Add new more specific error types

To avoid comparing strings when handling routing errors.

Author: lutovich

neo4j/exceptions.py

@@ -65,17 +65,9 @@ def hydrate(cls, message=None, code=None, **metadata):
             classification = "DatabaseError"
             category = "General"
             title = "UnknownError"
-        if classification == "ClientError":
-            try:
-                error_class = client_errors[code]
-            except KeyError:
-                error_class = ClientError
-        elif classification == "DatabaseError":
-            error_class = DatabaseError
-        elif classification == "TransientError":
-            error_class = TransientError
-        else:
-            error_class = cls
+
+        error_class = cls._extract_error_class(classification, code)
+
         inst = error_class(message)
         inst.message = message
         inst.code = code
@@ -85,6 +77,26 @@ def hydrate(cls, message=None, code=None, **metadata):
         inst.metadata = metadata
         return inst
 
+    @classmethod
+    def _extract_error_class(cls, classification, code):
+        if classification == "ClientError":
+            try:
+                return client_errors[code]
+            except KeyError:
+                return ClientError
+
+        elif classification == "TransientError":
+            try:
+                return transient_errors[code]
+            except KeyError:
+                return TransientError
+
+        elif classification == "DatabaseError":
+            return DatabaseError
+
+        else:
+            return cls
+
 
 class ClientError(CypherError):
     """ The Client sent a bad request - changing the request might yield a successful outcome.
@@ -101,6 +113,11 @@ class TransientError(CypherError):
     """
 
 
+class DatabaseUnavailableError(TransientError):
+    """
+    """
+
+
 class ConstraintError(ClientError):
     """
     """
@@ -116,11 +133,21 @@ class CypherTypeError(ClientError):
     """
 
 
+class NotALeaderError(ClientError):
+    """
+    """
+
+
 class Forbidden(ClientError, SecurityError):
     """
     """
 
 
+class ForbiddenOnReadOnlyDatabaseError(Forbidden):
+    """
+    """
+
+
 class AuthError(ClientError, SecurityError):
     """ Raised when authentication failure occurs.
     """
@@ -144,7 +171,7 @@ class AuthError(ClientError, SecurityError):
     "Neo.ClientError.Statement.TypeError": CypherTypeError,
 
     # Forbidden
-    "Neo.ClientError.General.ForbiddenOnReadOnlyDatabase": Forbidden,
+    "Neo.ClientError.General.ForbiddenOnReadOnlyDatabase": ForbiddenOnReadOnlyDatabaseError,
     "Neo.ClientError.General.ReadOnly": Forbidden,
     "Neo.ClientError.Schema.ForbiddenOnConstraintIndex": Forbidden,
     "Neo.ClientError.Schema.IndexBelongsToConstraint": Forbidden,
@@ -155,4 +182,12 @@ class AuthError(ClientError, SecurityError):
     "Neo.ClientError.Security.AuthorizationFailed": AuthError,
     "Neo.ClientError.Security.Unauthorized": AuthError,
 
+    # NotALeaderError
+    "Neo.ClientError.Cluster.NotALeader": NotALeaderError
+}
+
+transient_errors = {
+
+    # DatabaseUnavailableError
+    "Neo.TransientError.General.DatabaseUnavailable": DatabaseUnavailableError
 }

neo4j/v1/routing.py

@@ -25,7 +25,7 @@
 from neo4j.addressing import SocketAddress, resolve
 from neo4j.bolt import ConnectionPool, ServiceUnavailable, ProtocolError, DEFAULT_PORT, connect
 from neo4j.compat.collections import MutableSet, OrderedDict
-from neo4j.exceptions import CypherError
+from neo4j.exceptions import CypherError, DatabaseUnavailableError, NotALeaderError, ForbiddenOnReadOnlyDatabaseError
 from neo4j.util import ServerVersion
 from neo4j.v1.api import Driver, READ_ACCESS, WRITE_ACCESS, fix_statement, fix_parameters
 from neo4j.v1.exceptions import SessionExpired
@@ -251,8 +251,8 @@ class RoutingConnectionPool(ConnectionPool):
     """ Connection pool with routing table.
     """
 
-    FAILURE_CODES = ("Neo.TransientError.General.DatabaseUnavailable")
-    WRITE_FAILURE_CODES = ("Neo.ClientError.Cluster.NotALeader", "Neo.ClientError.General.ForbiddenOnReadOnlyDatabase")
+    CLUSTER_MEMBER_FAILURE_ERRORS = (ServiceUnavailable, SessionExpired, DatabaseUnavailableError)
+    WRITE_FAILURE_ERRORS = (NotALeaderError, ForbiddenOnReadOnlyDatabaseError)
 
     def __init__(self, connector, initial_address, routing_context, *routers, **config):
         super(RoutingConnectionPool, self).__init__(connector)
@@ -412,9 +412,9 @@ def acquire(self, access_mode=None):
     def _handle_connection_error(self, address, error):
         """ Handle routing connection send or receive error.
         """
-        if isinstance(error, (SessionExpired, ServiceUnavailable)) or error.code in self.FAILURE_CODES:
+        if isinstance(error, self.CLUSTER_MEMBER_FAILURE_ERRORS):
             self.remove(address)
-        elif error.code in self.WRITE_FAILURE_CODES:
+        elif isinstance(error, self.WRITE_FAILURE_ERRORS):
             self._remove_writer(address)
 
     def remove(self, address):