How can I reference a endpoint in my client app from a custom ExecutableResouce?

[JobaDiniz]

I'm new to creating custom resources in Aspire. Not even sure whether the below code is correct way of doing it.
But essentially I'm trying to create a ExecutableResource that launches temporal CLI (temporal server start-dev). This command creates 3 endpoints:

PS C:\Users\jdiniz> temporal server start-dev
CLI 1.1.2 (Server 1.25.2, UI 2.32.0)

Server:  localhost:7233
UI:      http://localhost:8233
Metrics: http://localhost:61644/metrics

public class TemporalExecutableResource(string name, string? executablePath) :
    ExecutableResource(name, executablePath ?? "temporal", string.Empty), IResourceWithEndpoints{}

public static class TemporalBuilderExtensions
{
    public static IResourceBuilder<TemporalExecutableResource> AddTemporalDevelopmentServer(this IDistributedApplicationBuilder builder, string name, string? executablePath = null, string[]? args = null)
    {
        args = args ?? [];
        string[] allArgs = args is { Length: > 0 }
            ? ["server", "start-dev", .. args]
            : ["server", "start-dev"];
        var temporal = new TemporalExecutableResource(name, executablePath);
        return builder.AddResource(temporal)
            .WithArgs(allArgs)
            .WithEndpoint(port: 7233, scheme: "grpc", name: "server", isProxied: false, isExternal: true)
            .WithHttpEndpoint(port: 8233, name: "ui", isProxied: false)
            .WithHttpEndpoint(port: 52723, name: "metrics", isProxied: false);
    }
}

This does not work as it should, but I'll figure out later, my question is more basic:

How can I reference these endpoints in the client app?

options.ClientOptions = new Temporalio.Client.TemporalClientConnectOptions("HOW TO REFERENCE the SERVER ENDPOINT HERE?")
{
    Namespace = "default",
    DataConverter = DataConverter.Default with { PayloadConverter = new DefaultPayloadConverter(NetFlowJsonSerializerOptions.Definition) }
};

[davidfowl]

First, there's a working temporal hosting integration on NuGet:

NuGet - https://www.nuget.org/packages/InfinityFlow.Aspire.Temporal
Github - https://github.com/InfinityFlowApp/aspire-temporal

How can I reference these endpoints in the client app?

Have you read

• https://learn.microsoft.com/en-us/dotnet/aspire/fundamentals/app-host-overview?tabs=docker#connection-string-and-endpoint-references
• https://learn.microsoft.com/en-us/dotnet/aspire/extensibility/custom-hosting-integration
• https://learn.microsoft.com/en-us/dotnet/aspire/extensibility/custom-client-integration

Most integrations implement IResourceWithConnectionString and create a connection string expression that will get passed to the "cleint" or "consuming" resource when WithReference is used.

There're extensive comments on what these APIs do and what they inject into the target application:

https://learn.microsoft.com/en-us/dotnet/api/aspire.hosting.resourcebuilderextensions.withreference?view=dotnet-aspire-8.0

ExecutableResource already implemets IResourceWithEndpoints, so adding it to your resouce implementation is not useful. At a lower level, you can get an endpoint by name by calling GetEndpoint and you can pass it to another resource (this example shows passing it to a project resource):

var builder = DistributedApplication.CreateBuilder(args);

var temporal = builder.AddTemporalDevelopmentServer("temporal");

builder.AddProject<Projects.Api>("api")
    .WithReference(temporal.GetEndpoint("grpc"));

builder.Build().Run();

This will pass the resolved URL (at the appropriate time) to the target project using the service discovery format described here.

OR you can set environment variables directly:

var builder = DistributedApplication.CreateBuilder(args);

var temporal = builder.AddTemporalDevelopmentServer("temporal");

builder.AddProject<Projects.Api>("api")
    .WithEnvironment("TemporalDevUrl", temporal.GetEndpoint("grpc"));

builder.Build().Run();

[JobaDiniz]

thanks. I'm starting to get the hang of it :). The missing piece was to add a IResourceWithConnectionString. But as you said, I could chose to not implement the interface and use .WithReference(temporal.GetEndpoint("grpc"). Did not know about this.

I've implemented like this:

public class TemporalExecutableResource(string name, string? executablePath) :
    ExecutableResource(name, executablePath ?? "temporal", string.Empty), IResourceWithConnectionString
{
    internal const string ServerEndpointName = "server";

    private EndpointReference? serverReference;
    public EndpointReference ServerEndpoint =>
        serverReference ??= new(this, ServerEndpointName);

    public ReferenceExpression ConnectionStringExpression =>
        ReferenceExpression.Create(
            $"{ServerEndpoint.Property(EndpointProperty.Host)}:{ServerEndpoint.Property(EndpointProperty.Port)}"
        );
}

public static class TemporalBuilderExtensions
{
    public static IResourceBuilder<TemporalExecutableResource> AddTemporalDevelopmentServer(this IDistributedApplicationBuilder builder, string name, string? executablePath = null, string[]? args = null)
    {
        args = args ?? [];
        string[] allArgs = args is { Length: > 0 }
            ? ["server", "start-dev", .. args]
            : ["server", "start-dev"];
        var temporal = new TemporalExecutableResource(name, executablePath);
        return builder.AddResource(temporal)
            .WithArgs(allArgs)
            .WithEndpoint(port: 7233, scheme: string.Empty, name: TemporalExecutableResource.ServerEndpointName, isProxied: false)
            .WithHttpEndpoint(port: 8233, name: "ui", isProxied: false)
            .WithHttpEndpoint(port: 52723, name: "metrics", isProxied: false);
    }
}

[davidfowl]

Great! I opened a doc issue to write up how endpoint references work.