c# – Azure表中的异步插入

如何将实体异步保存到Windows Azure表服务?

下面的代码同步工作,但在尝试异步保存时引发异常.

这个说法:

context.BeginSaveChangesWithRetries(SaveChangesOptions.Batch,
    (asyncResult => context.EndSaveChanges(asyncResult)), null);

System.ArgumentException中的结果:“当前对象未生成异步结果.参数名称:asyncResult”.

此外,在异步保存时创建服务上下文的正确模式是什么?我应该为每个写操作创建一个单独的上下文吗?是否太昂贵(例如需要通过网络拨打电话)?

TableStorageWriter.cs:

using System;
using System.Data.Services.Client;
using System.Diagnostics;
using Microsoft.WindowsAzure;
using Microsoft.WindowsAzure.StorageClient;

namespace WorkerRole1
{
    public class TableStorageWriter
    {
        private const string _tableName = "StorageTest";
        private readonly CloudStorageAccount _storageAccount;
        private CloudTableClient _tableClient;

        public TableStorageWriter()
        {
            _storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageConnectionString"));
            _tableClient = _storageAccount.CreateCloudTableClient();
            _tableClient.CreateTableIfNotExist(_tableName);
        }

        public void Write(string message)
        {
            try
            {
                DateTime now = DateTime.UtcNow;
                var entity = new StorageTestEntity
                    {
                        Message = message,
                        PartitionKey = string.Format("{0:yyyy-MM-dd}", now),
                        RowKey = string.Format("{0:HH:mm:ss.fff}-{1}", now, Guid.NewGuid())
                    };

                // Should I get this context before each write? It is efficient?
                TableServiceContext context = _tableClient.GetDataServiceContext();

                context.AddObject(_tableName, entity);

                // This statement works but it's synchronous
                context.SaveChangesWithRetries();

                // This attempt at saving asynchronously results in System.ArgumentException:
                // The current object did not originate the async result. Parameter name: asyncResult
                // context.BeginSaveChangesWithRetries(SaveChangesOptions.Batch,
                //                                  (asyncResult => context.EndSaveChanges(asyncResult)), null);
            }
            catch (StorageClientException e)
            {
                Debug.WriteLine("Error: {0}", e.Message);
                Debug.WriteLine("Extended error info: {0} : {1}",
                                e.ExtendedErrorInformation.ErrorCode,
                                e.ExtendedErrorInformation.ErrorMessage);
            }
        }
    }

    internal class StorageTestEntity : TableServiceEntity
    {
        public string Message { get; set; }
    }
}

从WorkerRole.cs调用:

using System.Net;
using System.Threading;
using Microsoft.WindowsAzure.ServiceRuntime;
using log4net;

namespace WorkerRole1
{
    public class WorkerRole : RoleEntryPoint
    {
        public override void Run()
        {
            var storageWriter = new TableStorageWriter();
            while (true)
            {
                Thread.Sleep(10000);
                storageWriter.Write("Working...");
            }
        }

        public override bool OnStart()
        {
            ServicePointManager.DefaultConnectionLimit = 12;
            return base.OnStart();
        }
    }
}

使用Windows Azure SDK for .NET 1.8的示例.

最佳答案
您应该调用EndSaveChangesWithRetries而不是EndSaveChanges,否则EndSaveChanges不能使用BeginSaveChangesWithRetries返回的IAsyncResult对象.那么,您可以尝试更改您的End方法调用,如下所示吗?

context.BeginSaveChangesWithRetries(SaveChangesOptions.Batch,
    (asyncResult => context.EndSaveChangesWithRetries(asyncResult)),
    null);

对于您的其他问题,我建议为每个调用创建一个新的TableServiceContext,因为DataServiceContext不是无状态的(MSDN),并且使用异步调用实现TableStorageWriter.Write的方式可能允许并发操作.实际上,在Storage Client Library 2.0中,我们显式地阻止了使用单个TableServiceContext对象的并发操作.此外,创建TableServiceContext不会导致对Azure存储的请求.

转载注明原文:c# – Azure表中的异步插入 - 代码日志