Make sure the protocol v5 downgrade for C* <4 if it is not explicitly specified

Author: aboudreault

cassandra/cluster.py

@@ -63,7 +63,7 @@
                                 BatchMessage, RESULT_KIND_PREPARED,
                                 RESULT_KIND_SET_KEYSPACE, RESULT_KIND_ROWS,
                                 RESULT_KIND_SCHEMA_CHANGE, ProtocolHandler,
-                                RESULT_KIND_VOID)
+                                RESULT_KIND_VOID, ProtocolException)
 from cassandra.metadata import Metadata, protect_name, murmur3, _NodeInfo
 from cassandra.policies import (TokenAwarePolicy, DCAwareRoundRobinPolicy, SimpleConvictionPolicy,
                                 ExponentialReconnectionPolicy, HostDistance,
@@ -3548,6 +3548,14 @@ def _try_connect(self, host):
                 break
             except ProtocolVersionUnsupported as e:
                 self._cluster.protocol_downgrade(host.endpoint, e.startup_version)
+            except ProtocolException as e:
+                # protocol v5 is out of beta in C* >=4.0-beta5 and is now the default driver
+                # protocol version. If the protocol version was not explicitly specified,
+                # and that the server raises a beta protocol error, we should downgrade.
+                if not self._cluster._protocol_version_explicit and e.is_beta_protocol_error:
+                    self._cluster.protocol_downgrade(host.endpoint, self._cluster.protocol_version)
+                else:
+                    raise
 
         log.debug("[control connection] Established new connection %r, "
                   "registering watchers and refreshing schema and topology",

cassandra/protocol.py

@@ -180,6 +180,10 @@ class ProtocolException(ErrorMessageSub):
     summary = 'Protocol error'
     error_code = 0x000A
 
+    @property
+    def is_beta_protocol_error(self):
+        return 'USE_BETA flag is unset' in str(self)
+
 
 class BadCredentials(ErrorMessageSub):
     summary = 'Bad credentials'