Add Serverless Framework Support Revision 2 (aws#127)

* Renamed ServerlessContext to ServerlessLambdaContext to be more precise about its purpose.
* Instead of explicitly using Context class's put_subsegment/put_segment methods, use LambdaContext's
grandparent class to store. LambdaContext's methods are really only used to acquire the FacadeSegment.
* Parameters when initializing the mimic segment are now required.
* Unit tests added to test these changes.

Author: chanchiem

aws_xray_sdk/core/models/mimic_segment.py

@@ -1,10 +1,14 @@
 from .segment import Segment
+from .facade_segment import FacadeSegment
 from ..exceptions.exceptions import MimicSegmentInvalidException
 
 
 class MimicSegment(Segment):
     """
-    The MimicSegment is an entity that mimics a segment for the use of the serverless context.
+    The MimicSegment is an entity that mimics a segment. It's primary use is for a special-case
+    in Lambda; specifically, for the Serverless Design Pattern. It is not recommended to use
+    this MimicSegment for any other purpose.
+
     When the MimicSegment is generated, its parent segment is assigned to be the FacadeSegment
     generated by the Lambda Environment. Upon serialization and transmission of the MimicSegment,
     it is converted to a locally-namespaced, subsegment. This is only done during serialization.
@@ -16,8 +20,8 @@ class MimicSegment(Segment):
     is available to be used.
     """
 
-    def __init__(self, facade_segment=None, original_segment=None):
-        if not original_segment or not facade_segment:
+    def __init__(self, facade_segment, original_segment):
+        if not issubclass(type(original_segment), Segment) or type(facade_segment) != FacadeSegment:
             raise MimicSegmentInvalidException("Invalid MimicSegment construction. "
                                                "Please put in the original segment and the facade segment.")
         super(MimicSegment, self).__init__(name=original_segment.name, entityid=original_segment.id,
@@ -27,7 +31,7 @@ def __init__(self, facade_segment=None, original_segment=None):
     def __getstate__(self):
         """
         Used during serialization. We mark the subsegment properties to let the dataplane know
-        that we want the mimic segment to be represented as a subsegment.
+        that we want the mimic segment to be transformed as a subsegment.
         """
         properties = super(MimicSegment, self).__getstate__()
         properties['type'] = 'subsegment'

aws_xray_sdk/core/serverless_context.py renamed to aws_xray_sdk/core/serverless_lambda_context.py

@@ -6,13 +6,12 @@
 from .models.mimic_segment import MimicSegment
 from .context import CXT_MISSING_STRATEGY_KEY
 from .lambda_launcher import LambdaContext
-from .context import Context
 
 
 log = logging.getLogger(__name__)
 
 
-class ServerlessContext(LambdaContext):
+class ServerlessLambdaContext(LambdaContext):
     """
     Context used specifically for running middlewares on Lambda through the
     Serverless design. This context is built on top of the LambdaContext, but
@@ -23,7 +22,7 @@ class ServerlessContext(LambdaContext):
     ensures that FacadeSegments exist through underlying calls to _refresh_context().
     """
     def __init__(self, context_missing='RUNTIME_ERROR'):
-        super(ServerlessContext, self).__init__()
+        super(ServerlessLambdaContext, self).__init__()
 
         strategy = os.getenv(CXT_MISSING_STRATEGY_KEY, context_missing)
         self._context_missing = strategy
@@ -38,15 +37,15 @@ def put_segment(self, segment):
         parent_facade_segment = self.__get_facade_entity()  # type: FacadeSegment
         mimic_segment = MimicSegment(parent_facade_segment, segment)
         parent_facade_segment.add_subsegment(mimic_segment)
-        Context.put_segment(self, mimic_segment)
+        super(LambdaContext, self).put_segment(mimic_segment)
 
     def end_segment(self, end_time=None):
         """
         Close the MimicSegment
         """
         # Close the last mimic segment opened then remove it from our facade segment.
         mimic_segment = self.get_trace_entity()
-        Context.end_segment(self, end_time)
+        super(LambdaContext, self).end_segment(end_time)
         if type(mimic_segment) == MimicSegment:
             # The facade segment can only hold mimic segments.
             facade_segment = self.__get_facade_entity()
@@ -58,7 +57,7 @@ def put_subsegment(self, subsegment):
         another subsegment if they are the last opened entity.
         :param subsegment: The subsegment to to be added as a subsegment.
         """
-        Context.put_subsegment(self, subsegment)
+        super(LambdaContext, self).put_subsegment(subsegment)
 
     def end_subsegment(self, end_time=None):
         """
@@ -69,7 +68,7 @@ def end_subsegment(self, end_time=None):
             system time will be used.
         :return: True on success, false if no parent mimic segment/subsegment is found.
         """
-        return Context.end_subsegment(self, end_time)
+        return super(LambdaContext, self).end_subsegment(end_time)
 
     def __get_facade_entity(self):
         """
@@ -92,12 +91,12 @@ def get_trace_entity(self):
         # Call to Context.get_trace_entity() returns the latest mimic segment/subsegment if they exist.
         # Otherwise, returns None through the following way:
         # No mimic segment/subsegment exists so Context calls LambdaContext's handle_context_missing().
-        # By default, Lambda's method returns no-op, so it will return None to ServerlessContext.
+        # By default, Lambda's method returns no-op, so it will return None to ServerlessLambdaContext.
         # Take that None as an indication to return the rightful handle_context_missing(), otherwise
         # return the entity.
-        entity = Context.get_trace_entity(self)
+        entity = super(LambdaContext, self).get_trace_entity()
         if entity is None:
-            return Context.handle_context_missing(self)
+            return super(LambdaContext, self).handle_context_missing()
         else:
             return entity
 
