Ef Core花里胡哨系列(8) 如何可控管理Ef Core的迁移?

发布时间:2024年01月03日

Ef Core花里胡哨系列(8) 如何可控管理Ef Core的迁移?

通常使用Ef Core迁移时,可能就是简单的使用命令dotnet-ef migrations add或者dotnet ef database update等等,基本都需要靠命令维护,非常的繁琐。特别是现在很多项目都是迭代型项目,很容易造成开发人员和运维人员的负担,所以,我们是否可以将其自动化?

自动迁移

自动迁移顾名思义,就是可以让程序启动的时候自己执行迁移,不需要运维人员参与,开发人员只需要保证迁移顺序的正确性即可。

自动建库

如果想使用首次自动建库,那我们就需要生成首次迁移时,直接删除首次迁移的文件,留下[Sample]DbContextModelSnapshot快照文件即可,当然,这些不是主要内容,只是用来引出下面的可控迁移

var app = builder.Build();


await using var scoped = app.Services.CreateAsyncScope();
using var db = scoped.ServiceProvider.GetRequiredService<SampleDbContext>();
try
{
    // db.Database.Migrate(); // 需要保留首次迁移文件,并且后续启动可以自动迁移
    db.Database.EnsureCreated(); // 不需要保留首次迁移文件
}
catch
{
    Console.WriteLine("init database error.");
}

可控迁移

可控迁移即我们可以通过封装Ef Core内置的各种Service来帮助我们实现控制迁移的效果。

EfMigrationHistory

我们要可控迁移,那么我们就需要想办法操控__EFMigrationsHistory这张表,它是Ef Core内置的表,用来记录迁移的记录,这张表是一张无状态的表,他只负责存储成功的迁移名称和迁移时Ef Core的版本,其它没有关联,我们如何管理它呢?我们只需在DbContext中创建一个同名的表即可,并且可以预先设计好其它审计用字段,后续不可更改。

例如我们重新设计这张表,除了迁移IdMigrationIdEf Core的版本ProductVersion外,我们添加迁移应用时间,和迁移应用类型字段。

[Table("__EFMigrationsHistory")]
public class EFMigrationsHistory
{
    [Key]
    [MaxLength(150)]
    public required string MigrationId { get; set; }

    [MaxLength(32)]
    public string ProductVersion { get; set; } = null!;

    [NotMapped]
    public string Sort => MigrationId.Split("_")[0];

    [Comment("迁移时间")]
    public DateTime? MigrationTime { get; set; } = DateTime.Now;

    [Column(TypeName = "varchar(20)")]
    public MigrationType MigrationType { get; set; } = MigrationType.Success;
}

添加迁移类型的目的是为了增加迁移执行顺序的丰富性,下面提供了成功Success、尝试但失败TryFail、尝试但成功TrySuccess以及跳过Skip等多种方式。其中HistoryInstall为记录型,主要是为了标记历史记录和安装时间。

public enum MigrationType
{
    Success,
    TryFail,
    TrySuccess,
    Skip,
    History,
    Install
}

随后我们将其添加到DbContext上下文中即可,我们的新结构会替代原来的结构实行职能。

public interface IMigrationDbContext
{
    DbSet<EFMigrationsHistory> EFMigrationsHistory { get; set; }
}

public class SampleDbContext : IMigrationDbContext
{
    public SampleDbContext(DbContextOptions<SampleDbContext> options) : base(options) 
    { 

    }

    public DbSet<EFMigrationsHistory> EFMigrationsHistory { get; set; }
}

迁移控制

我们已经将__EFMigrationsHistory注册到了DbContext的上下文中,成为了我们可用的表,我们接下来就是了解Ef Core是如何迁移的,我们如何加入自己的逻辑。

我们之前有提到__EFMigrationsHistory只记录了成功的迁移,如果迁移没有成功,则会立即中断,那么他是怎么实现的?其实就是读取本地的文件列表,然后按照迁移名称进行排序并和表中的对比,然后开始逐一执行。

