONFIG command may be renamed into something
# of hard to guess so that it will be still available for internal-use
# tools but not available for general clients.
#
# Example:
#
# rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
#
# It is also possilbe to completely kill a command renaming it into
# an empty string:
#
# rename-command CONFIG ""

################################### LIMITS ####################################

# 设置同一时间最大客户端连接数，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，
# 如果设置maxclients 0，表示不作限制。当客户端连接数到达限制时，Redis会关闭新的连接并向客户端返回max Number of clients reached错误信息
# maxclients 128

# Don't use more memory than the specified amount of bytes.
# When the memory limit is reached Redis will try to remove keys with an
# EXPIRE set. It will try to start freeing keys that are going to expire
# in little time and preserve keys with a longer time to live.
# Redis will also try to remove objects from free lists if possible.
#
# If all this fails, Redis will start to reply with errors to commands
# that will use more memory, like SET, LPUSH, and so on, and will continue
# to reply to most read-only commands like GET.
#
# WARNING: maxmemory can be a good idea mainly if you want to use Redis as a
# 'state' server or cache, not as a real DB. When Redis is used as a real
# database the memory usage will grow over the weeks, it will be obvious if
# it is going to use too much memory in the long run, and you'll have the time
# to upgrade. With maxmemory after the limit is reached you'll start to get
# errors for write operations, and this may even lead to DB inconsistency.
# 指定Redis最大内存限制，Redis在启动时会把数据加载到内存中，达到最大内存后，Redis会先尝试清除已到期或即将到期的Key，
# 当此方法处理后，仍然到达最大内存设置，将无法再进行写入操作，但仍然可以进行读取操作。
# Redis新的vm机制，会把Key存放内存，Value会存放在swap区
# maxmemory <bytes>

# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
# is reached? You can select among five behavior:
# 
# volatile-lru -> remove the key with an expire set using an LRU algorithm
# allkeys-lru -> remove any key accordingly to the LRU algorithm
# volatile-random -> remove a random key 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 expire at all, just return an error on write operations
# 
# Note: with all the kind of policies, Redis will return an error on write
#       operations, when there are not suitable keys for eviction.
#
#       At the date of writing this 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 volatile-lru

# LRU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can select as well the sample
# size to check. For instance for default Redis will check three keys and
# pick the one that was used less recently, you can change the sample size
# using the following configuration directive.
#
# maxmemory-samples 3

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

# 
# Note that you can have both the async dumps and the append only file if you
# like (you have to comment the "save" statements above to disable the dumps).
# Still if append only mode is enabled Redis will load the data from the
# log file at startup ignoring the dump.rdb file.
# 指定是否在每次更新操作后进行日志记录，Redis在默认情况下是异步的把数据写入磁盘，如果不开启，可能会在断电时导致一段时间内的数据丢失。
# 因为redis本身同步数据文件是按上面save条件来同步的，所以有的数据会在一段时间内只存在于内存中。默认为no
# IMPORTANT: Check the BGREWRITEAOF to check how to rewrite the append
# log file in background when it gets too big.

appendonly no

# 指定更新日志文件名，默认为appendonly.aof
# appendfilename appendonly.aof

# The fsync() call tells the Operating System to actually write data on disk
# instead to wait 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.

# 指定更新日志条件，共有3个可选值：
# no:表示等操作系统进行数据缓存同步到磁盘（快）
# always:表示每次更新操作后手动调用fsync()将数据写到磁盘（慢，安全）
# everysec:表示每秒同步一次（折衷，默认值）

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", that in pratical terms means that it is
# possible to lost 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 will growth by the specified percentage.
# 
# This is how it works: Redis remembers the size of the AOF file after the
# latest rewrite (or if no rewrite 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 precentage of zero in order to disable the automatic AOF
# rewrite feature.

