Add instrument names lock

Author: ocelotl

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

@@ -116,6 +116,7 @@ def __init__(self, name, version=None, schema_url=None):
         self._version = version
         self._schema_url = schema_url
         self._instrument_names = set()
+        self._instrument_names_lock = Lock()
 
     @property
     def name(self):
@@ -133,7 +134,8 @@ def _check_instrument_name(self, name):
         if name.strip().lower() in self._instrument_names:
             raise Exception(f"Instrument name {name} has been used already")
 
-        self._instrument_names.add(name)
+        with self._instrument_names_lock:
+            self._instrument_names.add(name)
 
     @abstractmethod
     def create_counter(self, name, unit="", description="") -> Counter: