AsyncioScopeManager based on contextvars and supporting Tornado 6

.travis.yml

@@ -8,12 +8,21 @@ python:
   - "3.7"
   - "3.8-dev"
 
+env:
+  - TORNADO=">=4,<5"
+  - TORNADO=">=5,<6"
+  - TORNADO=">=6"
+
 matrix:
   allow_failures:
     - python: "3.8-dev"
+  exclude:
+  - python: "2.7"
+    env: TORNADO=">=6"
 
 install:
   - make bootstrap
+  - pip install -q "tornado$TORNADO"
 
 script:
   - make test testbed lint

opentracing/scope_managers/contextvars.py

@@ -0,0 +1,131 @@
+# Copyright (c) The OpenTracing Authors.
+#
+# 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 contextlib import contextmanager
+from contextvars import ContextVar
+
+from opentracing import Scope, ScopeManager
+
+
+_SCOPE = ContextVar('scope')
+
+
+class ContextVarsScopeManager(ScopeManager):
+    """
+    :class:`~opentracing.ScopeManager` implementation for **asyncio**
+    that stores the :class:`~opentracing.Scope` using ContextVar.
+
+    The scope manager provides automatic :class:`~opentracing.Span` propagation
+    from parent coroutines, tasks and scheduled in event loop callbacks to
+    their children.
+
+    .. code-block:: python
+
+        async def child_coroutine():
+            # No need manual activation of parent span in child coroutine.
+            with tracer.start_active_span('child') as scope:
+                ...
+
+        async def parent_coroutine():
+            with tracer.start_active_span('parent') as scope:
+                ...
+                await child_coroutine()
+                ...
+
+    """
+
+    def activate(self, span, finish_on_close):
+        """
+        Make a :class:`~opentracing.Span` instance active.
+
+        :param span: the :class:`~opentracing.Span` that should become active.
+        :param finish_on_close: whether *span* should automatically be
+            finished when :meth:`Scope.close()` is called.
+
+        :return: a :class:`~opentracing.Scope` instance to control the end
+            of the active period for the :class:`~opentracing.Span`.
+            It is a programming error to neglect to call :meth:`Scope.close()`
+            on the returned instance.
+        """
+
+        return self._set_scope(span, finish_on_close)
+
+    @property
+    def active(self):
+        """
+        Return the currently active :class:`~opentracing.Scope` which
+        can be used to access the currently active :attr:`Scope.span`.
+
+        :return: the :class:`~opentracing.Scope` that is active,
+            or ``None`` if not available.
+        """
+
+        return self._get_scope()
+
+    def _set_scope(self, span, finish_on_close):
+        return _ContextVarsScope(self, span, finish_on_close)
+
+    def _get_scope(self):
+        return _SCOPE.get(None)
+
+
+class _ContextVarsScope(Scope):
+    def __init__(self, manager, span, finish_on_close):
+        super(_ContextVarsScope, self).__init__(manager, span)
+        self._finish_on_close = finish_on_close
+        self._token = _SCOPE.set(self)
+
+    def close(self):
+        if self.manager.active is not self:
+            return
+
+        _SCOPE.reset(self._token)
+
+        if self._finish_on_close:
+            self.span.finish()
+
+
+@contextmanager
+def no_parent_scope():
+    """
+    Context manager that resets current Scope. Intended to break span
+    propagation to children coroutines, tasks or scheduled callbacks.
+
+    .. code-block:: python
+
+        from opentracing.scope_managers.contextvars import no_parent_scope
+
+        def periodic()
+            # `periodic` span will be children of root only at the first time.
+            with self.tracer.start_active_span('periodic'):
+                # Now we break span propagation.
+                with no_parent_scope():
+                    self.loop.call_soon(periodic)
+
+        with self.tracer.start_active_span('root'):
+            self.loop.call_soon(periodic)
+    """
+    token = _SCOPE.set(None)
+    try:
+        yield
+    finally:
+        _SCOPE.reset(token)

setup.py

@@ -26,6 +26,9 @@
     include_package_data=True,
     zip_safe=False,
     platforms='any',
+    install_requires=[
+        'futures;python_version=="2.7"',
+    ],
     extras_require={
         'tests': [
             'doubles',
@@ -40,8 +43,7 @@
 
             'six>=1.10.0,<2.0',
             'gevent',
-            'tornado<6',
+            'tornado',
         ],
-        ':python_version == "2.7"': ['futures'],
     },
 )

testbed/README.md

@@ -18,7 +18,7 @@ Alternatively, due to the organization of the suite, it's possible to run direct
 
 ## Tested frameworks
 
-Currently the examples cover `threading`, `tornado`, `gevent` and `asyncio` (which requires Python 3). Each example uses their respective `ScopeManager` instance from `opentracing.scope_managers`, along with their related requirements and limitations.
+Currently the examples cover `threading`, `tornado`, `gevent`, `asyncio` (which requires Python 3) and `contextvars` (which requires Python 3.7 and higher). Each example uses their respective `ScopeManager` instance from `opentracing.scope_managers`, along with their related requirements and limitations.
 
 ### threading, asyncio and gevent
 
@@ -30,6 +30,10 @@ No automatic `Span` propagation between parent and children tasks is provided, a
 
 Currently, yielding over multiple children is not supported, as the context is effectively shared, and switching from coroutine to coroutine messes up the current active `Span`.
 
+### contextvars
+
+`ContextVarsScopeManager` uses [contextvars](https://docs.python.org/3/library/contextvars.html) module to both store **and** automatically propagate the context from parent coroutines / tasks / scheduled in event loop callbacks to their children.
+
 ## List of patterns
 
 - [Active Span replacement](test_active_span_replacement) - Start an isolated task and query for its results in another task/thread.
@@ -54,7 +58,3 @@ testbed/
 ```
 
 Supporting all the platforms is optional, and a warning will be displayed when doing `make testbed` in such case.
-
-## Flake8 support
-
-Currently `flake8` does not support the Python 3 `await`/`async` syntax, and does not offer a way to ignore such syntax.

testbed/__init__.py

@@ -1 +0,0 @@
-

testbed/__main__.py

@@ -1,17 +1,25 @@
 from importlib import import_module
 import logging
 import os
+import sys
 import six
 import unittest
+from tornado import version_info as tornado_version
 
 
 enabled_platforms = [
     'threads',
-    'tornado',
     'gevent',
 ]
+if tornado_version < (6, 0, 0, 0):
+    # Including testbed for Tornado coroutines and stack context.
+    # We don't need run testbed in case Tornado>=6, because it became
+    # asyncio-based framework and `stack_context` was deprecated.
+    enabled_platforms.append('tornado')
 if six.PY3:
     enabled_platforms.append('asyncio')
+if sys.version_info >= (3, 7):
+    enabled_platforms.append('contextvars')
 
 logging.basicConfig(level=logging.INFO)
 logger = logging.getLogger(__package__)
@@ -47,4 +55,6 @@ def get_test_directories():
         suite = loader.loadTestsFromModule(test_module)
         main_suite.addTests(suite)
 
-unittest.TextTestRunner(verbosity=3).run(main_suite)
+result = unittest.TextTestRunner(verbosity=3).run(main_suite)
+if result.failures or result.errors:
+    sys.exit(1)

testbed/test_active_span_replacement/test_contextvars.py

@@ -0,0 +1,54 @@
+from __future__ import print_function
+
+import asyncio
+
+from opentracing.mocktracer import MockTracer
+from ..testcase import OpenTracingTestCase
+from opentracing.scope_managers.contextvars import ContextVarsScopeManager
+from ..utils import stop_loop_when
+
+
+class TestAsyncioContextVars(OpenTracingTestCase):
+    def setUp(self):
+        self.tracer = MockTracer(ContextVarsScopeManager())
+        self.loop = asyncio.get_event_loop()
+
+    def test_main(self):
+        # Start an isolated task and query for its result -and finish it-
+        # in another task/thread
+        span = self.tracer.start_span('initial')
+        self.submit_another_task(span)
+
+        stop_loop_when(self.loop,
+                       lambda: len(self.tracer.finished_spans()) >= 3)
+        self.loop.run_forever()
+
+        initial, subtask, task = self.tracer.finished_spans()
+
+        self.assertEmptySpan(initial, 'initial')
+        self.assertEmptySpan(subtask, 'subtask')
+        self.assertEmptySpan(task, 'task')
+
+        # task/subtask are part of the same trace,
+        # and subtask is a child of task
+        self.assertSameTrace(subtask, task)
+        self.assertIsChildOf(subtask, task)
+
+        # initial task is not related in any way to those two tasks
+        self.assertNotSameTrace(initial, subtask)
+        self.assertHasNoParent(initial)
+
+    async def task(self, span):
+        # Create a new Span for this task
+        with self.tracer.start_active_span('task'):
+
+            with self.tracer.scope_manager.activate(span, True):
+                # Simulate work strictly related to the initial Span
+                pass
+
+            # Use the task span as parent of a new subtask
+            with self.tracer.start_active_span('subtask'):
+                pass
+
+    def submit_another_task(self, span):
+        self.loop.create_task(self.task(span))

testbed/test_client_server/test_contextvars.py

@@ -0,0 +1,79 @@
