Aspire PostgreSQL Entity Framework Core integration

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PostgreSQL is a powerful, open source object-relational database system with many years of active development that has earned it a strong reputation for reliability, feature robustness, and performance. The Aspire PostgreSQL integration provides a way to connect to existing PostgreSQL databases, or create new instances from the docker.io/library/postgres container image.

Hosting integration

The PostgreSQL hosting integration models various PostgreSQL resources as the following types.

PostgresServerResource
PostgresDatabaseResource
PostgresPgAdminContainerResource
PostgresPgWebContainerResource

To access these types and APIs for expressing them as resources in your AppHost project, install the 📦 Aspire.Hosting.PostgreSQL NuGet package:

aspire add postgresql

A Aspire CLI é interativa; escolha o resultado adequado quando solicitado:

Select an integration to add:

> postgresql (Aspire.Hosting.PostgreSQL)
> Other results listed as selectable options...

#:package Aspire.Hosting.PostgreSQL@*

<PackageReference Include="Aspire.Hosting.PostgreSQL" Version="*" />

Add PostgreSQL server resource

In your AppHost project, call AddPostgres on the builder instance to add a PostgreSQL server resource then call AddDatabase on the postgres instance to add a database resource as shown in the following example:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres");
var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

When Aspire adds a container image to the app host, as shown in the preceding example with the docker.io/library/postgres image, it creates a new PostgreSQL server instance on your local machine. A reference to your PostgreSQL server and database instance (the postgresdb variable) are used to add a dependency to the ExampleProject.
When adding a database resource to the app model, the database is created if it doesn’t already exist. The creation of the database relies on the AppHost eventing APIs, specifically ResourceReadyEvent. In other words, when the postgres resource is ready, the event is raised and the database resource is created.
The PostgreSQL server resource includes default credentials with a username of "postgres" and randomly generated password using the CreateDefaultPasswordParameter method.
The WithReference method configures a connection in the ExampleProject named "messaging".

Add PostgreSQL resource with database scripts

By default, when you add a PostgresDatabaseResource, it relies on the following script to create the database:

CREATE DATABASE "<QUOTED_DATABASE_NAME>"

To alter the default script, chain a call to the WithCreationScript method on the database resource builder:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres");

var databaseName = "app_db";
var creationScript = $$"""
    -- Create the database
    CREATE DATABASE {{databaseName}};

    """;

var db = postgres.AddDatabase(databaseName)
                 .WithCreationScript(creationScript);

builder.AddProject<Projects.ExampleProject>()
       .WithReference(db)
       .WaitFor(db);

// After adding all resources, run the app...

The preceding example creates a database named app_db. The script is run when the database resource is created. The script is passed as a string to the WithCreationScript method, which is then run in the context of the PostgreSQL resource.

Add PostgreSQL pgAdmin resource

When adding PostgreSQL resources to the builder with the AddPostgres method, you can chain calls to WithPgAdmin to add the dpage/pgadmin4 container. This container is a cross-platform client for PostgreSQL databases, that serves a web-based admin dashboard. Consider the following example:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
                      .WithPgAdmin();

var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

The preceding code adds a container based on the docker.io/dpage/pgadmin4 image. The container is used to manage the PostgreSQL server and database resources. The WithPgAdmin method adds a container that serves a web-based admin dashboard for PostgreSQL databases.

Configure the pgAdmin host port

To configure the host port for the pgAdmin container, call the WithHostPort method on the PostgreSQL server resource. The following example shows how to configure the host port for the pgAdmin container:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
                      .WithPgAdmin(pgAdmin => pgAdmin.WithHostPort(5050));

var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

The preceding code adds and configures the host port for the pgAdmin container. The host port is otherwise randomly assigned.

Add PostgreSQL pgWeb resource

When adding PostgreSQL resources to the builder with the AddPostgres method, you can chain calls to WithPgWeb to add the sosedoff/pgweb container. This container is a cross-platform client for PostgreSQL databases, that serves a web-based admin dashboard. Consider the following example:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
                      .WithPgWeb();

var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

The preceding code adds a container based on the docker.io/sosedoff/pgweb image. All registered PostgresDatabaseResource instances are used to create a configuration file per instance, and each config is bound to the pgweb container bookmark directory. For more information, see PgWeb docs: Server connection bookmarks.

Configure the pgWeb host port

To configure the host port for the pgWeb container, call the WithHostPort method on the PostgreSQL server resource. The following example shows how to configure the host port for the pgAdmin container:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
                      .WithPgWeb(pgWeb => pgWeb.WithHostPort(5050));

var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

The preceding code adds and configures the host port for the pgWeb container. The host port is otherwise randomly assigned.

