Reload HAProxy configuration with no downtime.

haproxy_reload

#!/bin/bash
#
# The trick here is to dump pids of all haproxy processes into a file
# (-p option) and then tell them to finish their work and exit (-sf).

HAPROXY=/usr/sbin/haproxy
HAPROXY_PID=/var/run/haproxy.pid
HAPROXY_CONFIG=/etc/haproxy/haproxy.cfg

$HAPROXY -f $HAPROXY_CONFIG -p $HAPROXY_PID -sf $(cat $HAPROXY_PID)