api: Implement "named" meters + Remove "Batcher" from Meter constructor (open-telemetry#431)

Implements open-telemetry#221.
Also fixes open-telemetry#394.

Stateful.py and stateless.py in metrics example folder are not changed to use the new loader in anticipation of open-telemetry#422 being merged first and removing them.

Lastly, moves InstrumentationInfo from trace.py in the sdk to utils.

Author: lzchen

README.md

@@ -70,12 +70,14 @@ with tracer.start_as_current_span('foo'):
 
 ```python
 from opentelemetry import metrics
-from opentelemetry.sdk.metrics import Counter, Meter
+from opentelemetry.sdk.metrics import Counter, MeterProvider
 from opentelemetry.sdk.metrics.export import ConsoleMetricsExporter
+from opentelemetry.sdk.metrics.export.controller import PushController
 
-metrics.set_preferred_meter_implementation(lambda T: Meter())
-meter = metrics.meter()
+metrics.set_preferred_meter_provider_implementation(lambda _: MeterProvider())
+meter = metrics.get_meter(__name__)
 exporter = ConsoleMetricsExporter()
+controller = PushController(meter, exporter, 5)
 
 counter = meter.create_metric(
     "available memory",
@@ -89,9 +91,6 @@ counter = meter.create_metric(
 label_values = ("staging",)
 counter_handle = counter.get_handle(label_values)
 counter_handle.add(100)
-
-exporter.export([(counter, label_values)])
-exporter.shutdown()
 ```
 
 See the [API documentation](https://open-telemetry.github.io/opentelemetry-python/) for more detail, and the [examples folder](./examples) for a more sample code.

docs/opentelemetry.sdk.metrics.rst

@@ -8,6 +8,7 @@ Submodules
 
    opentelemetry.sdk.metrics.export.aggregate
    opentelemetry.sdk.metrics.export.batcher
+   opentelemetry.sdk.util.instrumentation
 
 .. automodule:: opentelemetry.sdk.metrics
     :members:

docs/opentelemetry.sdk.trace.rst

@@ -7,6 +7,7 @@ Submodules
 .. toctree::
 
    opentelemetry.sdk.trace.export
+   opentelemetry.sdk.util.instrumentation
 
 .. automodule:: opentelemetry.sdk.trace
     :members:

docs/opentelemetry.sdk.util.instrumentation.rst

@@ -0,0 +1,4 @@
+opentelemetry.sdk.util.instrumentation
+==========================================
+
+.. automodule:: opentelemetry.sdk.util.instrumentation

examples/metrics/prometheus.py

@@ -21,15 +21,15 @@
 
 from opentelemetry import metrics
 from opentelemetry.ext.prometheus import PrometheusMetricsExporter
-from opentelemetry.sdk.metrics import Counter, Meter
+from opentelemetry.sdk.metrics import Counter, MeterProvider
 from opentelemetry.sdk.metrics.export.controller import PushController
 
 # Start Prometheus client
 start_http_server(port=8000, addr="localhost")
 
 # Meter is responsible for creating and recording metrics
-metrics.set_preferred_meter_implementation(lambda _: Meter())
-meter = metrics.meter()
+metrics.set_preferred_meter_provider_implementation(lambda _: MeterProvider())
+meter = metrics.get_meter(__name__)
 # exporter to export metrics to Prometheus
 prefix = "MyAppPrefix"
 exporter = PrometheusMetricsExporter(prefix)

examples/metrics/record.py

@@ -1,4 +1,4 @@
-# Copyright 2019, OpenTelemetry Authors
+# Copyright 2020, OpenTelemetry Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -19,13 +19,15 @@
 import time
 
 from opentelemetry import metrics
-from opentelemetry.sdk.metrics import Counter, Meter
+from opentelemetry.sdk.metrics import Counter, MeterProvider
 from opentelemetry.sdk.metrics.export import ConsoleMetricsExporter
 from opentelemetry.sdk.metrics.export.controller import PushController
 
