user-data: jinja template to render instance-data.json in cloud-config

Allow users to provide '## template: jinja' as the first line or their
#cloud-config or custom script user-data parts. When this header exists,
the cloud-config or script will be rendered as a jinja template.

All instance metadata keys and values present in
/run/cloud-init/instance-data.json will be available as jinja variables
for the template. This means any cloud-config module or script can
reference any standardized instance data in templates and scripts.

Additionally, any standardized instance-data.json keys scoped below a
'<v#>' key will be promoted as a top-level key for ease of reference in
templates. This means that '{{ local_hostname }}' is the same as using the
latest '{{ v#.local_hostname }}'.

Since instance-data is written to /run/cloud-init/instance-data.json, make
sure it is persisted across reboots when the cached datasource opject is
reloaded.

LP: #1791781

1 files changed, 101 insertions, 0 deletions

diff --git a/cloudinit/cmd/devel/tests/test_render.py b/cloudinit/cmd/devel/tests/test_render.py
new file mode 100644
index 00000000..fc5d2c0d
--- /dev/null
+++ b/cloudinit/cmd/devel/tests/test_render.py
@@ -0,0 +1,101 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+
+from six import StringIO
+import os
+
+from collections import namedtuple
+from cloudinit.cmd.devel import render
+from cloudinit.helpers import Paths
+from cloudinit.sources import INSTANCE_JSON_FILE
+from cloudinit.tests.helpers import CiTestCase, mock, skipUnlessJinja
+from cloudinit.util import ensure_dir, write_file
+
+
+class TestRender(CiTestCase):
+
+    with_logs = True
+
+    args = namedtuple('renderargs', 'user_data instance_data debug')
+
+    def setUp(self):
+        super(TestRender, self).setUp()
+        self.tmp = self.tmp_dir()
+
+    def test_handle_args_error_on_missing_user_data(self):
+        """When user_data file path does not exist, log an error."""
+        absent_file = self.tmp_path('user-data', dir=self.tmp)
+        instance_data = self.tmp_path('instance-data', dir=self.tmp)
+        write_file(instance_data, '{}')
+        args = self.args(
+            user_data=absent_file, instance_data=instance_data, debug=False)
+        with mock.patch('sys.stderr', new_callable=StringIO):
+            self.assertEqual(1, render.handle_args('anyname', args))
+        self.assertIn(
+            'Missing user-data file: %s' % absent_file,
+            self.logs.getvalue())
+
+    def test_handle_args_error_on_missing_instance_data(self):
+        """When instance_data file path does not exist, log an error."""
+        user_data = self.tmp_path('user-data', dir=self.tmp)
+        absent_file = self.tmp_path('instance-data', dir=self.tmp)
+        args = self.args(
+            user_data=user_data, instance_data=absent_file, debug=False)
+        with mock.patch('sys.stderr', new_callable=StringIO):
+            self.assertEqual(1, render.handle_args('anyname', args))
+        self.assertIn(
+            'Missing instance-data.json file: %s' % absent_file,
+            self.logs.getvalue())
+
+    def test_handle_args_defaults_instance_data(self):
+        """When no instance_data argument, default to configured run_dir."""
+        user_data = self.tmp_path('user-data', dir=self.tmp)
+        run_dir = self.tmp_path('run_dir', dir=self.tmp)
+        ensure_dir(run_dir)
+        paths = Paths({'run_dir': run_dir})
+        self.add_patch('cloudinit.cmd.devel.render.read_cfg_paths', 'm_paths')
+        self.m_paths.return_value = paths
+        args = self.args(
+            user_data=user_data, instance_data=None, debug=False)
+        with mock.patch('sys.stderr', new_callable=StringIO):
+            self.assertEqual(1, render.handle_args('anyname', args))
+        json_file = os.path.join(run_dir, INSTANCE_JSON_FILE)
+        self.assertIn(
+            'Missing instance-data.json file: %s' % json_file,
+            self.logs.getvalue())
+
+    @skipUnlessJinja()
+    def test_handle_args_renders_instance_data_vars_in_template(self):
+        """If user_data file is a jinja template render instance-data vars."""
+        user_data = self.tmp_path('user-data', dir=self.tmp)
+        write_file(user_data, '##template: jinja\nrendering: {{ my_var }}')
+        instance_data = self.tmp_path('instance-data', dir=self.tmp)
+        write_file(instance_data, '{"my-var": "jinja worked"}')
+        args = self.args(
+            user_data=user_data, instance_data=instance_data, debug=True)
+        with mock.patch('sys.stderr', new_callable=StringIO) as m_console_err:
+            with mock.patch('sys.stdout', new_callable=StringIO) as m_stdout:
+                self.assertEqual(0, render.handle_args('anyname', args))
+        self.assertIn(
+            'DEBUG: Converted jinja variables\n{', self.logs.getvalue())
+        self.assertIn(
+            'DEBUG: Converted jinja variables\n{', m_console_err.getvalue())
+        self.assertEqual('rendering: jinja worked', m_stdout.getvalue())
+
+    @skipUnlessJinja()
+    def test_handle_args_warns_and_gives_up_on_invalid_jinja_operation(self):
+        """If user_data file has invalid jinja operations log warnings."""
+        user_data = self.tmp_path('user-data', dir=self.tmp)
+        write_file(user_data, '##template: jinja\nrendering: {{ my-var }}')
+        instance_data = self.tmp_path('instance-data', dir=self.tmp)
+        write_file(instance_data, '{"my-var": "jinja worked"}')
+        args = self.args(
+            user_data=user_data, instance_data=instance_data, debug=True)
+        with mock.patch('sys.stderr', new_callable=StringIO):
+            self.assertEqual(1, render.handle_args('anyname', args))
+        self.assertIn(
+            'WARNING: Ignoring jinja template for %s: Undefined jinja'
+            ' variable: "my-var". Jinja tried subtraction. Perhaps you meant'
+            ' "my_var"?' % user_data,
+            self.logs.getvalue())
+
+# vi: ts=4 expandtab