exp/lighthorizon: Minor error-handling and deployment improvements. (#…

…4599)

- actually set the PARALLEL_DOWNLOADS parameter to use #4468
- return a 404 rather than a 500 if a ledger is missing as its more descriptive
- handle `count = 0` in average metric calculations

exp/lighthorizon/actions/accounts.go

@@ -3,6 +3,7 @@ package actions
 import (
 	"errors"
 	"net/http"
+	"os"
 	"strconv"
 
 	"github.com/stellar/go/support/log"
@@ -69,7 +70,11 @@ func NewTXByAccountHandler(lightHorizon services.LightHorizon) func(http.Respons
 		txns, err := lightHorizon.Transactions.GetTransactionsByAccount(ctx, paginate.Cursor, paginate.Limit, accountId)
 		if err != nil {
 			log.Error(err)
-			sendErrorResponse(r.Context(), w, supportProblem.ServerError)
+			if os.IsNotExist(err) {
+				sendErrorResponse(r.Context(), w, supportProblem.NotFound)
+			} else if err != nil {
+				sendErrorResponse(r.Context(), w, supportProblem.ServerError)
+			}
 			return
 		}
 

exp/lighthorizon/build/k8s/lighthorizon_web.yml

@@ -10,6 +10,7 @@ data:
   TXMETA_SOURCE: "s3://horizon-ledgermeta-prodnet-test"
   INDEXES_SOURCE: "s3://horizon-index-prodnet-test"
   NETWORK_PASSPHRASE: "Public Global Stellar Network ; September 2015"
+  MAX_PARALLEL_DOWNLOADS: 16
   CACHE_PATH: "/ledgercache"
 ---  
 apiVersion: v1

exp/lighthorizon/build/web/Dockerfile

@@ -17,4 +17,5 @@ COPY --from=builder /go/bin/lighthorizon ./
 ENTRYPOINT ./lighthorizon serve \
   --network-passphrase "$NETWORK_PASSPHRASE" \
   --ledger-cache "$CACHE_PATH" \
+  --parallel-downloads "$MAX_PARALLEL_DOWNLOADS" \
   "$TXMETA_SOURCE" "$INDEXES_SOURCE" \

exp/lighthorizon/services/main.go

@@ -204,5 +204,8 @@ func searchAccountTransactions(ctx context.Context,
 func getAverageDuration[
 	T constraints.Signed | constraints.Float,
 ](d time.Duration, count T) time.Duration {
+	if count == 0 {
+		return 0 // don't bomb on div-by-zero
+	}
 	return time.Duration(int64(float64(d.Nanoseconds()) / float64(count)))
 }