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# python
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p
I’d say in general, you should favor composition over inheritance.
I’d simply create a ComponentResource (e.g. 
Site
) that expects another component resource (e.g. 
Region
) as its dependency (you can pass it in the constructor).
🙏 1
i
do you have an example how you would do it? How can you access the resources from Sites from Region? I could not find a proper example
p
Use dependency injection
you can pass instance of 
Region
class to the constructor of 
Site
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class Site(pulumi.ComponentResource):
    def __init__(
        self,
        name: str,
        region: Region,
        opts: Optional[pulumi.ResourceOptions] = None,
    ):
        super().__init__("something:something:Site", name, {}, opts)
        ...
then you can create the region resource first and pass it to 
Site
constructor:
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region = Region(...)
site = Site("my-site", region=region)
pulumi does not enforce any dependency injection mechanism or design patterns so you’re free to use anything you want
I strongly recommend using ComponentResource. It’s a very thin layer (all it does is creating parent-child relationships and allow you to use parent providers) but it greatly improves readability of the stack resources.
i
excellent let me try this! When I understand it right, the Site Class will call the Region class and then It can access all the ressoruces?
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site = Site("my-site", region=region)
and this is the “trick”?
p
I wouldn’t call it a trick (you can do real magic in python). You simply pass the 
Region
object to the 
Site
class instance so it can access its properties.
Copy code
class Site(pulumi.ComponentResource):
    def __init__(
        self,
        name: str,
        region: Region,
        opts: Optional[pulumi.ResourceOptions] = None,
    ):
        super().__init__("something:something:Site", name, {}, opts)
=>      self.region_name = region.name
you’re gonna get the object in 
__init__
method so based on that you can create additional resources
let me copy’n’paste real life example from one of my repos:
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class GKECluster(ComponentResource):
    def __init__(
        self,
        name: str,
        network: gcp.compute.Network,
        opts: Optional[ResourceOptions] = None,
    ):
        super().__init__("jakub-bacic:gcp:GKECluster", name, {}, opts)

        self.subnetwork = gcp.compute.Subnetwork(
            name,
            ip_cidr_range=subnetwork_cidr_block,
            network=network.name,
            secondary_ip_ranges=[
                gcp.compute.SubnetworkSecondaryIpRangeArgs(
                    range_name="pods", ip_cidr_range="10.2.0.0/16"
                ),
                gcp.compute.SubnetworkSecondaryIpRangeArgs(
                    range_name="services", ip_cidr_range="10.3.0.0/16"
                ),
            ],
            private_ip_google_access=True,
            opts=ResourceOptions(parent=self),
        )
        ...
it’s just a part but it should help with get the idea
i
ok great! Again thanks for your help, let me try to adapt to my use-case!!!!
p
basically, my 
GKECluster
component resource expects the user to pass the already existing 
gcp.compute.Network
and then it’s gonna use it to create additional resources (dedicated subnetwork for GKE and the cluster itself of course)
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gke = GKECluster(
    common.default_resource_name,
    network=common.vpc_network,
    opts=pulumi.ResourceOptions(
        provider=common.gcp_provider,
    ),
)
^ here’s how I create an instance of this resource
how you’re gonna pass the required 
network
argument is up to you (as you can see, I import it from another module called 
common
)
b
@important-magician-41327 here's a great python component resource example: https://github.com/jen20/pulumi-aws-vpc/tree/master/python
🙏 1
i
@billowy-army-68599 can you also send me some example, how to call the Vpc Class?
b
i
ahhh…sorry I only looked in the Python folder
Great Example! Thanks, relates directly what I’m currently creating
I’ve done my “homework” and I have created a simple AWS Region and Subnet ComponentResource The goal of this code is to create in a region a VPC and trigger a Site class which creates Subnets per site. I want to illustrate the problem here: Because VPC can only exist once per Region, I have to pass the Region Class to the Site, do avoid Duplicate creation. As you can see this code does not Scale because I have to create the Region Class for every region. How Can I do this better, to loop thru every region and than call it from the Site Class?
Copy code
import pulumi as pulumi
import pulumi_aws as aws


class Region(pulumi.ComponentResource):
    def __init__(self,name,region,aws_providers,opts: pulumi.ResourceOptions = None):
        self
        name: str
        super().__init__('Region', name, None, opts)

