Support multiple config file with mod_wsgi

Unlike uwsgi, apache mod_wsgi does not support passing
commandline arguments to the python wsgi script it invokes.

As a result while you can pass --config-file when hosting the
api and metadata wsgi applications with uwsgi there is no
way to use multiple config files with mod_wsgi.

This change mirrors how this is supported in keystone today
by intoducing a new OS_NOVA_CONFIG_FILES env var to allow
operators to optional pass a ';' delimited list of config
files to load.

This change also add docs for this env var and the existing
undocumented OS_NOVA_CONFIG_DIR.

Closes-Bug: 1994056
Change-Id: I8e3ccd75cbb7f2e132b403cb38022787c2c0a37b
(cherry picked from commit 73fe84fa0ea6f7c7fa55544f6bce5326d87743a6)

4 files changed, 43 insertions, 5 deletions

diff --git a/doc/source/user/wsgi.rst b/doc/source/user/wsgi.rst
index 6b314b4832..63f949df1a 100644
--- a/doc/source/user/wsgi.rst
+++ b/doc/source/user/wsgi.rst
@@ -8,10 +8,16 @@ as Apache_ or nginx_).
 
 The nova project provides two automatically generated entry points that
 support this: ``nova-api-wsgi`` and ``nova-metadata-wsgi``. These read
-``nova.conf`` and ``api-paste.ini`` and generate the required module-level
-``application`` that most WSGI servers require. If nova is installed using pip,
-these two scripts will be installed into whatever the expected ``bin``
-directory is for the environment.
+``nova.conf`` and ``api-paste.ini`` by default and generate the required
+module-level ``application`` that most WSGI servers require.
+If nova is installed using pip, these two scripts will be installed into
+whatever the expected ``bin`` directory is for the environment.
+
+The config files and config directory can be overridden via the
+``OS_NOVA_CONFIG_FILES`` and ``OS_NOVA_CONFIG_DIR`` environment variables.
+File paths listed in ``OS_NOVA_CONFIG_FILES`` are relative to
+``OS_NOVA_CONFIG_DIR`` and delimited by ``;``.
+
 
 The new scripts replace older experimental scripts that could be found in the
 ``nova/wsgi`` directory of the code repository. The new scripts are *not*
diff --git a/nova/api/openstack/wsgi_app.py b/nova/api/openstack/wsgi_app.py
index d60069ce84..6a2b72a611 100644
--- a/nova/api/openstack/wsgi_app.py
+++ b/nova/api/openstack/wsgi_app.py
@@ -42,8 +42,11 @@ def _get_config_files(env=None):
     if env is None:
         env = os.environ
     dirname = env.get('OS_NOVA_CONFIG_DIR', '/etc/nova').strip()
+    files = env.get('OS_NOVA_CONFIG_FILES', '').split(';')
+    if files == ['']:
+        files = CONFIG_FILES
     return [os.path.join(dirname, config_file)
-            for config_file in CONFIG_FILES]
+            for config_file in files]
 
 
 def _setup_service(host, name):
diff --git a/nova/tests/unit/api/openstack/test_wsgi_app.py b/nova/tests/unit/api/openstack/test_wsgi_app.py
index 94e2fe5cb1..0eb7011c11 100644
--- a/nova/tests/unit/api/openstack/test_wsgi_app.py
+++ b/nova/tests/unit/api/openstack/test_wsgi_app.py
@@ -104,3 +104,18 @@ document_root = /tmp
             'disable_compute_service_check_for_ffu', True,
             group='workarounds')
         wsgi_app._setup_service('myhost', 'api')
+
+    def test__get_config_files_empty_env(self):
+        env = {}
+        result = wsgi_app._get_config_files(env)
+        expected = ['/etc/nova/api-paste.ini', '/etc/nova/nova.conf']
+        self.assertEqual(result, expected)
+
+    def test__get_config_files_with_env(self):
+        env = {
+            "OS_NOVA_CONFIG_DIR": "/nova",
+            "OS_NOVA_CONFIG_FILES": "api.conf",
+        }
+        result = wsgi_app._get_config_files(env)
+        expected = ['/nova/api.conf']
+        self.assertEqual(result, expected)
diff --git a/releasenotes/notes/multiple-config-files-with-mod_wsgi-f114ea5fdd8b9a51.yaml b/releasenotes/notes/multiple-config-files-with-mod_wsgi-f114ea5fdd8b9a51.yaml
new file mode 100644
index 0000000000..f4361477de
--- /dev/null
+++ b/releasenotes/notes/multiple-config-files-with-mod_wsgi-f114ea5fdd8b9a51.yaml
@@ -0,0 +1,14 @@
+---
+fixes:
+  - |
+    apache mod_wsgi does not support passing commandline arguments to the wsgi
+    application that it hosts. As a result when the nova api or metadata api
+    where run under mod_wsgi it was not posible to use multiple config files
+    or non-default file names i.e. nova-api.conf
+    This has been adressed by the intoduction of a new, optional, envionment
+    varible ``OS_NOVA_CONFIG_FILES``. ``OS_NOVA_CONFIG_FILES`` is a ``;``
+    seperated list fo file path relitive to ``OS_NOVA_CONFIG_DIR``.
+    When unset the default ``api-paste.ini`` and ``nova.conf`` will be used
+    form ``/etc/nova``. This is supported for the nova api and nova metadata
+    wsgi applications.
+