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HAProxy Cookbook & Useful Snippets

Collection of useful HAProxy configuration snippets for common tasks like URL rewriting and header manipulation.

URL Rewriting​

Map Subdomain to Path​

Example: http://sub1.example.com/a/b/c -> http://example.com/sub1/a/b/c

# Extract subdomain
http-request set-var(req.rewrite_example) req.hdr(host),lower,regsub(\.example\.com$,) if { hdr_end(host) -i .example.com }

# Set path to /subdomain/path
http-request set-path /%[var(req.rewrite_example)]%[path] if { var(req.rewrite_example) -m found }

# Forward to main domain
http-request set-header Host example.com if { var(req.rewrite_example) -m found }

Header Manipulation​

Update X-Forwarded-For​

Add client IP to the top of the list:

acl h_xff_exists req.hdr(X-Forwarded-For) -m found
http-request replace-header X-Forwarded-For (.*) %[src],1 if h_xff_exists

Strip Port from Host Header​

Example: www.domain.com:80 -> www.domain.com

http-request replace-value Host (.*):.* 1

Advanced Logic​

Layer 7 Control​

Refer to HAProxy Documentation - http-request.

# Replace host suffix
http-request replace-header Host (.*)[.]([^.])+[.]wode[.]co \1.incos.wode.co if { hdr_end(host) -i .wode.co }

# Set variables and headers based on host
http-request set-var(req.xRawHost) req.hdr(host) if { hdr_end(host) -i .zhensi.wode.co }
http-request set-var(req.xName) req.hdr(host),lower,regsub(([^.])\.wode\.co,\1) if { hdr_end(host) -i .zhensi.wode.co }
http-request set-header X-IncOS-Name req.xName if { var(req.xName) -m found }
http-request set-header X-IncOS-Host req.xRawHost if { var(req.xRawHost) -m found }

Logging​