sdk/trace: add Exporter interface and SimpleExportSpanProcessor

Exporter is an interface that allows different services to export recorded
spans in its own format. SimpleExportSpanProcessor is an implementation of
SpanProcessor that passes ended spans directly to a configured Exporter.

The current interface for exporters directly receives an SDK Span, it could
be improved in the future to receive a different object containing a
representation of the Span.

opentelemetry-sdk/src/opentelemetry/sdk/trace/export/__init__.py

@@ -0,0 +1,71 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+import typing
+from enum import Enum
+
+from .. import Span, SpanProcessor
+
+
+class SpanExportResult(Enum):
+    SUCCESS = 0
+    FAILED_RETRYABLE = 1
+    FAILED_NOT_RETRYABLE = 2
+
+
+class SpanExporter:
+    """Interface that allows different services to export recorded spans in
+    its own format.
+
+    To export data this MUST be registered to the :class`..Tracer` using a
+    `SimpleExportSpanProcessor` or a `BatchSpanProcessor`.
+    """
+
+    def export(self, spans: typing.Sequence[Span]) -> "SpanExportResult":
+        """Exports a batch of telemetry data.
+
+        Args:
+            spans: The list of `Span`s to be exported
+
+        Returns:
+            The result of the export
+        """
+
+    def shutdown(self) -> None:
+        """Shuts down the exporter.
+
+        Called when the SDK is shut down.
+        """
+
+
+class SimpleExportSpanProcessor(SpanProcessor):
+    """An implementation of `SpanProcessor` that passes ended spans directly
+    to the configured `SpanExporter`.
+    """
+
+    def __init__(self, span_exporter: SpanExporter):
+        self.span_exporter = span_exporter
+
+    def on_start(self, span: Span) -> None:
+        pass  # do nothing
+
+    def on_end(self, span: Span) -> None:
+        try:
+            self.span_exporter.export((span,))
+        except Exception as exc:
+            logging.warning("Exception while exporting data: %s", exc)
+
+    def shutdown(self) -> None:
+        self.span_exporter.shutdown()

opentelemetry-sdk/tests/trace/export/__init__.py

@@ -0,0 +1,13 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.

opentelemetry-sdk/tests/trace/export/test_export.py

@@ -0,0 +1,44 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+from opentelemetry.sdk import trace
+from opentelemetry.sdk.trace import export
+
+
+class TestSimpleExportSpanProcessor(unittest.TestCase):
+    def test_simple_span_processor(self):
+        class MySpanExporter(export.SpanExporter):
+            def __init__(self, destination):
+                self.destination = destination
+
+            def export(self, spans: trace.Span) -> export.SpanExportResult:
+                self.destination.extend(span.name for span in spans)
+                return export.SpanExportResult.SUCCESS
+
+        tracer = trace.Tracer()
+
+        spans_names_list = []
+
+        my_exporter = MySpanExporter(destination=spans_names_list)
+        span_processor = export.SimpleExportSpanProcessor(my_exporter)
+        tracer.add_span_processor(span_processor)
+
+        with tracer.start_span("foo"):
+            with tracer.start_span("bar"):
+                with tracer.start_span("xxx"):
+                    pass
+
+        self.assertListEqual(["xxx", "bar", "foo"], spans_names_list)