[QoS][EVM][Observability] QoS EVM: set request error on protocol error (#447)

## Summary

Fix: QoS EVM: set request error on protocol error

Author: adshmh

metrics/qos/evm/metrics.go

@@ -199,6 +199,14 @@ func PublishMetrics(logger polylog.Logger, observations *qos.EVMRequestObservati
 		errorType = requestError.String()
 	}
 
+	// TODO_TECHDEBT(@adshmh): Move this to the EVM interpreter logic:
+	// - Drop structs not generated from proto files: e.g. observation.EVMRequestError
+	// - Update the EVM interpreter to return an HTTP status code and an error_type string instead.
+	if requestErr := observations.GetRequestError(); requestErr != nil {
+		statusCode = int(requestErr.GetHttpStatusCode())
+		errorType = requestErr.GetErrorKind().String()
+	}
+
 	// Count each method as a separate request.
 	// This is required for batch requests.
 	for _, method := range methods {

observation/protocol/shannon.pb.go

@@ -123,6 +123,10 @@ func (i *EVMObservationInterpreter) GetRequestOrigin() string {
 	return i.Observations.GetRequestOrigin().String()
 }
 
+// TODO_TECHDEBT(@adshmh): Check for any request-level errors.
+// - Example: no responses received from any endpoints.
+// - Drop EVMRequestError struct, and use RequestError directly.
+//
 // GetRequestStatus interprets the observations to determine request status information:
 // - httpStatusCode: the suggested HTTP status code to return to the client
 // - requestError: error details (nil if successful)

observation/qos/evm.pb.go

@@ -19,6 +19,7 @@ option go_package = "github.com/buildwithgrove/path/observation/qos";
 import "path/qos/jsonrpc.proto";
 import "path/qos/request_origin.proto";
 import "path/qos/endpoint_selection_metadata.proto";
+import "path/qos/request_error.proto";
 import "path/metadata/metadata.proto";
 
 // EVMRequestValidationError enumerates possible causes for EVM request rejection:
@@ -64,7 +65,7 @@ enum EVMResponseValidationError {
 
 // EVMRequestObservations captures all observations made while serving a single EVM blockchain service request.
 message EVMRequestObservations {
-  // Next ID: 11
+  // Next ID: 12
 
   // JsonRpcRequest and endpoint_observations are no longer supported.
   // They are replaced by EVMRequestObservation.
@@ -109,6 +110,12 @@ message EVMRequestObservations {
 
   // endpoint_selection_metadata contains metadata about the endpoint selection process.
   EndpointSelectionMetadata endpoint_selection_metadata = 9;
+
+  // Internal error encountered processing the request, if any.
+  // Example: no endpoint responses received.
+  // On single JSONRPC request: applies to the single request.
+  // On batch JSONRPC requests: only set if the entire batch failed (e.g. no endpoint responses for any of the requests of the batch)
+  optional RequestError request_error = 11;
 }
 
 // EVMRequestObservation stores a single observation from an endpoint servicing the protocol response.
@@ -283,4 +290,4 @@ message EVMNoResponse {
 
   // Always set to NO_RESPONSE for this scenario
   EVMResponseValidationError response_validation_error = 2 [(metadata.semantic_meaning) = "Validity failure type"];
-}
+}

observation/qos/evm_interpreter.go

@@ -10,6 +10,7 @@ import (
 	pathhttp "github.com/buildwithgrove/path/network/http"
 	qosobservations "github.com/buildwithgrove/path/observation/qos"
 	"github.com/buildwithgrove/path/protocol"
+	"github.com/buildwithgrove/path/qos"
 	"github.com/buildwithgrove/path/qos/jsonrpc"
 )
 
@@ -218,13 +219,20 @@ func (rc requestContext) GetObservations() qosobservations.Observations {
 	// Convert endpoint selection validation results to proto format
 	validationResults := rc.convertValidationResults()
 
+	var requestError *qosobservations.RequestError
+	// Set request error as protocol-level error if no endpoint responses were received.
+	if len(rc.endpointResponses) == 0 {
+		requestError = qos.GetRequestErrorForProtocolError()
+	}
+
 	return qosobservations.Observations{
 		ServiceObservations: &qosobservations.Observations_Evm{
 			Evm: &qosobservations.EVMRequestObservations{
 				ChainId:              rc.chainID,
 				ServiceId:            string(rc.serviceID),
 				RequestPayloadLength: uint32(rc.requestPayloadLength),
 				RequestOrigin:        rc.requestOrigin,
+				RequestError:         requestError,
 				RequestObservations:  requestObservations,
 				EndpointSelectionMetadata: &qosobservations.EndpointSelectionMetadata{
 					RandomEndpointFallback: rc.endpointSelectionMetadata.RandomEndpointFallback,
@@ -260,9 +268,11 @@ func (rc requestContext) createNoResponseObservations() []*qosobservations.EVMRe
 	responseNoneObs := responseNoneObj.GetObservation()
 
 	return []*qosobservations.EVMRequestObservation{
-		{EndpointObservations: []*qosobservations.EVMEndpointObservation{
-			&responseNoneObs,
-		}},
+		{
+			EndpointObservations: []*qosobservations.EVMEndpointObservation{
+				&responseNoneObs,
+			},
+		},
 	}
 }