Separate no-op from interfaces (#311)

Fixes #66

ext/opentelemetry-ext-dbapi/tests/test_dbapi_integration.py

@@ -21,7 +21,7 @@
 
 class TestDBApiIntegration(unittest.TestCase):
     def setUp(self):
-        self.tracer = trace_api.Tracer()
+        self.tracer = trace_api.DefaultTracer()
         self.span = MockSpan()
         self.start_current_span_patcher = mock.patch.object(
             self.tracer,

ext/opentelemetry-ext-http-requests/tests/test_requests_integration.py

@@ -29,8 +29,8 @@ class TestRequestsIntegration(unittest.TestCase):
     # TODO: Copy & paste from test_wsgi_middleware
     def setUp(self):
         self.span_attrs = {}
-        self.tracer_source = trace.TracerSource()
-        self.tracer = trace.Tracer()
+        self.tracer_source = trace.DefaultTracerSource()
+        self.tracer = trace.DefaultTracer()
         self.get_tracer_patcher = mock.patch.object(
             self.tracer_source,
             "get_tracer",

ext/opentelemetry-ext-mysql/tests/test_mysql_integration.py

@@ -23,7 +23,7 @@
 
 class TestMysqlIntegration(unittest.TestCase):
     def test_trace_integration(self):
-        tracer = trace_api.Tracer()
+        tracer = trace_api.DefaultTracer()
         span = mock.create_autospec(trace_api.Span, spec_set=True)
         start_current_span_patcher = mock.patch.object(
             tracer,

opentelemetry-api/src/opentelemetry/metrics/__init__.py

@@ -184,14 +184,15 @@ def record(self, label_set: LabelSet, value: ValueT) -> None:
 
 
 # pylint: disable=unused-argument
-class Meter:
+class Meter(abc.ABC):
     """An interface to allow the recording of metrics.
 
     `Metric` s are used for recording pre-defined aggregation (gauge and
     counter), or raw values (measure) in which the aggregation and labels
     for the exported metric are deferred.
     """
 
+    @abc.abstractmethod
     def record_batch(
         self,
         label_set: LabelSet,
@@ -211,6 +212,7 @@ def record_batch(
                 corresponding value to record for that metric.
         """
 
+    @abc.abstractmethod
     def create_metric(
         self,
         name: str,
@@ -236,9 +238,8 @@ def create_metric(
 
         Returns: A new ``metric_type`` metric with values of ``value_type``.
         """
-        # pylint: disable=no-self-use
-        return DefaultMetric()
 
+    @abc.abstractmethod
     def get_label_set(self, labels: Dict[str, str]) -> "LabelSet":
         """Gets a `LabelSet` with the given labels.
 
@@ -247,6 +248,33 @@ def get_label_set(self, labels: Dict[str, str]) -> "LabelSet":
 
         Returns: A `LabelSet` object canonicalized using the given input.
         """
+
+
+class DefaultMeter(Meter):
+    """The default Meter used when no Meter implementation is available."""
+
+    def record_batch(
+        self,
+        label_set: LabelSet,
+        record_tuples: Sequence[Tuple["Metric", ValueT]],
+    ) -> None:
+        pass
+
+    def create_metric(
+        self,
+        name: str,
+        description: str,
+        unit: str,
+        value_type: Type[ValueT],
+        metric_type: Type[MetricT],
+        label_keys: Sequence[str] = (),
+        enabled: bool = True,
+        monotonic: bool = False,
+    ) -> "Metric":
+        # pylint: disable=no-self-use
+        return DefaultMetric()
+
+    def get_label_set(self, labels: Dict[str, str]) -> "LabelSet":
         # pylint: disable=no-self-use
         return DefaultLabelSet()
 
@@ -269,7 +297,7 @@ def meter() -> Meter:
 
     if _METER is None:
         # pylint:disable=protected-access
-        _METER = loader._load_impl(Meter, _METER_FACTORY)
+        _METER = loader._load_impl(DefaultMeter, _METER_FACTORY)
         del _METER_FACTORY
 
     return _METER

opentelemetry-api/src/opentelemetry/trace/__init__.py

@@ -66,6 +66,7 @@
     by `tracer_source`.
 """
 
+import abc
 import enum
 import types as python_types
 import typing
@@ -151,9 +152,10 @@ class SpanKind(enum.Enum):
     CONSUMER = 4
 
 
-class Span:
+class Span(abc.ABC):
     """A span represents a single operation within a trace."""
 
