fix(sdk): add max_spans limit to InMemorySpanExporter

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

@@ -3,6 +3,7 @@
 
 import threading
 import typing
+from collections import deque
 
 from opentelemetry.sdk.trace import ReadableSpan
 from opentelemetry.sdk.trace.export import SpanExporter, SpanExportResult
@@ -14,10 +15,15 @@ class InMemorySpanExporter(SpanExporter):
     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.
+
+    Args:
+        max_spans: Maximum number of spans to store in memory. When the limit
+            is reached, the oldest spans are dropped automatically. If ``None``
+            (default), there is no limit.
     """
 
-    def __init__(self) -> None:
-        self._finished_spans: list[ReadableSpan] = []
+    def __init__(self, max_spans: typing.Optional[int] = None) -> None:
+        self._finished_spans: deque[ReadableSpan] = deque(maxlen=max_spans)
         self._stopped = False
         self._lock = threading.Lock()
 
@@ -47,4 +53,4 @@ def shutdown(self) -> None:
         self._stopped = True
 
     def force_flush(self, timeout_millis: int = 30000) -> bool:
-        return True
+        return True

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

@@ -62,3 +62,18 @@ def test_return_code(self):
         # after shutdown export should fail
         ret = memory_exporter.export(span_list)
         self.assertEqual(ret, export.SpanExportResult.FAILURE)
+    def test_max_spans_limit(self):
+        """Test that max_spans limits memory usage by dropping oldest spans."""
+        exporter = InMemorySpanExporter(max_spans=2)
+        span = trace._Span("name", mock.Mock(spec=trace_api.SpanContext))
+        exporter.export([span, span, span])
+        span_list = exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 2)
+
+    def test_max_spans_none_is_unlimited(self):
+        """Test that max_spans=None (default) imposes no limit."""
+        exporter = InMemorySpanExporter(max_spans=None)
+        span = trace._Span("name", mock.Mock(spec=trace_api.SpanContext))
+        exporter.export([span] * 100)
+        span_list = exporter.get_finished_spans()
+        self.assertEqual(len(span_list), 100)