I don t want to say I found a bug but today I was surprised

Question

I don t want to say I found a bug but today I was surprised by a stack update failure when I was expecting Pulumi to simply delete the resource and rebuild it So I made a VPC and some subnets but forgot to add the az I wanted to put them in so I went ahead and added the az expecting the resource to destroy and rebuild The resource however failed in my pipeline saying that the network conflicted with an existing resource instead of simply deleting the resource and building it back

little-cartoon-10569 · Answer

Is the AZ you added the same as the default AZ If the AZ isn t actually changing despite the property changing then this might be expected behaviour Don t know never done it

purple-train-14007 · Answer

Nope different AZ The default was USW2C

purple-train-14007 · Answer

But the issue is it failed to adjust the resource rather than destroy and remake it acted as if it didn t know anything about the resource I pulled open the state file and also verified that it was tracking the subnets and VPC too

little-cartoon-10569 · Answer

It s not supposed to adjust the resource According to the docs changing the AZ is supposed to destroy and recreate it

little-cartoon-10569 · Answer

Did you also change the name of the resource at the same time

purple-train-14007 · Answer

That s what I meant

purple-train-14007 · Answer

But no I didn t change the name Simply added the az

little-cartoon-10569 · Answer

Have you set a name for any of the resources Maybe it was doing a delete before create which is the default and the created resource was conflicting with the old version of the same resource

purple-train-14007 · Answer

Nope all the names were the same

little-cartoon-10569 · Answer

Yes that s what I mean If you use the `name` property then there will be a conflict and it will fail

little-cartoon-10569 · Answer

You have to either omit the `name` or use `namePrefix`

purple-train-14007 · Answer

Ah no name is a string

little-cartoon-10569 · Answer

Yes the point is you re supplying the name rather than letting Pulumi make up a random one

purple-train-14007 · Answer

Ohhhhh

little-cartoon-10569 · Answer

This will cause what you re seeing

purple-train-14007 · Answer

So setting the resource name causes it not to delete

little-cartoon-10569 · Answer

No not necessarily

purple-train-14007 · Answer

For instance if I same VPCName = blah vpc

little-cartoon-10569 · Answer

You can also set the `deleteBeforeReplace` opt and it ll delete the resource first which prevent the name clash

purple-train-14007 · Answer

Ah ok I ll try that

little-cartoon-10569 · Answer

Generally the best thing is to not specify a name

little-cartoon-10569 · Answer

Pulumi will generate a name for you from the Pulumi name 1st arg and a random suffix

purple-train-14007 · Answer

But I want my stuff to have names in the AWS console otherwise I can t tell them apart

little-cartoon-10569 · Answer

You will get meaningful names but with a suffix

little-cartoon-10569 · Answer

You will be able to tell them apart

purple-train-14007 · Answer

Ok

purple-train-14007 · Answer

That s odd lol

little-cartoon-10569 · Answer

Note that some resources e g EC2 instances have special ways to name them For EC2 resources it s the `name` tag

little-cartoon-10569 · Answer

What s odd That Pulumi creates names

purple-train-14007 · Answer

Yeah

little-cartoon-10569 · Answer

Pulumi does it in order to avoid this problem

purple-train-14007 · Answer

But the names are unique

little-cartoon-10569 · Answer

AWS doesn t allow 2 resources of the same type with the same name

purple-train-14007 · Answer

Correct

little-cartoon-10569 · Answer

When you replace the resource Pulumi creates a new resource before deleting the old one Hence name clash

purple-train-14007 · Answer

But AWS CDK knows to delete the resource regardless of name

little-cartoon-10569 · Answer

You think of it as 1 resource but in AWS there s the old one and the new one

little-cartoon-10569 · Answer

So does Pulumi

little-cartoon-10569 · Answer

Pulumi has a default policy of not deleting on replace until the replacement resource is created

purple-train-14007 · Answer

Ok so I will not name the things then

purple-train-14007 · Answer

I will take it out of my component resource

little-cartoon-10569 · Answer

Yes If you do that then the created resource will have a different name than the old version of it And there will be no name conflict

purple-train-14007 · Answer

Thanks for explaining this I appreciate it innocent

quaint-hydrogen-7228 · Answer

AWS CDK will also have issues in some cases if you set the name explicitly if the resources need to be replaced due to what the underlying Cloudformation support The general rule there is the same do not set names explicitly if you do not have to