Add PostgreSQL server resource with data volume

To add a data volume to the PostgreSQL server resource, call the WithDataVolume method on the PostgreSQL server resource:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
                      .WithDataVolume(isReadOnly: false);

var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

The data volume is used to persist the PostgreSQL server data outside the lifecycle of its container. The data volume is mounted at the /var/lib/postgresql/data path in the PostgreSQL server container and when a name parameter isn’t provided, the name is generated at random. For more information on data volumes and details on why they’re preferred over bind mounts, see Docker docs: Volumes.

Some database integrations, including the Aspire PostgreSQL integration, can’t successfully use data volumes after deployment to Azure Container Apps (ACA). This is because ACA uses Server Message Block (SMB) to connect containers to data volumes, and some systems can’t use this connection. In the Aspire Dashboard, a database affected by this issue has a status of Activating or Activation Failed but is never listed as Running.

You can resolve the problem by using the managed service Azure Database for PostgreSQL to host the deployed database instead of a container in ACA, which is the recommended approach regardless of this issue. The following AppHost code shows how to deploy a database to Azure Database for PostgreSQL, but run it as a container, with a data volume, during development:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddAzurePostgresFlexibleServer("postgres")
                    .RunAsContainer(container =>
                    {
                        container.WithDataVolume();
                    });

builder.Build().Run();

Add PostgreSQL server resource with data bind mount

To add a data bind mount to the PostgreSQL server resource, call the WithDataBindMount method:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
                      .WithDataBindMount(
                          source: "/PostgreSQL/Data",
                          isReadOnly: false);

var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

Data bind mounts rely on the host machine’s filesystem to persist the PostgreSQL server data across container restarts. The data bind mount is mounted at the C:\PostgreSQL\Data on Windows (or /PostgreSQL/Data on Unix) path on the host machine in the PostgreSQL server container. For more information on data bind mounts, see Docker docs: Bind mounts.

Add PostgreSQL server resource with init bind mount

To add an init bind mount to the PostgreSQL server resource, call the WithInitBindMount method:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
                      .WithInitBindMount(@"C:\PostgreSQL\Init");

var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

The init bind mount relies on the host machine’s filesystem to initialize the PostgreSQL server database with the containers init folder. This folder is used for initialization, running any executable shell scripts or .sql command files after the postgres-data folder is created. The init bind mount is mounted at the C:\PostgreSQL\Init on Windows (or /PostgreSQL/Init on Unix) path on the host machine in the PostgreSQL server container.

Add PostgreSQL server resource with parameters

When you want to explicitly provide the username and password used by the container image, you can provide these credentials as parameters. Consider the following alternative example:

var builder = DistributedApplication.CreateBuilder(args);

var username = builder.AddParameter("username", secret: true);
var password = builder.AddParameter("password", secret: true);

var postgres = builder.AddPostgres("postgres", username, password);
var postgresdb = postgres.AddDatabase("postgresdb");

var exampleProject = builder.AddProject<Projects.ExampleProject>()
                            .WithReference(postgresdb);

// After adding all resources, run the app...

Hosting integration health checks

The PostgreSQL hosting integration automatically adds a health check for the PostgreSQL server resource. The health check verifies that the PostgreSQL server is running and that a connection can be established to it.

The hosting integration relies on the 📦 AspNetCore.HealthChecks.Npgsql NuGet package.

Using with non-.NET applications

The PostgreSQL hosting integration can be used with any application technology, not just .NET applications. When you use WithReference to reference a PostgreSQL resource, connection information is automatically injected as environment variables into the referencing application.

For applications that don’t use the client integration, you can access the connection information through environment variables. Here’s an example of how to configure environment variables for a non-.NET application:

var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
    .WithLifetime(ContainerLifetime.Persistent);

var database = postgres.AddDatabase("myDatabase");

// Example: Configure a non-.NET application with PostgreSQL access
var app = builder.AddExecutable("my-app", "node", "app.js", ".")
    .WithReference(database) // Provides ConnectionStrings__myDatabase
    .WithEnvironment(context =>
    {
        // Additional individual connection details as environment variables
        context.EnvironmentVariables["POSTGRES_HOST"] = postgres.Resource.PrimaryEndpoint.Property(EndpointProperty.Host);
        context.EnvironmentVariables["POSTGRES_PORT"] = postgres.Resource.PrimaryEndpoint.Property(EndpointProperty.Port);
        context.EnvironmentVariables["POSTGRES_USER"] = postgres.Resource.UserNameParameter;
        context.EnvironmentVariables["POSTGRES_PASSWORD"] = postgres.Resource.PasswordParameter;
        context.EnvironmentVariables["POSTGRES_DATABASE"] = database.Resource.DatabaseName;
    });

builder.Build().Run();

