How to use Cosmos DB in ABP?

There is a couple of ways to use Cosmos DB in C#. Cosmos DB has an SQL API and MongoDB API at the same time. Also there is a Entity Framework Provider of Cosmos DB which is based on SQL API but I recommend to use MongoDB Driver since Cosmos is a document based database. So, in this article, accessing to Cosmos DB will be with the MongoDB Driver.

Setting up Development Environment

There a Cosmos DB Emulator for development purposes. It's easy to setup for development.

You can follow those instructions to set up Cosmos DB for MongoDB Driver:

• [Install and develop locally with Azure Cosmos DB Emulator | Microsoft Docs](Install and develop locally with Azure Cosmos DB Emulator | Microsoft Docs)

Notice: Do not forget to start emulator with /EnableMongoDbEndpoint parameter from CLI. The example is presented here.

Start Development

1- Creating ABP Application

In this example, we'll use MongoDB Driver to connect Cosmos DB as I said before, so let's create project with -d mongodb

 abp new Acme.BookStore -d mongodb -v 5.0.0-rc.1

2- Configuring the Project

Determine your connection string. If you're using default configuration of Cosmos DB Emulator, your connection string should be like below:

mongodb://localhost:C2y6yDjf5%2FR%2Bob0N8A7Cgv30VRDJIWEHLM%2B4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw%2FJw%3D%3D@localhost:10255/AcmeBookStore?ssl=true

Format is presented as Connection String URI Format. So you can make changes based on this format according to your requirements.

• Replace connection string in src/Acme.BookStore.DbMigrator/appsettings.json and src/Acme.BookStore.Web/appsettings.json:

{
  "ConnectionStrings": {
-  "Default": "mongodb://localhost:27017/BookStore"
+  "Default": "mongodb://localhost:C2y6yDjf5%2FR%2Bob0N8A7Cgv30VRDJIWEHLM%2B4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw%2FJw%3D%3D@localhost:10255/AcmeBookStore?ssl=true"
  }
}

3- Configure & Run Migrations

Some more changes are required before running migrations. Creating a scheme isn't required anymore.

• Go BookStoreDbMigrationService.cs file under Acme.BookStore.Domain/Data folder nd remove MigrateDatabaseSchemaAsync:

public async Task MigrateAsync()
{
    Logger.LogInformation("Started database migrations...");
-    await MigrateDatabaseSchemaAsync();
    await SeedDataAsync();
    Logger.LogInformation($"Successfully completed host database migrations.");
    var tenants = await _tenantRepository.GetListAsync(includeDetails: true);
-    var migratedDatabaseSchemas = new HashSet<string>();
    foreach (var tenant in tenants)
    {
        using (_currentTenant.Change(tenant.Id))
        {
            if (tenant.ConnectionStrings.Any())
            {
                var tenantConnectionStrings = tenant.ConnectionStrings
                    .Select(x => x.Value)
                    .ToList();
-                if (!migratedDatabaseSchemas.IsSupersetOf(tenantConnectionStrings))
-                {
-                    await MigrateDatabaseSchemaAsync(tenant);
-
-                    migratedDatabaseSchemas.AddIfNotContains(tenantConnectionStrings);
-                }
            }
            await SeedDataAsync(tenant);
        }
        Logger.LogInformation($"Successfully completed {tenant.Name} tenant database migrations.");
    }
    Logger.LogInformation("Successfully completed all database migrations.");
    Logger.LogInformation("You can safely end this process...");
}

• Also you should remove entire method

-private async Task MigrateDatabaseSchemaAsync(Tenant tenant = null)
-{
-    Logger.LogInformation(
-    $"Migrating schema for {(tenant == null ? "host" : tenant.Name + " tenant")} database...");
-
-    foreach (var migrator in _dbSchemaMigrators)
-    {
-    await migrator.MigrateAsync();
-    }
-}

• DbMigrator is ready to execute now. Run Acme.BookStore.DbMigrator project and complete data seeding.

After you see screen below, your application is completely ready.

4- Run the Project

Run the Acme.BookStore.Web project and see the result. All existing modules are working smooth with Cosmos DB.