Allow span limits to be unset

Ths spec recommends most span limits to default to 128 and allow users
to change it via environment variables. It does not dictate that limits
should always be set though. So users should be able to remove these
limits. This commit accepts `"none"` as a valid value for the limit
config environment variables.

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Added example for running Django with auto instrumentation.
   ([#1803](https://github.com/open-telemetry/opentelemetry-python/pull/1803))
+- Allow span limits (OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT, OTEL_SPAN_EVENT_COUNT_LIMIT, OTEL_SPAN_LINK_COUNT_LIMIT)
+  to be set to "none".
+  ([#1830](https://github.com/open-telemetry/opentelemetry-python/pull/1830))
 
 ### Changed
 - Fixed OTLP gRPC exporter silently failing if scheme is not specified in endpoint.

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

@@ -58,12 +58,22 @@
 
 logger = logging.getLogger(__name__)
 
-SPAN_ATTRIBUTE_COUNT_LIMIT = int(
-    environ.get(OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT, 128)
+
+def _get_limit_from_env(limit_name, default) -> Optional[int]:
+    value = environ.get(limit_name, default).strip().lower()
+    if value == "none":
+        return None
+    return int(value)
+
+
+SPAN_ATTRIBUTE_COUNT_LIMIT = _get_limit_from_env(
+    OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT, "128"
 )
 
-_SPAN_EVENT_COUNT_LIMIT = int(environ.get(OTEL_SPAN_EVENT_COUNT_LIMIT, 128))
-_SPAN_LINK_COUNT_LIMIT = int(environ.get(OTEL_SPAN_LINK_COUNT_LIMIT, 128))
+_SPAN_EVENT_COUNT_LIMIT = _get_limit_from_env(
+    OTEL_SPAN_EVENT_COUNT_LIMIT, "128"
+)
+_SPAN_LINK_COUNT_LIMIT = _get_limit_from_env(OTEL_SPAN_LINK_COUNT_LIMIT, "128")
 _VALID_ATTR_VALUE_TYPES = (bool, str, int, float)
 # pylint: disable=protected-access
 _TRACE_SAMPLER = sampling._get_from_env_or_default()

opentelemetry-sdk/src/opentelemetry/sdk/util/__init__.py

@@ -97,10 +97,11 @@ class BoundedDict(MutableMapping):
     """
 
     def __init__(self, maxlen):
-        if not isinstance(maxlen, int):
-            raise ValueError
-        if maxlen < 0:
-            raise ValueError
+        if maxlen is not None:
+            if not isinstance(maxlen, int):
+                raise ValueError
+            if maxlen < 0:
+                raise ValueError
         self.maxlen = maxlen
         self.dropped = 0
         self._dict = OrderedDict()  # type: OrderedDict

opentelemetry-sdk/tests/test_util.py

@@ -134,6 +134,14 @@ def test_extend_drop(self):
         self.assertEqual(len(blist), list_len)
         self.assertEqual(blist.dropped, len(other_list))
 
+    def test_no_limit(self):
+        blist = BoundedList(maxlen=None)
+        for num in range(100):
+            blist.append(num)
+
+        for num in range(100):
+            self.assertEqual(blist[num], num)
+
 
 class TestBoundedDict(unittest.TestCase):
     base = collections.OrderedDict(
@@ -211,3 +219,11 @@ def test_bounded_dict(self):
 
         with self.assertRaises(KeyError):
             _ = bdict["new-name"]
+
+    def test_no_limit(self):
+        bdict = BoundedDict(maxlen=None)
+        for num in range(100):
+            bdict[num] = num
+
+        for num in range(100):
+            self.assertEqual(bdict[num], num)