This configuration provides the non-.NET application with several environment variables:

ConnectionStrings__myDatabase: The complete PostgreSQL connection string
POSTGRES_HOST: The hostname/IP address of the PostgreSQL server
POSTGRES_PORT: The port number the PostgreSQL server is listening on
POSTGRES_USER: The database username
POSTGRES_PASSWORD: The dynamically generated password
POSTGRES_DATABASE: The name of the database

Your non-.NET application can then read these environment variables to connect to the PostgreSQL database using the appropriate database driver for that technology (for example, psycopg2 for Python, pg for Node.js, or pq for Go).

Client integration

To get started with the Aspire PostgreSQL Entity Framework Core client integration, install the 📦 Aspire.Npgsql.EntityFrameworkCore.PostgreSQL NuGet package in the client-consuming project, that is, the project for the application that uses the PostgreSQL client. The Aspire PostgreSQL Entity Framework Core client integration registers your desired DbContext subclass instances that you can use to interact with PostgreSQL.

dotnet add package Aspire.Npgsql.EntityFrameworkCore.PostgreSQL

#:package Aspire.Npgsql.EntityFrameworkCore.PostgreSQL@*

<PackageReference Include="Aspire.Npgsql.EntityFrameworkCore.PostgreSQL" Version="*" />

Add Npgsql database context

In the Program.cs file of your client-consuming project, call the AddNpgsqlDbContext extension method on any IHostApplicationBuilder to register your System.Data.Entity.DbContext subclass for use via the dependency injection container. The method takes a connection name parameter.

builder.AddNpgsqlDbContext<YourDbContext>(
    connectionName: "postgresdb");

After adding YourDbContext to the builder, you can get the YourDbContext instance using dependency injection. For example, to retrieve your data source object from an example service define it as a constructor parameter and ensure the ExampleService class is registered with the dependency injection container:

public class ExampleService(YourDbContext context)
{
    // Use context...
}

For more information on dependency injection, see .NET dependency injection.

Enrich an Npgsql database context

You may prefer to use the standard Entity Framework method to obtain a database context and add it to the dependency injection container:

builder.Services.AddDbContext<YourDbContext>(options =>
    options.UseNpgsql(builder.Configuration.GetConnectionString("postgresdb")
        ?? throw new InvalidOperationException("Connection string 'postgresdb' not found.")));

You have more flexibility when you create the database context in this way, for example:

You can reuse existing configuration code for the database context without rewriting it for Aspire.
You can use Entity Framework Core interceptors to modify database operations.
You can choose not to use Entity Framework Core context pooling, which may perform better in some circumstances.

If you use this method, you can enhance the database context with Aspire-style retries, health checks, logging, and telemetry features by calling the EnrichNpgsqlDbContext method:

builder.EnrichNpgsqlDbContext<YourDbContext>(
    configureSettings: settings =>
    {
        settings.DisableRetry = false;
        settings.CommandTimeout = 30;
    });

The settings parameter is an instance of the NpgsqlEntityFrameworkCorePostgreSQLSettings class.

Configuration

The Aspire PostgreSQL Entity Framework Core integration provides multiple configuration approaches and options to meet the requirements and conventions of your project.

Use a connection string

When using a connection string from the ConnectionStrings configuration section, you provide the name of the connection string when calling the AddNpgsqlDbContext method:

builder.AddNpgsqlDbContext<MyDbContext>("pgdb");

The connection string is retrieved from the ConnectionStrings configuration section:

{
  "ConnectionStrings": {
    "pgdb": "Host=myserver;Database=test"
  }
}

The EnrichNpgsqlDbContext won’t make use of the ConnectionStrings configuration section since it expects a DbContext to be registered at the point it’s called.

For more information, see the ConnectionString.

Use configuration providers

The Aspire PostgreSQL Entity Framework Core integration supports Microsoft.Extensions.Configuration. It loads the NpgsqlEntityFrameworkCorePostgreSQLSettings from configuration files such as appsettings.json by using the Aspire:Npgsql:EntityFrameworkCore:PostgreSQL key. If you have set up your configurations in the Aspire:Npgsql:EntityFrameworkCore:PostgreSQL section you can just call the method without passing any parameter.

