more consistent error handling

Author: lnproxy

cmd/http-relay/main.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"io"
 	"log"
 	"net/http"
 	"net/url"
@@ -82,18 +83,23 @@ func specApiHandler(w http.ResponseWriter, r *http.Request) {
 	x := lnproxy.ProxyParameters{}
 	err := json.NewDecoder(r.Body).Decode(&x)
 	if err != nil {
-		log.Println("error decoding request:", err)
-		json.NewEncoder(w).Encode(makeJsonError("error decoding request"))
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			log.Println("error reading request:", err)
+		} else {
+			log.Println("error decoding request:", string(body))
+		}
+		json.NewEncoder(w).Encode(makeJsonError("bad request"))
 		return
 	}
 
 	proxy_invoice, err := lnproxy.Relay(lnd, relayParameters, x)
 	if errors.Is(err, lnproxy.ClientFacing) {
-		log.Println("client facing error:", err)
+		log.Printf("client facing error for %#v:%v\n", x, err)
 		json.NewEncoder(w).Encode(makeJsonError(strings.TrimSpace(err.Error())))
 		return
 	} else if err != nil {
-		log.Println("internal error:", err)
+		log.Printf("internal error for %#v:%v\n", x, err)
 		json.NewEncoder(w).Encode(makeJsonError("internal error"))
 		return
 	}

lnproxy.go

@@ -96,7 +96,7 @@ func Wrap(ln lnc.LN, r RelayParameters, x ProxyParameters, p lnc.DecodedInvoice)
 			// 150/151 is electrum's trampoline
 		default:
 			log.Printf("unhandled feature flag: %s\n", x.Invoice)
-			return nil, 0, fmt.Errorf("unknown feature flag: %s", flag)
+			return nil, 0, errors.Join(ClientFacing, fmt.Errorf("unknown feature flag: %s", flag))
 		}
 	}
 
@@ -109,6 +109,7 @@ func Wrap(ln lnc.LN, r RelayParameters, x ProxyParameters, p lnc.DecodedInvoice)
 
 	min_fee_budget_msat, min_cltv_delta, err := ln.EstimateRoutingFee(p, 0)
 	if err != nil {
+		log.Println("could not find route:", x.Invoice, err)
 		return nil, 0, errors.Join(ClientFacing, errors.New("could not find route"))
 	}
 
@@ -185,7 +186,7 @@ func Relay(ln lnc.LN, r RelayParameters, x ProxyParameters) (string, error) {
 	go func() {
 		_, err := ln.WatchInvoice(q.Hash)
 		if err != nil {
-			log.Println("Error while watching wrapped invoice:", x.Invoice, err)
+			log.Println("error while watching wrapped invoice:", x.Invoice, err)
 			err := ln.CancelInvoice(q.Hash)
 			if err != nil {
 				log.Println("error while canceling invoice:", x.Invoice, err)
@@ -199,7 +200,7 @@ func Relay(ln lnc.LN, r RelayParameters, x ProxyParameters) (string, error) {
 			CltvLimit:      q.CltvExpiry - r.CltvDeltaAlpha,
 		})
 		if err != nil {
-			log.Println("Error paying original invoice:", x.Invoice, err)
+			log.Println("error paying original invoice:", x.Invoice, err)
 			err := ln.CancelInvoice(q.Hash)
 			if err != nil {
 				log.Println("error while canceling invoice:", x.Invoice, err)
@@ -208,9 +209,9 @@ func Relay(ln lnc.LN, r RelayParameters, x ProxyParameters) (string, error) {
 		}
 		err = ln.SettleInvoice(preimage)
 		if err != nil {
-			log.Panicln("Error while settling original invoice:", x.Invoice, err)
+			log.Panicln("error while settling original invoice:", x.Invoice, err)
 		}
-		log.Println("Relay circuit successful")
+		log.Println("relay circuit successful")
 	}()
 
 	return proxy_invoice, nil