        # #Get all available AZ's in VPC
        self.available = aws.get_availability_zones(state="available",
                                                opts=pulumi.ResourceOptions(
                                                provider=aws_providers.get(region)
                                                )
        )

        #Create VPC
        self.vpc = aws.ec2.Vpc(f"vpc_sdwan_{region}", 
                            cidr_block=f"10.0.0.0/16",
                            tags={
                                "Name": f"vpc_sdwan_{region}", 
                                "Owner": "cloudPOC"},
                            opts=pulumi.ResourceOptions(
                            provider=aws_providers.get(region),
                            )
        )        


class Site(pulumi.ComponentResource):
    def __init__(self,name,site,region,aws_providers,region_eu,opts: pulumi.ResourceOptions = None):
        self
        name: str
        self.region = region,
        self.aws_providers = aws_providers
        self.region_eu = region_eu
        super().__init__('Site', name, None, opts)

        self.subnet_lan = aws.ec2.Subnet(f"subnet_lan_site{site}",
            vpc_id=region_eu.vpc.id,
            cidr_block=f"10.0.0.0/28",
            availability_zone=region_eu.available.names[0],
            tags={
                    "Name": f"subnet_lan_site{site}",
                    "Owner": "cloudPOC"
                },
            opts=pulumi.ResourceOptions(
            provider=aws_providers.get(region),
            )
        )

#create AWS providers for every region
regions=["eu-central-1","us-east-1"]
aws_providers = {
        region: aws.Provider(f"aws-provider-{region}", region=region)
        for region in regions
    }

#create Region Object for every region
region_eu = Region("Region_eu-central-1","eu-central-1",aws_providers)
region_us = Region("Region_us-east-1","us-east-1",aws_providers)

#create sites
site1 = Site("Site1",1,"eu-central-1",aws_providers,region_eu)
site2 = Site("Site2",2,"eu-central-1",aws_providers,region_eu)
site3 = Site("Site3",3,"us-east-1",aws_providers,region_eu)
site4 = Site("Site4",4,"us-east-1",aws_providers,region_eu)
p
Can you elaborate why it doesn’t scale? I don’t see any issue with the fact you’re gonna create multiple 
Region
instances if that fits the real life scenario.
I think you’d have to pinpoint the issue you’re worried about to further improve that.
One thing I can suggest (but it’s just a refactor) is to rely on implicit provider injection available in pulumi. If you specify no provider -> resource will try to use the provider assigned to the parent resource. You can write your 
Region
class like this:
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class Region(pulumi.ComponentResource):
    def __init__(self, name: str, region: str,opts: Optional[pulumi.ResourceOptions] = None):
        super().__init__('Region', name, None, opts)

        ...

        #Create VPC
        self.vpc = aws.ec2.Vpc(
            f"vpc_sdwan_{region}", 
            cidr_block="10.0.0.0/16",
            tags={
                "Name": f"vpc_sdwan_{region}", 
                "Owner": "cloudPOC",
            },
            opts=pulumi.ResourceOptions(
==>              parent=self,
            ),
        )
and you can assign the provider when creating an instance of this class:
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region_eu = Region(
    "Region_eu-central-1", 
    region="eu-central-1", 
=>  opts=pulumi.ResourceOptions(
=>      provider=aws_providers_for_this_region,
=>  ),
)
🙌 1
Benefits of that approach: • you can reuse your 
Region
component resource with default provider (in case you have a much simpler project where you don’t create providers explicitly) • assigning 
parent
gives you a nice, hierarchical view over your resources instead of flat/one-level mess (just implement the changes above and see the difference in 
pulumi preview
) BTW, the way you’re gonna assign parents is totally up to you. You can even make 
Region
a parent of 
Site
resource if that fits your infrastructure design 🙂.
i
Thanks Jakub! Great advice with the AWS providers, much cleaner. I still have a minor error, maybe you see the issue?
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import pulumi as pulumi
import pulumi_aws as aws


class Region(pulumi.ComponentResource):
    def __init__(self, name: str, region: str, opts: pulumi.ResourceOptions = None):
        super().__init__('Region', name, None, opts)

        # #Get all available AZ's in VPC
        self.available = aws.get_availability_zones(state="available",
                                                opts=pulumi.ResourceOptions(
                                                parent=self
                                                )
        )

