Add support for Juju network spaces

Juju 2.0 provides support for network spaces, allowing
charm authors to support direct binding of relations and
extra-bindings onto underlying network spaces.

Add public and cluster extra bindings to this charm to
support separation of client facing and cluster network
traffic using Juju network spaces.

Existing network configuration options will still be
preferred over any Juju provided network bindings, ensuring
that upgrades to existing deployments don't break.

Change-Id: I78ab6993ad5bd324ea52e279c6ca2630f965544c

hooks/utils.py

@@ -13,6 +13,9 @@ from charmhelpers.core.hookenv import (
     unit_get,
     cached,
     config,
+    network_get_primary_address,
+    log, DEBUG,
+    status_set,
 )
 from charmhelpers.core import unitdata
 from charmhelpers.fetch import (
@@ -88,6 +91,32 @@ def get_host_ip(hostname=None):
             return answers[0].address
 
 
+@cached
+def get_public_addr():
+    if config('ceph-public-network'):
+        return get_network_addrs('ceph-public-network')[0]
+
+    try:
+        return network_get_primary_address('public')
+    except NotImplementedError:
+        log("network-get not supported", DEBUG)
+
+    return get_host_ip()
+
+
+@cached
+def get_cluster_addr():
+    if config('ceph-cluster-network'):
+        return get_network_addrs('ceph-cluster-network')[0]
+
+    try:
+        return network_get_primary_address('cluster')
+    except NotImplementedError:
+        log("network-get not supported", DEBUG)
+
+    return get_host_ip()
+
+
 def get_networks(config_opt='ceph-public-network'):
     """Get all configured networks from provided config option.
 
@@ -102,6 +131,31 @@ def get_networks(config_opt='ceph-public-network'):
     return []
 
 
+def get_network_addrs(config_opt):
+    """Get all configured public networks addresses.
+
+    If public network(s) are provided, go through them and return the
+    addresses we have configured on any of those networks.
+    """
+    addrs = []
+    networks = config(config_opt)
+    if networks:
+        networks = networks.split()
+        addrs = [get_address_in_network(n) for n in networks]
+        addrs = [a for a in addrs if a]
+
+    if not addrs:
+        if networks:
+            msg = ("Could not find an address on any of '%s' - resolve this "
+                   "error to retry" % (networks))
+            status_set('blocked', msg)
+            raise Exception(msg)
+        else:
+            return [get_host_ip()]
+
+    return addrs
+
+
 def assert_charm_supports_ipv6():
     """Check whether we are able to support charms ipv6."""
     if lsb_release()['DISTRIB_CODENAME'].lower() < "trusty":