Look clients up in the IPinfo Lite file with SWWAF_LOOKUP_SOURCE=file (closes #22)

SWWAF_LOOKUP_SOURCE=file looks every client up in the file
SWWAF_LOOKUP_DB_PATH names, without GeoJS. file without the path, the
path with another source, or a file that cannot be read stops the start.
The file is read whole into memory, so overwriting it in place cannot
disturb a lookup, and read again 2 seconds after its last change; a
replacement that cannot be read is logged, counted and sent as a
file_error alert, and the old one stays in use. Metrics give when it
was read and the failed reads. Tests write their databases through
internal/lookup/lookuptest.

Deviation: go.mod and go.sum written by hand; go runs only through make.
Judgement call: the 2-second wait, as the rule files have.

Model: opus-5-5

internal/lookup/file.go

@@ -0,0 +1,233 @@
+package lookup
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+	"github.com/oschwald/maxminddb-golang/v2"
+
+	"sneak.berlin/go/smallwebwaf/internal/alerts"
+)
+
+// quietTime is how long the lookup database must go without a change
+// before it is read again, so that a file still being copied in is read
+// only once whole.
+const quietTime = 2 * time.Second
+
+// FileParams are what OpenFile needs.
+type FileParams struct {
+	// Path is the lookup database, the IPinfo Lite file in its .mmdb form
+	// (SWWAF_LOOKUP_DB_PATH).
+	Path string
+	// Now tells the time, normally time.Now.
+	Now func() time.Time
+	// ProcessLog receives each reading of the file, and why a replacement
+	// of it cannot be read.
+	ProcessLog *slog.Logger
+	// Alerts receive a file_error alert for each replacement that cannot
+	// be read.
+	Alerts *alerts.Queue
+}
+
+// File looks up clients' AS numbers and countries in the lookup database,
+// held in memory, and reads it again when it is replaced. It is safe for
+// concurrent use.
+type File struct {
+	params FileParams
+
+	mu sync.Mutex
+	// reader is the database in use, and lastRead when it was read.
+	// readFailures are the replacements that could not be read.
+	reader       *maxminddb.Reader
+	lastRead     time.Time
+	readFailures int
+}
+
+// record is what the lookup database holds about a network, of the fields
+// smallwebwaf reads.
+type record struct {
+	ASN         string `maxminddb:"asn"`
+	ASName      string `maxminddb:"as_name"`
+	CountryCode string `maxminddb:"country_code"`
+}
+
+// OpenFile reads the lookup database. A file that cannot be read, or that
+// is not a .mmdb file, is an error.
+func OpenFile(params FileParams) (*File, error) {
+	reader, err := read(params.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	f := &File{params: params}
+	f.use(reader)
+
+	return f, nil
+}
+
+// LookUp returns what the lookup database says about client: its AS
+// number, such as AS64496, the AS's name, and its country, such as DE,
+// each "" when the database does not give it, as for an address missing
+// from it. The database is asked about the client's first address, as
+// GeoJS is.
+func (f *File) LookUp(client netip.Prefix) Answer {
+	f.mu.Lock()
+	reader := f.reader
+	f.mu.Unlock()
+
+	var found record
+
+	// A record that cannot be decoded places the client nowhere, as a
+	// missing one does.
+	err := reader.Lookup(client.Addr()).Decode(&found)
+	if err != nil {
+		found = record{}
+	}
+
+	return Answer{
+		Client:   client,
+		ASN:      found.ASN,
+		ASName:   found.ASName,
+		Country:  found.CountryCode,
+		Answered: f.params.Now(),
+	}
+}
+
+// LastRead returns when the lookup database in use was read.
+func (f *File) LastRead() time.Time {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	return f.lastRead
+}
+
