3

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront'; import as origins from 'aws-cdk-lib/aws-cloudfront-origins'; import as s3 from 'aws-cdk-lib/aws-s3';

interface CloudFrontStackProps extends cdk.StackProps { bucket: s3.IBucket; }

export class CloudFrontStack extends cdk.Stack { public readonly distribution: cloudfront.Distribution;

constructor(scope: cdk.App, id: string, props: CloudFrontStackProps) { super(scope, id, props);

// Create CloudFront distribution without OAC
this.distribution = new cloudfront.Distribution(this, 'MyDistribution', {
  defaultBehavior: {
    origin: new origins.S3Origin(props.bucket),
    viewerProtocolPolicy: cloudfront.ViewerProtocolPolicy.REDIRECT_TO_HTTPS,
  },
});

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface ModifyCloudFrontStackProps extends cdk.StackProps { distributionId: string; }

export class ModifyCloudFrontStack extends cdk.Stack { constructor(scope: cdk.App, id: string, props: ModifyCloudFrontStackProps) { super(scope, id, props);

// Create an Origin Access Control
const oac = new cloudfront.CfnOriginAccessControl(this, 'OAC', {
  originAccessControlConfig: {
    name: 'MyOAC',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always',
    signingProtocol: 'sigv4',
  },
});

// Fetch the CloudFront distribution by ID
const distribution = cloudfront.CfnDistribution.fromDistributionId(this, 'Distribution', props.distributionId);

// Add the OAC to the distribution
distribution.node.addOverride('Properties.DistributionConfig.Origins.0.OriginAccessControlId', oac.ref);

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface ModifyCloudFrontStackProps extends cdk.StackProps { distributionId: string; }

export class ModifyCloudFrontStack extends cdk.Stack { constructor(scope: cdk.App, id: string, props: ModifyCloudFrontStackProps) { super(scope, id, props);

// Create an Origin Access Control
const oac = new cloudfront.CfnOriginAccessControl(this, 'OAC', {
  originAccessControlConfig: {
    name: 'MyOAC',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always',
    signingProtocol: 'sigv4',
  },
});

// Fetch the CloudFront distribution by ID
const distribution = cloudfront.CfnDistribution.fromDistributionId(this, 'Distribution', props.distributionId);

// Add the OAC to the distribution
distribution.node.addOverride('Properties.DistributionConfig.Origins.0.OriginAccessControlId', oac.ref);

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface ModifyCloudFrontStackProps extends cdk.StackProps { distributionId: string; }

export class ModifyCloudFrontStack extends cdk.Stack { constructor(scope: cdk.App, id: string, props: ModifyCloudFrontStackProps) { super(scope, id, props);

// Create an Origin Access Control
const oac = new cloudfront.CfnOriginAccessControl(this, 'OAC', {
  originAccessControlConfig: {
    name: 'MyOAC',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always',
    signingProtocol: 'sigv4',
  },
});

// Fetch the CloudFront distribution by ID
const distribution = cloudfront.CfnDistribution.fromDistributionId(this, 'Distribution', props.distributionId);

// Add the OAC to the distribution
distribution.node.addOverride('Properties.DistributionConfig.Origins.0.OriginAccessControlId', oac.ref);

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface Stack3Props extends cdk.StackProps { distribution: cloudfront.IDistribution; // Accepting the distribution object }

export class Stack3 extends cdk.Stack { constructor(scope: cdk.App, id: string, props: Stack3Props) { super(scope, id, props);

// Step 1: Create the Origin Access Control (OAC)
const oac = new cloudfront.CfnOriginAccessControl(this, 'MyOAC', {
  originAccessControlConfig: {
    name: 'MyOriginAccessControl',
    description: 'OAC for S3 bucket origin',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always', // Always sign requests to the origin
    signingProtocol: 'sigv4',  // Use SigV4 signing
  },
});

// Step 2: Modify the distribution's origin settings
const cfnDistribution = props.distribution.node.defaultChild as cloudfront.CfnDistribution;

// Find the origin to modify (ensure the origin ID matches the S3 bucket origin)
const s3Origin = cfnDistribution.distributionConfig.origins?.find((origin) =>
  origin.id === 'S3Origin' // Replace 'S3Origin' with the actual origin ID from Stack 2
);

if (s3Origin) {
  // Attach the OAC to the origin
  s3Origin.originAccessControlId = oac.attrId;

  // Optionally, remove any public access settings or update other properties
  delete s3Origin.customOriginConfig; // If applicable
} else {
  throw new Error('S3 origin not found in the distribution');
}

