Merge lp:~james-page/charm-helpers/network-spaces into lp:charm-helpers

[James Page]

Add support for Juju 2.0 network spaces

Juju 2.0 adds a new hook tool called network-get to query for network
information for named relations and extra-bindings.

Add basic hook tool support and associated unit tests.

[Charles Butler (lazypower)]

LGTM +1

*caveat I have not validated this in a hookenv.

review: Approve

=== modified file 'charmhelpers/core/hookenv.py'
--- charmhelpers/core/hookenv.py	2015-12-10 22:32:57 +0000
+++ charmhelpers/core/hookenv.py	2016-03-07 12:57:24 +0000
@@ -976,3 +976,16 @@
     for callback, args, kwargs in reversed(_atexit):
         callback(*args, **kwargs)
     del _atexit[:]
+
+
+@translate_exc(from_exc=OSError, to_exc=NotImplementedError)
+def network_get_primary_address(binding):
+    '''
+    Retrieve the primary network address for a named binding
+
+    :param binding: string. The name of a relation of extra-binding
+    :return: string. The primary IP address for the named binding
+    :raise: NotImplementedError if run on Juju < 2.0
+    '''
+    cmd = ['network-get', '--primary-address', binding]
+    return subprocess.check_output(cmd).strip()

=== modified file 'tests/core/test_hookenv.py'
--- tests/core/test_hookenv.py	2015-12-10 22:44:10 +0000
+++ tests/core/test_hookenv.py	2016-03-07 12:57:24 +0000
@@ -1602,3 +1602,18 @@
         self.assertEqual(result, expect)
         check_output.assert_called_with(['storage-get', '--format=json',
                                          '-s', storage_id])
+
+    @patch('subprocess.check_output')
+    def test_network_get_primary(self, check_output):
+        '''Ensure that network-get is called correctly and output is returned'''
+        check_output.return_value = '192.168.22.1'
+        ip = hookenv.network_get_primary_address('mybinding')
+        check_output.assert_called_with(['network-get', '--primary-address', 'mybinding'])
+        self.assertEqual(ip, '192.168.22.1')
+
+    @patch('subprocess.check_output')
+    def test_network_get_primary_unsupported(self, check_output):
+        '''Ensure that NotImplementedError is thrown when run on Juju < 2.0''' 
+        check_output.side_effect = OSError(2, 'network-get')
+        self.assertRaises(NotImplementedError, hookenv.network_get_primary_address,
+                          'mybinding')