The following example shows an appsettings.json file that configures some of the available options:

{
  "Aspire": {
    "Npgsql": {
      "EntityFrameworkCore": {
        "PostgreSQL": {
          "ConnectionString": "Host=myserver;Database=postgresdb",
          "DisableHealthChecks": true,
          "DisableTracing": true
        }
      }
    }
  }
}

For the complete PostgreSQL Entity Framework Core client integration JSON schema, see Aspire.Npgsql.EntityFrameworkCore.PostgreSQL/ConfigurationSchema.json.

Use inline delegates

You can also pass the Action<NpgsqlEntityFrameworkCorePostgreSQLSettings> delegate to set up some or all the options inline, for example to set the ConnectionString:

builder.AddNpgsqlDbContext<YourDbContext>(
    "pgdb",
    static settings => settings.ConnectionString = "<YOUR CONNECTION STRING>");

Configure multiple DbContext classes

If you want to register more than one DbContext with different configuration, you can use $"Aspire:Npgsql:EntityFrameworkCore:PostgreSQL:{typeof(TContext).Name}" configuration section name. The json configuration would look like:

{
  "Aspire": {
    "Npgsql": {
      "EntityFrameworkCore": {
        "PostgreSQL": {
          "ConnectionString": "<YOUR CONNECTION STRING>",
          "DisableHealthChecks": true,
          "DisableTracing": true,
          "AnotherDbContext": {
            "ConnectionString": "<ANOTHER CONNECTION STRING>",
            "DisableTracing": false
          }
        }
      }
    }
  }
}

Then calling the AddNpgsqlDbContext method with AnotherDbContext type parameter would load the settings from AnotherDbContext section.

builder.AddNpgsqlDbContext<AnotherDbContext>();

By default, the Aspire PostgreSQL Entity Framework Core integrations handles the following:

Adds the DbContextHealthCheck, which calls EF Core’s CanConnectAsync method. The name of the health check is the name of the TContext type.
Integrates with the /health HTTP endpoint, which specifies all registered health checks must pass for app to be considered ready to accept traffic

Observability and telemetry

Aspire integrations automatically set up Logging, Tracing, and Metrics configurations.

Logging

The Aspire PostgreSQL Entity Framework Core integration uses the following Log categories:

Microsoft.EntityFrameworkCore.ChangeTracking
Microsoft.EntityFrameworkCore.Database.Command
Microsoft.EntityFrameworkCore.Database.Connection
Microsoft.EntityFrameworkCore.Database.Transaction
Microsoft.EntityFrameworkCore.Migrations
Microsoft.EntityFrameworkCore.Infrastructure
Microsoft.EntityFrameworkCore.Migrations
Microsoft.EntityFrameworkCore.Model
Microsoft.EntityFrameworkCore.Model.Validation
Microsoft.EntityFrameworkCore.Query
Microsoft.EntityFrameworkCore.Update

Tracing

The Aspire PostgreSQL Entity Framework Core integration will emit the following tracing activities using OpenTelemetry:

Npgsql

Metrics

The Aspire PostgreSQL Entity Framework Core integration will emit the following metrics using OpenTelemetry:

Microsoft.EntityFrameworkCore:
- ec_Microsoft_EntityFrameworkCore_active_db_contexts
- ec_Microsoft_EntityFrameworkCore_total_queries
- ec_Microsoft_EntityFrameworkCore_queries_per_second
- ec_Microsoft_EntityFrameworkCore_total_save_changes
- ec_Microsoft_EntityFrameworkCore_save_changes_per_second
- ec_Microsoft_EntityFrameworkCore_compiled_query_cache_hit_rate
- ec_Microsoft_Entity_total_execution_strategy_operation_failures
- ec_Microsoft_E_execution_strategy_operation_failures_per_second
- ec_Microsoft_EntityFramew_total_optimistic_concurrency_failures
- ec_Microsoft_EntityF_optimistic_concurrency_failures_per_second
Npgsql:
- ec_Npgsql_bytes_written_per_second
- ec_Npgsql_bytes_read_per_second
- ec_Npgsql_commands_per_second
- ec_Npgsql_total_commands
- ec_Npgsql_current_commands
- ec_Npgsql_failed_commands
- ec_Npgsql_prepared_commands_ratio
- ec_Npgsql_connection_pools
- ec_Npgsql_multiplexing_average_commands_per_batch
- ec_Npgsql_multiplexing_average_write_time_per_batch

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