Observer for http requests

docs/conf.py

@@ -20,7 +20,7 @@
 # -- Project information -----------------------------------------------------
 
 project = 'PyOData'
-copyright = '2019 SAP SE or an SAP affiliate company'
+copyright = '2021 SAP SE or an SAP affiliate company'
 author = 'SAP'
 
 # The short X.Y version

docs/usage/advanced.rst

@@ -95,3 +95,42 @@ it is enough to set log level to the desired value.
  logging.basicConfig()
  root_logger = logging.getLogger()
  root_logger.setLevel(logging.DEBUG)
+
+Observing HTTP traffic
+----------------------
+
+There are cases where you need access to the transport protocol (http). For
+example: you need to read value of specific http header. Pyodata provides
+simple mechanism to observe all http requests and access low level properties
+from underlying network library (e.g. **python requests**).
+
+You can use basic predefined observer class
+``pyodata.utils.RequestObserverLastCall`` to catch last response headers:
+
+.. code-block:: python
+
+ from pyodata.utils import RequestObserverLastCall
+
+ last = RequestObserverLastCall()
+ northwind.entity_sets.Employees.get_entity(1).execute(last)
+ print(last.response.headers)
+
+You can also write your own observer to cover more specific cases. This is an example of
+custom observer which stores status code of the last response.
+
+.. code-block:: python
+
+ from pyodata.utils import RequestObserver
+
+ class CatchStatusCode(RequestObserver):
+
+ def __init__(self):
+ self.status_code = None
+
+ def http_response(self, response, request):
+ self.status_code = response.status_code
+
+ last_status = RequestObserverLastCall()
+
+ northwind.entity_sets.Employees.get_entity(1).execute(last_status)
+ print(last_status.status_code)

pyodata/utils/__init__.py

@@ -0,0 +1,5 @@
+"""Utilities for Python OData client"""
+
+from .request_observer import RequestObserver, RequestObserverLastCall
+
+__all__ = ["RequestObserver", "RequestObserverLastCall"]

pyodata/utils/request_observer.py

@@ -0,0 +1,34 @@
+"""
+Interface for request observer, which allows to catch odata request processing details
+
+Author: Michal Nezerka <michal.nezerka@gmail.com>
+Date: 2021-05-14
+"""
+
+from abc import ABC, abstractmethod
+
+
+class RequestObserver(ABC):
+ """
+ The RequestObserver interface declares methods for observing odata request processing.
+ """
+
+ @abstractmethod
+ def http_response(self, response, request) -> None:
+ """
+ Get http response together with related http request object.
+ """
+
+
+class RequestObserverLastCall(RequestObserver):
+ """
+ The implementation of RequestObserver that stored request and response of the last call
+ """
+
+ def __init__(self):
+ self.response = None
+ self.request = None
+
+ def http_response(self, response, request):
+ self.response = response
+ self.request = request

pyodata/v2/model.py

@@ -1018,6 +1018,8 @@ def association(self, association_name, namespace=None):
  except KeyError:
  pass
 
+ raise KeyError('Association does not exist')
+
  @property
  def associations(self):
  return list(itertools.chain(*(decl.list_associations() for decl in list(self._decls.values()))))
@@ -1048,6 +1050,8 @@ def association_set(self, set_name, namespace=None):
  except KeyError:
  pass
 
+ raise KeyError('Association set does not exist')
+
  @property
  def association_sets(self):
  return list(itertools.chain(*(decl.list_association_sets() for decl in list(self._decls.values()))))

pyodata/v2/service.py

@@ -22,6 +22,7 @@
  from urllib2 import quote
 
 from pyodata.exceptions import HttpError, PyODataException, ExpressionError, ProgramError
+from pyodata.utils import RequestObserver
 from . import model
 
 LOGGER_NAME = 'pyodata.service'
@@ -296,7 +297,7 @@ def add_headers(self, value):
 
  self._headers.update(value)
 
- def execute(self):
+ def execute(self, observer: RequestObserver = None):
  """Fetches HTTP response and returns processed result
 
  Sends the query-request to the OData service, returning a client-side Enumerable for
@@ -320,6 +321,9 @@ def execute(self):
  response = self._connection.request(
  self.get_method(), url, headers=headers, params=params, data=body)
 
+ if observer:
+ observer.http_response(response, response.request)
+
  self._logger.debug('Received response')
  self._logger.debug(' url: %s', response.url)
  self._logger.debug(' headers: %s', response.headers)

tests/test_service_v2.py

@@ -6,6 +6,7 @@
 import pytest
 from unittest.mock import patch
 
+from pyodata.utils import RequestObserverLastCall
 import pyodata.v2.model
 import pyodata.v2.service
 from pyodata.exceptions import PyODataException, HttpError, ExpressionError, ProgramError
@@ -2372,3 +2373,33 @@ def test_custom_with_get_entity(service):
 
  entity = service.entity_sets.MasterEntities.get_entity('12345').custom("foo", "bar").execute()
  assert entity.Key == '12345'
+
+
+@responses.activate
+def test_request_observer(service):
+ """Test use of request observer"""
+
+ responses.add(
+ responses.GET,
+ f"{service.url}/MasterEntities('12345')",
+ headers={'h1-key': 'h1-val', 'h2-key': 'h2-val'},
+ json={'d': {'Key': '12345'}},
+ status=200)
+
+ last = RequestObserverLastCall()
+ entity = service.entity_sets.MasterEntities.get_entity('12345').execute(last)
+
+ assert last.request is not None
+
+ assert len(last.request.headers) > 0
+ assert 'Accept' in last.request.headers
+
+ assert last.response is not None
+ assert last.response.status_code == 200
+ assert len(last.response.headers) == 3
+ assert 'Content-type' in last.response.headers
+ assert 'h1-key' in last.response.headers
+ assert 'h2-key' in last.response.headers
+ assert last.response.headers['Content-type'] == 'application/json'
+ assert last.response.headers['h1-key'] == 'h1-val'
+ assert last.response.headers['h2-key'] == 'h2-val'