Restrict attribute keys to non-empty strings

According to the spec:

> The attribute key, which MUST be a non-null and non-empty string.

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/common/common.md

Author: owais

CHANGELOG.md

@@ -20,6 +20,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2044](https://github.com/open-telemetry/opentelemetry-python/pull/2044))
 - `opentelemetry-sdk` Fixed bugs (#2041, #2042 & #2045) in Span Limits
   ([#2044](https://github.com/open-telemetry/opentelemetry-python/pull/2044))
+- `opentelemetry-api` Attribute keys must be non-empty strings.
+  ([#2057](https://github.com/open-telemetry/opentelemetry-python/pull/2057))
 
 ## [0.23.1](https://github.com/open-telemetry/opentelemetry-python/pull/1987) - 2021-07-26
 

opentelemetry-api/src/opentelemetry/attributes/__init__.py

@@ -47,7 +47,11 @@ def _clean_attribute(
         - It needs to be encoded/decoded e.g, bytes to strings.
     """
 
-    if key is None or key == "":
+    #if key is None or key == "":
+    #    _logger.warning("invalid key `%s` (empty or null)", key)
+    #    return None
+
+    if not isinstance(key, str) or not key:
         _logger.warning("invalid key `%s` (empty or null)", key)
         return None
 

opentelemetry-api/tests/attributes/test_attributes.py

@@ -31,6 +31,16 @@ def assertValid(self, value, key="k"):
     def assertInvalid(self, value, key="k"):
         self.assertIsNone(_clean_attribute(key, value, None))
 
+    def test_attribute_key_validation(self):
+        # only non-empty strings are valid keys
+        self.assertInvalid(1, "")
+        self.assertInvalid(1, 1)
+        self.assertInvalid(1, {})
+        self.assertInvalid(1, [])
+        self.assertInvalid(1, b"1")
+        self.assertValid(1, "k")
+        self.assertValid(1, "1")
+
     def test_clean_attribute(self):
         self.assertInvalid([1, 2, 3.4, "ss", 4])
         self.assertInvalid([dict(), 1, 2, 3.4, 4])
@@ -142,10 +152,10 @@ def test_bounded_dict(self):
     def test_no_limit_code(self):
         bdict = BoundedAttributes(maxlen=None, immutable=False)
         for num in range(100):
-            bdict[num] = num
+            bdict[str(num)] = num
 
         for num in range(100):
-            self.assertEqual(bdict[num], num)
+            self.assertEqual(bdict[str(num)], num)
 
     def test_immutable(self):
         bdict = BoundedAttributes()