Pulumi inputs outpus and resource dependency Python GCP

Question

I'm having some trouble in trying to understand how to pass an output of a resource as an input to another resource, so they have a dependency and the order at the creation time works properly.

Scenario: Resource B has a dependency from Resource A.

I was trying to pass to resource B something like these

opts = ResourceOptions(depends_on=[ResourceA])

But for some reason, it acts as that parameter wasn't there and keeps creating Resource B before creating Resource A, therefore throwing an error.

If I execute pulumi up a second time, as Resource A exists, Resource B gets created.

I noticed that you could also pass an output as an input of another resource, and because of this, Pulumi understands that there is a relationship and makes it so automatically

https://www.pulumi.com/docs/intro/concepts/inputs-outputs/

But I can't get my head around it in how to pass that, so, any help regarding this would be appreciate it.

I also used the following explanation regarding how to use ResourceOptions, which I think that I'm using it correctly as the code above, but still no case

How to control resource creation order in Pulumi

Thanks in advance.

score 0 · Accepted Answer · edited Nov 14 '21 at 15:30

@mrthopson,

Let me try to explain using one of the public examples. I took it from this Pulumi example:

https://github.com/pulumi/examples/blob/master/aws-ts-eks/index.ts

// Create a VPC for our cluster.
const vpc = new awsx.ec2.Vpc("vpc", { numberOfAvailabilityZones: 2 });

// Create the EKS cluster itself and a deployment of the Kubernetes dashboard.
const cluster = new eks.Cluster("cluster", {
    vpcId: vpc.id,
    subnetIds: vpc.publicSubnetIds,
    instanceType: "t2.medium",
    desiredCapacity: 2,
    minSize: 1,
    maxSize: 2,
});

The example first creates a VPC in AWS. The VPC contains a number of different networks and the identifiers of these networks are exposed as outputs. When we create the EKS cluster, we pass the ids of the public subnets (output vpc.publicSubnetIds) as an input to the cluster (input: subnetIds).

That is the only thing you need to do to have a dependency from the EKS cluster on the VPC. When running Pulumi, the engine will find out it first needs to create the VPC and only after that it can create the EKS cluster.

Ringo

thanks for the time in replying. I think I have understand it, I'm gonna try it in python and see how it goes. For the dependsOn part, I was passing in the wrong part, I was passing it in the "resourceArgs" part and I should have pass it to the "resource". After doing so, Pulumi managed to make the dependencies. I will try it later with your suggestion as I reckon is how Pulumi recommends to manage the dependencies and it looks more code efficient. Cheers — MrThompson, Nov 15 '21 at 23:38

Pulumi inputs outpus and resource dependency Python GCP

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