A cheating Guide for HA Proxy !

• apt install --no-install-recommends software-properties-common
• add-apt-repository ppa:vbernat/haproxy-2.8 -y It is the latest LTS Version
• sudo apt install haproxy=2.4.\* Maintain Future Upgrades

• The config file path: /etc/haproxy/haproxy.cfg
• It contains many lines, do not touch them !

use HTTP Mode if you want to:

• routing traffic to particular servers based on the URL, HTTP headers or body
• modifying the URL and headers
• reading and setting cookies
• determining the health of a server based on its HTTP responses

• We can add a header called X-Forwarded-For to the incoming request before it's passed along to the Web server option forwardfor if-none
• Also add Forwarded for Header. Forwarded was officially proposedin RFC 7239 and serves the same purpose as X-Forwarded-For

option forwardfor if-none
http-request set-header Forwarded for=%[src]

• Add stats enable to defaults section to enable it
• Go to /haproxy?stats of the target frontend

• Round-Robin
• Weighted Round-Robin
• Weighted/Normal LeastConn
• Weighted/Normal Hash URI
• First Available

Fetch methods and What they do

• path exact string match
• path_beg URL begins with string
• path_dir subdirectory match
• path_end suffix match
• path_len length match
• path_reg regex match
• path_sub substring match

• acl iswest url_param(region) -i -m str west Exact match http://mysite.com/?region=west and -i means case-insensitive
• Match multiple strings : acl iswest url_param(region) -i -m str west westcoast wc
• Regex Matching : acl iswest url_param(west) -m reg .+

• acl ismobile req.hdr(User-Agent) -i -m reg (android|iphone) Filter the Mobile User-Agents and use a seperate backend for them. reg says contains android or iphone
• Filter based on the Host Header : acl ischeapshoes req.hdr(Host) -i -m str www.cheapshoes.com, acl isexpensiveshoes req.hdr(Host) -i -m str www.expensiveshoes.com
• Match more host on on ACL Rule : acl ischeapshoes req.hdr(Host) -i -m str cheapshoes.com www.cheapshoes.com
• with req.hdr(<Header_Name>) can get a header with its name

• Use redirect prefix
• By default, HAProxy uses an HTTP response code 302

301 The current and all future requests should use the new URL.

302 The current request should be forwarded to the new URL. Future requests should use the original URL.

303 The current request should be forwarded to the new URL, but as a GET. For example, if a client sends a POST request to a form that submits a shopping cart, they could be redirected to another page that shows details of the purchase, but using a GET request. This page can be bookmarked, refreshed, etc. without resubmitting the form. This is available in HTTP/1.1.

307 The current request should be forwarded to the new URL, but do not change the HTTP verb used. For example, if POST was used before, use POST again. Future requests should use the original URL. This is available in HTTP/1.1.

308 The current and all future requests should use the new URL. Do not change the HTTP verb used. For example, if POST was used before, use POST again. This is available in HTTP/1.1.