Hackers Chronicle - Online Cyber Security News: Load Balancing

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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipybvTyxMYGeHrvEwrVBcT-kUT58xnUwFzVVC3e0NsVS6_nizojFEnAcCpx9taJFEKFTlWxwdhkBAtm7J_Ew69rq4XOyKayQLdg0hli6nDuGc3zA-oJBTDuHL8Ty2gZKpkKMHtPGpqmBE/s1600/haproxy-stats-hackerschronicle-com.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Enable HAProxy stats in Cent OS" border="0" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipybvTyxMYGeHrvEwrVBcT-kUT58xnUwFzVVC3e0NsVS6_nizojFEnAcCpx9taJFEKFTlWxwdhkBAtm7J_Ew69rq4XOyKayQLdg0hli6nDuGc3zA-oJBTDuHL8Ty2gZKpkKMHtPGpqmBE/s1600/haproxy-stats-hackerschronicle-com.png" title="Enable HAProxy stats in Cent OS" width="400" /></a></div>
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HAProxy Stats provides a lot of information about data transfer, total connection, server state etc. After installing HAProxy if you want to view HAProxy stats in your web browser, You can easily configure it by making few changes in your <a href="http://www.hackerschronicle.com/search/label/HAProxy" target="_blank">HAProxy</a> configuration using following steps.<br />
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<h3>
1: Enable Stats in HAProxy</h3>
To enable stats edit your haproxy configuration file(<span class="highlight">/etc/haproxy/haproxy.cfg</span>) and add below entry after defaults section.<br />
<div class="content shadow-radial">
listen  stats   192.168.10.10:1936<br />
mode            http<br />
log             global<br />
<br />
maxconn 10<br />
<br />
clitimeout      100s<br />
srvtimeout      100s<br />
contimeout      100s<br />
timeout queue   100s<br />
<br />
stats enable<br />
stats hide-version<br />
stats refresh 30s<br />
stats show-node<br />
stats auth admin:password<br />
stats uri  /haproxy?stats</div>
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<h3>
2: Access HAProxy Stats</h3>
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Your can access HAProxy stats using following url. Change ip with your haproxy server ip address.<br />
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URL: http://192.168.10.10:1936/haproxy?stats<br />
Login user: admin<br />
Login password: password</div>
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<h3>
3: Change Login Details</h3>
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If you want to changed login details of HAProxy stats, edit your configuration and update “stats auth” value like below<br />
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stats auth  username:password</div>
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Save configuration file and restart HAProxy to update service.<br />
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<h3>
4: Change HAProxy Stats URL</h3>
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To change url of haproxy stats edit configuration file and update following value.<br />
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stats uri  /ha-stats<br />
or<br />
stats uri  /stats</div>
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<br />
Save configuration file and restart HAProxy to update service.<br />
<div class="command wobble-horizontal">
service haproxy restart </div>
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Now you can access url like <span class="system pop">http://192.168.10.10:1936/ha-stats</span> or <span class="system pop">http://192.168.10.10:1936/stats</span>.<br />
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<b>Congratulation’s!</b> HAProxy stats configuration has been completed successfully. Read next article to <a href="http://www.hackerschronicle.com/search/label/HAProxy">setup ACL in HAProxy</a>.</div>

HAProxy Stats provides a lot of information about data transfer, total connection, server state etc. After installing HAProxy if you wan...

