企业架构LB-服务器的负载均衡之HAProxy实现

学习目标和内容

1、能够通过HAProxy实现负载均衡

###1、介绍

Introduction

HAProxy, which stands for High Availability Proxy, is a popular opensource software TCP/HTTP LoadBalancer and proxying solution which can be run on Linux, Solaris, and FreeBSD. Its most common use is to improve the performance and reliability of a server environment by distributing the workload across multiple servers(e.g. web, application, database). It is used in many high-profile environments, including: GitHub, Imgur, Instagram, and Twitter. In this guide, we will provide a general overview of what HAProxy is,basic load-balancing terminology, and examples of how it might be used to improve the performance and reliability of your own server environment.

No Load Balancing

A simple web application environment with no load balancing might look like the following: In this example, the user connects directly to your web server, at your domain.com and there is no load balancing. If your single webserver goes down, the user will no longer be able to access your webserver. Additionally, if many users are trying to access your server simultaneously and it is unable to handle the load, they may have a slow experience or they may not be able to connect at all.

Layer 4 Load Balancing

The simplest way to load balance network traffic to multiple servers is to use layer 4 (transport layer) load balancing. Load balancing this way will forward user traffic based on IP range and port (i.e. if a request comes in for yourdomain.com, the traffic will be forwarded to the backend that handles all the requests for yourdomain.com on port 80). For more details on layer 4, check out the TCP subsection of our Introduction to Networking. Here is a diagram of a simple example of layer 4 load balancing: The user accesses the load balancer, which forwards the user's request to the web-backend group of backend servers. Whichever backend server is selected will respond directly to the user's request. Generally, all of the servers in the web-backend should be serving identical content--otherwise the user might receive inconsistent content. Note that both web servers connect to the same database server.

Layer 7 Load Balancing

Another, more complex way to load balance network traffic is to use layer 7 (application layer) load balancing. Using layer 7 allows the load balancer to forward requests to different backend servers based on the content of the user's request. This mode of load balancing allows you to run multiple web application servers under the same domain and port. For more details on layer 7, check out the HTTP subsection of our Introduction to Networking. Here is a diagram of a simple example of layer 7 load balancing: In this example, if a user requests yourdomain.com/blog, they are forwarded to the blog backend, which is a set of servers that run a blog application. Other requests are forwarded to web-backend,which might be running another application. Both backends use the same database server, in this example

###2、安装

yum方式安装

shell > yum install haproxy

源码编译方式安装

###3、配置

HAProxy version 1.8.30 - Starter Guide

源配置文件说明

# cd /etc/haproxy/
# cp haproxy.cfg haproxy.cfg.bak
# vim haproxy.cfg
**********************************************************************
#---------------------------------------------------------------------
# Example configuration for a possible web application.  See the
# full configuration options online.
#
#   http://haproxy.1wt.eu/download/1.4/doc/configuration.txt
#
#---------------------------------------------------------------------#---------------------------------------------------------------------
# Global settings    
#---------------------------------------------------------------------
global    #全局配置文件# to have these messages end up in /var/log/haproxy.log you will# need to:     #配置日志## 1) configure syslog to accept network log events.  This is done#    by adding the '-r' option to the SYSLOGD_OPTIONS in#    /etc/sysconfig/syslog    #修改syslog配置文件## 2) configure local2 events to go to the /var/log/haproxy.log#   file. A line like the following can be added to#   /etc/sysconfig/syslog    #定义日志设备##    local2.*                       /var/log/haproxy.log#log         127.0.0.1 local2        #日志配置，所有的日志都记录本地，通过local2输出chroot      /var/lib/haproxy        #改变haproxy的工作目录pidfile     /var/run/haproxy.pid    #指定pid文件的路径maxconn     4000                    #最大连接数的设定user        haproxy                 #指定运行服务的用户group       haproxy                 #指定运行服务的用户组daemon# turn on stats unix socketstats socket /var/lib/haproxy/stats#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------
defaultsmode                    http                  #默认使用协议,可以为{http|tcp|health} http:是七层协议 tcp:是四层 health：只返回OKlog                     global                #全局日志记录option                  httplog               #详细记录http日志option                  dontlognull           #不记录空日志option http-server-close                      #启用http-server-closeoption forwardfor       except 127.0.0.0/8    #来自这些信息的都不forwardforoption                  redispatch            #重新分发，ServerID对应的服务器宕机后，强制定向到其他运行正常的服务器retries                 3                      #3次连接失败则认为服务不可用timeout http-request    10s                    #默认http请求超时时间timeout queue           1m                     #默认队列超时时间timeout connect         10s                    #默认连接超时时间timeout client          1m                     #默认客户端超时时间timeout server          1m                     #默认服务器超时时间timeout http-keep-alive 10s                    #默认持久连接超时时间timeout check           10s                    #默认检查时间间隔maxconn                 3000                   #最大连接数#---------------------------------------------------------------------
# main frontend which proxys to the backends
#---------------------------------------------------------------------
frontend  main *:5000#定义ACL规则以如".html"结尾的文件；-i：忽略大小写acl url_static       path_beg       -i /static /images /javascript /stylesheetsacl url_static       path_end       -i .jpg .gif .png .css .jsuse_backend static          if url_static    #调用后端服务器并检查ACL规则是否被匹配default_backend             app              #客户端访问时默认调用后端服务器地址池#---------------------------------------------------------------------
# static backend for serving up images, stylesheets and such
#---------------------------------------------------------------------
backend static                    #定义后端服务器balance     roundrobin        #定义算法;基于权重进行轮询server      static 127.0.0.1:4331 check    check:启动对后端server的健康状态检测#---------------------------------------------------------------------
# round robin balancing between the various backends
#---------------------------------------------------------------------
backend appbalance     roundrobinserver  app1 127.0.0.1:5001 checkserver  app2 127.0.0.1:5002 checkserver  app3 127.0.0.1:5003 checkserver  app4 127.0.0.1:5004 check

