User-Defined Types has increased Template above size limits [hit 4 MB limit]

[brwilkinson]

Bicep version
Bicep CLI version 0.36.177 (09988bb)

Describe the bug
I just spent two days converting a Bicep project that I have to use User-Defined Types. The overall experience was extremely positive, and I was able to do the conversion in two full days of work.

I used the -whatif deployment and linting to work through all issues and ensure i had coverage of using the types etc.

At the end of the day, I have run into an issue with my main.bicep template size.

• The compiled template is now 5MB
  • This exceeds the 4MB limit
  • template-limits

Message=The request content size exceeds the maximum size of 4 MB

If i switch to the branch without user-defined types and build the template it shows

• 43324 lines and 3.4 MB

If i switch to the new branch with user-defined types and build the template it shows

• 122177 lines and 5.5 MB (I already commented out many modules to only the ones I am using in production).

The thing is that this top-level template only has Modules in it and no Resources.

This is not the actual template, however it's nearly identical

• https://github.com/brwilkinson/AzureDeploymentFramework/blob/main/ADF/bicep/01-ALL-RG.bicep

As shown below, only deployments in exist in this top level... so the issue here is not max deployment size, where I can break it down into smaller nested deployment. I am hitting the max template size overall.

module dp_Deployment_NSG 'NSG.bicep' = if (bool(Stage.NSG)) {
  name: 'dp${Deployment}-NSG'
  params: {
    // move these to Splatting later
    DeploymentID: DeploymentID
    DeploymentInfo: DeploymentInfo
    Environment: Environment
    Extensions: Extensions
    Global: Global
    Prefix: Prefix
    Stage: Stage
  }
  dependsOn: [
    dp_Deployment_OMS
  ]
}

Today is day three of this conversion, so I am at the very beginning, and I am still feeling out the custom type definitions. I actually have not got very granular on my types yet. However, I already hit a blocker.

• I expect the size might? double again once I get more granular on my types, which is what I want/was planning to continue to do.

I am sure I can find some ways to review the 122177 lines are json ARM templates and look for some ways to figure out how to make it more efficient. ✅

• Any guidance or direction would be helpful. ❔

I will leave it at that for now. I will update if/once I find anything useful..

[brwilkinson]

I was wondering @SydneyhSmith is this something where a solution is already in planning?

I assume there is no bug, however there might be some way to work around the limit? I guess in short, is there anywhere I can understand more on what the category "scopes" references?

I'm interested to continue with my exploration into user-defined types, so interested to determine where I can spend my efforts, without getting blocked.

Now that I can define custom types, then reference the type definitions in a bicep file, then reference with 'using' to the Bicep file, in my param file, I'll likely default to bicepparam format for all of my data files and projects (not just Bicep ARM deploys) ... Then compile it to json at run time. This way I get the intellisense and schema validation for parameters across many different project types. I won't ever deploy the Bicep, just use it for schema and data inputs for other projects (to replace anywhere I use json today or psd1 today).

• so I have a short term path forward, however obviously Bicep deploys are the main use case that I would like to fully leverage the UDT, once this issue gets some kind of solution.

• I know alot of demos for Bicep are broken out into small individual deploys, however I am into mono repo large single projects, since it's easier to maintain, plus are portable across deployment tools/platforms. These have a single point of entry, with feature flags for what actually gets deployed, which leads to the large template size. Hence this current issue.

TL;DR Looking forward to hearing more on scopes.?!

[SydneyhSmith]

@brwilkinson we don't have a committed plan at this point but are doing a lot of brainstorming on how we could improve a variety of "issues" folks hit in Bicep around scoping rules, module representation and size limitations... we want to make sure to include your scenario as an example thinking through this category of work

[brwilkinson]

Thank you for the context @SydneyhSmith this is helpful.

[brwilkinson]

@anthony-c-martin is there anything I could do with local deploy to pre-compile the Bicep + Bicep params locally to get around the template size limit?

I was thinking maybe it could build down to the final ARM template, with all parameters and Types already resolved to values, then pass that to ARM?

[brwilkinson]

• JsonCTemplatePolicy causes template size inflation leading to 4MB limit errors azure-cli#31952