Add function to install interceptors from list (#36)

Author: dray92

opentracing_instrumentation/client_hooks/__init__.py

@@ -19,9 +19,13 @@
 # THE SOFTWARE.
 from __future__ import absolute_import
 
+from collections import Sequence
+
 import importlib
 import logging
 
+import six
+
 
 def install_all_patches():
     """
@@ -60,14 +64,38 @@ def install_patches(patchers='all'):
     if patchers is None or patchers == 'all':
         install_all_patches()
         return
-    if type(patchers) is list:
-        for patch_func_name in patchers:
-            logging.info('Loading client hook %s', patch_func_name)
-            patch_func = _load_symbol(patch_func_name)
-            logging.info('Applying client hook %s', patch_func_name)
-            patch_func()
-        return
-    raise ValueError('patchers argument must be None, "all", or a list')
+    if not _valid_args(patchers):
+        raise ValueError('patchers argument must be None, "all", or a list')
+
+    for patch_func_name in patchers:
+        logging.info('Loading client hook %s', patch_func_name)
+        patch_func = _load_symbol(patch_func_name)
+        logging.info('Applying client hook %s', patch_func_name)
+        patch_func()
+
+
+def install_client_interceptors(client_interceptors=()):
+    """
+    Install client interceptors for the patchers.
+
+    :param client_interceptors: a list of client interceptors to install.
+        Should be a list of classes
+    """
+    if not _valid_args(client_interceptors):
+        raise ValueError('client_interceptors argument must be a list')
+
+    from ..http_client import ClientInterceptors
+
+    for client_interceptor in client_interceptors:
+        logging.info('Loading client interceptor %s', client_interceptor)
+        interceptor_class = _load_symbol(client_interceptor)
+        logging.info('Adding client interceptor %s', client_interceptor)
+        ClientInterceptors.append(interceptor_class())
+
+
+def _valid_args(value):
+    return isinstance(value, Sequence) and \
+        not isinstance(value, six.string_types)
 
 
 def _load_symbol(name):

tests/opentracing_instrumentation/__init__.py

@@ -0,0 +1,57 @@
+# Copyright (c) 2017 Uber Technologies, Inc.
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+from __future__ import absolute_import
+
+from mock import patch
+import pytest
+
+from opentracing_instrumentation.client_hooks import install_client_interceptors
+from opentracing_instrumentation.interceptors import OpenTracingInterceptor
+
+
+class TestClientInterceptor(OpenTracingInterceptor):
+
+    def process(self, request, span):
+        pass
+
+
+def Any(cls):
+
+    class Any(cls):
+
+        def __eq__(self, other):
+            return isinstance(other, cls)
+
+    return Any()
+
+
+def test_install_client_interceptors_non_list_arg():
+    with pytest.raises(ValueError):
+        install_client_interceptors('abc')
+
+
+def test_install_client_interceptors():
+    # TODO: can this path be obtained programmatically?
+    path_to_interceptor = ('tests.opentracing_instrumentation.'
+                           'test_install_client_hooks.TestClientInterceptor')
+    with patch('opentracing_instrumentation.http_client.ClientInterceptors') as MockClientInterceptors:
+        install_client_interceptors([path_to_interceptor])
+
+    MockClientInterceptors.append.assert_called_once_with(Any(TestClientInterceptor))