net: add renderers for automatically selecting the renderer.

Previously, the distro had hard coded which network renderer it would
use. This adds support for just picking the right renderer based
on what is available.

Now, that can be set via a priority in system_info, but should
generally work. That config looks like:
 system_info:
   network:
     renderers: ["eni", "sysconfig"]

When no renderers are found, a specific RendererNotFoundError is raised.
stages.py is modified to catch that and log it at error level. This
path should not really be exercised, but could occur if for example an
Ubuntu system did not have ifupdown, or a rhel system did not have
sysconfig. In such a system previously we would have quietly rendered
ENI configuration but that would have been ignored. This is one step
better in that we at least log the error.

1 files changed, 45 insertions, 0 deletions

diff --git a/tests/unittests/test_net.py b/tests/unittests/test_net.py
index dca44b37..902204a0 100644
--- a/tests/unittests/test_net.py
+++ b/tests/unittests/test_net.py
@@ -4,6 +4,7 @@ from cloudinit import net
 from cloudinit.net import cmdline
 from cloudinit.net import eni
 from cloudinit.net import network_state
+from cloudinit.net import renderers
 from cloudinit.net import sysconfig
 from cloudinit.sources.helpers import openstack
 from cloudinit import util
@@ -1050,6 +1051,50 @@ class TestEniRoundTrip(CiTestCase):
             expected, [line for line in found if line])
 
 
+class TestNetRenderers(CiTestCase):
+    @mock.patch("cloudinit.net.renderers.sysconfig.available")
+    @mock.patch("cloudinit.net.renderers.eni.available")
+    def test_eni_and_sysconfig_available(self, m_eni_avail, m_sysc_avail):
+        m_eni_avail.return_value = True
+        m_sysc_avail.return_value = True
+        found = renderers.search(priority=['sysconfig', 'eni'], first=False)
+        names = [f[0] for f in found]
+        self.assertEqual(['sysconfig', 'eni'], names)
+
+    @mock.patch("cloudinit.net.renderers.eni.available")
+    def test_search_returns_empty_on_none(self, m_eni_avail):
+        m_eni_avail.return_value = False
+        found = renderers.search(priority=['eni'], first=False)
+        self.assertEqual([], found)
+
+    @mock.patch("cloudinit.net.renderers.sysconfig.available")
+    @mock.patch("cloudinit.net.renderers.eni.available")
+    def test_first_in_priority(self, m_eni_avail, m_sysc_avail):
+        # available should only be called until one is found.
+        m_eni_avail.return_value = True
+        m_sysc_avail.side_effect = Exception("Should not call me")
+        found = renderers.search(priority=['eni', 'sysconfig'], first=True)
+        self.assertEqual(['eni'], [found[0]])
+
+    @mock.patch("cloudinit.net.renderers.sysconfig.available")
+    @mock.patch("cloudinit.net.renderers.eni.available")
+    def test_select_positive(self, m_eni_avail, m_sysc_avail):
+        m_eni_avail.return_value = True
+        m_sysc_avail.return_value = False
+        found = renderers.select(priority=['sysconfig', 'eni'])
+        self.assertEqual('eni', found[0])
+
+    @mock.patch("cloudinit.net.renderers.sysconfig.available")
+    @mock.patch("cloudinit.net.renderers.eni.available")
+    def test_select_none_found_raises(self, m_eni_avail, m_sysc_avail):
+        # if select finds nothing, should raise exception.
+        m_eni_avail.return_value = False
+        m_sysc_avail.return_value = False
+
+        self.assertRaises(net.RendererNotFoundError, renderers.select,
+                          priority=['sysconfig', 'eni'])
+
+
 def _gzip_data(data):
     with io.BytesIO() as iobuf:
         gzfp = gzip.GzipFile(mode="wb", fileobj=iobuf)