stellar#5099: use parallelJobSize as the alternate default for reinge…

…st max flush size if lower than default of 100

services/horizon/cmd/db.go

@@ -399,11 +399,9 @@ func runDBReingestRange(ledgerRanges []history.LedgerRange, reingestForce bool,
 		return errors.New("--force is incompatible with --parallel-workers > 1")
 	}
 
-	// set to 0 to allow system default to be applied for flush max,
-	// unless parallel workers are define, then set flush size to the number of workers.
-	maxLedgersPerFlush := uint32(0)
-	if parallelWorkers > 0 {
-		maxLedgersPerFlush = uint32(parallelWorkers)
+	maxLedgersPerFlush := ingest.MaxLedgersPerFlush
+	if parallelJobSize < maxLedgersPerFlush {
+		maxLedgersPerFlush = parallelJobSize
 	}
 
 	ingestConfig := ingest.Config{

services/horizon/internal/ingest/main.go

@@ -68,6 +68,10 @@ const (
 
 	defaultCoreCursorName           = "HORIZON"
 	stateVerificationErrorThreshold = 3
+
+	// 100 ledgers per flush has shown in stress tests
+	// to be best point on performance curve, default to that.
+	MaxLedgersPerFlush uint32 = 100
 )
 
 var log = logpkg.DefaultLogger.WithField("service", "ingest")
@@ -282,9 +286,7 @@ func NewSystem(config Config) (System, error) {
 
 	maxLedgersPerFlush := config.MaxLedgerPerFlush
 	if maxLedgersPerFlush < 1 {
-		// 100 ledgers per flush has shown in stress tests
-		// to be best point on performance curve, default to that.
-		maxLedgersPerFlush = 100
+		maxLedgersPerFlush = MaxLedgersPerFlush
 	}
 
 	system := &system{

services/horizon/internal/ingest/main_test.go

@@ -106,6 +106,7 @@ func TestNewSystem(t *testing.T) {
 
 	assert.Equal(t, config, system.runner.(*ProcessorRunner).config)
 	assert.Equal(t, system.ctx, system.runner.(*ProcessorRunner).ctx)
+	assert.Equal(t, system.maxLedgerPerFlush, MaxLedgersPerFlush)
 }
 
 func TestStateMachineRunReturnsUnexpectedTransaction(t *testing.T) {