`setupBatchBackend` leaks ledger backend on `PrepareRange` failure

[aristidesstaffieri]

What version are you using?

latest

Problem

File: internal/services/ingest_backfill.go lines 402-414

Buggy code:

func (m *ingestService) setupBatchBackend(ctx context.Context, batch BackfillBatch) (ledgerbackend.LedgerBackend, error) {
    backend, err := m.ledgerBackendFactory(ctx)
    if err != nil {
        return nil, fmt.Errorf("creating ledger backend: %w", err)
    }

    ledgerRange := ledgerbackend.BoundedRange(batch.StartLedger, batch.EndLedger)
    if err := backend.PrepareRange(ctx, ledgerRange); err != nil {
        // BUG: backend is never closed here
        return nil, fmt.Errorf("preparing backend range: %w", err)
    }

    return backend, nil
}

Description: When PrepareRange fails, the function returns nil for the backend, so the caller's defer backend.Close() cannot clean it up. Each leaked backend holds network connections and potentially streaming goroutines. During parallel backfill with many batches, repeated PrepareRange failures can exhaust file descriptors or memory.

Suggested fix:

if err := backend.PrepareRange(ctx, ledgerRange); err != nil {
    _ = backend.Close()
    return nil, fmt.Errorf("preparing backend range: %w", err)
}