Fix reverse proxy pattern (#103)

* Reverse proxied middleware pattern

* Added Zuul headers

Author: avara1986

pyms/flask/app/create_app.py

@@ -7,6 +7,7 @@
 from pyms.config import get_conf
 from pyms.config.conf import validate_conf
 from pyms.constants import LOGGER_NAME, CONFIG_BASE
+from pyms.flask.app.utils import SingletonMeta, ReverseProxied
 from pyms.flask.healthcheck import healthcheck_blueprint
 from pyms.flask.services.driver import ServicesManager
 from pyms.logger import CustomJsonFormatter
@@ -15,24 +16,6 @@
 logger = logging.getLogger(LOGGER_NAME)
 
 
-class SingletonMeta(type):
-    """
-    The Singleton class can be implemented in different ways in Python. Some
-    possible methods include: base class, decorator, metaclass. We will use the
-    metaclass because it is best suited for this purpose.
-    """
-    _instances = {}
-    _singleton = True
-
-    def __call__(cls, *args, **kwargs):
-        if cls not in cls._instances or not cls._singleton:
-            cls._instances[cls] = super(SingletonMeta, cls).__call__(*args, **kwargs)
-        else:
-            cls._instances[cls].__init__(*args, **kwargs)
-
-        return cls._instances[cls]
-
-
 class Microservice(metaclass=SingletonMeta):
     """The class Microservice is the core of all microservices built with PyMS.
     You can create a simple microservice such as:
@@ -184,6 +167,9 @@ def init_app(self) -> Flask:
 
         application.root_path = self.path
 
+        # Fix connexion issue https://github.com/zalando/connexion/issues/527
+        application.wsgi_app = ReverseProxied(application.wsgi_app)
+
         return application
 
     def init_metrics(self):

pyms/flask/app/utils.py

@@ -0,0 +1,62 @@
+class SingletonMeta(type):
+    """
+    The Singleton class can be implemented in different ways in Python. Some
+    possible methods include: base class, decorator, metaclass. We will use the
+    metaclass because it is best suited for this purpose.
+    """
+    _instances = {}
+    _singleton = True
+
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances or not cls._singleton:
+            cls._instances[cls] = super(SingletonMeta, cls).__call__(*args, **kwargs)
+        else:
+            cls._instances[cls].__init__(*args, **kwargs)
+
+        return cls._instances[cls]
+
+
+class ReverseProxied:
+    """
+    Create a Proxy pattern https://microservices.io/patterns/apigateway.html.
+    You can run the microservice A in your local machine in http://localhost:5000/my-endpoint/
+    If you deploy your microservice, in some cases this microservice run behind a cluster, a gateway... and this
+    gateway redirect traffic to the microservice with a specific path like yourdomian.com/my-ms-a/my-endpoint/.
+    This class understand this path if the gateway send a specific header
+    """
+
+    def __init__(self, app):
+        self.app = app
+
+    @staticmethod
+    def _extract_prefix(environ):
+        """
+        Get Path from environment from:
+        - Traefik with HTTP_X_SCRIPT_NAME https://docs.traefik.io/v2.0/middlewares/headers/
+        - Nginx and Ingress with HTTP_X_SCRIPT_NAME https://www.nginx.com/resources/wiki/start/topics/examples/forwarded/
+        - Apache with HTTP_X_SCRIPT_NAME https://stackoverflow.com/questions/55619013/proxy-and-rewrite-to-webapp
+        - Zuul with  HTTP_X_FORWARDER_PREFIX https://cloud.spring.io/spring-cloud-netflix/multi/multi__router_and_filter_zuul.html
+        :param environ:
+        :return:
+        """
+        # Get path from Traefik, Nginx and Apache
+        path = environ.get('HTTP_X_SCRIPT_NAME', '')
+        if not path:
+            # Get path from Zuul
+            path = environ.get('HTTP_X_FORWARDED_PREFIX', '')
+        if path and not path.startswith("/"):
+            path = "/" + path
+        return path
+
+    def __call__(self, environ, start_response):
+        script_name = self._extract_prefix(environ)
+        if script_name:
+            environ['SCRIPT_NAME'] = script_name
+            path_info = environ['PATH_INFO']
+            if path_info.startswith(script_name):
+                environ['PATH_INFO'] = path_info[len(script_name):]
+
+        scheme = environ.get('HTTP_X_SCHEME', '')
+        if scheme:
+            environ['wsgi.url_scheme'] = scheme
+        return self.app(environ, start_response)

pyms/flask/services/swagger.py

@@ -83,7 +83,7 @@ def init_app(self, config, path):
 
         # Fix Connexion issue https://github.com/zalando/connexion/issues/1135
         if application_root == "/":
-            params["base_path"] = ""
+            del params["base_path"]
 
         app.add_api(**params)
         # Invert the objects, instead connexion with a Flask object, a Flask object with

tests/test_flask.py

@@ -7,7 +7,7 @@
 from pyms.constants import CONFIGMAP_FILE_ENVIRONMENT
 from pyms.flask.app import Microservice, config
 from pyms.flask.services.driver import DriverService
-from tests.common import MyMicroserviceNoSingleton, MyMicroservice
+from tests.common import MyMicroservice
 
 
 def home():
@@ -73,6 +73,18 @@ def test_disabled_service(self):
             self.assertTrue(isinstance(self.app.ms.metrics, DriverService))
         assert "'MyMicroservice' object has no attribute 'metrics'" in str(excinfo.value)
 
+    def test_reverse_proxy(self):
+        response = self.client.get('/my-proxy-path/ui/', headers={"X-Script-Name": "/my-proxy-path"})
+        self.assertEqual(200, response.status_code)
+
+    def test_reverse_proxy_no_slash(self):
+        response = self.client.get('/my-proxy-path/ui/', headers={"X-Script-Name": "my-proxy-path"})
+        self.assertEqual(200, response.status_code)
+
+    def test_reverse_proxy_zuul(self):
+        response = self.client.get('/my-proxy-path-zuul/ui/', headers={"X-Forwarded-Prefix": "my-proxy-path-zuul"})
+        self.assertEqual(200, response.status_code)
+
 
 class MicroserviceTest(unittest.TestCase):
     """