Example HAProxy 1.6+ config for serving static content from AWS S3 bucket

haproxy.cfg

# This config will serve up: http://<haproxy>/foo/index.html
#
# This post was indispensable
# https://stackoverflow.com/questions/39964607/haproxy-forward-request-to-s3-hosted-site

global
    #debug # Uncomment this line to debug and then comment out daemon
    daemon
    maxconn 256

defaults
    mode http
    log global
    timeout connect 5000ms
    timeout client 50000ms
    timeout server 50000ms

frontend http-in
    bind *:80
  
    # URL ACL
    acl s3 path_beg /foo

    # BACKEND SERVER RULES
    use_backend S3 if s3

backend S3
    # must be in "Virtual Hosted–Style Method" format as per S3 docs - https://docs.aws.amazon.com/AmazonS3/latest/dev/VirtualHosting.html
    http-request set-header Host <s3-bucketname>.s3.<s3-location>.amazonaws.com 
    
    # required for stripping and rewriting pathname
    http-request set-path %[path,regsub(^/foo,)]
    
    # cannot be s3.amazonaws.com
    server CDN s3.<s3-location>.amazonaws.com:80