+// ReadFailures returns how many replacements of the lookup database could
+// not be read.
+func (f *File) ReadFailures() int {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	return f.readFailures
+}
+
+// Watch watches the directory of the lookup database until ctx is done,
+// and reads the file again once it has gone without a change for
+// quietTime, after it is replaced, written or removed, and after Watch
+// starts watching. If the directory cannot be watched, that is logged, and
+// the database read at start stays in use.
+func (f *File) Watch(ctx context.Context) {
+	watcher, err := fsnotify.NewWatcher()
+	if err == nil {
+		defer func() {
+			_ = watcher.Close()
+		}()
+
+		err = watcher.Add(filepath.Dir(f.params.Path))
+	}
+
+	if err != nil {
+		f.params.ProcessLog.Error("cannot watch the lookup database for replacements",
+			"error", err.Error())
+
+		return
+	}
+
+	f.params.ProcessLog.Info("watching the lookup database for replacements",
+		"file", f.params.Path)
+
+	f.readAfterChanges(ctx, watcher.Events, watcher.Errors)
+}
+
+// readAfterChanges reads the lookup database again once quietTime has
+// passed without a change to it from events, until ctx is done, and logs
+// the errors from errs. A change to another file in its directory does not
+// count. The wait starts at once, as if for a change, so that a file
+// replaced after OpenFile read it, and before its directory was watched,
+// is read too.
+func (f *File) readAfterChanges(
+	ctx context.Context, events <-chan fsnotify.Event, errs <-chan error,
+) {
+	path := filepath.Clean(f.params.Path)
+
+	quiet := time.NewTimer(quietTime)
+	defer quiet.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case event := <-events:
+			if filepath.Clean(event.Name) == path {
+				quiet.Reset(quietTime)
+			}
+		case <-quiet.C:
+			f.readAgain()
+		case err := <-errs:
+			f.params.ProcessLog.Warn("watching the lookup database failed",
+				"error", err.Error())
+		}
+	}
+}
+
+// readAgain reads the lookup database again, in place of the one in use,
+// or, if it cannot be read, counts that, raises a file_error alert for it
+// and logs it, and the one in use stays in use.
+func (f *File) readAgain() {
+	reader, err := read(f.params.Path)
+	if err != nil {
+		const kept = "the lookup database cannot be read, " +
+			"and the one read before stays in use"
+
+		f.mu.Lock()
+		f.readFailures++
+		f.mu.Unlock()
+
+		// Raised before it is logged, so that the alert is there once the
+		// log line is.
+		f.params.Alerts.Raise(alerts.Alert{
+			Event:  alerts.EventFileError,
+			Reason: kept,
+			Detail: map[string]any{"file": f.params.Path, "error": err.Error()},
+		})
+		f.params.ProcessLog.Error(kept, "error", err.Error())
+
+		return
+	}
+
+	f.use(reader)
+}
+
+// use puts reader in use, in place of the database read before, and logs
+// that the file was read.
+func (f *File) use(reader *maxminddb.Reader) {
+	f.mu.Lock()
+	f.reader = reader
+	f.lastRead = f.params.Now()
+	f.mu.Unlock()
+
+	f.params.ProcessLog.Info("read the lookup database", "file", f.params.Path)
+}
+
+// read reads the lookup database at path. The whole file is read into
+// memory, rather than mapped into it as the reader can, so that a file
+// overwritten in place cannot change, or end, under a lookup.
+func read(path string) (*maxminddb.Reader, error) {
+	data, err := os.ReadFile(path) //nolint:gosec // the file the admin names
+	if err != nil {
+		return nil, fmt.Errorf("SWWAF_LOOKUP_DB_PATH cannot be read: %w", err)
+	}
+
+	reader, err := maxminddb.OpenBytes(data)
+	if err != nil {
+		return nil, fmt.Errorf("SWWAF_LOOKUP_DB_PATH %s is not a .mmdb file: %w", path, err)
+	}
+
+	return reader, nil
+}

