entity-framework - EF 代码首次迁移错误 "Object has been disconnected or does not exist at the server"

Question

我在 SQL Server 2008 上使用 Entity Framework 6.1.1，并且我有一个长时间运行的代码首次迁移(大约 20 分钟)。它走到最后，然后给出以下错误。

System.Runtime.Remoting.RemotingException: Object '/f10901d8_94fe_4db4_bb9d_51cd19292b01/bq6vk4vkuz5tkri2x8nwhsln_106.rem' has been disconnected or does not exist at the server.
   at System.Data.Entity.Migrations.Design.ToolingFacade.ToolLogger.Verbose(String sql)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ExecuteSql(DbTransaction transaction, MigrationStatement migrationStatement, DbInterceptionContext interceptionContext)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable`1 migrationStatements, DbTransaction transaction, DbInterceptionContext interceptionContext)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable`1 migrationStatements, DbConnection connection)
   at System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClass30.<ExecuteStatements>b__2e()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass1.<Execute>b__0()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action operation)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable`1 migrationStatements, DbTransaction existingTransaction)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable`1 migrationStatements)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.ExecuteStatements(IEnumerable`1 migrationStatements)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteOperations(String migrationId, XDocument targetModel, IEnumerable`1 operations, IEnumerable`1 systemOperations, Boolean downgrading, Boolean auto)
   at System.Data.Entity.Migrations.DbMigrator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
   at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
   at System.Data.Entity.Migrations.DbMigrator.UpdateInternal(String targetMigration)
   at System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClassc.<Update>b__b()
   at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
   at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration)
   at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run()
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Update(String targetMigration, Boolean force)
   at System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0()
   at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)

迁移的目的是更新数据库中存储某些二进制数据的 MIME 类型的字段。它遍历每一行，读取二进制数据，尝试确定它是什么类型的内容，然后将适当的 MIME 类型值写入该行。

下面的脚本使用 ADO.NET 生成要运行的更新语句列表。我使用 ADO.NET，因为我必须使用 .NET 的图像库 (System.Drawing.Imaging.ImageFormat) 来确定每一行中二进制内容的类型(它将是 jpeg、png 或 pdf)。

public override void Up()
{
    List<string> updateStatements = new List<string>();

    using(SqlConnection conn = new SqlConnection(ConfigurationManager.AppSettings["ConnectionString"]))
    {
        SqlCommand cmd = new SqlCommand("SELECT Table1ID, Image FROM Table1"), conn);
        conn.Open();

        //read each record and update the content type value based on the type of data stored
        using (SqlDataReader reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                long idValue = Convert.ToInt64(reader["Table1ID"]);
                byte[] data = (byte[])reader["Image"];
                string contentType = GetMimeType(data);
                updateStatements.Add(string.Format("UPDATE Table1 SET Content_Type = {0} WHERE Table1ID = {1}", contentType, idValue));
            }
        }
    }

    foreach (string updateStatement in updateStatements)
        Sql(updateStatement);
}

public string GetMimeType(byte[] document)
{
    if (document != null && document.Length > 0)
    {
        ImageFormat format = null;

        try
        {
            MemoryStream ms = new MemoryStream(document);
            Image img = Image.FromStream(ms);
            format = img.RawFormat;
        }
        catch (Exception)
        {
            /* PDF documents will throw exceptions since they aren't images but you can check if it's really a PDF
             * by inspecting the first four bytes with will be 0x25 0x50 0x44 0x46 ("%PDF"). */
            if (document[0] == 0x25 && document[1] == 0x50 && document[2] == 0x44 && document[3] == 0x46)
                return PDF;
            else
                return NULL;
        }

        if (format.Equals(ImageFormat.Jpeg))
        {
            return JPG;
        }
        else if (format.Equals(System.Drawing.Imaging.ImageFormat.Png))
        {
            return PNG;
        }
    }

    return NULL;
}

我见过 this five year old post并且它链接到的文章似乎不再存在。至少我找不到他们。

有谁知道这里发生了什么？

-- 更新 --
这似乎与迁移运行所需的时间有关。我创建了一个迁移，除了 sleep 22 分钟之外什么都不做

public override void Up()
{
    System.Threading.Thread.Sleep(1320000);
}

我得到了同样的错误。所以这似乎是一个超时的事情。我不是 100% 他们所指的服务器上的对象，我找不到太多关于这个问题的信息，因为它与代码优先迁移有关。

我尝试设置 CommandTimeout迁移中的属性 Configuration.cs文件到 5000 但它没有帮助。我还尝试设置 SQL Server 的 Remove query timeout设置为 0 以防止任何超时，但它也没有帮助。

Answer 1

摘自 [GitHub EntityFramework 6 Issue #96][ https://github.com/aspnet/EntityFramework6/issues/96#issuecomment-289782427]

The issue is that the ToolLogger lease lifetime (base class MigrationsLogger is a MarshalByRefObject) is at the default (5 minutes). The ToolingFacade creates the logger, which lives in the main program's app domain. The migrations run in a different app domain. If a migration takes longer than 5 minutes, the attempt to log any further information results in this error. A solution would be to increase the lease lifetime in the main program. So... in the main program, prior to creating the ToolingFacade, set the lease lifetime to a longer time period:

using System.Runtime.Remoting.Lifetime;
...
LifetimeServices.LeaseTime = TimeSpan.FromHours(1);