(aws-cdk): (Unable to create nested stack with > 500 resources)

[benliger1987]

Describe the bug

I am using a nested stack inside of a regular stack to get past the resource limit of 500 in a stack. After moving 413 resources to a nested stack I receive the following error on deployment:

[Info at /dev/Frontend/LambdasApi-dev] Number of resources: 413 is approaching allowed maximum of 500

Please note that /dev/Frontend/LambdasApi-dev refers to my nested stack.

As per the resource limits stated in this table here:

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cloudformation-limits.html

Nested stacks should have a max resource limit of 2500, not 500 hence the bug.

The part of the repository that gives this warning is here, the nested stack class simply extends the stack with some modifications, resource limit is not one of those modifications:

aws-cdk/packages/aws-cdk-lib/core/lib/stack.ts

Line 1086 in 8e42fe6

Annotations.of(this).addInfo(`Number of resources: ${numberOfResources} is approaching allowed maximum of ${this.maxResources}`);

Expected Behavior

I would expect to be able to create 2500 resources in a nested stack as per the documentation here:

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cloudformation-limits.html

Current Behavior

I receive a warning message if I am close to going over 500 resources in a nested stack and presumably an error if I do go over 500

Reproduction Steps

1. Create a stack
2. Create a nested stack within the first stack
3. Populate the nested stack with >400 resources to receive the warning and >500 to presumably get an error

Possible Solution

Implement custom resource limits for Nested Stacks

Additional Information/Context

No response

CDK CLI Version

2.111.0

Framework Version

No response

Node.js Version

18.16.0

OS

Ubuntu

Language

TypeScript

Language Version

No response

Other information

No response

[pahud]

We probably should fix the logic here

https://github.com/aws/aws-cdk/blame/1a586f2935764bce56c4658165291ffacde7e0b1/packages/aws-cdk-lib/core/lib/stack.ts#L39

https://github.com/aws/aws-cdk/blame/1a586f2935764bce56c4658165291ffacde7e0b1/packages/aws-cdk-lib/core/lib/stack.ts#L1445-L1448

Before that, I guess you can unblock it by setting the context variable described here:

https://github.com/aws/aws-cdk/blob/1a586f2935764bce56c4658165291ffacde7e0b1/packages/aws-cdk-lib/README.md?plain=1#L1240C13-L1240C13

[scanlonp]

Hi @benliger1987, in my mind, there is a difference between a nested stack and a child stack. The nested stack is the entire structure, which is made up of parent and child stacks, similar to a tree vs nodes. It does not seem plausible that just because a single stack is a child stack, that its resource limit jumps from 500 to 2500. I believe the 2500 limit is the sum of all the child stack's resources in the entire nested structure. (Otherwise this somewhat unbounds the resource limit.)

Was this your understanding too? If so this may well be a bug.

If not, your solution could be to split the stack that is approaching the individual stack limit into smaller stacks.

In any case, the documentation is ambiguous and should be clarified.

[benliger1987]

Im not sure what you're referring to by child stacks? There are only regular stacks and nested stacks no?

[scanlonp]

My mental model does not have quite the same terminology as the documentation, apologies. Going off this page (https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-nested-stacks.html), I see that what I was calling "child stacks" are "nested stacks". You are correct.

After re-reading both documentation pages, I saw that the Resources row in the Quotas column states Maximum number of resources that you can declare in your AWS CloudFormation template is 500 resources. This says to me that in any one stack template, 500 resources is the hard cap.
However, nested stacks can operate on (create, update, or delete) up to 2500 resources.

So I think the error message you are getting is correct. A nested stack could create up to 2500 resources per operation, but they will not be in a single template.

[benliger1987]

I kind of see where you're getting at but not sure I fully follow your rationale. Would someone from AWS perhaps be able to weigh in here?

[scanlonp]

I am at AWS! But I can see if someone with cloudformation specific domain knowledge has any context. However, I see the 500 resource limit per template as clear cut.

[azhong-git]

Following the unblock advice from #28186 (comment) to set "@aws-cdk/core:stackResourceLimit": 0 in cdk.json.

However I am seeing the following error. What is the actual maximum number of resources?

 [ValidationError]: Template format error: Number of resources, 502, is greater than maximum allowed, 500

[TheRealAmazonKendra]

@scanlonp's assessment is correct here. Each stack, nested or otherwise, can only have up to 500 resources each. If you are performing some operation on the entire set of nested stacks within your stack hierarchy, you can perform that operation on up to 2500 resources at a time.

So, you could have five stacks with 500 resources each in your stack hierarchy, or any other combination that is within that limit. See https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-nested-stacks.html for more details.

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