internal/lookup/file_internal_test.go

@@ -0,0 +1,379 @@
+package lookup
+
+import (
+	"context"
+	"log/slog"
+	"net/netip"
+	"net/url"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+	"testing/synctest"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+	"github.com/maxmind/mmdbwriter/mmdbtype"
+
+	"sneak.berlin/go/smallwebwaf/internal/alerts"
+	"sneak.berlin/go/smallwebwaf/internal/lookup/lookuptest"
+)
+
+// testNetblock is the netblock the tests' lookup databases place, and
+// testClient a client in it.
+const (
+	testNetblock = "203.0.113.0/24"
+	testClient   = "203.0.113.9/32"
+)
+
+func TestFilePlacesClientsAndCountsAnAddressMissingFromItAsUnknown(t *testing.T) {
+	t.Parallel()
+
+	germany := lookuptest.Network{ASN: "AS64496", ASName: "Example Net", Country: "DE"}
+	northKorea := lookuptest.Network{ASN: "AS64511", ASName: "Other Net", Country: "KP"}
+	path := filepath.Join(t.TempDir(), "ipinfo_lite.mmdb")
+	lookuptest.Write(t, path, map[string]lookuptest.Network{
+		testNetblock:    germany,
+		"2001:db8::/32": northKorea,
+	})
+
+	now := time.Date(2026, 10, 7, 0, 0, 0, 0, time.UTC)
+
+	f, err := OpenFile(FileParams{
+		Path:       path,
+		Now:        func() time.Time { return now },
+		ProcessLog: slog.New(slog.DiscardHandler),
+		Alerts:     newQueue(),
+	})
+	if err != nil {
+		t.Fatalf("open %s: %v", path, err)
+	}
+
+	for client, want := range map[string]lookuptest.Network{
+		testClient: germany,
+		// An IPv6 client is its /64.
+		"2001:db8:1:2::/64": northKorea,
+		"198.51.100.7/32":   {},
+	} {
+		prefix := netip.MustParsePrefix(client)
+
+		got := f.LookUp(prefix)
+		if got != (Answer{
+			Client: prefix, ASN: want.ASN, ASName: want.ASName, Country: want.Country,
+			Answered: now,
+		}) {
+			t.Errorf("%s has the answer %+v, want %+v, answered %s", client, got, want, now)
+		}
+	}
+}
+
+func TestRecordThatCannotBeReadPlacesTheClientNowhere(t *testing.T) {
+	t.Parallel()
+
+	// The AS number is a number, where a string belongs. The writer writes
+	// a record's fields in the order of their names, so as_name is read
+	// before the AS number fails.
+	path := filepath.Join(t.TempDir(), "ipinfo_lite.mmdb")
+	lookuptest.WriteRecords(t, path, map[string]mmdbtype.Map{
+		testNetblock: {
+			"asn":          mmdbtype.Uint32(64496),
+			"as_name":      mmdbtype.String("Example Net"),
+			"country_code": mmdbtype.String("DE"),
+		},
+	})
+
+	f := openFile(t, path, newQueue())
+
+	answer := f.LookUp(netip.MustParsePrefix(testClient))
+	if answer.ASN != "" || answer.ASName != "" || answer.Country != "" {
+		t.Errorf("%s is placed %+v, want nowhere", testClient, answer)
+	}
+}
+
+func TestFileThatCannotBeReadIsAnError(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	missing := filepath.Join(dir, "missing.mmdb")
+	notDatabase := filepath.Join(dir, "not.mmdb")
+	writeFile(t, notDatabase, "not a lookup database\n")
+
+	for path, want := range map[string]string{
+		missing: "SWWAF_LOOKUP_DB_PATH cannot be read: open " + missing +
+			": no such file or directory",
+		notDatabase: "SWWAF_LOOKUP_DB_PATH " + notDatabase +
+			" is not a .mmdb file: error opening database: invalid MaxMind DB file",
+	} {
+		_, err := OpenFile(FileParams{
+			Path:       path,
+			Now:        time.Now,
+			ProcessLog: slog.New(slog.DiscardHandler),
+			Alerts:     newQueue(),
+		})
+		if err == nil || err.Error() != want {
+			t.Errorf("opening %s failed with %v, want %s", path, err, want)
+		}
+	}
+}
+
+// The tests below run readAfterChanges in a synctest bubble, where time is
