Introduce protocol_version field for TP registration

1. MAX_SDK_PROTOCOL_VERSION is the maximum version that the
validator can support. The SDK shall consider registration
attempt unsuccessful if validator cannot support a feature.
2. A protocol_version field is sent in TpRegisterRequest message.
This is acknowledged back with a echoed protocol_version if
validator can handle the request successfully. Otherwise
registration attempt would be rejected.

Signed-off-by: S m, Aruna <[email protected]>

protos/processor.proto

@@ -22,9 +22,11 @@ import "transaction.proto";
 
 
 // The registration request from the transaction processor to the
-// validator/executor
+// validator/executor.
+//
+// The protocol_version field is used to check if the validator supports
+// requested features by a transaction processor.
 message TpRegisterRequest {
-
     // A settled upon name for the capabilities of the transaction processor.
     // For example: intkey, xo
     string family = 1;
@@ -42,6 +44,11 @@ message TpRegisterRequest {
     // The maximum number of transactions that this transaction processor can
     // handle at once.
     uint32 max_occupancy = 5;
+
+    // Validator can make use of this field to check if the requested features
+    // are supported. Registration requests can be either accepted or rejected
+    // based on this field.
+    uint32 protocol_version = 6;
 }
 
 // A response sent from the validator to the transaction processor
@@ -54,6 +61,10 @@ message TpRegisterResponse {
     }
 
     Status status = 1;
+
+    // Respond back with protocol_version, the value that can be used by SDK to
+    // know if validator supports expected feature.
+    uint32 protocol_version = 2;
 }
 
 // The unregistration request from the transaction processor to the

validator/sawtooth_validator/execution/processor_handlers.py

@@ -26,6 +26,11 @@
 LOGGER = logging.getLogger(__name__)
 
 DEFAULT_MAX_OCCUPANCY = 10
+# This is the version used by the SDK to match if the validator supports
+# features it requested during registration. It should only be incremented
+# when there are changes in TpRegisterRequest.
+# Remember to sync this information in SDK if changed here.
+MAX_SDK_PROTOCOL_VERSION = 1
 
 
 class ProcessorRegisterHandler(Handler):
@@ -44,14 +49,25 @@ def handle(self, connection_id, message_content):
         else:
             max_occupancy = request.max_occupancy
 
-        LOGGER.info(
-            'registered transaction processor: connection_id=%s, family=%s, '
-            'version=%s, namespaces=%s, max_occupancy=%s',
-            connection_id,
-            request.family,
-            request.version,
-            list(request.namespaces),
-            max_occupancy)
+
+        # Reject the request if requested version cannot be handled,
+        # validator does backward compatible support.
+        if request.protocol_version > MAX_SDK_PROTOCOL_VERSION:
+            ack = processor_pb2.TpRegisterResponse()
+            ack.status = ack.ERROR
+            # Send protocol_version of validator, so that the SDK can cross
+            # verify if it can get all services requested for.
+            ack.protocol_version = request.protocol_version
+            LOGGER.error(
+                'Validator version %s does not support the features requested'
+                ' by the %s version of transaction processor',
+                str(MAX_SDK_PROTOCOL_VERSION),
+                str(request.protocol_version))
+
+            return HandlerResult(
+                status=HandlerStatus.RETURN,
+                message_out=ack,
+                message_type=validator_pb2.Message.TP_REGISTER_RESPONSE)
 
         processor_type = processor_manager.ProcessorType(
             request.family,
@@ -66,6 +82,18 @@ def handle(self, connection_id, message_content):
 
         ack = processor_pb2.TpRegisterResponse()
         ack.status = ack.OK
+        # Echo back the requested protocol_version, so that the SDK can
+        # cross verify that it can get all services requested
+        ack.protocol_version = request.protocol_version
+
+        LOGGER.info(
+            'registered transaction processor: connection_id=%s, family=%s, '
+            'version=%s, namespaces=%s, max_occupancy=%s',
+            connection_id,
+            request.family,
+            request.version,
+            list(request.namespaces),
+            max_occupancy)
 
         return HandlerResult(
             status=HandlerStatus.RETURN,