Creat a Fail-To_Bid error (prebid#636)

* Initial implementation

* Makes naming more consistent

errortypes/errortypes.go

@@ -7,6 +7,7 @@ const (
 	TimeoutCode
 	BadInputCode
 	BadServerResponseCode
+	FailedToRequestBidsCode
 )
 
 // We should use this code for any Error interface that is not in this package
@@ -70,6 +71,23 @@ func (err *BadServerResponse) Code() int {
 	return BadServerResponseCode
 }
 
+// FailedToRequestBids is an error to cover the case where an adapter failed to generate any http requests to get bids,
+// but did not generate any error messages. This should not happen in practice and will signal that an adapter is poorly
+// coded. If there was something wrong with a request such that an adapter could not generate a bid, then it should
+// generate an error explaining the deficiency. Otherwise it will be extremely difficult to debug the reason why an
+// adapter is not bidding.
+type FailedToRequestBids struct {
+	Message string
+}
+
+func (err *FailedToRequestBids) Error() string {
+	return err.Message
+}
+
+func (err *FailedToRequestBids) Code() int {
+	return FailedToRequestBidsCode
+}
+
 // DecodeError provides the error code for an error, as defined above
 func DecodeError(err error) int {
 	if ce, ok := err.(Coder); ok {

exchange/bidder.go

@@ -85,6 +85,10 @@ func (bidder *bidderAdapter) requestBid(ctx context.Context, request *openrtb.Bi
 	reqData, errs := bidder.Bidder.MakeRequests(request)
 
 	if len(reqData) == 0 {
+		// If the adapter failed to generate both requests and errors, this is an error.
+		if len(errs) == 0 {
+			errs = append(errs, &errortypes.FailedToRequestBids{Message: "The adapter failed to generate any bid requests, but also failed to generate an error explaining why"})
+		}
 		return nil, errs
 	}
 

exchange/exchange.go

@@ -239,6 +239,8 @@ func errorsToMetric(errs []error) map[pbsmetrics.AdapterError]struct{} {
 			ret[pbsmetrics.AdapterErrorBadInput] = s
 		case errortypes.BadServerResponseCode:
 			ret[pbsmetrics.AdapterErrorBadServerResponse] = s
+		case errortypes.FailedToRequestBidsCode:
+			ret[pbsmetrics.AdapterErrorFailedToRequestBids] = s
 		default:
 			ret[pbsmetrics.AdapterErrorUnknown] = s
 		}

pbsmetrics/metrics.go

@@ -143,17 +143,19 @@ func AdapterBids() []AdapterBid {
 
 // Adapter execution status
 const (
-	AdapterErrorBadInput          AdapterError = "badinput"
-	AdapterErrorBadServerResponse AdapterError = "badserverresponse"
-	AdapterErrorTimeout           AdapterError = "timeout"
-	AdapterErrorUnknown           AdapterError = "unknown_error"
+	AdapterErrorBadInput            AdapterError = "badinput"
+	AdapterErrorBadServerResponse   AdapterError = "badserverresponse"
+	AdapterErrorTimeout             AdapterError = "timeout"
+	AdapterErrorFailedToRequestBids AdapterError = "failedtorequestbid"
+	AdapterErrorUnknown             AdapterError = "unknown_error"
 )
 
 func AdapterErrors() []AdapterError {
 	return []AdapterError{
 		AdapterErrorBadInput,
 		AdapterErrorBadServerResponse,
 		AdapterErrorTimeout,
+		AdapterErrorFailedToRequestBids,
 		AdapterErrorUnknown,
 	}
 }