docker介紹和簡單使用

docker介紹

docker

為什么會有docker出現?

一款產品從開發到上線,從操作系統到運行環境,再到應用配置,作為開發+運維直接的協作我們需要關心很多東西,這也是互聯網公司不得 不面對問題,特別是各種版本迭代之后,不同版本的兼容,都是對運維人員考驗

軟件可以帶環境安裝,也就是說安裝的時候把原始環境一模一樣的復制過來,開發人員利用Docker可以消除協作編碼時的'不能跑通'的問題.

 

Docker 理念

一處構建,處處都能夠運行

 

docker能干什么?

讓開發者不必安裝和配置復雜的數據庫，也無需在不兼容語言工具鏈版本之間切換時擔心。應用容器化之后，其復雜性就被轉移到能夠輕松構建、共享和運行的容器中。當有新同事安排到新的代碼庫時，無需再費時費力地安裝軟件和解釋設置過程。以 Dockerfile 文件形式發布的代碼使用起來非常簡單：首先安裝 Docker 和編輯器，然后拉取作為 Docker 鏡像打包在一起的依賴資源，短短數分鍾，就能夠構建和調試應用了。

 

官網:

中文官網:http://www.docker-cn.com/

docker-hub官網: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

鏡像

鏡像概念

• 是一種輕量級,可執行的獨立軟件包,用於打包軟件運行環境和基於運行環境開發的軟件,簡單理解為類
• union文件系統是一種分層,輕量級並且高性能的文件系統,它支持對文件系統的修改作為一次提交來一層層的疊加,同時可以將不同目錄掛在到同一個虛擬系統下.Union文件系統是docker鏡像的基礎.鏡像可以通過分層來進行集成,基於基礎鏡像,可以制作各種具體的應用鏡像
• 一次同時加載多個文件系統,在外面看起來,只能看到一個文件系統,聯合加載會把各層系統疊加起來,這樣最總文件系統會包含所有底層的文件和目錄

最大的好處就是共享資源:

比如:有多個鏡像都從相同的base鏡像構建而來,那么宿主機只需要在磁盤上保存一份base鏡像,同時內存中也只需要加載一份base鏡像,就可以為所有容器服務了.而且鏡像的每一層都是可以被共享的

鏡像命令

查看鏡像

docker images  #查看本機上的鏡像
                      -a #列出本機所有的鏡像(包含映象層)
                      -q #顯示鏡像ID
                      --digests #顯示鏡像摘要
                      --no-trunc #顯示完整鏡像信息

查找鏡像

docker search 鏡像名
#docker search -s 30 mysql 
#查找超過30個收藏的mysql鏡像

拉鏡像到本地

docker pull 鏡像
#docker pull mysql

刪除鏡像

#刪除單個鏡像
docker rmi -f 鏡像名/鏡像id

#刪除多個
docker -rmi -f 鏡像1 鏡像2

#全部刪除
docker -rmi -f $(docker imags -qa

 

容器

容器是用鏡像創建的運行實例 它可以被啟動,停止,刪除,每個容器都是可以相互隔離保證安全的平台,可以把容器看做一個簡易版的linux壞境

容器鏡像是輕量的、可執行的獨立軟件包，包含軟件運行所需的所有內容：代碼、運行時環境、系統工具、系統庫和設置。容器化軟件適用於基於 Linux 和 Windows 的應用，在任何環境中都能夠始終如一地運行。容器賦予了軟件獨立性，使其免受外在環境差異（例如，開發和預演環境的差異）的影響，從而有助於減少團隊間在相同基礎設施上運行不同軟件時的沖突。

• 輕量

  • 在一台機器上運行的多個 Docker 容器可以共享這台機器的操作系統內核；它們能夠迅速啟動，只需占用很少的計算和內存資源。鏡像是通過文件系統層進行構造的，並共享一些公共文件。這樣就能盡量降低磁盤用量，並能更快地下載鏡像。

• 標准

  • Docker 容器基於開放式標准，能夠在所有主流 Linux 版本、Microsoft Windows 以及包括 VM、裸機服務器和雲在內的任何基礎設施上運行。
• 安全
  • Docker 賦予應用的隔離性不僅限於彼此隔離，還獨立於底層的基礎設施。Docker 默認提供最強的隔離，因此應用出現問題，也只是單個容器的問題，而不會波及到整台機器。

容器對於虛擬機有什么優點?