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HAproxy is open source proxy that can be used to enable <a href="http://en.wikipedia.org/wiki/High_availability">high availability</a> and <a href="http://en.wikipedia.org/wiki/Load_balancing_(computing)">load balancing</a> for web applications. It was designed especially for high load projects so it is very fast and predictable, HAProxy is based on single-process model.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjA5j4GnrTrI8gUBenIJIvo5wtPO1FwxsLGHQo-XFNyKTk41I7c3BuMI3Sq7_begyT0pIfOTO9rqsVU77YMOZDepziJvEN34rvTERZJhas11TTLWzXlFCwsGOok5EnvjbJpMoIBohezUmM/s1600/HAProxy-logo.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="Installing HAProxy on CentOS for Load Balancing" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjA5j4GnrTrI8gUBenIJIvo5wtPO1FwxsLGHQo-XFNyKTk41I7c3BuMI3Sq7_begyT0pIfOTO9rqsVU77YMOZDepziJvEN34rvTERZJhas11TTLWzXlFCwsGOok5EnvjbJpMoIBohezUmM/s1600/HAProxy-logo.png" title="Installing HAProxy on CentOS for Load Balancing" /></a></div>
In this post I’ll describe sample setup of HAProxy: users’ requests are load balanced between two web servers <strong>Web1</strong> and <strong>Web2</strong>, if one of them goes down then all the request are processed by alive server, once dead servers recovers load balancing enables again. See topology to the right.<br />
<h3>
Installation</h3>
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HAProxy is included into repositories for major Linux distributions, so if you’re using <a href="http://www.hackerschronicle.com/search/label/Centos">Centos</a>, <a href="http://www.hackerschronicle.com/search/label/Redhat">Redhat</a> or <a href="http://www.hackerschronicle.com/search/label/Fedora">Fedora</a> type the following command:<br />
<br />
<div class="command wobble-horizontal">
#yum install haproxy</div>
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<br />
If you’re Ubuntu, Debian or Linux Mint user use this one instead:<br />
<br />
<div class="command wobble-horizontal">
#apt-get install haproxy</div>
<h3>
Configuration</h3>
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As soon as HAProxy is installed it’s time to edit its configuration file, usually it’s placed in <span class="highlight system pop">/etc/haproxy/haproxy.cfg</span>.<br />
Official documentation for HAProxy 1.4 (stable) is <a href="http://haproxy.1wt.eu/download/1.4/doc/configuration.txt">here</a>.<br />
<br />
Here is configuration file to implement setup shown at the diagram and described above:<br />
<div class="content shadow-radial">
global<br />
user daemon<br />
group daemon<br />
daemon<br />
log 127.0.0.1 daemon<br />
<br />
listen http<br />
bind 1.2.3.4:80<br />
mode http<br />
option tcplog<br />
<br />
log global<br />
option dontlognull<br />
<br />
balance roundrobin<br />
clitimeout 60000<br />
srvtimeout 60000<br />
contimeout 5000<br />
retries 3<br />
server web1 web1.hackerschronicle.com:80 check<br />
server web2 web2.hackerschronicle.com:80 check<br />
cookie web1 insert nocache<br />
cookie web2 insert nocache</div>
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Let’s stop on most important parts of this configuration file. Section <strong>global</strong> specifies user and group which will be used to run haproxy process (<strong>daemon</strong> in our example). Line <strong>daemon</strong> tells HAProxy to run in background, <strong>log 127.0.0.1 daemon</strong> specifies syslog facility for sending logs from HAProxy.<br />
<br />
Section <strong>listen http</strong> contains line <strong>bind 1.2.3.4:80</strong> that specifies IP address and port that will be used to accept users’ requests (they will be load balanced between Web1 and Web2). Line <strong>mode http</strong> means that HAProxy will filter all requests different from HTTP and will do load balancing over HTTP protocol.<br />
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Line <strong>balance roundrobin</strong> specifies load balancing algorithm according to which each web server (Web1 and Web2) will be used in turns according to their weights. In our example weights for both servers are the same so load balancing is fair.<br />
<br />
Lines <strong>server web1</strong> … and <strong>server web2</strong> … specify web servers for load balancing and failover, in our case they are load balanced according to round robin algorithm and have the same priority/weight.<br />
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The last two lines in configuration files are optional, they makes it possible to preserve cookies, it means for example that if you logged in to web application hosted at Web1 and then HAProxy forwarded your next request to Web2 you will still have logged in session opened as cookies with session id from Web1 will be sent to you from Web2 as well.</div>
<h3>
Start HAProxy Service</h3>
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# service haproxy start<br />
# chkconfig haproxy on</div>
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<br />
<strong>Congratulation’s!</strong> you have successfully configured HAProxy load balancer. Read next article to <a href="http://www.hackerschronicle.com/search/label/HAProxy">enable haproxy stats</a> and <a href="http://www.hackerschronicle.com/search/label/HAProxy">setup ACL in HAProxy</a>.</div>

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