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface Stack3Props extends cdk.StackProps { distribution: cloudfront.IDistribution; // Accept the Distribution object }

export class Stack3 extends cdk.Stack { constructor(scope: cdk.App, id: string, props: Stack3Props) { super(scope, id, props);

// Step 1: Create the Origin Access Control (OAC)
const oac = new cloudfront.CfnOriginAccessControl(this, 'MyOAC', {
  originAccessControlConfig: {
    name: 'MyOriginAccessControl',
    description: 'OAC for S3 bucket origin',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always',
    signingProtocol: 'sigv4',
  },
});

// Step 2: Access the underlying CloudFormation resource
const cfnDistribution = props.distribution.node.defaultChild as cloudfront.CfnDistribution;

// Step 3: Modify the origins in the DistributionConfig
if (cfnDistribution.distributionConfig.origins) {
  const s3Origin = cfnDistribution.distributionConfig.origins.find(
    (origin: any) => origin.id === 'S3Origin' // Replace 'S3Origin' with the correct ID
  );

  if (s3Origin) {
    // Attach the OAC to the origin
    s3Origin.originAccessControlId = oac.attrId;
  } else {
    throw new Error('S3 origin not found in the distribution');
  }
} else {
  throw new Error('Origins property is undefined in DistributionConfig');
}

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface Stack3Props extends cdk.StackProps { distribution: cloudfront.IDistribution; // Accept the Distribution object }

export class Stack3 extends cdk.Stack { constructor(scope: cdk.App, id: string, props: Stack3Props) { super(scope, id, props);

// Step 1: Create the Origin Access Control (OAC)
const oac = new cloudfront.CfnOriginAccessControl(this, 'MyOAC', {
  originAccessControlConfig: {
    name: 'MyOriginAccessControl',
    description: 'OAC for S3 bucket origin',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always',
    signingProtocol: 'sigv4',
  },
});

// Step 2: Access the underlying CloudFormation resource
const cfnDistribution = props.distribution.node.defaultChild as cloudfront.CfnDistribution;

// Step 3: Modify the origins in the DistributionConfig
if (cfnDistribution.distributionConfig.origins) {
  const s3Origin = cfnDistribution.distributionConfig.origins.find(
    (origin: any) => origin.id === 'S3Origin' // Replace 'S3Origin' with the correct ID
  );

  if (s3Origin) {
    // Attach the OAC to the origin
    s3Origin.originAccessControlId = oac.attrId;
  } else {
    throw new Error('S3 origin not found in the distribution');
  }
} else {
  throw new Error('Origins property is undefined in DistributionConfig');
}

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface S3OriginStackProps extends cdk.StackProps { cloudFrontDistribution: cloudfront.IDistribution; }

export class S3OriginStack extends cdk.Stack { constructor(scope: cdk.App, id: string, props: S3OriginStackProps) { super(scope, id, props);

// Step 1: Create the Origin Access Control (OAC)
const oac = new cloudfront.CfnOriginAccessControl(this, 'MyOAC', {
  originAccessControlConfig: {
    name: 'MyOriginAccessControl',
    description: 'OAC for S3 bucket origin',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always',
    signingProtocol: 'sigv4',
  },
});

// Step 2: Access the low-level CloudFormation resource (CfnDistribution)
const cfnDistribution = props.cloudFrontDistribution.node.defaultChild as cloudfront.CfnDistribution;

// Step 3: Use CloudFormation overrides to modify the origin
this.addOverrideToOrigin(cfnDistribution, oac.attrId);

}

private addOverrideToOrigin(cfnDistribution: cloudfront.CfnDistribution, oacId: string) { // Add a CloudFormation override for the origins property this.node.addDependency(cfnDistribution); // Ensure this stack depends on the distribution

cfnDistribution.addOverride('Properties.DistributionConfig.Origins', [
  {
    Id: 'S3Origin', // Replace with the actual Origin ID
    DomainName: '<your-s3-bucket-name>.s3.amazonaws.com',
    S3OriginConfig: {
      OriginAccessControlId: oacId,
    },
  },
]);

} }

[DAMSCROW]

import as cdk from 'aws-cdk-lib'; import as cloudfront from 'aws-cdk-lib/aws-cloudfront';

interface S3OriginStackProps extends cdk.StackProps { cloudFrontDistribution: cloudfront.IDistribution; }

export class S3OriginStack extends cdk.Stack { constructor(scope: cdk.App, id: string, props: S3OriginStackProps) { super(scope, id, props);

