為什麼要叢集：

通常為了，提高網站的響應速度，總是把一些經常用到的資料放到記憶體中，而不是放到資料庫中，Redis是一個很好的Cache工具，當然了還有Memcached，這裡只講Redis。在我們的電商系統中，熱點資料量往往巨大，比如單點登入、使用者瀏覽商品的資訊、使用者資訊、使用者收藏的商品資訊、短息提醒資料等等，也都用到了redis，如何使redis可以橫向可伸縮擴充套件，這需要由多臺機器協同提供服務，一臺掛掉了，另一臺馬上頂上去，即分散式的redis叢集，就對系統的效能非常重要。

Redis叢集的幾個重要特徵：

(1).Redis 叢集的分片特徵在於將鍵空間分拆了16384個槽位，每一個節點負責其中一些槽位。

(2).Redis提供一定程度的可用性,可以在某個節點宕機或者不可達的情況下繼續處理命令.

(3).Redis 叢集中不存在中心（central）節點或者代理（proxy）節點， 叢集的其中一個主要設計目標是達到線性可擴充套件性（linear scalability）。

(4).Redis叢集要想正常工作，必須要三個主節點，在我搭建的叢集環境中，三個主節點都需要有一個從節點，所以一共六個節點，通俗來講也就是需要開啟6個redis服務。

一、安裝Redis

關於如何在Linux上安裝Redis，可以參考我的這篇部落格，裡面有詳細的安裝步驟，注意在搭建Redis的叢集環境我使用的Redis版本為4.0.1《

整體結構：

二、進群環境的配置

（1）在這裡我就開啟三臺Ubuntu16.04.1，因為電腦8G的記憶體不夠用，如果你電腦記憶體大可以開啟4臺或者更多。在這三臺中我都安裝好了最新版本的Redis。

（2）叢集配置檔案的修改

第一臺配置檔案的修改：首先在usr/redis目錄下，把上面安裝好的的redis檔案放到該目錄下面，具體哪些檔案可參考下圖。

需要的檔案有：

 然後通過下面的命令把上面的檔案複製到usr/redis/目錄下面：

首先在usr目錄下面建立一個redis和s2目錄：sudo mkdir redis;     sudo mkdir s2

目錄建立好後，到上面圖中的目錄下面，開啟終端，執行：cp redis* /usr/redis/，上面圖中的檔案就會到usr/redis/目錄下面，最後到usr/redis/目錄下面，開啟終端，執行sudo cp redis* /usr/redis/s2/，這是該目錄下面也就會有相同的檔案了。

 修改redis.conf檔案中Cluster的配置，修改如下：

首先由於許可權的問題，我們先要切換到root身份：sudo passwd root命令，先修改root的密碼，修改之後，再執行su root  接著輸入你設定的root密碼就可以切換到root身份，如下：

最後在root身份執行下圖中的命令就可修改redis.conf檔案：

這裡只貼出來修改的程式碼：（紅色標註的部分為修改部分）

# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# bind 127.0.0.1  //註釋掉

# 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 no   //yes該為no

# Accept connections on the specified port, default is 6379 (IANA #815344).
# If port 0 is specified Redis will not listen on a TCP socket.
port 6379

# TCP listen() backlog.
#
# In high requests-per-second environments you need an high backlog in order
# to avoid slow clients connections issues. Note that the Linux kernel
# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
# in order to get the desired effect.
tcp-backlog 511

# Unix socket.
#
# Specify the path for the Unix socket that will be used to listen for
# incoming connections. There is no default, so Redis will not listen
# on a unix socket when not specified.
#
# unixsocket /tmp/redis.sock
# unixsocketperm 700

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

# TCP keepalive.
#
# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
# of communication. This is useful for two reasons:
#
# 1) Detect dead peers.
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# On Linux, the specified value (in seconds) is the period used to send ACKs.
# Note that to close the connection the double of the time is needed.
# On other kernels the period depends on the kernel configuration.
#
# A reasonable value for this option is 300 seconds, which is the new
# Redis default starting with Redis 3.2.1.
tcp-keepalive 300
################################ REDIS CLUSTER  ###############################
#
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# WARNING EXPERIMENTAL: Redis Cluster is considered to be stable code, however
# in order to mark it as "mature" we need to wait for a non trivial percentage
# of users to deploy it in production.
# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#
# Normal Redis instances can't be part of a Redis Cluster; only nodes that are
# started as cluster nodes can. In order to start a Redis instance as a
# cluster node enable the cluster support uncommenting the following:
#
cluster-enabled yes

