The following code fails with

reading Service Discovery test.svc.cluster.local Namespace (DNS_PRIVATE): couldn't find resource

during

pulumi preview

. Because the call to

getDnsNamespaceOutput

uses the output of

new aws.servicediscovery.PrivateDnsNamespace

as input, I would've expected the code to work, because the call to the get method should only be executed after the resource has been created and its name is available. Code:

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

const vpc = new aws.ec2.Vpc("vpc");

const serviceDiscoveryDnsNamespace = new aws.servicediscovery.PrivateDnsNamespace("services", {
    name: `test.svc.cluster.local`,
    vpc: vpc.id
});

const serviceDiscoveryNamespace = aws.servicediscovery.getDnsNamespaceOutput({
    name: serviceDiscoveryDnsNamespace.name,
    type: "DNS_PRIVATE"
});

What am I missing here?

This is a quirk in how dependencies work with invoke (pulumi functions). As you're using a constant string, the value is "known", so doesn't respect the resource not being created yet. A workaround is to use the resource id as well:

name: serviceDiscoveryDnsNamespace.id.apply(_ => serviceDiscoveryDnsNamespace.name),

Why is name a constant string? It is of type

pulumi.Output<string>

The input of the resource is a constant string. Invokes don't follow the same dependency rules as resources. There's a related issue here: https://github.com/pulumi/pulumi/issues/14243

I see, thanks

Out of curiosity, why are you doing a

getDnsNamespace

on a resource you just created?

Because of encapsulation. I've a ComponentResource in which I need both the ID as well as the name of the Service Discovery DNS namespace - because registering a new service with the namespace requires the ID and the service discovery node in an App Mesh virtual node requires the name - and I don't want to polute the interface of the ComponentResource just because AWS is inconsistent in its inputs.

the ID and name both appear to be in the resource registration, all inputs are also outputs

Ok?

I think what you're saying is you don't want to pass both name and id in at the same time to the component?

Yes. If the namespace were an existing one - which the component absolutely allows - the caller of the component would be required to first fetch the namespace to have both name and id.

there is a better way of solving for that problem, but good luck 👍

What would be the better way? I just started with pulumi, trying to find my way around. So, I would be very happy to learn better ways. My "Ok?" answer wasn't dismissive, I just didn't understand what you wanted to tell me with your comment

You can pass the resource itself into the component constructor, instead of its outputs. This would negate the need for using the function to fetch the details

I see, thanks. Is this the recommended way?

It's something I do for more complex interactions between components. I'm not sure I've seen it in examples