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/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 Exporter, ExportResult
+
+
+class InMemorySpanExporter(Exporter):
+    """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 retrieve 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]) -> ExportResult:
+        """Stores a list of spans in memory."""
+        if self._stopped:
+            return ExportResult.FAILED_NONE_RETRYABLE
+        with self._lock:
+            self._finished_spans.extend(spans)
+        return ExportResult.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/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.SimpleSpanProcessor(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.SimpleSpanProcessor(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.SimpleSpanProcessor(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.ExportResult.SUCCESS)
+
+        memory_exporter.shutdown()
+
+        # after shutdown export should fail
+        ret = memory_exporter.export(span_list)
+        self.assertEqual(ret, export.ExportResult.FAILED_NONE_RETRYABLE)