+// a clock of the test's own: time.Sleep moves it on at once, and
+// synctest.Wait returns once readAfterChanges waits again, so that every
+// reading due by then is done. The test sends the changes itself, as the
+// watch of a directory cannot run in a bubble.
+
+func TestReplacementCopiedOverTheFileInTwoPartsIsReadOnlyWhole(t *testing.T) {
+	t.Parallel()
+
+	synctest.Test(t, func(t *testing.T) {
+		dir := t.TempDir()
+		path := filepath.Join(dir, "ipinfo_lite.mmdb")
+		writeDatabase(t, path, "DE")
+
+		queue := newQueue()
+		f := openFile(t, path, queue)
+		changes := watch(t, f)
+
+		other := filepath.Join(dir, "replacement.mmdb")
+		writeDatabase(t, other, "KP")
+
+		replacement, err := os.ReadFile(other) //nolint:gosec // a file the test wrote
+		if err != nil {
+			t.Fatalf("read %s: %v", other, err)
+		}
+
+		// The file in use is overwritten in place, and keeps giving what
+		// it gave. Its first part alone is not a .mmdb file.
+		file, err := os.Create(path) //nolint:gosec // a file the test wrote
+		if err != nil {
+			t.Fatalf("create %s: %v", path, err)
+		}
+
+		defer func() {
+			_ = file.Close()
+		}()
+
+		half := len(replacement) / 2
+		write(t, file, replacement[:half])
+
+		changes <- fsnotify.Event{Name: path, Op: fsnotify.Write}
+
+		time.Sleep(quietTime - time.Nanosecond)
+		synctest.Wait()
+		wantCountry(t, f, "DE")
+
+		// The second part starts the wait again.
+		write(t, file, replacement[half:])
+
+		changes <- fsnotify.Event{Name: path, Op: fsnotify.Write}
+
+		time.Sleep(quietTime - time.Nanosecond)
+		synctest.Wait()
+		wantCountry(t, f, "DE")
+
+		time.Sleep(time.Nanosecond)
+		synctest.Wait()
+		wantCountry(t, f, "KP")
+
+		if !f.LastRead().Equal(time.Now()) || f.ReadFailures() != 0 {
+			t.Errorf("read at %s, with %d failures; want read now, with none",
+				f.LastRead(), f.ReadFailures())
+		}
+
+		wantAlerts(t, queue)
+	})
+}
+
+func TestReplacementThatCannotBeReadLeavesTheFileInUseWithOneAlert(t *testing.T) {
+	t.Parallel()
+
+	synctest.Test(t, func(t *testing.T) {
+		path := filepath.Join(t.TempDir(), "ipinfo_lite.mmdb")
+		writeDatabase(t, path, "DE")
+
+		queue := newQueue()
+		f := openFile(t, path, queue)
+		read := f.LastRead()
+		changes := watch(t, f)
+
+		writeFile(t, path, "not a lookup database\n")
+
+		changes <- fsnotify.Event{Name: path, Op: fsnotify.Write}
+
+		// Long after, the replacement has been read once.
+		time.Sleep(time.Hour)
+		synctest.Wait()
+		wantCountry(t, f, "DE")
+
+		if !f.LastRead().Equal(read) || f.ReadFailures() != 1 {
+			t.Errorf("read at %s, with %d failures; want read at %s, with one",
+				f.LastRead(), f.ReadFailures(), read)
+		}
+
+		wantAlerts(t, queue, alerts.Alert{
+			Time:   read.Add(quietTime),
+			Event:  alerts.EventFileError,
+			Reason: "the lookup database cannot be read, and the one read before stays in use",
+			Detail: map[string]any{
+				"file": path,
+				"error": "SWWAF_LOOKUP_DB_PATH " + path + " is not a .mmdb file: " +
+					"error opening database: invalid MaxMind DB file",
+			},
+		})
+	})
+}
+
+func TestChangeOfAnotherFileInTheDirectoryIsNoReplacement(t *testing.T) {
+	t.Parallel()
+
+	synctest.Test(t, func(t *testing.T) {
+		dir := t.TempDir()
+		path := filepath.Join(dir, "ipinfo_lite.mmdb")
+		writeDatabase(t, path, "DE")
+
+		f := openFile(t, path, newQueue())
+		changes := watch(t, f)
+
+		// The wait that starts with the watch ends with a reading.
+		time.Sleep(quietTime)
+		synctest.Wait()
+		writeDatabase(t, path, "KP")
+
