Example configuration to log all http request (with post body)

sample_haproxy.conf

global
    log 127.0.0.1 local0
    user root
    group root
    daemon

defaults
    log     global
    mode    http
    option  httplog
    option  dontlognull
    retries 3
    option redispatch
    timeout connect 5000
    timeout client  120000
    timeout server  90000

frontend www-http
    bind 0.0.0.0:9000

    option http-buffer-request
    declare capture request len 400000
    http-request capture req.body id 0
    log-format {"%[capture.req.hdr(0)]"}

    default_backend node-servers

backend node-servers
    server node google.com:80 maxconn 20