• docker有着比虛擬機更少的抽象層.由於docker不需要Hypevisor實現硬件資源虛擬化,在運行docker容器上的程序直接使用都是實際物理機的硬件資源,因此在cpu和內存的利用率上docker將會在效率上有明顯優勢
• docker利用的是宿主機內核,不需要guest os.因此當新建一個容器時,docker不需要和虛擬機一樣重新加載一個操作系統內核.避免加載操作系統內核比較浪費時間的過程.所以docker開啟時秒級的,而虛擬機時分鍾級別的.

 

 

容器命令

啟動容器

docker run    [option] 鏡像id
        --name #為容器定義一個新的名字
        -d          #后台運行,返回容器id,開啟守護容器式
        -i            #以交互模式運行容器,通常與-t同時使用
        -t            #為容器分配一個偽終端
        -p            #指定端口映射
                        #hostport : containerPort
        -P             #隨機分配端口

示例:

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

 

查看容器

docker ps [option]
    -a        #列出當前所有正在運行的容器+歷史上運行過的
    -l        #顯示最新創建的容器
    -n        #顯示最近n個創建的容器
    -q        #靜默模式,只顯示容器編號
    --no-trunc    #不截斷輸出

 

啟動容器

docker start 鏡像名/鏡像ID

退出容器

exit #容器停止並且退出
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     ~         #強制停止容器
docker rm       ~          #刪除單個容器  刪除多個參照鏡像

 

查看容器日志

docker logs -f -t --tail 容器id
#-t 加入時間戳
#-f 跟隨最新的日志打印
# --tail 顯示最后多少條

 

容器交互

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

docker attach 容器id/鏡像名 #直接進入容器命令終端,不會啟動新的進程

docker exec #是在容器中打開新的終端,並且可以打開新的進程

 容器提交

容器卷

docker 理念

將運用與運行的環境打包形成容器運行,運行可以伴隨着容器,但是我們隊數據的要求是希望持久化的

容器之間希望有可能共享數據

 

容器卷的設計目的就是數據的持久化,完全獨立於容器的生存周期,因此docker不會再容器刪除時發刪除其掛在的數據卷

特點

• 數據卷可在容器之間共享或重用數據
• 卷中的更改可以直接生效
• 數據卷中的更改不會包含在鏡像的更新中
• 數據卷的生命周期一直持續到沒有容器使用它位置

命令添加容器卷

docker run -it -v /宿主機絕對路徑目錄:/容器內目錄   鏡像名

簡單例子:

創建了關聯文件夾以后,里面的數據進行共享

無論在目錄下哪個文件編寫內容都可以進行同步

即使關閉了容器,編寫了內容,再開啟容器,那么數據也是可以進行同步的

 

例子2:

 

 

 

 

容器卷權限

docker run -it -v /宿主機絕對路勁:/容器目錄:ro 鏡像名

#ro read only

 

Dockerfile

dockerfile 簡單實例

Dockerfile是什么?

       Docker images  --à DockerFile 是對鏡像源碼級的描述

 

例子:

用dockerfile添加數據卷

•  根目錄下新建mydocker文件夾並進入
• 可在dockerfile中使用volume指令來給鏡像添加一個或者多個容器卷
• file構建
• build后生成鏡像 獲得一個新的鏡像
• run 容器

mkdir mydocker
cd mydocker/
vim dockerfile
    

dockerfile文件:

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

#根據dockerfile創建一個新的鏡像
docker build -f /mydocker/dockerfile -t mycentos

#查看新建的鏡像
docker images 

有了新的鏡像之后我們就可以運行容器實例且自帶容器卷

 

我們來看centos的dockerfile

dockerfile的解析過程

1. 每條保留字指令都必須為大寫字母且后面要跟隨至少一個參數
2. 指令按照從上到下,順序執行
3. #表示注釋
4. 每條指令都會創建一個新的鏡像層,並對鏡像進行提交

總結:

• 從應用角度看,dockerfile,docker鏡像和docker容器分別代表軟件的三個不同的階段,
• Dockerfile是軟件的原材料
• docker鏡像是軟件的交付品
• docker容器則可以認為是軟件的運行態