        #Create VPC
        self.vpc = aws.ec2.Vpc(f"vpc_sdwan_{region}", 
                            cidr_block=f"10.0.0.0/16",
                            tags={
                                "Name": f"vpc_sdwan_{region}", 
                                "Owner": "cloudPOC"},
                            opts=pulumi.ResourceOptions(
                            parent=self,
                            )
        )        



class Site(pulumi.ComponentResource):
    def __init__(self,name,site,region,aws_providers,region_eu,opts: pulumi.ResourceOptions = None):
        self
        name: str
        self.region = region,
        self.aws_providers = aws_providers
        self.region_eu = region_eu
        super().__init__('Site', name, None, opts)

        self.subnet_lan = aws.ec2.Subnet(f"subnet_lan_site{site}",
            vpc_id=region_eu.vpc.id,
            cidr_block=f"10.0.0.0/28",
            availability_zone=region_eu.available.names[0],
            tags={
                    "Name": f"subnet_lan_site{site}",
                    "Owner": "cloudPOC"
                },
            opts=pulumi.ResourceOptions(
            provider=aws_providers.get(region),
            )
        )


#create Region Object for every region
region_eu = Region("Region_eu-central-1", "eu-central-1", opts= pulumi.ResourceOptions(provider="eu-central-1",))
I got this error:
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File "/home/coder/myproject/venv/lib/python3.8/site-packages/pulumi/runtime/stack.py", line 133, in __init__
        func()
      File "/home/coder/.pulumi/bin/pulumi-language-python-exec", line 106, in <lambda>
        coro = pulumi.runtime.run_in_stack(lambda: runpy.run_path(args.PROGRAM, run_name='__main__'))
      File "/usr/lib/python3.8/runpy.py", line 282, in run_path
        return _run_code(code, mod_globals, init_globals,
      File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
        exec(code, run_globals)
      File "/home/coder/myproject/./__main__.py", line 59, in <module>
        region_eu = Region("Region_eu-central-1", "eu-central-1", opts= pulumi.ResourceOptions(provider="eu-central-1",))
      File "/home/coder/myproject/./__main__.py", line 7, in __init__
        super().__init__('Region', name, None, opts)
      File "/home/coder/myproject/venv/lib/python3.8/site-packages/pulumi/resource.py", line 913, in __init__
        Resource.__init__(self, t, name, False, props, opts, remote, False)
      File "/home/coder/myproject/venv/lib/python3.8/site-packages/pulumi/resource.py", line 772, in __init__
        providers = convert_providers(opts.provider, opts.providers)
      File "/home/coder/myproject/venv/lib/python3.8/site-packages/pulumi/runtime/resource.py", line 651, in convert_providers
        return convert_providers(None, [provider])
      File "/home/coder/myproject/venv/lib/python3.8/site-packages/pulumi/runtime/resource.py", line 661, in convert_providers
        result[p.package] = p
    AttributeError: 'str' object has no attribute 'package'
    error: an unhandled error occurred: Program exited with non-zero exit code: 1
Regarding scaling, this is now the solution, I don’t need to manually create a variable per region, I will now use a dictionary instead:
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#create Region Object for every region
for region in regions:
    aws_region[region] = Region(f"Region_{region}", region, opts= pulumi.ResourceOptions(provider=region))

#create sites
site1 = Site("Site1",1,"eu-central-1",aws_region["eu-central-1"])
site2 = Site("Site2",1,"eu-central-1",aws_region["eu-central-1"])
site3 = Site("Site3",1,"eu-central-1",aws_region["us-east-1"])
site4 = Site("Site4",1,"eu-central-1",aws_region["us-east-1"])
creating a dictionary with all the unique Region objects and call it with the Site object, to avoid duplicate resource creation
p
Two things I can quickly comment: • minor thing but I have to say it: 
opts: pulumi.ResourceOptions = None
is a wrong type hint, it should be 
opts: Optional[pulumi.ResourceOptions]
(if it’s not optional, it shouldn’t be 
None
at any point) • you’re passing a 
str
value instead of provider instance in:
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region_eu = Region("Region_eu-central-1", "eu-central-1", opts= pulumi.ResourceOptions(provider="eu-central-1",))
creating a dict definitely sounds like a plan
if it’s something constant for your projects, define that in code
if it can vary from stack to stack, read these values from stack config file so you can easily edit that in one place if you need
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