@@ -116,11 +115,11 @@ def set_trace_entity(self, trace_entity):
             # behavior would be invoked.
             mimic_segment = trace_entity
 
-        Context.set_trace_entity(self, mimic_segment)
+        super(LambdaContext, self).set_trace_entity(mimic_segment)
         self.__get_facade_entity().subsegments = [mimic_segment]
 
     def _is_subsegment(self, entity):
-        return super(ServerlessContext, self)._is_subsegment(entity) and type(entity) != MimicSegment
+        return super(ServerlessLambdaContext, self)._is_subsegment(entity) and type(entity) != MimicSegment
 
     @property
     def context_missing(self):

aws_xray_sdk/ext/django/middleware.py

@@ -1,9 +1,9 @@
 import logging
 
 from aws_xray_sdk.core import xray_recorder
-from aws_xray_sdk.core.lambda_launcher import check_in_lambda
+from aws_xray_sdk.core.lambda_launcher import check_in_lambda, LambdaContext
 from aws_xray_sdk.core.models import http
-from aws_xray_sdk.core.serverless_context import ServerlessContext
+from aws_xray_sdk.core.serverless_lambda_context import ServerlessLambdaContext
 from aws_xray_sdk.core.utils import stacktrace
 from aws_xray_sdk.ext.util import calculate_sampling_decision, \
     calculate_segment_name, construct_xray_header, prepare_response_header
@@ -28,9 +28,11 @@ def __init__(self, get_response):
         self.get_response = get_response
 
         # The case when the middleware is initialized in a Lambda Context, we make sure
-        # to use the ServerlessContext so that the middleware properly functions.
-        if check_in_lambda() is not None:
-            xray_recorder.context = ServerlessContext()
+        # to use the ServerlessLambdaContext so that the middleware properly functions.
+        # We also check if the current context is a LambdaContext to not override customer
+        # provided contexts.
+        if check_in_lambda() is not None and type(xray_recorder.context) == LambdaContext:
+            xray_recorder.context = ServerlessLambdaContext()
 
     # hooks for django version >= 1.10
     def __call__(self, request):

aws_xray_sdk/ext/flask/middleware.py

@@ -1,9 +1,9 @@
 import flask.templating
 from flask import request
 
-from aws_xray_sdk.core.lambda_launcher import check_in_lambda
+from aws_xray_sdk.core.lambda_launcher import check_in_lambda, LambdaContext
 from aws_xray_sdk.core.models import http
-from aws_xray_sdk.core.serverless_context import ServerlessContext
+from aws_xray_sdk.core.serverless_lambda_context import ServerlessLambdaContext
 from aws_xray_sdk.core.utils import stacktrace
 from aws_xray_sdk.ext.util import calculate_sampling_decision, \
     calculate_segment_name, construct_xray_header, prepare_response_header
@@ -21,9 +21,11 @@ def __init__(self, app, recorder):
         self.app.teardown_request(self._handle_exception)
 
         # The case when the middleware is initialized in a Lambda Context, we make sure
-        # to use the ServerlessContext so that the middleware properly functions.
-        if check_in_lambda() is not None:
-            self._recorder.context = ServerlessContext()
+        # to use the ServerlessLambdaContext so that the middleware properly functions.
+        # We also check if the current context is a LambdaContext to not override customer
+        # provided contexts.
+        if check_in_lambda() is not None and type(self._recorder.context) == LambdaContext:
+            self._recorder.context = ServerlessLambdaContext()
 
         _patch_render(recorder)
 

tests/test_mimic_segment.py

@@ -30,9 +30,17 @@ def test_ready():
 def test_invalid_init():
     with pytest.raises(MimicSegmentInvalidException):
         MimicSegment(facade_segment=None, original_segment=original_segment)
+    with pytest.raises(MimicSegmentInvalidException):
         MimicSegment(facade_segment=facade_segment, original_segment=None)
+    with pytest.raises(MimicSegmentInvalidException):
         MimicSegment(facade_segment=Subsegment("Test", "local", original_segment), original_segment=None)
+    with pytest.raises(MimicSegmentInvalidException):
         MimicSegment(facade_segment=None, original_segment=Subsegment("Test", "local", original_segment))
+    with pytest.raises(MimicSegmentInvalidException):
+        MimicSegment(facade_segment=facade_segment, original_segment=Subsegment("Test", "local", original_segment))
+    with pytest.raises(MimicSegmentInvalidException):
+        MimicSegment(facade_segment=original_segment, original_segment=facade_segment)
+    MimicSegment(facade_segment=facade_segment, original_segment=original_segment)
 
 
 def test_init_similar():

tests/test_serverless_context.py renamed to tests/test_serverless_lambda_context.py

@@ -1,8 +1,7 @@
 import os
 import pytest
 
-from aws_xray_sdk.core import serverless_context
-from aws_xray_sdk.core import context
+from aws_xray_sdk.core.serverless_lambda_context import ServerlessLambdaContext
 from aws_xray_sdk.core.lambda_launcher import LAMBDA_TRACE_HEADER_KEY
 from aws_xray_sdk.core.exceptions.exceptions import AlreadyEndedException, SegmentNotFoundException
 from aws_xray_sdk.core.models.segment import Segment
@@ -16,7 +15,7 @@
 HEADER_VAR = "Root=%s;Parent=%s;Sampled=1" % (TRACE_ID, PARENT_ID)
 
 os.environ[LAMBDA_TRACE_HEADER_KEY] = HEADER_VAR
-context = serverless_context.ServerlessContext()
+context = ServerlessLambdaContext()
 
 service_name = "Test Flask Server"