fix(auth): revert mTLS auto-enablement configuration warnings to debug level

Author: nbayati

packages/google-auth/google/auth/transport/_mtls_helper.py

@@ -51,12 +51,6 @@
 _LOGGER = logging.getLogger(__name__)
 
 
-# A flag to track if we have already logged a warning about mTLS auto-enablement failures.
-# This prevents log spam when client libraries create transports or session instances
-# frequently within a single process.
-_has_logged_mtls_warning = False
-
-
 _PASSPHRASE_REGEX = re.compile(
     b"-----BEGIN PASSPHRASE-----(.+)-----END PASSPHRASE-----", re.DOTALL
 )
@@ -737,7 +731,6 @@ def check_use_client_cert():
     Returns:
         bool: Whether the client certificate should be used for mTLS connection.
     """
-    global _has_logged_mtls_warning
     env_override = _check_use_client_cert_env()
     if env_override is not None:
         return env_override
@@ -752,13 +745,11 @@ def check_use_client_cert():
             with open(cert_path, "r") as f:
                 content = json.load(f)
         except (FileNotFoundError, OSError, json.JSONDecodeError) as e:
-            if not _has_logged_mtls_warning:
-                _LOGGER.warning(
-                    "mTLS auto-enablement failed: Could not read/parse certificate file at %s. Error: %s",
-                    cert_path,
-                    e,
-                )
-                _has_logged_mtls_warning = True
+            _LOGGER.debug(
+                "mTLS auto-enablement failed: Could not read/parse certificate file at %s. Error: %s",
+                cert_path,
+                e,
+            )
             return False
 
         # Structural validation
@@ -768,12 +759,10 @@ def check_use_client_cert():
                 return True
 
         # If we got here, the file exists but the expected structure is missing
-        if not _has_logged_mtls_warning:
-            _LOGGER.warning(
-                "mTLS auto-enablement failed: Certificate configuration file at %s is missing the required ['cert_configs']['workload'] section.",
-                cert_path,
-            )
-            _has_logged_mtls_warning = True
+        _LOGGER.debug(
+            "mTLS auto-enablement failed: Certificate configuration file at %s is missing the required ['cert_configs']['workload'] section.",
+            cert_path,
+        )
     return False