+from __future__ import print_function
+
+
+import asyncio
+
+import opentracing
+from opentracing.ext import tags
+from opentracing.mocktracer import MockTracer
+from opentracing.scope_managers.contextvars import ContextVarsScopeManager
+from ..testcase import OpenTracingTestCase
+from ..utils import get_logger, get_one_by_tag, stop_loop_when
+
+
+logger = get_logger(__name__)
+
+
+class Server(object):
+    def __init__(self, *args, **kwargs):
+        tracer = kwargs.pop('tracer')
+        queue = kwargs.pop('queue')
+        super(Server, self).__init__(*args, **kwargs)
+
+        self.tracer = tracer
+        self.queue = queue
+
+    async def run(self):
+        value = await self.queue.get()
+        self.process(value)
+
+    def process(self, message):
+        logger.info('Processing message in server')
+
+        ctx = self.tracer.extract(opentracing.Format.TEXT_MAP, message)
+        with self.tracer.start_active_span('receive',
+                                           child_of=ctx) as scope:
+            scope.span.set_tag(tags.SPAN_KIND, tags.SPAN_KIND_RPC_SERVER)
+
+
+class Client(object):
+    def __init__(self, tracer, queue):
+        self.tracer = tracer
+        self.queue = queue
+
+    async def send(self):
+        with self.tracer.start_active_span('send') as scope:
+            scope.span.set_tag(tags.SPAN_KIND, tags.SPAN_KIND_RPC_CLIENT)
+
+            message = {}
+            self.tracer.inject(scope.span.context,
+                               opentracing.Format.TEXT_MAP,
+                               message)
+            await self.queue.put(message)
+
+        logger.info('Sent message from client')
+
+
+class TestAsyncioContextVars(OpenTracingTestCase):
+    def setUp(self):
+        self.tracer = MockTracer(ContextVarsScopeManager())
+        self.queue = asyncio.Queue()
+        self.loop = asyncio.get_event_loop()
+        self.server = Server(tracer=self.tracer, queue=self.queue)
+
+    def test(self):
+        client = Client(self.tracer, self.queue)
+        self.loop.create_task(self.server.run())
+        self.loop.create_task(client.send())
+
+        stop_loop_when(self.loop,
+                       lambda: len(self.tracer.finished_spans()) >= 2)
+        self.loop.run_forever()
+
+        spans = self.tracer.finished_spans()
+        self.assertIsNotNone(get_one_by_tag(spans,
+                                            tags.SPAN_KIND,
+                                            tags.SPAN_KIND_RPC_SERVER))
+        self.assertIsNotNone(get_one_by_tag(spans,
+                                            tags.SPAN_KIND,
+                                            tags.SPAN_KIND_RPC_CLIENT))

testbed/test_common_request_handler/README.md

@@ -5,7 +5,8 @@ This example shows a `Span` used with `RequestHandler`, which is used as a middl
 Implementation details:
 - For `threading`, no active `Span` is consumed as the tasks may be run concurrently on different threads, and an explicit `SpanContext` has to be saved to be used as parent.
 - For `gevent` and `asyncio`, as no automatic `Span` propagation is done, an explicit `Span` has to be saved to be used as parent (observe an instrumentation library could help to do that implicitly - we stick to the simplest case, though).
-- For `tornado`, as the `StackContext` automatically propapates the context (even is the tasks are called through different coroutines), we **do** leverage the active `Span`.
+- For `tornado` (as the `StackContext`) and `contextvars` automatically propagates the context (even is the tasks are called through different coroutines), we **do** leverage the active `Span`.
+
 
 
 RequestHandler implementation:
@@ -20,6 +21,6 @@ RequestHandler implementation:
                                           child_of=self.context,
                                           ignore_active_span=True)
         else:
-            # Used by tornado.
+            # Used by tornado and contextvars.
             span = self.tracer.start_span('send')
 ```

testbed/test_common_request_handler/test_asyncio.py

@@ -1,7 +1,5 @@
 from __future__ import print_function
 
-import functools
-
 import asyncio
 
 from opentracing.ext import tags