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

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

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

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

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

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

修改完之後 按下ESC 鍵，再按下  :wq!儲存突出。同理，s2中的redis也是這樣修改的但是，需要修改一下埠號，不能喝上面的埠號重複，s2中的埠號為6390。

使用相同的方式修改第二臺上redis的配置：只不過在該臺機器上只有一個redis服務(節點)

上面這兩臺伺服器中的三個redis服務地址分別為：192.168.0.109:6379    192.168.0.109:6390    192.168.0.111:6379，在進行第三部的時候要用到。

（3）第三臺機器的配置

上面的兩步中我們共開起了三臺主redis節點，所以在第三臺伺服器上我們也要開啟三臺從節點，結果如下：

其中s1、s2、s3中檔案和上面的一樣，即三臺從的redis節點。我們需要一個一個安裝上面的配置修改redis.conf檔案，只不過需要注意，三個節點的埠號是不一樣的。s1、s2、s3的埠號分別是:6379   6380  6381

到現在個個redis節點的配置檔案也修改好了，下面我們要分別啟動s1  s2  s3 和上面的三個主redis服務了~~~~~~

 接下來，這三個服務都會生產一個這樣的檔案：

因為redis-trib.rb是ruby寫的，不信可以開啟看看。而在我們的Ubuntu16.04.1上是有ruby的環境的，但是還是強烈建議執行以下下面的指令 安裝ruby，同時還要安裝 ruby的Redis庫，不過沒關係，我們可以按照下面的步驟安裝。

• 安裝Redis-Cluster的依賴庫(可能在安裝依賴庫的時候特別慢，可以使用加速器，我就不在這裡說了，你懂的)

  • 安裝Ruby

    sudo apt-get install ruby

  • 
    安裝Redis.gem

    sudo gem intall redis

耐心等待，因為很慢的(#^.^#)。安裝好之後，執行下面圖中劃的命令：

 解釋：./redis-trib.rb  create --replicas 1 192.168.0.109:6379 192.168.0.109:6390 192.168.0.110:6379 192.168.0.111:6379 192.168.0.111:6380 192.168.0.111:6381

這些IP都是上面redis服務的IP，注意他們之間是有空格分開的。

如果出現上面的資訊說明安裝成功了！！！

其中：192.168.0.109:6379、192.168.0.110:6379/192.168.0.111:6379是主，192.168.0.111:6380/192.168.0.109:6390、192.168.0.111:6381是從的。

（4）測試是否成功

在到192.168.0.110:6379中看看有沒有值：

看到沒，值同步過來了！！！！

三、面對Redis-ClusterC#該如何操作

 step1：使用VS2017新建一個控制檯程式

step2: Install-Package StackExchange.Redis

 step3:編寫程式碼：

 1 using StackExchange.Redis;
 2 using System;
 3 using System.Collections.Generic;
 4 using System.Linq;
 5 using System.Text;
 6 using System.Threading.Tasks;
 7 
 8 namespace LinuxRedisCluster
 9 {
10     class Program
11     {
12         static void Main(string[] args)
13         {
14             using (ConnectionMultiplexer redis = ConnectionMultiplexer.Connect("192.168.0.109:6379,192.168.0.109:6390,192.168.0.110:6379,192.168.0.111:6379,192.168.0.111:6380,192.168.0.111:6381"))
15             {
16 
17                 IDatabase db = redis.GetDatabase();
18                 for (int i = 0; i < 1000; i++)
19                 {
20                     db.StringSet("name"+i, "guozheng"+i);
21                 }
22                 
23 
24                 //var myname = db.StringGet("name");
25                // Console.WriteLine(myname);
26             }
27 
28             Console.ReadKey();
29         }
30     }
31 }

step4:檢視結果：

 四、總結：

關於redis如何叢集的詳細資訊，可以參考Redis手冊：叢集教程

也可以參考下面這些部落格：

http://www.cnblogs.com/huangxincheng/p/5615037.html

http://www.cnblogs.com/piscesLoveCc/p/5779795.html

覺得可以的話，希望點下推薦哈~你們的推薦是我的動力。

基礎篇

實戰篇

作者：郭崢

出處：http://www.cnblogs.com/runningsmallguo/

本文版權歸作者和部落格園共有，歡迎轉載，但未經作者同意必須保留此段宣告，且在文章頁面明顯位置給出原文連結。