如此我们就可以模仿他的操作,来实现我们自己的逻辑。

迁移管理

我喜欢将迁移输出到类库,这个方便读取和管理,需要调用的地方只需引用该类库即可。

services.AddDbContext<SampleDbContext>(opts =>
{
    optionsBuilder.UseMySql(connStr, new MySqlServerVersion(new Version(8, 0)), opts => opts.MigrationsAssembly("Sample.Migrations"));
});

每个迁移文件都分为两部分,xxxx.csxxxx.Designer.cs,其中xxxx.Designer.cs中以下部分是我们需要的部分。

  • [DbContext(typeof(SampleDbContext))]这个特性向我们指明了迁移对应的DbContext是哪个,也就是说,我们可以自定义多个DbContext从其判断执行不同的迁移。
  • [Migration("20231108075812_XXXXX")]这个特性向我们指明了迁移名称,当然,也代表了迁移的顺序。
[DbContext(typeof(SampleDbContext))]
[Migration("20231108075812_XXXXX")]
partial class 20231108075812_XXXXX
{

}

而且,我们可以根据需要扩充这些特性,来满足我们不同的顺序需求:

/// <summary>
/// 标记的迁移失败会自动跳过
/// </summary>
[AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
public class TryMigrationsAttribute : Attribute
{
    public TryMigrationsAttribute()
    { }
}

/// <summary>
/// 标记需要跳过的Migration
/// </summary>
[AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
public class SkipMigrationsAttribute : Attribute
{
    public SkipMigrationsAttribute()
    { }
}

好了,所有的东西都准备完成了,我们来实现真正的迁移管理。

我们首选需要获取迁移所在的程序集:

private static Assembly EfAssembly => Assembly.Load("Sample.Migrations");

然后根据需要,获取DbContext中的迁移服务,就可以迁移指定的迁移了:

var migrator = dbContext.GetService<IMigrator>();

以下是完整的代码,包括多个DbContext如何实现互不干扰以及指定迁移,自动归档迁移等等。

public class MigrationManager<TMainDbContext, TMySqlDbContext, TOracleDbContext, TPostgreSQLDbContext, TSqlServerDbContext>
    where TMainDbContext : DbContext, IMigrationDbContext, new()
    where TMySqlDbContext : DbContext, IMigrationDbContext, new()
    where TOracleDbContext : DbContext, IMigrationDbContext, new()
    where TPostgreSQLDbContext : DbContext, IMigrationDbContext, new()
    where TSqlServerDbContext : DbContext, IMigrationDbContext, new()
{
    private readonly IServiceProvider ServiceProvider;

    private readonly ILogger Logger;

    protected TMainDbContext DB => ServiceProvider.GetRequiredService<TMainDbContext>();

    public MigrationManager(IServiceProvider serviceProvider, ILogger logger)
    {
        ServiceProvider = serviceProvider;
        Logger = logger;
    }

    private static Assembly EfAssembly => Assembly.Load("Sample.Migrations");

    private static DatabaseType DbType => AppSettings.Get<DbOptions>()?.GetUseableWriteHost()?.DbType ?? DatabaseType.MySql;
    private static string DbTypeName => DbType.ToString();

    public static string GetEfVersion()
    {
        return Microsoft.EntityFrameworkCore.Infrastructure.ProductInfo.GetVersion();
    }

    /// <summary>
    /// 获取的是本地文件中的所有版本,而不是数据库
    /// </summary>
    /// <returns></returns>
    public IEnumerable<EFMigrationsHistory> GetList()
    {
        var migrations = EfAssembly.GetTypes().Where(x =>
                x.Namespace != null && x.Namespace.Contains(DbTypeName) &&
                x.GetCustomAttributes<MigrationAttribute>().Any() && x.GetCustomAttribute<DbContextAttribute>()?.ContextType.BaseType == typeof(TMainDbContext))
            .Select(x =>
                new EFMigrationsHistory()
                {
                    MigrationId = x.GetCustomAttribute<MigrationAttribute>()!.Id,
                    ProductVersion = GetEfVersion(),
                })
            .AsQueryable();

        return migrations;
    }

    public IEnumerable<Type> GetClassList()
    {
        var migrations = EfAssembly.GetTypes().Where(x =>
                x.Namespace != null && x.Namespace.Contains(DbTypeName) &&
                x.GetCustomAttributes<MigrationAttribute>().Any() && x.GetCustomAttribute<DbContextAttribute>()?.ContextType.BaseType == typeof(TMainDbContext))
            .AsQueryable();

        return migrations;
    }

    /// <summary>
    /// 将部署前的迁移都加入迁移记录表中
    /// </summary>
    /// <returns></returns>
    public async Task DiscardNoPendingMigrationsHistoryAsync()
    {
        Logger.LogInformation("Migration-Discard: 准备部署前写入历史迁移");

        var lastVersion = await GetLastVersion();

