PostgreSQL client integration

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To get started with the Aspire PostgreSQL Entity Framework Core (EF 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 EF 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="*" />

For an introduction to the PostgreSQL EF Core integration, see Get started with the PostgreSQL Entity Framework Core integrations.

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 Microsoft.EntityFrameworkCore.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.

Properties of the PostgreSQL resources

When you add a reference to a PostgreSQL resource in the AppHost, using the WithReference method, Aspire injects several properties into the consuming project. These properties are available as environment variables that you can use to connect to and interact with PostgreSQL.

The properties injected depend on the type of resource you reference:

PostgreSQL server properties

When you reference a PostgresServerResource (the server), the following properties are injected:

Property Name	Environment Variable	Description
`Host`	`[RESOURCE]_HOST`	The hostname or IP address of the PostgreSQL server.
`Port`	`[RESOURCE]_PORT`	The port number the PostgreSQL server is listening on.
`Username`	`[RESOURCE]_USERNAME`	The username for authenticating to the PostgreSQL server.
`Password`	`[RESOURCE]_PASSWORD`	The password for authenticating to the PostgreSQL server.

PostgreSQL database properties

When you reference a PostgresDatabaseResource (a specific database), the following properties are injected:

Property Name	Environment Variable	Description
`Host`	`[RESOURCE]_HOST`	The hostname or IP address of the PostgreSQL server.
`Port`	`[RESOURCE]_PORT`	The port number the PostgreSQL server is listening on.
`Username`	`[RESOURCE]_USERNAME`	The username for authenticating to the PostgreSQL server.
`Password`	`[RESOURCE]_PASSWORD`	The password for authenticating to the PostgreSQL server.
`DatabaseName`	`[RESOURCE]_DATABASENAME`	The name of the specific database.
`ConnectionString`	`ConnectionStrings__[RESOURCE]`	The full connection string for the database.
`JDBCConnectionString`	`[RESOURCE]_JDBCCONNECTIONSTRING`	The JDBC connection string for the database.

Here’s an example of how these properties are used when you call WithReference:

var builder = DistributedApplication.CreateBuilder(args);

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

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

In this example, the ExampleProject will have access to environment variables like POSTGRESDB_HOST, POSTGRESDB_PORT, POSTGRESDB_USERNAME, POSTGRESDB_PASSWORD, POSTGRESDB_DATABASENAME, POSTGRESDB_JDBCCONNECTIONSTRING, and the connection string ConnectionStrings__postgresdb.

Enrich an Npgsql database context

You may prefer to use the standard EF Core 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 EF 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 EF 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 EF 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 EF 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 EF Core integration will emit the following tracing activities using OpenTelemetry:

Npgsql

Metrics

The Aspire PostgreSQL EF 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