+		changes <- fsnotify.Event{Name: filepath.Join(dir, "other.mmdb"), Op: fsnotify.Create}
+
+		time.Sleep(quietTime)
+		synctest.Wait()
+		wantCountry(t, f, "DE")
+
+		changes <- fsnotify.Event{Name: path, Op: fsnotify.Write}
+
+		time.Sleep(quietTime)
+		synctest.Wait()
+		wantCountry(t, f, "KP")
+	})
+}
+
+func TestReplacementSavedBeforeTheWatchStartsIsRead(t *testing.T) {
+	t.Parallel()
+
+	synctest.Test(t, func(t *testing.T) {
+		path := filepath.Join(t.TempDir(), "ipinfo_lite.mmdb")
+		writeDatabase(t, path, "DE")
+
+		f := openFile(t, path, newQueue())
+
+		// Saved after OpenFile read the file, and before its directory was
+		// watched, so that no change is seen for it.
+		writeDatabase(t, path, "KP")
+		watch(t, f)
+		time.Sleep(quietTime)
+		synctest.Wait()
+		wantCountry(t, f, "KP")
+	})
+}
+
+// newQueue returns a queue of alerts for a webhook that is never sent
+// them, so that they wait in it for the test to look at.
+func newQueue() *alerts.Queue {
+	return alerts.New(alerts.Params{
+		WebhookURL: &url.URL{Scheme: "https", Host: "alerts.example"},
+		Events:     alerts.Events(),
+		Cooldown:   15 * time.Minute,
+		Now:        time.Now,
+	})
+}
+
+// writeDatabase writes a lookup database at path that places testNetblock
+// in country, and no other address.
+func writeDatabase(t *testing.T, path, country string) {
+	t.Helper()
+
+	lookuptest.Write(t, path, map[string]lookuptest.Network{
+		testNetblock: {ASN: "AS64496", ASName: "Example Net", Country: country},
+	})
+}
+
+// openFile opens the lookup database at path, which raises its alerts to
+// queue.
+func openFile(t *testing.T, path string, queue *alerts.Queue) *File {
+	t.Helper()
+
+	f, err := OpenFile(FileParams{
+		Path:       path,
+		Now:        time.Now,
+		ProcessLog: slog.New(slog.DiscardHandler),
+		Alerts:     queue,
+	})
+	if err != nil {
+		t.Fatalf("open %s: %v", path, err)
+	}
+
+	return f
+}
+
+// watch runs f's readAfterChanges until the test ends, and returns the
+// channel that sends it changes.
+func watch(t *testing.T, f *File) chan<- fsnotify.Event {
+	t.Helper()
+
+	changes := make(chan fsnotify.Event)
+	ctx, stop := context.WithCancel(t.Context())
+	stopped := make(chan struct{})
+
+	go func() {
+		f.readAfterChanges(ctx, changes, nil)
+		close(stopped)
+	}()
+
+	t.Cleanup(func() {
+		stop()
+		<-stopped
+	})
+
+	return changes
+}
+
+// wantCountry checks the country f gives testClient.
+func wantCountry(t *testing.T, f *File, want string) {
+	t.Helper()
+
+	got := f.LookUp(netip.MustParsePrefix(testClient)).Country
+	if got != want {
+		t.Errorf("%s is in %q, want %q", testClient, got, want)
+	}
+}
+
+// wantAlerts checks the alerts waiting in queue, and that it held none
+// back.
+func wantAlerts(t *testing.T, queue *alerts.Queue, want ...alerts.Alert) {
+	t.Helper()
+
+	waiting := queue.Snapshot().Waiting[alerts.DestinationWebhook]
+	if len(waiting) != len(want) || (len(want) > 0 && !reflect.DeepEqual(waiting, want)) {
+		t.Errorf("alerts waiting %+v, want %+v", waiting, want)
+	}
+
+	if queue.Suppressed() != 0 {
+		t.Errorf("%d alerts held back, want none", queue.Suppressed())
+	}
+}
+
+// writeFile writes content to the file at path.
+func writeFile(t *testing.T, path, content string) {
+	t.Helper()
+
+	err := os.WriteFile(path, []byte(content), 0o600)
+	if err != nil {
+		t.Fatalf("write %s: %v", path, err)
+	}
+}
+
+// write writes data to the end of file.
+func write(t *testing.T, file *os.File, data []byte) {
+	t.Helper()
+
+	_, err := file.Write(data)
+	if err != nil {
+		t.Fatalf("write: %v", err)
+	}
+}