+    @abc.abstractmethod
     def end(self, end_time: typing.Optional[int] = None) -> None:
         """Sets the current time as the span's end time.
 
@@ -163,6 +165,7 @@ def end(self, end_time: typing.Optional[int] = None) -> None:
         implementations are free to ignore or raise on further calls.
         """
 
+    @abc.abstractmethod
     def get_context(self) -> "SpanContext":
         """Gets the span's SpanContext.
 
@@ -172,15 +175,15 @@ def get_context(self) -> "SpanContext":
         Returns:
             A :class:`.SpanContext` with a copy of this span's immutable state.
         """
-        # pylint: disable=no-self-use
-        return INVALID_SPAN_CONTEXT
 
+    @abc.abstractmethod
     def set_attribute(self, key: str, value: types.AttributeValue) -> None:
         """Sets an Attribute.
 
         Sets a single Attribute with the key and value passed as arguments.
         """
 
+    @abc.abstractmethod
     def add_event(
         self,
         name: str,
@@ -194,12 +197,14 @@ def add_event(
         timestamp if the `timestamp` argument is omitted.
         """
 
+    @abc.abstractmethod
     def add_lazy_event(self, event: Event) -> None:
         """Adds an `Event`.
 
         Adds an `Event` that has previously been created.
         """
 
+    @abc.abstractmethod
     def update_name(self, name: str) -> None:
         """Updates the `Span` name.
 
@@ -209,15 +214,15 @@ def update_name(self, name: str) -> None:
         on the implementation.
         """
 
+    @abc.abstractmethod
     def is_recording_events(self) -> bool:
         """Returns whether this span will be recorded.
 
         Returns true if this Span is active and recording information like
         events with the add_event operation and attributes using set_attribute.
         """
-        # pylint: disable=no-self-use
-        return False
 
+    @abc.abstractmethod
     def set_status(self, status: Status) -> None:
         """Sets the Status of the Span. If used, this will override the default
         Span status, which is OK.
@@ -362,6 +367,29 @@ def get_context(self) -> "SpanContext":
     def is_recording_events(self) -> bool:
         return False
 
+    def end(self, end_time: typing.Optional[int] = None) -> None:
+        pass
+
+    def set_attribute(self, key: str, value: types.AttributeValue) -> None:
+        pass
+
+    def add_event(
+        self,
+        name: str,
+        attributes: types.Attributes = None,
+        timestamp: typing.Optional[int] = None,
+    ) -> None:
+        pass
+
+    def add_lazy_event(self, event: Event) -> None:
+        pass
+
+    def update_name(self, name: str) -> None:
+        pass
+
+    def set_status(self, status: Status) -> None:
+        pass
+
 
 INVALID_SPAN_ID = 0x0000000000000000
 INVALID_TRACE_ID = 0x00000000000000000000000000000000
@@ -374,8 +402,8 @@ def is_recording_events(self) -> bool:
 INVALID_SPAN = DefaultSpan(INVALID_SPAN_CONTEXT)
 
 
-class TracerSource:
-    # pylint:disable=no-self-use,unused-argument
+class TracerSource(abc.ABC):
+    @abc.abstractmethod
     def get_tracer(
         self,
         instrumenting_module_name: str,
@@ -402,10 +430,24 @@ def get_tracer(
                 instrumenting library.  Usually this should be the same as
                 ``pkg_resources.get_distribution(instrumenting_library_name).version``.
         """
-        return Tracer()
 
 
-class Tracer:
+class DefaultTracerSource(TracerSource):
+    """The default TracerSource, used when no implementation is available.
+
+    All operations are no-op.
+    """
+
+    def get_tracer(
+        self,
+        instrumenting_module_name: str,
+        instrumenting_library_version: str = "",
+    ) -> "Tracer":
+        # pylint:disable=no-self-use,unused-argument
+        return DefaultTracer()
+
+
+class Tracer(abc.ABC):
     """Handles span creation and in-process context propagation.
 
