Store list of collected configs in cachedir

This will allow tools like os-apply-config to read the list even when
they are run out of band from os-collect-config.

Change-Id: Ic4eaf649e234f4a1367d20c7ec52e93e787a7bb3

README.rst

@@ -25,7 +25,7 @@ path = MyResource
 stack_name = my.stack
 ```
 
-These sources will be polled and whenever any of them changes, default.command will be run. OS_CONFIG_FILES will be set in the environment as a colon (":") separated list of the current copy of each metadata source. So in the example above, "os-refresh-config" would be executed with something like this in OS_CONFIG_FILES:
+These sources will be polled and whenever any of them changes, default.command will be run. A file will be written to the cache dir, os_config_files.json, which will be a json list of the file paths to the current copy of each metadata source. This list will also be set as a colon separated list in the environment variable OS_CONFIG_FILES for the command that is run. So in the example above, "os-refresh-config" would be executed with something like this in OS_CONFIG_FILES:
 
 ```
 /var/run/os-collect-config/ec2.json:/var/run/os-collect-config/cfn.json

os_collect_config/cache.py

@@ -74,3 +74,15 @@ def commit(name):
     dest_path = get_path(name)
     if os.path.exists(dest_path):
         shutil.copy(dest_path, '%s.last' % dest_path)
+
+
+def store_meta_list(name, data_keys):
+    '''Store a json list of the files that should be present after store.'''
+    final_list = [get_path(k) for k in data_keys]
+    dest = get_path(name)
+    with tempfile.NamedTemporaryFile(prefix='tmp_meta_list.',
+                                     dir=os.path.dirname(dest),
+                                     delete=False) as out:
+        out.write(json.dumps(final_list))
+    os.rename(out.name, dest)
+    return dest

os_collect_config/collect.py

@@ -116,6 +116,8 @@ def collect_all(collectors, store=False, requests_impl_map=None):
         else:
             paths_or_content[collector] = content
 
+    if any_changed:
+        cache.store_meta_list('os_config_files', collectors)
     return (any_changed, paths_or_content)
 
 

os_collect_config/tests/test_cache.py

@@ -14,8 +14,10 @@
 # limitations under the License.
 
 import fixtures
+import json
 import os
 import testtools
+from testtools import matchers
 
 from os_collect_config import cache
 
@@ -73,5 +75,13 @@ class TestCache(testtools.TestCase):
         self.assertTrue(changed)
         self.assertTrue(os.path.exists(path))
 
+        # And the meta list
+        list_path = cache.store_meta_list('foo_list', ['foo'])
+        self.assertTrue(os.path.exists(list_path))
+        with open(list_path) as list_file:
+            list_list = json.loads(list_file.read())
+        self.assertThat(list_list, matchers.IsInstance(list))
+        self.assertIn(path, list_list)
+
     def test_commit_no_cache(self):
         self.assertEquals(None, cache.commit('neversaved'))

os_collect_config/tests/test_collect.py

@@ -90,8 +90,14 @@ class TestCollect(testtools.TestCase):
         self._call_main(occ_args)
         proc_args = calls[0]
         self.assertEqual(expected_cmd, proc_args['args'])
+        list_path = os.path.join(cache_dir.path, 'os_config_files.json')
+        with open(list_path) as list_file:
+            config_list = json.loads(list_file.read())
+        self.assertThat(config_list, matchers.IsInstance(list))
+        env_config_list = proc_args['env']['OS_CONFIG_FILES'].split(':')
+        self.assertEquals(env_config_list, config_list)
         keys_found = set()
-        for path in proc_args['env']['OS_CONFIG_FILES'].split(':'):
+        for path in env_config_list:
             self.assertTrue(os.path.exists(path))
             with open(path) as cfg_file:
                 contents = json.loads(cfg_file.read())