        Logger.LogInformation($"Migration-Discard: 部署前迁移最后版本 [{lastVersion?.MigrationId}]");

        var applied = await GetAppliedMigrationsAsync();

        Logger.LogInformation($"Migration-Discard: 部署前已经应用的迁移 [{applied.Count()}] 条记录");


        var migrations = lastVersion is null
            ? GetList().ToList()
            : GetList().Where(x => String.CompareOrdinal(x.Sort, lastVersion.Sort) <= 0 && (applied != null && !applied.Contains(x.MigrationId))).ToList();

        if (migrations is not null && migrations.Any())
        {
            migrations.ForEach(x=>x.MigrationType = MigrationType.History);
            DB.AddRange(migrations);

            await DB.SaveChangesAsync();
        }

        Logger.LogInformation($"Migration-Discard: 部署前写入的历史迁移 [{migrations?.Count ?? 0}] 条记录");
    }

    /// <summary>
    /// 获取最后一个版本
    /// </summary>
    /// <returns></returns>
    public async Task<EFMigrationsHistory?> GetLastVersion()
    {
        var applied = await DB.EFMigrationsHistory.ToListAsync();

        var thisContextLocal = GetList().Select(x => x.MigrationId);

        var thisContextVersions = applied.Where(x => thisContextLocal.Contains(x.MigrationId));

        return thisContextVersions.MaxBy(x => x.Sort);
    }

    /// <summary>
    /// 获取未应用的迁移
    /// </summary>
    /// <returns></returns>
    public async Task<IEnumerable<EFMigrationsHistory>> GetPendingMigrationsAsync()
    {
        var lastVersion = await GetLastVersion();

        if (lastVersion is null)
        {
            return GetList();
        }

        return GetList().Where(x => String.CompareOrdinal(x.Sort, lastVersion.Sort) > 0).OrderBy(x => x.Sort);
    }

    public async Task<IEnumerable<Type>> GetPendingMigrationsClassAsync()
    {
        var lastVersion = await GetLastVersion();

        if (lastVersion is null)
        {
            return GetClassList();
        }

        return GetClassList().Where(x => String.CompareOrdinal(x.GetCustomAttribute<MigrationAttribute>()!.Id, lastVersion.MigrationId) > 0).OrderBy(x => x.GetCustomAttribute<MigrationAttribute>()!.Id);
    }

    private IMigrator GetMigrator()
    {
        DbContext dbContext = DbType switch
        {
            DatabaseType.SqlServer => new TSqlServerDbContext(),
            DatabaseType.Oracle => new TOracleDbContext(),
            DatabaseType.PostgreSQL => new TPostgreSQLDbContext(),
            DatabaseType.MySql or _ => new TMySqlDbContext(),
        };
        return dbContext.GetService<IMigrator>();
    }

    /// <summary>
    /// 应用迁移
    /// </summary>
    /// <param name="migrations"></param>
    /// <returns></returns>
    public async Task ApplyMigrationsAsync(IEnumerable<EFMigrationsHistory> migrations)
    {
        if (!migrations.Any())
        {
            return;
        }

        var migrator = GetMigrator();

        foreach (var migration in migrations)
        {
            await migrator.MigrateAsync(migration.MigrationId);
        }
    }