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

################################## 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 1024

################################ VIRTUAL MEMORY ###############################

### WARNING! Virtual Memory is deprecated in Redis 2.4
### The use of Virtual Memory is strongly discouraged.

### WARNING! Virtual Memory is deprecated in Redis 2.4
### The use of Virtual Memory is strongly discouraged.

# Virtual Memory allows Redis to work with datasets bigger than the actual
# amount of RAM needed to hold the whole dataset in memory.
# In order to do so very used keys are taken in memory while the other keys
# are swapped into a swap file, similarly to what operating systems do
# with memory pages.
# 指定是否启用虚拟内存机制，默认值为no，
# VM机制将数据分页存放，由Redis将访问量较少的页即冷数据swap到磁盘上，访问多的页面由磁盘自动换出到内存中
# 把vm-enabled设置为yes，根据需要设置好接下来的三个VM参数，就可以启动VM了
vm-enabled no
# vm-enabled yes

# This is the path of the Redis swap file. As you can guess, swap files
# can't be shared by different Redis instances, so make sure to use a swap
# file for every redis process you are running. Redis will complain if the
# swap file is already in use.
#
# Redis交换文件最好的存储是SSD（固态硬盘）
# 虚拟内存文件路径，默认值为/tmp/redis.swap，不可多个Redis实例共享
# *** WARNING *** if you are using a shared hosting the default of putting
# the swap file under /tmp is not secure. Create a dir with access granted
# only to Redis user and configure Redis to create the swap file there.
vm-swap-file /tmp/redis.swap

# With vm-max-memory 0 the system will swap everything it can. Not a good
# default, just specify the max amount of RAM you can in bytes, but it's
# better to leave some margin. For instance specify an amount of RAM
# that's more or less between 60 and 80% of your free RAM.
# 将所有大于vm-max-memory的数据存入虚拟内存，无论vm-max-memory设置多少，所有索引数据都是内存存储的（Redis的索引数据就是keys）
# 也就是说当vm-max-memory设置为0的时候，其实是所有value都存在于磁盘。默认值为0
vm-max-memory 0

# Redis swap文件分成了很多的page，一个对象可以保存在多个page上面，但一个page上不能被多个对象共享，vm-page-size是要根据存储的数据大小来设定的。
# 建议如果存储很多小对象，page大小最后设置为32或64bytes；如果存储很大的对象，则可以使用更大的page，如果不确定，就使用默认值
vm-page-size 32

# 设置swap文件中的page数量由于页表（一种表示页面空闲或使用的bitmap）是存放在内存中的，在磁盘上每8个pages将消耗1byte的内存
# swap空间总容量为 vm-page-size * vm-pages
#
# With the default of 32-bytes memory pages and 134217728 pages Redis will
# use a 4 GB swap file, that will use 16 MB of RAM for the page table.
#
# It's better to use the smallest acceptable value for your application,
# but the default is large in order to work in most conditions.
vm-pages 134217728

# Max number of VM I/O threads running at the same time.
# This threads are used to read/write data from/to swap file, since they
# also encode and decode objects from disk to memory or the reverse, a bigger
# number of threads can help with big objects even if they can't help with
# I/O itself as the physical device may not be able to couple with many
# reads/writes operations at the same time.
# 设置访问swap文件的I/O线程数，最后不要超过机器的核数，如果设置为0，那么所有对swap文件的操作都是串行的，可能会造成比较长时间的延迟，默认值为4
vm-max-threads 4

############################### ADVANCED CONFIG ###############################

# Hashes are encoded in a special way (much more memory efficient) when they
# have at max a given numer of elements, and the biggest element does not
# exceed a given threshold. You can configure this limits with the following
# configuration directives.
# 指定在超过一定的数量或者最大的元素超过某一临界值时，采用一种特殊的哈希算法
hash-max-zipmap-entries 512
hash-max-zipmap-value 64

# Similarly to hashes, small lists are also encoded in a special way in order
# to save a lot of space. The special representation is only used when
# you are under the following limits:
list-max-ziplist-entries 512
list-max-ziplist-value 64

# Sets have a special encoding in just one case: when a set is composed
# of just strings that happens 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

# 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 an hash table
# that is rhashing, 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
# active rehashing 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 form time to time
# to queries with 2 milliseconds delay.
# 指定是否激活重置哈希，默认为开启
activerehashing yes

################################## INCLUDES ###################################

# 指定包含其他的配置文件，可以在同一主机上多个Redis实例之间使用同一份配置文件，而同时各实例又拥有自己的特定配置文件
# include /path/to/local.conf
# include /path/to/other.conf

 

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