ProphetLamb/csharp-mongo-migrations

Simple database migrations for `MongoDB.Driver` using ASP.NET.

MongoDB Migrations

Simple database migrations for MongoDB.Driver using ASP.NET DI.

Quick start

Install the NuGet package & Implement the database migrations system in your solution using the following steps:

dotnet add package csharp-mongodb-migrations

1. Inject migrations service
2. Update settings
3. Await migrations
4. Implement migrations

Inject migrations service

Inject AddMigrations into your services.

• If migrations are not in the Assembly.GetEntryAssembly, then manually specify the assemblies in the parameters of AddMigrations.
• Call AddMigrations after configuring options.

using MongoDB.Migration;

services
    .Configure<MyDatabaseSettings>(builder.Configuration.GetSection("Database:MyDatabaseSettings"))
    .AddMigrations()

Update settings

Implement IMongoMigratable for your database settings.

• Options must be configured before injecting services.
• A Database.Alias must be unique: The name used to identify the database during runtime.
• A Database.Name must be unique: The name of the actual MongoDB database.
• Assign a unique constant value to MigrationDescriptor.Database.Alias.

public sealed record MyDatabaseSettings : IOptions<MyDatabaseSettings>, IMongoMigratable
{
    public required string ConnectionString { get; init; }
    public required string DatabaseName { get; init; }
    public required string MyCollectionName { get; init; }

    MyDatabaseSettings IOptions<MyDatabaseSettings>.Value => this;

    public MongoMigrableDefinition GetMigratableDefinition()
    {
        return new()
        {
            ConnectionString = ConnectionString,
            Database = new("MyDatabase", DatabaseName),
            MirgrationStateCollectionName = "DATABASE_MIGRATIONS"
        };
    }
}

Await migrations

Wait for migrations to complete using IMongoMigrationCompletion before accessing the database at any point.

• WaitAsync may not ever be called in constructors.
• WaitAsync is fast when the migration is completed, or the database is not configured.

sealed class MyRepository(IOptions<MyDatabaseSettings> databaseSettings, IMongoMigrationCompletion migrationCompletion) {
    private readonly IMongoCollection<MyModel> _myCollection = new MongoClient(databaseSettings.ConnectionString)
        .GetDatabase(databaseSettings.DatabaseName)
        .GetCollection<MyModel>(databaseSettings.MyCollectionName);

    public async Task<MyModel> GetOrSetAsync(MyModel insertModel, CancellationToken cancellationToken = default) {
        var migrated = await migrationCompletion.WaitAsync(databaseSettings.Value, cancellationToken).ConfigureAwait(false);
        // ... do stuff
    }
}

Implement migrations

Add IMongoMigrations between version 0 and 1 and so on.

• The alias used for the MongoMigrationAttribute must match the name in IMongoMigratable.GetMigrationSettings().Database.Alias.

[MongoMigration("MyDatabase", 0, 1, Description = "Add composite index to MyCollection")]
public sealed class MyCollectionAddCompositeIndexMigration(IOptions<MyDatabaseSettings> optionsAccessor) : IMongoMigration
{
    public async Task DownAsync(IMongoDatabase database, CancellationToken cancellationToken = default)
    {
    }

    public async Task UpAsync(IMongoDatabase database, CancellationToken cancellationToken = default)
    {
    }
}

Fixing database versions

A fixed database version ensures that the migration always produces a database of the specified version, even if the initial version was higher than the fixed version.

• Fixing upgrades the database, if the initial version is lower than the fixed version.
• Fixing downgrades the database, if the initial version is higher than the fixed version.
• Fixing the database to a version is especially useful for a procedural feature rollout.

Fix a specific version by setting the long? MigrateToFixedVersion property in your IMongoMigratable; if the property is null - by default - a migration to the latest version will occur.

public MongoMigrableDefinition GetMigratableDefinition()
{
    return new()
    {
        ConnectionString = ConnectionString,
        Database = new("MyDatabase", DatabaseName),
        MirgrationStateCollectionName = "DATABASE_MIGRATIONS",
        MigrateToFixedVersion = 42069,
    };
}

Migrations without ASP.NET DI

MongoDB Migration extensively uses ASP.NET to prepare the environment required for processing of migrations. Without ASP.NET most features are unavailable, but the core - DatabaseMirationProcessor - public API; it is accessible to the user.

1. Describe your database in the MongoMigrableDefinition record.
2. Wrap instances of all available IMongoMigrations in the MigrationDescriptor record.
3. Instantiate DatabaseMirationProcessor for your database.
4. Call MigrateToVersionAsync with the available MigrationDescriptors.

Testing

Tests require a local mongodb instance without authentication at port 27017: mongodb://localhost:27017.

Disclaimer

csharp-mongo-migration is not affiliated with or endorsed by MongoDB, Inc. MONGODB & MONGO are registered trademarks of MongoDB, Inc. 2023.