// Step 1: Create the Origin Access Control (OAC)
const oac = new cloudfront.CfnOriginAccessControl(this, 'MyOAC', {
  originAccessControlConfig: {
    name: 'MyOriginAccessControl',
    description: 'OAC for S3 bucket origin',
    originAccessControlOriginType: 's3',
    signingBehavior: 'always',
    signingProtocol: 'sigv4',
  },
});

// Step 2: Access the low-level CloudFormation resource (CfnDistribution)
const cfnDistribution = props.cloudFrontDistribution.node.defaultChild as cloudfront.CfnDistribution;

// Step 3: Use CloudFormation overrides to modify the origin
this.addOverrideToOrigin(cfnDistribution, oac.attrId);

}

private addOverrideToOrigin(cfnDistribution: cloudfront.CfnDistribution, oacId: string) { // Add a CloudFormation override for the origins property this.node.addDependency(cfnDistribution); // Ensure this stack depends on the distribution

cfnDistribution.addOverride('Properties.DistributionConfig.Origins', [
  {
    Id: 'S3Origin', // Replace with the actual Origin ID
    DomainName: '<your-s3-bucket-name>.s3.amazonaws.com',
    S3OriginConfig: {
      OriginAccessControlId: oacId,
    },
  },
]);

} }

[DAMSCROW]

To create clear diagrammatic representations of the three solutions—highlighting where cyclic dependencies occur in the first two solutions and how the third solution avoids it—you can follow these detailed steps. I'll walk you through each diagram and explain how to address the cyclic dependency issue.

Solution 1: Two-stack Approach (S3 Bucket and Global CloudFront Stack)

Objective: This is the initial approach where the S3 bucket is created first, and then the CloudFront distribution is created. The goal is to set the S3 origin using an OAC in the CloudFront stack.

Steps to Draw the Diagram:

1. Stack 1 (S3 Bucket Stack):

Start with a box labeled S3 Bucket Stack.

Inside, show an S3 bucket resource that is created.

2. Stack 2 (Global CloudFront Stack):

Draw a second box labeled Global CloudFront Stack.

Inside this, show a CloudFront Distribution resource, with a link to the S3 Bucket in Stack 1 as the origin (use arrows to indicate this relationship).

3. OAC Creation:

Inside the Global CloudFront Stack, create a small box or label that indicates the creation of the Origin Access Control (OAC) linked to the CloudFront distribution.

4. Cyclic Dependency Issue:

The cyclic dependency occurs here.

CloudFront Distribution needs the OAC to be created for the S3 bucket as part of the origin configuration. However, to configure the OAC, the S3 bucket policy needs to be updated (with access for CloudFront), and this can't happen until the CloudFront distribution exists (so it can be linked to the S3 bucket).

Draw a feedback loop from the CloudFront Distribution back to the S3 bucket and show how the S3 bucket policy needs the CloudFront Distribution ARN to update, causing the cyclic dependency.

5. Explanation:

Cyclic dependency occurs because the S3 bucket's policy cannot be updated until the CloudFront distribution is created, but the CloudFront distribution cannot be set without updating the bucket's policy with the OAC configuration.

This creates a loop where both stacks depend on each other in a circular manner.

Sources explaining cyclic dependency:

AWS documentation on cyclic dependencies and resource ordering.

---

Solution 2: Three-stack Approach (S3 Bucket, Global CloudFront, and S3 Origin Stack)

Objective: This approach splits the process into three stacks, creating the CloudFront distribution first with the default S3 origin, then adjusting the origin settings in a third stack.

Steps to Draw the Diagram:

1. Stack 1 (S3 Bucket Stack):

Same as before, start with the S3 bucket creation.

2. Stack 2 (Global CloudFront Stack):

Create the CloudFront distribution with the S3 bucket as the origin.

OAC creation is still inside the CloudFront Stack, but at this point, the S3 origin is still set to the default (public access).

3. Stack 3 (S3 Origin Stack):

Add a new box labeled S3 Origin Stack.

Show the CloudFront distribution from Stack 2 being imported here.

In this stack, OAC is applied to the CloudFront distribution.

Bucket Policy Update: After the OAC is set, the bucket's policy is updated to reflect the correct permissions for the CloudFront distribution.

4. Cyclic Dependency Issue:

The cycle still exists between the stacks.

Stack 1 creates the bucket, but Stack 2 cannot set the OAC properly until Stack 3 has been executed, and Stack 3 cannot run until Stack 2 has completed.

5. Explanation:

The issue here is that the process involves multiple stacks that depend on each other. Although you’ve broken the process into three parts, the bucket policy still can’t be updated until the distribution is complete, causing the cyclic dependency between the stacks.

