sdk: add Exporter interface, SimpleSpanProcessor and InMemorySpanExpo…

…rter (#119)

* 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.

* sdk/trace/exporter: add InMemorySpanExporter

InMemorySpanExporter is a simple implementation of the Exporter interface
that saves the exported spans in a list in memory.  This class is useful
for testing purposes.

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

@@ -0,0 +1,78 @@
+# 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
+
+logger = logging.getLogger(__name__)
+
+
+class SpanExportResult(Enum):
+    SUCCESS = 0
+    FAILED_RETRYABLE = 1
+    FAILED_NOT_RETRYABLE = 2
+
+
+class SpanExporter:
+    """Interface for exporting spans.
+
+    Interface to be implemented by services that want to export recorded 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):
+    """Simple SpanProcessor implementation.
+
+    SimpleExportSpanProcessor is 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
+
+    def on_end(self, span: Span) -> None:
+        try:
+            self.span_exporter.export((span,))
+        # pylint: disable=broad-except
+        except Exception as exc:
+            logger.warning("Exception while exporting data: %s", exc)
+
+    def shutdown(self) -> None:
+        self.span_exporter.shutdown()

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

@@ -0,0 +1,58 @@
+# 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 threading
+import typing
+
+from .. import Span
+from . import SpanExporter, SpanExportResult
+
+
+class InMemorySpanExporter(SpanExporter):
+    """Implementation of :class:`.Exporter` that stores spans in memory.
+
+    This class can be used for testing purposes. It stores the exported spans
+    in a list in memory that can be retrieved using the
+    :func:`.get_finished_spans` method.
+    """
+
+    def __init__(self):
+        self._finished_spans = []
+        self._stopped = False
+        self._lock = threading.Lock()
+
+    def clear(self):
+        """Clear list of collected spans."""
+        with self._lock:
+            self._finished_spans.clear()
+
+    def get_finished_spans(self):
+        """Get list of collected spans."""
+        with self._lock:
+            return tuple(self._finished_spans)
+
+    def export(self, spans: typing.Sequence[Span]) -> SpanExportResult:
+        """Stores a list of spans in memory."""
+        if self._stopped:
+            return SpanExportResult.FAILED_NOT_RETRYABLE
+        with self._lock:
+            self._finished_spans.extend(spans)
+        return SpanExportResult.SUCCESS
+
+    def shutdown(self):
+        """Shut downs the exporter.
+
+        Calls to export after the exporter has been shut down will fail.
+        """
+        self._stopped = True

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)

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

@@ -0,0 +1,97 @@
+# 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 unittest import mock
+
+from opentelemetry import trace as trace_api
+from opentelemetry.sdk import trace
+from opentelemetry.sdk.trace import export
+from opentelemetry.sdk.trace.export.in_memory_span_exporter import (
+    InMemorySpanExporter,
+)
+
+
+class TestInMemorySpanExporter(unittest.TestCase):
+    def test_get_finished_spans(self):
+        tracer = trace.Tracer()
+
+        memory_exporter = InMemorySpanExporter()
+        span_processor = export.SimpleExportSpanProcessor(memory_exporter)
+        tracer.add_span_processor(span_processor)
+
+        with tracer.start_span("foo"):
+            with tracer.start_span("bar"):
+                with tracer.start_span("xxx"):
+                    pass
+
+        span_list = memory_exporter.get_finished_spans()
+        spans_names_list = [span.name for span in span_list]
+        self.assertListEqual(["xxx", "bar", "foo"], spans_names_list)
+
+    def test_clear(self):
+        tracer = trace.Tracer()
+
+        memory_exporter = InMemorySpanExporter()
+        span_processor = export.SimpleExportSpanProcessor(memory_exporter)
+        tracer.add_span_processor(span_processor)
+
+        with tracer.start_span("foo"):
+            with tracer.start_span("bar"):
+                with tracer.start_span("xxx"):
+                    pass
+
+        memory_exporter.clear()
+        span_list = memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 0)
+
+    def test_shutdown(self):
+        tracer = trace.Tracer()
+
+        memory_exporter = InMemorySpanExporter()
+        span_processor = export.SimpleExportSpanProcessor(memory_exporter)
+        tracer.add_span_processor(span_processor)
+
+        with tracer.start_span("foo"):
+            with tracer.start_span("bar"):
+                with tracer.start_span("xxx"):
+                    pass
+
+        span_list = memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 3)
+
+        memory_exporter.shutdown()
+
+        # after shutdown no new spans are accepted
+        with tracer.start_span("foo"):
+            with tracer.start_span("bar"):
+                with tracer.start_span("xxx"):
+                    pass
+
+        span_list = memory_exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 3)
+
+    def test_return_code(self):
+        span = trace.Span("name", mock.Mock(spec=trace_api.SpanContext))
+        span_list = (span,)
+        memory_exporter = InMemorySpanExporter()
+
+        ret = memory_exporter.export(span_list)
+        self.assertEqual(ret, export.SpanExportResult.SUCCESS)
+
+        memory_exporter.shutdown()
+
+        # after shutdown export should fail
+        ret = memory_exporter.export(span_list)
+        self.assertEqual(ret, export.SpanExportResult.FAILED_NOT_RETRYABLE)