+# The preferred tracer implementation must be set, as the opentelemetry-api
+# defines the interface with a no-op implementation.
+metrics.set_preferred_meter_provider_implementation(lambda _: MeterProvider())
 # Meter is responsible for creating and recording metrics
-metrics.set_preferred_meter_implementation(lambda _: Meter())
-meter = metrics.meter()
+meter = metrics.get_meter(__name__)
 # exporter to export metrics to the console
 exporter = ConsoleMetricsExporter()
 # controller collects metrics created from meter and exports it via the

examples/metrics/simple_example.py

@@ -1,4 +1,4 @@
-# Copyright 2019, OpenTelemetry Authors
+# Copyright 2020, OpenTelemetry Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -23,9 +23,8 @@
 import time
 
 from opentelemetry import metrics
-from opentelemetry.sdk.metrics import Counter, Measure, Meter
+from opentelemetry.sdk.metrics import Counter, Measure, MeterProvider
 from opentelemetry.sdk.metrics.export import ConsoleMetricsExporter
-from opentelemetry.sdk.metrics.export.batcher import UngroupedBatcher
 from opentelemetry.sdk.metrics.export.controller import PushController
 
 batcher_mode = "stateful"
@@ -44,18 +43,15 @@ def usage(argv):
         usage(sys.argv)
         sys.exit(1)
 
-# Batcher used to collect all created metrics from meter ready for exporting
-# Pass in True/False to indicate whether the batcher is stateful.
-# True indicates the batcher computes checkpoints from over the process
-# lifetime.
-# False indicates the batcher computes checkpoints which describe the updates
-# of a single collection period (deltas)
-batcher = UngroupedBatcher(batcher_mode == "stateful")
-
-# If a batcher is not provided, a default batcher is used
 # Meter is responsible for creating and recording metrics
-metrics.set_preferred_meter_implementation(lambda _: Meter(batcher))
-meter = metrics.meter()
+metrics.set_preferred_meter_provider_implementation(lambda _: MeterProvider())
+
+# Meter's namespace corresponds to the string passed as the first argument Pass
+# in True/False to indicate whether the batcher is stateful. True indicates the
+# batcher computes checkpoints from over the process lifetime. False indicates
+# the batcher computes checkpoints which describe the updates of a single
+# collection period (deltas)
+meter = metrics.get_meter(__name__, batcher_mode == "stateful")
 
 # Exporter to export metrics to the console
 exporter = ConsoleMetricsExporter()

examples/opentelemetry-example-app/src/opentelemetry_example_app/metrics_example.py

@@ -28,7 +28,7 @@
 
 class TestPrometheusMetricExporter(unittest.TestCase):
     def setUp(self):
-        self._meter = metrics.Meter()
+        self._meter = metrics.MeterProvider().get_meter(__name__)
         self._test_metric = self._meter.create_metric(
             "testname",
             "testdesc",
@@ -74,7 +74,7 @@ def test_export(self):
             self.assertIs(result, MetricsExportResult.SUCCESS)
 
     def test_counter_to_prometheus(self):
-        meter = metrics.Meter()
+        meter = metrics.MeterProvider().get_meter(__name__)
         metric = meter.create_metric(
             "test@name",
             "testdesc",
@@ -111,7 +111,7 @@ def test_counter_to_prometheus(self):
 
     def test_invalid_metric(self):
 
-        meter = metrics.Meter()
+        meter = metrics.MeterProvider().get_meter(__name__)
         metric = meter.create_metric(
             "tesname", "testdesc", "unit", int, TestMetric
         )

ext/opentelemetry-ext-prometheus/tests/test_prometheus_exporter.py

@@ -1,4 +1,4 @@
-# Copyright 2019, OpenTelemetry Authors
+# Copyright 2020, OpenTelemetry Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -27,10 +27,13 @@
 
 """
 import abc
+import logging
 from typing import Callable, Dict, Optional, Sequence, Tuple, Type, TypeVar
 
 from opentelemetry.util import loader
 
+logger = logging.getLogger(__name__)
+
 ValueT = TypeVar("ValueT", int, float)
 
 
@@ -224,6 +227,56 @@ def record(self, value: ValueT, label_set: LabelSet) -> None:
         """
 