Sources explaining multi-stack dependencies:

AWS documentation and forums on using multiple stacks for CloudFront and S3 resource management.

---

Solution 3: External Lambda Solution (No Cyclic Dependency)

Objective: This solution introduces an external Lambda function to handle the bucket policy update after the CloudFront distribution is created.

Steps to Draw the Diagram:

1. Stack 1 (S3 Bucket Stack):

Same as before, the S3 bucket is created.

2. Stack 2 (Global CloudFront Stack):

CloudFront distribution is created with S3 bucket as the origin and OAC configured immediately.

3. Lambda Trigger (External Lambda):

Create a box labeled External Lambda.

Show that the Lambda function is triggered after the CloudFront distribution is created.

The Lambda will update the S3 bucket policy with the required permissions for the CloudFront distribution to work with OAC.

4. No Cyclic Dependency:

The Lambda function runs after the CloudFront distribution is fully created, allowing the S3 bucket policy to be updated independently.

This breaks the cycle because the Lambda can be invoked separately from the CloudFront creation, and thus no interdependent resources are waiting for each other.

5. Explanation:

The external Lambda function is the key to avoiding the cyclic dependency. It updates the bucket policy after the CloudFront distribution has been created, eliminating the circular reference between resources.

The update is done after the resources are independently created, so no stack is waiting for the other to finish before proceeding.

Sources explaining using Lambda to avoid circular dependencies:

AWS CloudFormation Custom Resources.

AWS Lambda event-driven architecture to resolve cyclic dependencies.

---

Step-by-Step Summary to Draw the Diagrams:

1. Solution 1 Diagram (Two-stack):

Draw two boxes: S3 Bucket Stack and Global CloudFront Stack.

Add arrows showing the dependency between them, with a circular feedback loop.

Label the issue clearly: "Cyclic Dependency" due to CloudFront needing the S3 bucket policy update (with OAC).

2. Solution 2 Diagram (Three-stack):

Draw three boxes: S3 Bucket Stack, Global CloudFront Stack, and S3 Origin Stack.

Add arrows to show dependencies between the stacks, with a feedback loop.

Label the issue: "Cyclic Dependency" between stacks due to the bucket policy needing to be updated after the distribution is created.

3. Solution 3 Diagram (Lambda-based):

Draw the same three boxes as in Solution 2.

Add an External Lambda function triggered after the CloudFront distribution.

Show that the Lambda updates the S3 bucket policy without causing cyclic dependency.

Label the solution: "No Cyclic Dependency" due to external Lambda handling the update independently.

By following these steps and using this approach, you can clearly illustrate the problem and solution to your technical architect. The diagrams will help explain the issue in a structured way, supported by existing solutions from AWS and the broader community.

[DAMSCROW]

To create clear diagrammatic representations of the three solutions—highlighting where cyclic dependencies occur in the first two solutions and how the third solution avoids it—you can follow these detailed steps. I'll walk you through each diagram and explain how to address the cyclic dependency issue.

Solution 1: Two-stack Approach (S3 Bucket and Global CloudFront Stack)

Objective: This is the initial approach where the S3 bucket is created first, and then the CloudFront distribution is created. The goal is to set the S3 origin using an OAC in the CloudFront stack.

Steps to Draw the Diagram:

1. Stack 1 (S3 Bucket Stack):

Start with a box labeled S3 Bucket Stack.

Inside, show an S3 bucket resource that is created.

2. Stack 2 (Global CloudFront Stack):

Draw a second box labeled Global CloudFront Stack.

Inside this, show a CloudFront Distribution resource, with a link to the S3 Bucket in Stack 1 as the origin (use arrows to indicate this relationship).

3. OAC Creation:

Inside the Global CloudFront Stack, create a small box or label that indicates the creation of the Origin Access Control (OAC) linked to the CloudFront distribution.

4. Cyclic Dependency Issue:

The cyclic dependency occurs here.

CloudFront Distribution needs the OAC to be created for the S3 bucket as part of the origin configuration. However, to configure the OAC, the S3 bucket policy needs to be updated (with access for CloudFront), and this can't happen until the CloudFront distribution exists (so it can be linked to the S3 bucket).

Draw a feedback loop from the CloudFront Distribution back to the S3 bucket and show how the S3 bucket policy needs the CloudFront Distribution ARN to update, causing the cyclic dependency.

5. Explanation:

Cyclic dependency occurs because the S3 bucket's policy cannot be updated until the CloudFront distribution is created, but the CloudFront distribution cannot be set without updating the bucket's policy with the OAC configuration.

