Cloudfront distribution fills in 0'd defaultTtl / minTtl / maxTtl if not set

[mivtachyahu]

What happened?

I would like my defaultCacheBehaviour to use the "Use origin cache headers" setting.
In terraform I achieve this by not setting defaultTtl, minTtl or maxTtl.

If I do this in pulumi, it fills them in with 0's instead. There appears to be no option to "Use origin cache headers"

Expected Behavior

Not setting a defaultTtl, minTtl and maxTtl should use the "Use origin cache headers" behaviour instead of filling these in with 0's.

Steps to reproduce

1. Create a cloudfront distribution with a forwardedValues set for the defaultCacheBehavior
2. Do not set a defaultTtl, minTtl, or maxTtl

Output of pulumi about

CLI
Version 3.76.1
Go Version go1.20.6
Go Compiler gc

Plugins
NAME VERSION
aws 5.42.0
nodejs unknown

Host
OS darwin
Version 13.4
Arch arm64

This project is written in nodejs: executable='/Users/matthewbrown/.nvm/versions/node/v18.15.0/bin/node' version='v18.15.0'

Additional context

No response

Contributing

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[aq17]

Hi @mivtachyahu , could you provider an example or reproduction of your program? Also, what language are you using – it looks like 0's should be the correct default value for these attributes in each language regardless

[mivtachyahu]

Hi @aq17 - I'm using TypeScript.
Here's an example piece of code with minTtl / maxTtl / defaultTtl values unset:

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

const bucket = new aws.s3.Bucket("myBucket");

const distributionArgs: aws.cloudfront.DistributionArgs = {
    enabled: true,
    origins: [{
        domainName: bucket.bucketRegionalDomainName,
        originId: bucket.arn,
    }],
    defaultCacheBehavior: {
        targetOriginId: bucket.arn,
        viewerProtocolPolicy: "redirect-to-https",
        allowedMethods: ["GET", "HEAD", "OPTIONS"],
        cachedMethods: ["GET", "HEAD", "OPTIONS"],
        forwardedValues: {
            cookies: {
                forward: 'none',           
            },
            queryString: false,
        },
    },
    restrictions: {
        geoRestriction: {
            restrictionType: "none",
        },
    },
    viewerCertificate: {
        cloudfrontDefaultCertificate: true,
    }
};



const cdn = new aws.cloudfront.Distribution("cdn", distributionArgs);

export const cdnUrl = cdn.domainName;

Which yields this config in the aws console:

On a whim I decided to update the example above with the default values for maxTtl / defaultTtl from reading the aws-sdk code and a 0 of minTtl:

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

const bucket = new aws.s3.Bucket("myBucket");

const distributionArgs: aws.cloudfront.DistributionArgs = {
    enabled: true,
    origins: [{
        domainName: bucket.bucketRegionalDomainName,
        originId: bucket.arn,
    }],

    defaultCacheBehavior: {
        targetOriginId: bucket.arn,
        viewerProtocolPolicy: "redirect-to-https",
        allowedMethods: ["GET", "HEAD", "OPTIONS"],
        cachedMethods: ["GET", "HEAD", "OPTIONS"],
        forwardedValues: {
            cookies: {
                forward: 'none',           
            },
            queryString: false,
        },
        minTtl: 0,
        defaultTtl: 86400,
        maxTtl: 31536000,
    },
    restrictions: {
        geoRestriction: {
            restrictionType: "none",
        },
    },
    viewerCertificate: {
        cloudfrontDefaultCertificate: true,
    }
};



const cdn = new aws.cloudfront.Distribution("cdn", distributionArgs);

// Export the CloudFront distribution domain name
export const cdnUrl = cdn.domainName;

And it turns out this does yield the config setting that I was after in AWS

But that behaviour isn't documented anywhere, and I assume it's probably the bug that they probably should have the default values from the aws-sdk if they're not set instead of 0s?

[mikhailshilkov]

I believe this is tracked upstream in hashicorp/terraform-provider-aws#19382 which was recently closed with a doc change:

To achieve the setting of 'Use origin cache headers' without a linked cache policy, use the following TTL values: min_ttl = 0, max_ttl = 31536000, default_ttl = 86400. See this issue for additional context.

Since the upstream decided not to fix this, I think I'll go ahead and close this issue by design as well.