wsgi-stack: Refactor the error handling view into a middleware class.

rhodecode/lib/middleware/error_handling.py

@@ -0,0 +1,104 @@
+# -*- coding: utf-8 -*-
+
+# Copyright (C) 2016-2016  RhodeCode GmbH
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License, version 3
+# (only), as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This program is dual-licensed. If you wish to learn more about the
+# RhodeCode Enterprise Edition, including its added features, Support services,
+# and proprietary license terms, please see https://rhodecode.com/licenses/
+
+
+import logging
+
+from pyramid import httpexceptions
+from pyramid.httpexceptions import HTTPError, HTTPInternalServerError
+from pyramid.threadlocal import get_current_request
+
+from rhodecode.lib.exceptions import VCSServerUnavailable
+from rhodecode.lib.vcs.exceptions import VCSCommunicationError
+
+
+log = logging.getLogger(__name__)
+
+
+class PylonsErrorHandlingMiddleware(object):
+    """
+    This middleware is wrapped around the old pylons application to catch
+    errors and invoke our error handling view to return a proper error page.
+    """
+    def __init__(self, app, error_view, reraise=False):
+        self.app = app
+        self.error_view = error_view
+        self.reraise = reraise
+
+    def __call__(self, environ, start_response):
+        # We need to use the pyramid request here instead of creating a custom
+        # instance from the environ because this request maybe passed to the
+        # error handler view which is a pyramid view and expects a pyramid
+        # request which has been processed by the pyramid router.
+        request = get_current_request()
+
+        response = self.handle_request(request)
+        return response(environ, start_response)
+
+    def is_vcs_response(self, response):
+        return 'X-RhodeCode-Backend' in response.headers
+
+    def is_http_error(self, response):
+        # webob type error responses
+        return (400 <= response.status_int <= 599)
+
+    def is_error_handling_needed(self, response):
+        return (self.is_http_error(response) and not
+                self.is_vcs_response(response))
+
+    def handle_request(self, request):
+        """
+        Calls the underlying WSGI app (typically the old RhodeCode pylons app)
+        and returns the response if no error happened. In case of an error it
+        invokes the error handling view to return a proper error page as
+        response.
+
+        - old webob type exceptions get converted to pyramid exceptions
+        - pyramid exceptions are passed to the error handler view
+        """
+        try:
+            response = request.get_response(self.app)
+            if self.is_error_handling_needed(response):
+                response = webob_to_pyramid_http_response(response)
+                return self.error_view(response, request)
+        except HTTPError as e:  # pyramid type exceptions
+            return self.error_view(e, request)
+        except Exception as e:
+            log.exception(e)
+
+            if self.reraise:
+                raise
+
+            if isinstance(e, VCSCommunicationError):
+                return self.error_view(VCSServerUnavailable(), request)
+
+            return self.error_view(HTTPInternalServerError(), request)
+
+        return response
+
+
+def webob_to_pyramid_http_response(webob_response):
+    ResponseClass = httpexceptions.status_map[webob_response.status_int]
+    pyramid_response = ResponseClass(webob_response.status)
+    pyramid_response.status = webob_response.status
+    pyramid_response.headers.update(webob_response.headers)
+    if pyramid_response.headers['content-type'] == 'text/html':
+        pyramid_response.headers['content-type'] = 'text/html; charset=UTF-8'
+    return pyramid_response