How to configure cross-resource references for multi-layer reference relationships

[jingliming]

as the terraform example show，I try to generate managed resource with upjet, if i want to config the zone_mappings as a cross-resource reference in alicloud_alb_load_balancer, How can I achieve this?

variable "name" {
  default = "terraform-example"
}

data "alicloud_resource_manager_resource_groups" "default" {
}

data "alicloud_alb_zones" "default" {
}

resource "alicloud_vpc" "default" {
  vpc_name   = var.name
  cidr_block = "10.4.0.0/16"
}

resource "alicloud_vswitch" "default" {
  count        = 2
  vpc_id       = alicloud_vpc.default.id
  cidr_block   = format("10.4.%d.0/24", count.index + 1)
  zone_id      = data.alicloud_alb_zones.default.zones[count.index].id
  vswitch_name = format("${var.name}_%d", count.index + 1)
}

resource "alicloud_alb_load_balancer" "default" {
  load_balancer_edition  = "Basic"
  address_type           = "Internet"
  vpc_id                 = alicloud_vpc.default.id
  address_allocated_mode = "Fixed"
  resource_group_id      = data.alicloud_resource_manager_resource_groups.default.groups.0.id
  load_balancer_name     = var.name
  load_balancer_billing_config {
    pay_type = "PayAsYouGo"
  }
  modification_protection_config {
    status = "NonProtection"
  }
  zone_mappings {
    vswitch_id = alicloud_vswitch.default.0.id
    zone_id    = data.alicloud_alb_zones.default.zones.0.id
  }
  zone_mappings {
    vswitch_id = alicloud_vswitch.default.1.id
    zone_id    = data.alicloud_alb_zones.default.zones.1.id
  }
  tags = {
    Created = "TF"
  }
}

[sergenyalcin]

@jingliming Do you mean whole zone_mappings block or vswitch_id field in the zone_mappings block?

[sergenyalcin]

If you want to generate a reference for the vswitch_id field, then you need to add the following type of configuration fir this:

r.References["zone_mappings.vswitch_id"] = config.Reference{
	TerraformName:     "alicloud_vswitch",
}

[jingliming]

@sergenyalcin Thanks for your reply. For a dependency with only a single attribute, it seems to work, but there is also a zoneId attribute in this example. I tried to configure it this way, but it did not work as expected. What should I do?

p.AddResourceConfigurator("alicloud_alb_load_balancer", func(r *config.Resource) {
		r.ShortGroup = string(common.LOADBALANCER)
		r.Kind = "ALBInstance"
		r.References["vpc_id"] = config.Reference{
			TerraformName: "alicloud_vpc",
		}
		r.References["zone_mappings.vswitch_id"] = config.Reference{
			TerraformName: "alicloud_vswitch",
		}
		r.References["zone_mappings.zone_id"] = config.Reference{
			TerraformName: "alicloud_vswitch",
		}
		r.UseAsync = true
	})

the generated manifest yaml is:

    zoneMappings:
    - vswitchIdSelector:
        matchLabels:
          testing.upbound.io/example-name: default
      zoneIdSelector:
        matchLabels:
          testing.upbound.io/example-name: alicloud_alb_zones
    - vswitchIdSelector:
        matchLabels:
          testing.upbound.io/example-name: default
      zoneIdSelector:
        matchLabels:
          testing.upbound.io/example-name: alicloud_alb_zones

The expected configuration should be that zoneId is belong to the vSwitch where it is selected by the vswitchIdSelector. ZoneId could find in the status.atProvider.zoneId of vSwitch

https://registry.terraform.io/providers/aliyun/alicloud/1.247.0/docs/resources/alb_load_balancer
The zone_mappings supports the following:
allocation_id - (Optional, Computed, Available since v1.243.0) The ID of the EIP instance.
eip_type - (Optional, Computed, Available since v1.243.0) The type of the EIP instance.
intranet_address - (Optional, Computed, Available since v1.243.0) IPv4 private network address.
vswitch_id - (Required) The ID of the vSwitch that corresponds to the zone. Each zone can use only one vSwitch and subnet.
zone_id - (Required) The ID of the zone to which the SLB instance belongs.

[jingliming]

Maybe another way is to not use labelSelector for ZoneId, and then use ZoneId as the value of label to query vSwitch, like this:

apiVersion: vpc.alicloud.crossplane.io/v1alpha1
kind: VSwitch
metadata:
  annotations:
    meta.upbound.io/example-id: polardb/v1alpha1/database
  labels:
    testing.upbound.io/example-name: mingyuan-iac
    testing.upbound.io/zone-id: cn-hangzhou-h
  name: mingyuan-iac-vswitch
spec:
  ......

apiVersion: loadbalancer.alicloud.crossplane.io/v1alpha1
kind: ALBInstance
metadata:
  annotations:
    meta.upbound.io/example-id: loadbalancer/v1alpha1/albinstance
  labels:
    testing.upbound.io/example-name: mingyuan-iac
  name: mingyuan-iac
spec:
  forProvider:
    ......
    zoneMappings:
    - vswitchIdSelector:
        matchLabels:
          testing.upbound.io/zone-id: cn-hangzhou-h
      zoneId: cn-hangzhou-h
    - vswitchIdSelector:
        matchLabels:
          testing.upbound.io/zone-id: cn-hangzhou-i
      zoneId: cn-hangzhou-i

[sergenyalcin]

@jingliming, As @mbbush mentioned, the default reference extractor is the ID extractor. This means that if you add a reference configuration and don't override the extractor, it will use the ID field as the reference resolution value. For example, for the following one, the zone_mappings.vswitch_id field's value will correspond to the alicloud_vswitch resource's status.atProvider.id value.

r.References["zone_mappings.vswitch_id"] = config.Reference{
	TerraformName:     "alicloud_vswitch",
}

If you want to extract another field, you need to implement a special extractor function and specify this function's codepath in the configuration. Let me give an example for this from provider-upjet-aws. In the provider-upjet-aws, many reference fields use status.atProvider.arn instead of status.atProvider.id. This is a step-by-step execution for applying a specific extractor:

1. Implementation of extractor: https://github.com/crossplane-contrib/provider-upjet-aws/blob/a1784c7e569a7975de9d6cd926a80fb3e2b345d3/config/common/common.go#L49. This is a function registration for extracting a specific field from status.
2. Creating a code file path for this: https://github.com/crossplane-contrib/provider-upjet-aws/blob/a1784c7e569a7975de9d6cd926a80fb3e2b345d3/config/common/common.go#L33.
3. Then, in the reference configuration, refer to this code file path for consuming the special extractor: https://github.com/crossplane-contrib/provider-upjet-aws/blob/a1784c7e569a7975de9d6cd926a80fb3e2b345d3/config/efs/config.go#L51

So for you:

1. First, implement a special extractor for status.atProvider.zoneId.
2. Then create a constant (for reusability) that shows the whole code path with the function name.
3. Finally, refer to this code path for consuming the zone ID extractor.

[mbbush]

ZoneId could find in the status.atProvider.zoneId of vSwitch

If you create a cross-resource reference the way @sergenyalcin suggested above, then upjet uses the external name of the resource being referenced to fill in the field in the resource that has the selector.

If that's not the behavior you want, then you can use the Extractor field. https://github.com/crossplane-contrib/provider-upjet-aws/blob/a1784c7e569a7975de9d6cd926a80fb3e2b345d3/config/s3/config.go#L105-L108 has one example that uses the ExtractParamPath. The boolean parameter determines whether the path you specify in the string arg is extracted from spec.forProvider or status.atProvider.