Deprecate multiple config block parsing.

With the introduction of set_defaults, as well as new documentation
features for default values in oslo_config, the CORS middleware
has been placed in the odd position where its configuration behaves
inconsistently. If you configure via add_origin, then defaults set
in set_defaults are not honored. If you configure via multiple
configuration blocks ([cors.foo]), then the defaults are also not
honored.

Additionally, with the conversion of allowed_origin into a list_opt,
there is less direct need for multiple config-block parsing.

In order to ensure that the middleware behaves consistently with
the rest of oslo, as well as adheres to a set of basic sane assumptions
made by consumers, this patch deprecates the code path that searches
oslo's configuration for multiple [cors.*] blocks. Subsequent patches
will add additional deprecation flags to this end.

Change-Id: I49c15ccc2dce03b0dea33ec45ef6e271e58582da

2 files changed, 7 insertions, 25 deletions

diff --git a/doc/source/cors.rst b/doc/source/cors.rst
index 2788096..765a681 100644
--- a/doc/source/cors.rst
+++ b/doc/source/cors.rst
@@ -45,7 +45,7 @@ domain, using oslo_config::
 
     app = cors.CORS(your_wsgi_application, cfg.CONF)
 
-In your application's config file, then include a default configuration block
+In your application's config file, then include a configuration block
 something like this::
 
     [cors]
@@ -55,30 +55,6 @@ something like this::
     allow_headers=X-Custom-Header
     expose_headers=X-Custom-Header
 
-This middleware permits you to override the rules for multiple
-`allowed_origin`'s. To express this in your configuration file, first begin
-with a `[cors]` group as above, into which you place your default
-configuration values. Then add as many additional configuration groups as
-necessary, naming them `[cors.something]` (each name must be unique). The
-purpose of the suffix to `cors.` is legibility, we recommend using a
-reasonable human-readable string::
-
-    [cors.ironic_webclient]
-    # CORS Configuration for a hypothetical ironic webclient, which overrides
-    # authentication
-    allowed_origin=https://ironic.example.com:443
-    allow_credentials=True
-
-    [cors.horizon]
-    # CORS Configuration for horizon, which uses global options.
-    allowed_origin=https://horizon.example.com:443
-
-    [cors.wildcard]
-    # CORS Configuration for the CORS specified domain wildcard, which only
-    # permits HTTP GET requests.
-    allowed_origin=*
-    allow_methods=GET
-
 If your software requires specific headers or methods for proper operation, you
 may include these as latent properties. These will be evaluated in addition
 to any found in configuration::
diff --git a/oslo_middleware/cors.py b/oslo_middleware/cors.py
index 3d7b49b..6826016 100644
--- a/oslo_middleware/cors.py
+++ b/oslo_middleware/cors.py
@@ -16,6 +16,7 @@
 import copy
 import logging
 
+import debtcollector
 from oslo_config import cfg
 from oslo_middleware import base
 import six
@@ -204,6 +205,11 @@ class CORS(base.ConfigurableMiddleware):
         # prefixed with 'cors.'
         for section in self.oslo_conf.list_all_sections():
             if section.startswith('cors.'):
+                debtcollector.deprecate('Multiple configuration blocks are '
+                                        'deprecated and will be removed in '
+                                        'future versions. Please consolidate '
+                                        'your configuration in the [cors] '
+                                        'configuration block.')
                 # Register with the preconstructed defaults
                 self.oslo_conf.register_opts(subgroup_opts, section)
                 self.add_origin(**self.oslo_conf[section])