 

dockerfile需要定義一進城需要的一切東西,dockerfile設計的內容包括執行代碼或者是文件,環境,變量,依賴包,運行時的環境,動態鏈接庫,操作系統的發行版,服務京城和內核進城

docker鏡像,在dockerfile定義一個文件以后,docker build 會產生一個docker鏡像,當運行docker鏡像時,會真正開始提供服務

 

dockerfile保留字

FROM #基礎鏡像,當前新鏡像時基於哪個鏡像的

MAINTAINER #鏡像維護者的姓名和郵箱地址

RUN #容器構建時需要運行的命令

EXPOSE #當前容器對外暴露的端口

ENV # 用來在構建鏡像過程中設置環境變量

ADD #將宿主機目錄下的文件拷貝進鏡像且ADD命令會自動處理url和解壓tar壓縮包

COPY #將從構建上下文目錄中<源目錄>的文件/目錄復制到一個新的鏡像內的<目標路徑>位置 
        #用法 COPY src dest 或者 COPY ["src","dest"]

VOLUME #容器數據卷,用於數據的保存和持久化

CMD #dockerfile可以有多個CMD命令,但只有最后一個生效 CMD會被docker run之后的參數替換

ENTRYPOINT #和CMD一樣 指定一個容器啟動時要運行的命令但是可以追加命令

ONBUILD #當構建一個被繼承的dockerfile時運行命令,父鏡像在被子鏡像繼承后父鏡像的onbuild被觸發

 

例子1:

構建一個自帶vim和net-tool的centos鏡像

dockerfile文件內容:

FROM centos

MAINTAINER chen<[e-mail]>

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的區別

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

根據dockerfile創建鏡像

Docker run myip 執行myip鏡像 
如果執行 docker run myip –i 那么-i會覆蓋[]里面的內容
變成 CMD –i那么久會報錯

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

當我們用ENTRYPOINT 的時候是追加的狀態
那么運行 docker run myip2
實際上是執行了 curl –s –i http://ip.cn (-i是查看請求頭)

 

例子3

自定制tomcat

 

 

 

安裝mysql和redis

例子:4 

運行mysql

docker pull mysql:5.6

創建容器且配置數據卷 和mysql密碼
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
###############################
進入mysql
docker exec -it  容器id  /bin/bash
mysql -uroot –p
123456

 

Win10 連接docker的mysql

ifconfig

 

 

 

用docker做數據庫的備份

 

例子5

用docker 使用redis

docker pull redis:3.2

啟動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

 

配置文件寫入redis.conf文件(不是文件夾)

# Redis配置文件樣例

# 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默認不是以守護進程的方式運行，可以通過該配置項修改，使用yes啟用守護進程
# 啟用守護進程后，Redis會把pid寫到一個pidfile中，在/var/run/redis.pid
daemonize no

# 當Redis以守護進程方式運行時，Redis默認會把pid寫入/var/run/redis.pid文件，可以通過pidfile指定
pidfile /var/run/redis.pid

# 指定Redis監聽端口，默認端口為6379
# 如果指定0端口，表示Redis不監聽TCP連接
port 6379

# 綁定的主機地址
# 你可以綁定單一接口，如果沒有綁定，所有接口都會監聽到來的連接
# 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

# 當客戶端閑置多長時間后關閉連接，如果指定為0，表示關閉該功能
timeout 0

# 指定日志記錄級別，Redis總共支持四個級別：debug、verbose、notice、warning，默認為verbose
# debug (很多信息, 對開發／測試比較有用)
# 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

# 日志記錄方式，默認為標准輸出，如果配置為redis為守護進程方式運行，而這里又配置為標准輸出，則日志將會發送給/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

# 設置數據庫的數量，默認數據庫為0，可以使用select <dbid>命令在連接上指定數據庫id
# dbid是從0到‘databases’-1的數目
databases 16

################################ SNAPSHOTTING  #################################
# 指定在多長時間內，有多少次更新操作，就將數據同步到數據文件，可以多個條件配合
# 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.
#
#   滿足以下條件將會同步數據:
#   900秒（15分鍾）內有1個更改
#   300秒（5分鍾）內有10個更改
#   60秒內有10000個更改
#   Note: 可以把所有“save”行注釋掉，這樣就取消同步操作了

save 900 1
save 300 10
save 60 10000

# 指定存儲至本地數據庫時是否壓縮數據，默認為yes，Redis采用LZF壓縮，如果為了節省CPU時間，可以關閉該選項，但會導致數據庫文件變的巨大
rdbcompression yes

# 指定本地數據庫文件名，默認值為dump.rdb
dbfilename dump.rdb

# 工作目錄.
# 指定本地數據庫存放目錄，文件名由上一個dbfilename配置項指定
# 
# Also the Append Only File will be created inside this directory.
# 
# 注意，這里只能指定一個目錄，不能指定文件名
dir ./