internal/lookup/lookup.go

@@ -1,6 +1,7 @@
-// Package lookup looks up each client's AS number and country through
-// the GeoJS web service, and keeps the answers in memory, for at most
-// 100,000 clients and for 7 days each. The answers are written to
+// Package lookup looks up each client's AS number and country, through
+// the GeoJS web service or in the lookup database, the IPinfo Lite file
+// SWWAF_LOOKUP_DB_PATH names. GeoJS's answers are kept in memory, for at
+// most 100,000 clients and for 7 days each, and are written to
 // lookups.json and read from it by the state package.
 package lookup
 
@@ -113,11 +114,12 @@ type GeoJS struct {
 	retryAt    time.Time
 }
 
-// Answer is what GeoJS said about a client, as lookups.json holds it: its
-// AS number, such as AS64496, and the AS's name, both "" when GeoJS knows
-// no AS number for it; its country, "" when GeoJS cannot place it; when
-// GeoJS said so, and when the answer was last used. The zero Answer is
-// that of a client with no answer.
+// Answer is what GeoJS or the lookup database said about a client: its AS
+// number, such as AS64496, and the AS's name, both "" when the source knows
+// no AS number for it; its country, "" when the source cannot place it;
+// when the source said so; and, for GeoJS's answers, which lookups.json
+// holds, when the answer was last used. The zero Answer is that of a
+// client with no answer.
 //
 //nolint:tagliatelle // the state files use snake_case, as the request log does
 type Answer struct {

internal/lookup/lookuptest/lookuptest.go

@@ -0,0 +1,83 @@
+// Package lookuptest writes lookup databases, IPinfo Lite files in their
+// .mmdb form, for the tests of the packages that read them.
+package lookuptest
+
+import (
+	"bytes"
+	"net"
+	"os"
+	"testing"
+
+	"github.com/maxmind/mmdbwriter"
+	"github.com/maxmind/mmdbwriter/mmdbtype"
+)
+
+// fileMode is the mode of the files written: read and written by their
+// owner alone.
+const fileMode = 0o600
+
+// Network is what a lookup database holds about a netblock, of the fields
+// smallwebwaf reads: its AS number, such as AS64496, the AS's name, and
+// its country, such as DE.
+type Network struct {
+	ASN     string
+	ASName  string
+	Country string
+}
+
+// Write writes a lookup database at path that places each netblock in
+// networks, such as 203.0.113.0/24, as its Network says, and no other
+// address.
+func Write(tb testing.TB, path string, networks map[string]Network) {
+	tb.Helper()
+
+	records := make(map[string]mmdbtype.Map, len(networks))
+	for netblock, network := range networks {
+		records[netblock] = mmdbtype.Map{
+			"asn":          mmdbtype.String(network.ASN),
+			"as_name":      mmdbtype.String(network.ASName),
+			"country_code": mmdbtype.String(network.Country),
+		}
+	}
+
+	WriteRecords(tb, path, records)
+}
+
+// WriteRecords writes a lookup database at path that holds each record in
+// records for its netblock, and nothing for any other address.
+func WriteRecords(tb testing.TB, path string, records map[string]mmdbtype.Map) {
+	tb.Helper()
+
+	tree, err := mmdbwriter.New(mmdbwriter.Options{
+		DatabaseType: "ipinfo_lite",
+		// The tests' clients are in the netblocks kept for documentation.
+		IncludeReservedNetworks: true,
+	})
+	if err != nil {
+		tb.Fatalf("new lookup database: %v", err)
+	}
+
+	for netblock, record := range records {
+		_, network, err := net.ParseCIDR(netblock)
+		if err != nil {
+			tb.Fatalf("netblock %q: %v", netblock, err)
+		}
+
+		err = tree.Insert(network, record)
+		if err != nil {
+			tb.Fatalf("insert %s: %v", netblock, err)
+		}
+	}
+
+	var database bytes.Buffer
+
+	_, err = tree.WriteTo(&database)
+	if err != nil {
+		tb.Fatalf("write the lookup database: %v", err)
+	}
+
+	err = os.WriteFile(path, database.Bytes(), fileMode)
+	if err != nil {
+		tb.Fatalf("write %s: %v", path, err)
+	}
+}