update limits as per specification (#1597)

Author: alrex

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1571](https://github.com/open-telemetry/opentelemetry-python/pull/1571)])
 - Rename `TRACE_` to `TRACES_` for environment variables
   ([#1595](https://github.com/open-telemetry/opentelemetry-python/pull/1595)])
+- Limits for Span attributes, events and links have been updated to 128
+  ([1597](https://github.com/open-telemetry/opentelemetry-python/pull/1597)])
 
 ### Added
 - Added `end_on_exit` argument to `start_as_current_span`

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

@@ -61,11 +61,11 @@
 logger = logging.getLogger(__name__)
 
 SPAN_ATTRIBUTE_COUNT_LIMIT = int(
-    environ.get(OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT, 1000)
+    environ.get(OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT, 128)
 )
 
-SPAN_EVENT_COUNT_LIMIT = int(environ.get(OTEL_SPAN_EVENT_COUNT_LIMIT, 1000))
-SPAN_LINK_COUNT_LIMIT = int(environ.get(OTEL_SPAN_LINK_COUNT_LIMIT, 1000))
+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))
 VALID_ATTR_VALUE_TYPES = (bool, str, int, float)
 # pylint: disable=protected-access
 TRACE_SAMPLER = sampling._get_from_env_or_default()