feat: Add the backup dump

Collections are enumerated live rather than from a list, so a collection added later is backed up with no code change. Documents are written as the raw BSON the driver returned, so Decimal128, ObjectId, DateTime and binary subtypes survive byte for byte.
2026-09-07 11:16:38 +00:00
parent 525dc6af00
commit 3f66370b1f
3 changed files with 420 additions and 0 deletions
@@ -0,0 +1,206 @@
+package backup
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"go.mongodb.org/mongo-driver/v2/bson"
+	"go.mongodb.org/mongo-driver/v2/mongo"
+)
+
+func seed(t *testing.T, client *mongo.Client, dbName string) {
+	t.Helper()
+	ctx := context.Background()
+	db := client.Database(dbName)
+	if _, err := db.Collection("servers").InsertMany(ctx, []any{
+		bson.M{"_id": bson.NewObjectID(), "name": "alpha", "instance_id": "i1"},
+		bson.M{"_id": bson.NewObjectID(), "name": "beta", "instance_id": "i1"},
+	}); err != nil {
+		t.Fatalf("insert servers: %v", err)
+	}
+	if _, err := db.Collection("audit_logs").InsertOne(ctx, bson.M{"action": "login"}); err != nil {
+		t.Fatalf("insert audit_logs: %v", err)
+	}
+}
+
+func dumpToFile(t *testing.T, opt DumpOptions) (string, Manifest) {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "out.tar.gz")
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	opt.Out = f
+	m, err := Dump(context.Background(), opt)
+	if cerr := f.Close(); cerr != nil {
+		t.Fatalf("close: %v", cerr)
+	}
+	if err != nil {
+		t.Fatalf("Dump: %v", err)
+	}
+	return path, m
+}
+
+func TestDumpEnumeratesEveryCollection(t *testing.T) {
+	client, dbName := testDB(t)
+	seed(t, client, dbName)
+
+	_, m := dumpToFile(t, DumpOptions{
+		Client: client, Database: dbName, KeyHex: validKeyHex, VantageVersion: "test",
+	})
+
+	if _, ok := m.Collection("servers"); !ok {
+		t.Fatal("servers missing from the manifest")
+	}
+	if _, ok := m.Collection("audit_logs"); !ok {
+		t.Fatal("audit_logs missing; enumeration must not filter by a hardcoded list")
+	}
+	servers, _ := m.Collection("servers")
+	if servers.Documents != 2 {
+		t.Fatalf("servers documents %d, want 2", servers.Documents)
+	}
+	if m.MongoDB != dbName {
+		t.Fatalf("manifest database %q, want %q", m.MongoDB, dbName)
+	}
+	if m.MongoServerVersion == "" {
+		t.Fatal("manifest records no MongoDB server version")
+	}
+	if m.Hostname == "" {
+		t.Fatal("manifest records no hostname")
+	}
+}
+
+func TestDumpRecordsKeyFingerprint(t *testing.T) {
+	client, dbName := testDB(t)
+	seed(t, client, dbName)
+
+	_, m := dumpToFile(t, DumpOptions{Client: client, Database: dbName, KeyHex: validKeyHex})
+
+	want, err := FingerprintHex(validKeyHex)
+	if err != nil {
+		t.Fatalf("FingerprintHex: %v", err)
+	}
+	if m.KeyFingerprint == nil || *m.KeyFingerprint != want {
+		t.Fatalf("fingerprint %v, want %s", m.KeyFingerprint, want)
+	}
+}
+
+func TestDumpRefusesWithoutAKey(t *testing.T) {
+	client, dbName := testDB(t)
+	seed(t, client, dbName)
+
+	var buf bytes.Buffer
+	_, err := Dump(context.Background(), DumpOptions{
+		Client: client, Database: dbName, Out: &buf,
+	})
+	if !errors.Is(err, ErrNoKey) {
+		t.Fatalf("got %v, want ErrNoKey", err)
+	}
+	if buf.Len() != 0 {
+		t.Fatal("refusal must happen before anything is written")
+	}
+}
+
+func TestDumpAllowNoKeyStampsNull(t *testing.T) {
+	client, dbName := testDB(t)
+	seed(t, client, dbName)
+
+	_, m := dumpToFile(t, DumpOptions{Client: client, Database: dbName, AllowNoKey: true})
+	if m.KeyFingerprint != nil {
+		t.Fatalf("want a null fingerprint, got %v", *m.KeyFingerprint)
+	}
+}
+
+func TestDumpRejectsMalformedKey(t *testing.T) {
+	client, dbName := testDB(t)
+	var buf bytes.Buffer
+	_, err := Dump(context.Background(), DumpOptions{
+		Client: client, Database: dbName, KeyHex: "nonsense", Out: &buf,
+	})
+	if !errors.Is(err, ErrBadKey) {
+		t.Fatalf("got %v, want ErrBadKey", err)
+	}
+}
+
+func TestDumpExcludeIsRecordedAndOmitted(t *testing.T) {
+	client, dbName := testDB(t)
+	seed(t, client, dbName)
+
+	path, m := dumpToFile(t, DumpOptions{
+		Client: client, Database: dbName, KeyHex: validKeyHex,
+		Exclude: []string{"audit_logs"},
+	})
+
+	if _, ok := m.Collection("audit_logs"); ok {
+		t.Fatal("excluded collection is in the manifest's collection list")
+	}
+	if len(m.Excluded) != 1 || m.Excluded[0] != "audit_logs" {
+		t.Fatalf("excluded recorded as %v", m.Excluded)
+	}
+
+	r, err := Open(path)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer r.Close()
+	if _, err := r.OpenCollection("audit_logs"); err == nil {
+		t.Fatal("excluded collection is present in the archive")
+	}
+}
+
+func TestDumpPreservesAwkwardBSONTypes(t *testing.T) {
+	client, dbName := testDB(t)
+	ctx := context.Background()
+
+	dec, err := bson.ParseDecimal128("1234.5678")
+	if err != nil {
+		t.Fatalf("ParseDecimal128: %v", err)
+	}
+	doc := bson.M{
+		"_id":     bson.NewObjectID(),
+		"decimal": dec,
+		"when":    bson.NewDateTimeFromTime(mustTime(t)),
+		"binary":  bson.Binary{Subtype: 0x00, Data: []byte{0x01, 0x02, 0x03}},
+		"nothing": nil,
+		"nested":  bson.A{bson.M{"deep": bson.A{1, 2, 3}}},
+	}
+	if _, err := client.Database(dbName).Collection("odd").InsertOne(ctx, doc); err != nil {
+		t.Fatalf("insert: %v", err)
+	}
+
+	path, _ := dumpToFile(t, DumpOptions{Client: client, Database: dbName, KeyHex: validKeyHex})
+
+	original, err := client.Database(dbName).Collection("odd").FindOne(ctx, bson.M{}).Raw()
+	if err != nil {
+		t.Fatalf("read back: %v", err)
+	}
+
+	r, err := Open(path)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer r.Close()
+	rc, err := r.OpenCollection("odd")
+	if err != nil {
+		t.Fatalf("OpenCollection: %v", err)
+	}
+	defer rc.Close()
+	archived, err := io.ReadAll(rc)
+	if err != nil {
+		t.Fatalf("read: %v", err)
+	}
+	if !bytes.Equal(archived, []byte(original)) {
+		t.Fatal("archived BSON differs from what the driver returned")
+	}
+}
+
+func mustTime(t *testing.T) time.Time {
+	t.Helper()
+	return time.Date(2026, 9, 7, 12, 0, 0, 0, time.UTC)
+}