 
+class MeterProvider(abc.ABC):
+    @abc.abstractmethod
+    def get_meter(
+        self,
+        instrumenting_module_name: str,
+        stateful: bool = True,
+        instrumenting_library_version: str = "",
+    ) -> "Meter":
+        """Returns a `Meter` for use by the given instrumentation library.
+
+        This function may return different `Meter` types (e.g. a no-op meter
+        vs. a functional meter).
+
+        Args:
+            instrumenting_module_name: The name of the instrumenting module
+                (usually just ``__name__``).
+
+                This should *not* be the name of the module that is
+                instrumented but the name of the module doing the instrumentation.
+                E.g., instead of ``"requests"``, use
+                ``"opentelemetry.ext.http_requests"``.
+
+            stateful: True/False to indicate whether the meter will be
+                    stateful. True indicates the meter computes checkpoints
+                    from over the process lifetime. False indicates the meter
+                    computes checkpoints which describe the updates of a single
+                    collection period (deltas).
+
+            instrumenting_library_version: Optional. The version string of the
+                instrumenting library.  Usually this should be the same as
+                ``pkg_resources.get_distribution(instrumenting_library_name).version``.
+        """
+
+
+class DefaultMeterProvider(MeterProvider):
+    """The default MeterProvider, used when no implementation is available.
+
+    All operations are no-op.
+    """
+
+    def get_meter(
+        self,
+        instrumenting_module_name: str,
+        stateful: bool = True,
+        instrumenting_library_version: str = "",
+    ) -> "Meter":
+        # pylint:disable=no-self-use,unused-argument
+        return DefaultMeter()
+
+
 MetricT = TypeVar("MetricT", Counter, Gauge, Measure)
 
 
@@ -322,45 +375,69 @@ def get_label_set(self, labels: Dict[str, str]) -> "LabelSet":
 # Once https://github.com/python/mypy/issues/7092 is resolved,
 # the following type definition should be replaced with
 # from opentelemetry.util.loader import ImplementationFactory
-ImplementationFactory = Callable[[Type[Meter]], Optional[Meter]]
-
-_METER = None
-_METER_FACTORY = None
+ImplementationFactory = Callable[
+    [Type[MeterProvider]], Optional[MeterProvider]
+]
+
+_METER_PROVIDER = None
+_METER_PROVIDER_FACTORY = None
+
+
+def get_meter(
+    instrumenting_module_name: str,
+    stateful: bool = True,
+    instrumenting_library_version: str = "",
+) -> "Meter":
+    """Returns a `Meter` for use by the given instrumentation library.
+    This function is a convenience wrapper for
+    opentelemetry.metrics.meter_provider().get_meter
+    """
+    return meter_provider().get_meter(
+        instrumenting_module_name, stateful, instrumenting_library_version
+    )
 
 
-def meter() -> Meter:
-    """Gets the current global :class:`~.Meter` object.
+def meter_provider() -> MeterProvider:
+    """Gets the current global :class:`~.MeterProvider` object.
 
     If there isn't one set yet, a default will be loaded.
     """
-    global _METER, _METER_FACTORY  # pylint:disable=global-statement
+    global _METER_PROVIDER, _METER_PROVIDER_FACTORY  # pylint:disable=global-statement
 
-    if _METER is None:
+    if _METER_PROVIDER is None:
         # pylint:disable=protected-access
         try:
-            _METER = loader._load_impl(Meter, _METER_FACTORY)  # type: ignore
+            _METER_PROVIDER = loader._load_impl(
+                MeterProvider, _METER_PROVIDER_FACTORY  # type: ignore
+            )
         except TypeError:
             # if we raised an exception trying to instantiate an
-            # abstract class, default to no-op tracer impl
-            _METER = DefaultMeter()
-        del _METER_FACTORY
+            # abstract class, default to no-op meter impl
+            logger.warning(
+                "Unable to instantiate MeterProvider from meter provider factory.",
+                exc_info=True,
+            )
+            _METER_PROVIDER = DefaultMeterProvider()
+        _METER_PROVIDER_FACTORY = None
 
-    return _METER
+    return _METER_PROVIDER
 
 
-def set_preferred_meter_implementation(factory: ImplementationFactory) -> None:
-    """Set the factory to be used to create the meter.
+def set_preferred_meter_provider_implementation(
+    factory: ImplementationFactory,
+) -> None:
+    """Set the factory to be used to create the meter provider.
 
     See :mod:`opentelemetry.util.loader` for details.
 
     This function may not be called after a meter is already loaded.
 
     Args:
-        factory: Callback that should create a new :class:`Meter` instance.
+        factory: Callback that should create a new :class:`MeterProvider` instance.
     """
-    global _METER, _METER_FACTORY  # pylint:disable=global-statement
+    global _METER_PROVIDER_FACTORY  # pylint:disable=global-statement
 
-    if _METER:
-        raise RuntimeError("Meter already loaded.")
+    if _METER_PROVIDER:
+        raise RuntimeError("MeterProvider already loaded.")
 
-    _METER_FACTORY = factory
+    _METER_PROVIDER_FACTORY = factory