实际配置文件使用

#---------------------------------------------------------------------
# Example configuration for a possible web application.  See the
# full configuration options online.
#
#   http://haproxy.1wt.eu/download/1.4/doc/configuration.txt
#
#---------------------------------------------------------------------
​
#---------------------------------------------------------------------
# Global settings
#---------------------------------------------------------------------
global# to have these messages end up in /var/log/haproxy.log you will# need to:## 1) configure syslog to accept network log events.  This is done#    by adding the '-r' option to the SYSLOGD_OPTIONS in#    /etc/sysconfig/syslog## 2) configure local2 events to go to the /var/log/haproxy.log#   file. A line like the following can be added to#   /etc/sysconfig/syslog##    local2.*                       /var/log/haproxy.log#log         127.0.0.1 local2
​chroot      /var/lib/haproxypidfile     /var/run/haproxy.pidmaxconn     4000user        haproxygroup       haproxydaemon
​# turn on stats unix socketstats socket /var/lib/haproxy/stats
​
#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------
defaultsmode                    httplog                     globaloption                  httplogoption                  dontlognulloption http-server-closeoption forwardfor       except 127.0.0.0/8option                  redispatchretries                 3timeout http-request    10stimeout queue           1mtimeout connect         10stimeout client          1mtimeout server          1mtimeout http-keep-alive 10stimeout check           10smaxconn                 3000
listen statsmode httpbind *:1090stats enablestats hide-versionstats uri    /hadmin?statsstats realm  Haproxy\ Statisticsstats auth    admin:adminstats admin if TRUE
#---------------------------------------------------------------------
# main frontend which proxys to the backends
#---------------------------------------------------------------------
#1、修改haproxy默认监听在80端口
frontend  main *:80#2、下面几行注释掉#stats uri /status#acl url_static       path_beg       -i /static /images /javascript /stylesheets#acl url_static       path_end       -i .jpg .gif .png .css .js
​#use_backend static          if url_static#3、代理转发到后端服务器  app段default_backend             app
​
#---------------------------------------------------------------------
# static backend for serving up images, stylesheets and such
#---------------------------------------------------------------------
#backend static
#    balance     roundrobin
#    server      static 127.0.0.1:4331 check
​
#---------------------------------------------------------------------
# round robin balancing between the various backends
#---------------------------------------------------------------------
#4、后端app段定义
backend appbalance     roundrobin#定义真实后端服务器IPserver  app1 192.168.17.100:80 checkserver  app2 192.168.17.104:80 check#server  app1 192.168.17.100:80 weight 1#server  app2 192.168.17.104:80 weight 1#server  app3 127.0.0.1:5003 check#server  app4 127.0.0.1:5004 check