FerretDB · b1ron · Nov 28, 2023 · Nov 28, 2023 · Nov 28, 2023 · Nov 28, 2023
@@ -0,0 +1,117 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package integration
+
+import (
+	"errors"
+	"net/url"
+	"sync"
+	"testing"
+
+	"github.com/AlekSi/pointer"
+	"github.com/FerretDB/FerretDB/integration/setup"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
+)
+
+func TestCursor(t *testing.T) {
+	t.Parallel()
+
+	// use a single connection pool
+	s := setup.SetupWithOpts(t, &setup.SetupOpts{
+		ExtraOptions: url.Values{
+			"minPoolSize": []string{"1"},
+			"maxPoolSize": []string{"1"},
+		},
+	})
+
+	opts := &options.FindOptions{
+		BatchSize: pointer.ToInt32(1),
+	}
+
+	ctx := s.Ctx
+	collection1 := s.Collection
+	databaseName := s.Collection.Database().Name()
+	collectionName := s.Collection.Name()
+
+	u, err := url.Parse(s.MongoDBURI)
+	require.NoError(t, err)
+
+	// client2 uses the same connection pool
+	client2, err := mongo.Connect(ctx, options.Client().ApplyURI(u.String()))
+	require.NoError(t, err)
+
+	collection2 := client2.Database(databaseName).Collection(collectionName)
+
+	arr, _ := generateDocuments(0, 2)
+	_, err = collection2.InsertMany(ctx, arr)
+	require.NoError(t, err)
+
+	t.Run("CursorIDIsZeroAfterLastGetMore", func(t *testing.T) {
+		cur, err := collection2.Find(ctx, bson.D{}, opts)
+		require.NoError(t, err)
+		assert.Equal(t, 1, cur.RemainingBatchLength())
+
+		cur.Next(ctx)
+		cur.Next(ctx)
+		assert.NotEqual(t, int64(0), cur.ID())
+
+		assert.Equal(t, 0, cur.RemainingBatchLength())
+		cur.Next(ctx)                       // last getMore does a network request to confirm there's no more documents to fetch
+		assert.Equal(t, int64(0), cur.ID()) // ID is 0 if the cursor has been closed or exhausted
+
+		assert.False(t, cur.TryNext(ctx)) // .
+	})
+
+	t.Run("CursorNotFoundAfterDisconnect", func(t *testing.T) {
+		t.Skip("not valid")
+
+		cur, err := collection2.Find(ctx, bson.D{}, opts)
+		require.NoError(t, err)
+
+		cursorID := cur.ID()
+
+		var wg sync.WaitGroup
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+
+			command := bson.D{
+				{"getMore", cursorID},
+				{"collection", collection1.Name()},
+			}
+
+			for {
+				result := bson.M{}
+				err := collection1.Database().RunCommand(ctx, command).Decode(result)
+				if errors.Is(err, mongo.ErrNoDocuments) {
+					break
+				}
+
+				require.NoError(t, err)
+
+			}
+
+		}()
+
+		err = client2.Disconnect(ctx)
+		require.NoError(t, err)
+
+		wg.Wait()
+	})
+}