    /// <summary>
    /// 应用迁移, 会跳过尝试迁移失败的迁移
    /// </summary>
    /// <param name="migrations"></param>
    /// <returns></returns>
    public async Task ApplyMigrationsClassAsync(IEnumerable<Type> migrations)
    {
        if (!migrations.Any())
        {
            return;
        }

        var migrator = GetMigrator();

        var skipMigrations = new List<EFMigrationsHistory>();

        foreach (var migration in migrations)
        {
            var id = migration.GetCustomAttribute<MigrationAttribute>()!.Id;
            if (migration.GetCustomAttributes<TryMigrationsAttribute>().Any())
            {
                try
                {
                    await migrator.MigrateAsync(id);
                }
                catch (Exception ex)
                {
                    var skip = new EFMigrationsHistory
                    {
                        MigrationId = id,
                        ProductVersion = GetEfVersion(),
                        MigrationType = MigrationType.TryFail
                    };

                    var errMsg = @$"迁移 [{id}] 已尝试并跳过!\n
迁移失败!\n
提示信息为: {ex.Message}\n
请检查 Migrations 文件! 或者手动更改 __MigrationsHistory 表, 将该迁移添加入表中标记为已应用即可.
                    ";

                    Logger.LogWarning(ex, errMsg);

                    DB.AddRange(skip);
                    await DB.SaveChangesAsync();
                }
            }
            else if (migration.GetCustomAttributes<SkipMigrationsAttribute>().Any())
            {
                var skip = new EFMigrationsHistory
                {
                    MigrationId = id,
                    ProductVersion = GetEfVersion(),
                    MigrationType = MigrationType.Skip
                };

                var errMsg = @$"迁移 [{id}] 已跳过!\n
或者手动更改 __MigrationsHistory 表, 将该迁移添加入表中标记为已应用即可.
                    ";

                Logger.LogWarning(errMsg);

                DB.AddRange(skip);
                await DB.SaveChangesAsync();
            }
            else
            {
                try
                {
                    await migrator.MigrateAsync(id);
                }
                catch (Exception ex)
                {
                    var errMsg = @$"迁移 [{id}] 失败!\n
迁移失败!\n
提示信息为: {ex.Message}\n
请检查 Migrations 文件! 或者手动更改 __MigrationsHistory 表, 将该迁移添加入表中标记为已应用即可.
                    ";

                    Logger.LogWarning(ex, errMsg);
                }
            }

            Logger.LogInformation($"迁移 [{id}] 已应用.");
        }
    }

    /// <summary>
    /// 获取已应用的迁移
    /// </summary>
    /// <returns></returns>
    public async Task<IEnumerable<string>> GetAppliedMigrationsAsync()
    {
        return await DB.Database.GetAppliedMigrationsAsync();
    }

    /// <summary>
    /// 开始迁移入口
    /// </summary>
    /// <returns></returns>
    public async Task StartupInitMigrationsAsync()
    {
        Logger.LogInformation($"Migration-Main: 迁移程序开始执行...");

        var migrationsHistory = await GetAppliedMigrationsAsync();

        Logger.LogInformation($"Migration-Main: 已应用的迁移 [{string.Join(",", migrationsHistory)}]");

        if (migrationsHistory.Any())
        {
            var pendingMigrations = await GetPendingMigrationsClassAsync();

            Logger.LogInformation($"Migration-Main: 获取未应用的迁移 [{string.Join(",", pendingMigrations.Select(x => x.GetCustomAttribute<MigrationAttribute>()!.Id))}]");

            await ApplyMigrationsClassAsync(pendingMigrations);
        }

        await DiscardNoPendingMigrationsHistoryAsync();
    }

    public async Task EnsureHasEfMigrationsHistoryTableAsync()
    {
        if (!await DB.IsExistTableAsync(typeof(EFMigrationsHistory)))
        {
            await DB.EnsureTableCreatedAsync(typeof(EFMigrationsHistory));

            var migrationInit = new EFMigrationsHistory()
            {
                MigrationId = $"{DateTime.UtcNow.AddMonths(-6).ToString("yyyyMMddHHmmss")}_Install",
                MigrationType = MigrationType.Install,
                ProductVersion = MigrationManager<DataDbContext, MySqlDbContext, OracleDbContext, PostgreSQLDbContext, SqlServerDbContext>.GetEfVersion()
            };

            DB.Add(migrationInit);

            await DB.SaveChangesAsync();
        }
    }
}
文章来源:https://blog.csdn.net/cc1998414/article/details/135356787
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