单个 MongoDB 实例上的 C# MongoDB 驱动程序事务

Question

我正在使用 MongoDB 4.0.8 和 C# 驱动程序 2.8.1，并尝试Transactions在我的项目中实现。我复制粘贴了以下代码示例：

static async Task<bool> UpdateProducts()
{
    //Create client connection to our MongoDB database
    var client = new MongoClient(MongoDBConnectionString);

    //Create a session object that is used when leveraging transactions
    var session = client.StartSession();

    //Create the collection object that represents the "products" collection
    var products = session.Client.GetDatabase("MongoDBStore").GetCollection<Product>("products");

    //Clean up the collection if there is data in there
    products.Database.DropCollection("products");

    //Create some sample data
    var TV = new Product { Description = "Television", SKU = 4001, Price = 2000 };
    var Book = new Product { Description = "A funny book", SKU = 43221, Price = 19.99 };
    var DogBowl = new Product { Description = "Bowl for Fido", SKU = 123, Price = 40.00 };

    //Begin transaction
    session.StartTransaction(new TransactionOptions(
                                                    readConcern: ReadConcern.Snapshot,
                                                    writeConcern: WriteConcern.WMajority));

    try
    {
        //Insert the sample data 
        await products.InsertOneAsync(session, TV);
        await products.InsertOneAsync(session, Book);
        await products.InsertOneAsync(session, DogBowl);

        var filter = new FilterDefinitionBuilder<Product>().Empty;
        var results = await products.Find(filter).ToListAsync();

        //Increase all the prices by 10% for all products
        var update = new UpdateDefinitionBuilder<Product>().Mul<Double>(r => r.Price, 1.1);
        await products.UpdateManyAsync(session, filter, update); //,options);

        //Made it here without error? Let's commit the transaction
        session.CommitTransaction();

        //Let's print the new results to the console
        Console.WriteLine("Original Prices:\n");
        results = await products.Find<Product>(filter).ToListAsync();
        foreach (Product d in results)
        {
            Console.WriteLine(String.Format("Product Name: {0}\tPrice: {1:0.00}", d.Description, d.Price));
        }
    }
    catch (Exception e)
    {
        Console.WriteLine("Error writing to MongoDB: " + e.Message);
        session.AbortTransaction();
    }
    return true;
}

但在第一个Insert命令中，我收到此错误：

Command insert failed:
Transaction numbers are only allowed on a replica set member or mongos.

文档说：

从 4.0 版本开始，MongoDB 提供了针对副本集执行多文档事务的功能。

我的项目中没有副本，我只有一个数据库实例，这是我的主要数据库实例。如果有我可以用来实施的解决方案或解决方法Transactions？我有更新多个集合的方法，我真的认为它可以节省我使用它的时间。

Answer 1

正如文档所述，事务仅适用于副本集。因此您需要将 mongodb 服务器作为单节点副本集运行。为此，请执行以下步骤...

步骤1： 停止mongodb服务器。

步骤 2： 将设置添加到mongod.cfgreplication文件中。这是我自己的例子

storage:
  dbPath: C:\DATA
  directoryPerDB: true
  journal:
    enabled: true

systemLog:
  destination: file
  logAppend: true
  path:  C:\DATA\log\mongod.log

net:
  port: 27017
  bindIp: 127.0.0.1

replication:
   replSetName: MyRepSet

步骤3：打开 mongodb shell 并发出以下命令来启动副本集。

storage:
  dbPath: C:\DATA
  directoryPerDB: true
  journal:
    enabled: true

systemLog:
  destination: file
  logAppend: true
  path:  C:\DATA\log\mongod.log

net:
  port: 27017
  bindIp: 127.0.0.1

replication:
   replSetName: MyRepSet

步骤4：重启mongod

顺便说一句，如果您想编写如下所示的更清晰、更方便的事务代码，请查看我的库MongoDB.Entities

rs.initiate()