Overview
This interface layer implements a public address protocol useful for load balancers and their subordinates. The load balancers (providers) set their own public address and port, which is then available to the subordinates (requirers).
Usage
Provides
By providing the public-address interface, your charm is providing an HTTP
server that can load-balance for another HTTP based service.
Your charm need only provide the address and port on which it is serving its
content, as soon as the {relation_name}.available state is set:
from charmhelpers.core import hookenv
@when('website.available')
def configure_website(website):
website.set_address_port(hookenv.unit_get('public-address'), hookenv.config('port'))Requires
By requiring the public-address interface, your charm is consuming one or
more HTTP servers, to load-balance a set of servers, etc.
Your charm should respond to the {relation_name}.available state, which
indicates that there is at least one HTTP server connected.
The get_addresses_ports() method returns a list of available addresses and
ports.
The return value is a list of dicts of the following form:
[
{
'public-address': address_of_host,
'port': port_for_host,
},
# ...
]A trivial example of handling this interface would be:
from charmhelpers.core import hookenv
@when('loadbalancer.available')
def update_reverse_proxy_config(loadbalancer):
hosts = loadbalancer.get_addresses_ports()
for host in hosts:
hookenv.log('The loadbalancer for this unit is {}:{}'.format(
host['public-address'],
host['port']))