Interface layer for the basic http interface protocol
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johnsca Merge pull request #12 from hyperbolic2346/mwilson/network-spaces
Adding network space support for http interface.
Latest commit 5134e94 Jan 18, 2018


This interface layer implements the basic form of the http interface protocol, which is used for things such as reverse-proxies, load-balanced servers, REST service discovery, et cetera.



By providing the http interface, your charm is providing an HTTP server that can be load-balanced, reverse-proxied, used as a REST endpoint, etc.

Your charm need only provide the port on which it is serving its content, as soon as the {relation_name}.available state is set:

def configure_website(website):


By requiring the http interface, your charm is consuming one or more HTTP servers, as a REST endpoint, 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 services() method returns a list of available HTTP services and their associated hosts and ports.

The return value is a list of dicts of the following form:

        'service_name': name_of_service,
        'hosts': [
                'hostname': address_of_host,
                'port': port_for_host,
            # ...
    # ...

A trivial example of handling this interface would be:

from charms.reactive.helpers import data_changed

def update_reverse_proxy_config(reverseproxy):
    services =
    if not data_changed('', services):
    for service in services:
        for host in service['hosts']:
            hookenv.log('{} has a unit {}:{}'.format(