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

# 主從復制。使用slaveof從 Redis服務器復制一個Redis實例。注意，該配置僅限於當前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.
# 設置當本機為slav服務時，設置master服務的ip地址及端口，在Redis啟動時，它會自動從master進行數據同步
# slaveof <masterip> <masterport>


# 當master服務設置了密碼保護時，slav服務連接master的密碼
# 下文的“requirepass”配置項可以指定密碼
# 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.
# 設置Redis連接密碼，如果配置了連接密碼，客戶端在連接Redis時需要通過auth <password>命令提供密碼，默認關閉
# 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 ####################################

# 設置同一時間最大客戶端連接數，默認無限制，Redis可以同時打開的客戶端連接數為Redis進程可以打開的最大文件描述符數，
# 如果設置maxclients 0，表示不作限制。當客戶端連接數到達限制時，Redis會關閉新的連接並向客戶端返回max Number of clients reached錯誤信息
# 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最大內存限制，Redis在啟動時會把數據加載到內存中，達到最大內存后，Redis會先嘗試清除已到期或即將到期的Key，
# 當此方法處理后，仍然到達最大內存設置，將無法再進行寫入操作，但仍然可以進行讀取操作。
# Redis新的vm機制，會把Key存放內存，Value會存放在swap區
# 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進行日志記錄，Redis在默認情況下是異步的把數據寫入磁盤，如果不開啟，可能會在斷電時導致一段時間內的數據丟失。
# 因為redis本身同步數據文件是按上面save條件來同步的，所以有的數據會在一段時間內只存在於內存中。默認為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，默認為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.

# 指定更新日志條件，共有3個可選值：
# no:表示等操作系統進行數據緩存同步到磁盤（快）
# always:表示每次更新操作后手動調用fsync()將數據寫到磁盤（慢，安全）
# everysec:表示每秒同步一次（折衷，默認值）

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.
# 指定是否啟用虛擬內存機制，默認值為no，
# VM機制將數據分頁存放，由Redis將訪問量較少的頁即冷數據swap到磁盤上，訪問多的頁面由磁盤自動換出到內存中
# 把vm-enabled設置為yes，根據需要設置好接下來的三個VM參數，就可以啟動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交換文件最好的存儲是SSD（固態硬盤）
# 虛擬內存文件路徑，默認值為/tmp/redis.swap，不可多個Redis實例共享
# *** 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.
# 將所有大於vm-max-memory的數據存入虛擬內存，無論vm-max-memory設置多少，所有索引數據都是內存存儲的（Redis的索引數據就是keys）
# 也就是說當vm-max-memory設置為0的時候，其實是所有value都存在於磁盤。默認值為0
vm-max-memory 0

# Redis swap文件分成了很多的page，一個對象可以保存在多個page上面，但一個page上不能被多個對象共享，vm-page-size是要根據存儲的數據大小來設定的。
# 建議如果存儲很多小對象，page大小最后設置為32或64bytes；如果存儲很大的對象，則可以使用更大的page，如果不確定，就使用默認值
vm-page-size 32

# 設置swap文件中的page數量由於頁表（一種表示頁面空閑或使用的bitmap）是存放在內存中的，在磁盤上每8個pages將消耗1byte的內存
# swap空間總容量為 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.
# 設置訪問swap文件的I/O線程數，最后不要超過機器的核數，如果設置為0，那么所有對swap文件的操作都是串行的，可能會造成比較長時間的延遲，默認值為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.
# 指定在超過一定的數量或者最大的元素超過某一臨界值時，采用一種特殊的哈希算法
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，默認為開啟
activerehashing yes

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

# 指定包含其他的配置文件，可以在同一主機上多個Redis實例之間使用同一份配置文件，而同時各實例又擁有自己的特定配置文件
# include /path/to/local.conf
# include /path/to/other.conf

 

 

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