     This class provides methods for manipulating the context, creating spans,
@@ -414,8 +456,9 @@ class Tracer:
 
     # Constant used to represent the current span being used as a parent.
     # This is the default behavior when creating spans.
-    CURRENT_SPAN = Span()
+    CURRENT_SPAN = DefaultSpan(INVALID_SPAN_CONTEXT)
 
+    @abc.abstractmethod
     def get_current_span(self) -> "Span":
         """Gets the currently active span from the context.
 
@@ -426,9 +469,8 @@ def get_current_span(self) -> "Span":
             The currently active :class:`.Span`, or a placeholder span with an
             invalid :class:`.SpanContext`.
         """
-        # pylint: disable=no-self-use
-        return INVALID_SPAN
 
+    @abc.abstractmethod
     def start_span(
         self,
         name: str,
@@ -478,10 +520,9 @@ def start_span(
         Returns:
             The newly-created span.
         """
-        # pylint: disable=unused-argument,no-self-use
-        return INVALID_SPAN
 
     @contextmanager  # type: ignore
+    @abc.abstractmethod
     def start_as_current_span(
         self,
         name: str,
@@ -531,10 +572,8 @@ def start_as_current_span(
             The newly-created span.
         """
 
-        # pylint: disable=unused-argument,no-self-use
-        yield INVALID_SPAN
-
     @contextmanager  # type: ignore
+    @abc.abstractmethod
     def use_span(
         self, span: "Span", end_on_exit: bool = False
     ) -> typing.Iterator[None]:
@@ -552,6 +591,47 @@ def use_span(
             end_on_exit: Whether to end the span automatically when leaving the
                 context manager.
         """
+
+
+class DefaultTracer(Tracer):
+    """The default Tracer, used when no Tracer implementation is available.
+
+    All operations are no-op.
+    """
+
+    def get_current_span(self) -> "Span":
+        # pylint: disable=no-self-use
+        return INVALID_SPAN
+
+    def start_span(
+        self,
+        name: str,
+        parent: ParentSpan = Tracer.CURRENT_SPAN,
+        kind: SpanKind = SpanKind.INTERNAL,
+        attributes: typing.Optional[types.Attributes] = None,
+        links: typing.Sequence[Link] = (),
+        start_time: typing.Optional[int] = None,
+        set_status_on_exception: bool = True,
+    ) -> "Span":
+        # pylint: disable=unused-argument,no-self-use
+        return INVALID_SPAN
+
+    @contextmanager  # type: ignore
+    def start_as_current_span(
+        self,
+        name: str,
+        parent: ParentSpan = Tracer.CURRENT_SPAN,
+        kind: SpanKind = SpanKind.INTERNAL,
+        attributes: typing.Optional[types.Attributes] = None,
+        links: typing.Sequence[Link] = (),
+    ) -> typing.Iterator["Span"]:
+        # pylint: disable=unused-argument,no-self-use
+        yield INVALID_SPAN
+
+    @contextmanager  # type: ignore
+    def use_span(
+        self, span: "Span", end_on_exit: bool = False
+    ) -> typing.Iterator[None]:
         # pylint: disable=unused-argument,no-self-use
         yield
 
@@ -576,9 +656,14 @@ def tracer_source() -> TracerSource:
 
     if _TRACER_SOURCE is None:
         # pylint:disable=protected-access
-        _TRACER_SOURCE = loader._load_impl(
-            TracerSource, _TRACER_SOURCE_FACTORY
-        )
+        try:
+            _TRACER_SOURCE = loader._load_impl(
+                TracerSource, _TRACER_SOURCE_FACTORY  # type: ignore
+            )
+        except TypeError:
+            # if we raised an exception trying to instantiate an
+            # abstract class, default to no-op tracer impl
+            _TRACER_SOURCE = DefaultTracerSource()
         del _TRACER_SOURCE_FACTORY
 
     return _TRACER_SOURCE

opentelemetry-api/tests/metrics/test_metrics.py

@@ -20,7 +20,7 @@
 # pylint: disable=no-self-use
 class TestMeter(unittest.TestCase):
     def setUp(self):
-        self.meter = metrics.Meter()
+        self.meter = metrics.DefaultMeter()
 
     def test_record_batch(self):
         counter = metrics.Counter()