This creates a loop where both stacks depend on each other in a circular manner.

Sources explaining cyclic dependency:

AWS documentation on cyclic dependencies and resource ordering.

---

Solution 2: Three-stack Approach (S3 Bucket, Global CloudFront, and S3 Origin Stack)

Objective: This approach splits the process into three stacks, creating the CloudFront distribution first with the default S3 origin, then adjusting the origin settings in a third stack.

Steps to Draw the Diagram:

1. Stack 1 (S3 Bucket Stack):

Same as before, start with the S3 bucket creation.

2. Stack 2 (Global CloudFront Stack):

Create the CloudFront distribution with the S3 bucket as the origin.

OAC creation is still inside the CloudFront Stack, but at this point, the S3 origin is still set to the default (public access).

3. Stack 3 (S3 Origin Stack):

Add a new box labeled S3 Origin Stack.

Show the CloudFront distribution from Stack 2 being imported here.

In this stack, OAC is applied to the CloudFront distribution.

Bucket Policy Update: After the OAC is set, the bucket's policy is updated to reflect the correct permissions for the CloudFront distribution.

4. Cyclic Dependency Issue:

The cycle still exists between the stacks.

Stack 1 creates the bucket, but Stack 2 cannot set the OAC properly until Stack 3 has been executed, and Stack 3 cannot run until Stack 2 has completed.

5. Explanation:

The issue here is that the process involves multiple stacks that depend on each other. Although you’ve broken the process into three parts, the bucket policy still can’t be updated until the distribution is complete, causing the cyclic dependency between the stacks.

Sources explaining multi-stack dependencies:

AWS documentation and forums on using multiple stacks for CloudFront and S3 resource management.

---

Solution 3: External Lambda Solution (No Cyclic Dependency)

Objective: This solution introduces an external Lambda function to handle the bucket policy update after the CloudFront distribution is created.

Steps to Draw the Diagram:

1. Stack 1 (S3 Bucket Stack):

Same as before, the S3 bucket is created.

2. Stack 2 (Global CloudFront Stack):

CloudFront distribution is created with S3 bucket as the origin and OAC configured immediately.

3. Lambda Trigger (External Lambda):

Create a box labeled External Lambda.

Show that the Lambda function is triggered after the CloudFront distribution is created.

The Lambda will update the S3 bucket policy with the required permissions for the CloudFront distribution to work with OAC.

4. No Cyclic Dependency:

The Lambda function runs after the CloudFront distribution is fully created, allowing the S3 bucket policy to be updated independently.

This breaks the cycle because the Lambda can be invoked separately from the CloudFront creation, and thus no interdependent resources are waiting for each other.

5. Explanation:

The external Lambda function is the key to avoiding the cyclic dependency. It updates the bucket policy after the CloudFront distribution has been created, eliminating the circular reference between resources.

The update is done after the resources are independently created, so no stack is waiting for the other to finish before proceeding.

Sources explaining using Lambda to avoid circular dependencies:

AWS CloudFormation Custom Resources.

AWS Lambda event-driven architecture to resolve cyclic dependencies.

---

Step-by-Step Summary to Draw the Diagrams:

1. Solution 1 Diagram (Two-stack):

Draw two boxes: S3 Bucket Stack and Global CloudFront Stack.

Add arrows showing the dependency between them, with a circular feedback loop.

Label the issue clearly: "Cyclic Dependency" due to CloudFront needing the S3 bucket policy update (with OAC).

2. Solution 2 Diagram (Three-stack):

Draw three boxes: S3 Bucket Stack, Global CloudFront Stack, and S3 Origin Stack.

Add arrows to show dependencies between the stacks, with a feedback loop.

Label the issue: "Cyclic Dependency" between stacks due to the bucket policy needing to be updated after the distribution is created.

3. Solution 3 Diagram (Lambda-based):

Draw the same three boxes as in Solution 2.

Add an External Lambda function triggered after the CloudFront distribution.

Show that the Lambda updates the S3 bucket policy without causing cyclic dependency.

Label the solution: "No Cyclic Dependency" due to external Lambda handling the update independently.

By following these steps and using this approach, you can clearly illustrate the problem and solution to your technical architect. The diagrams will help explain the issue in a structured way, supported by existing solutions from AWS and the broader community.

[DAMSCROW]

Let’s break this down step by step in a very simple way:

---

The Initial Setup (Two Stacks Approach)

You had two stacks:

1. S3 Bucket Stack: This creates the S3 bucket.

2. Global CloudFront Stack: This creates the CloudFront distribution and tries to assign the S3 Origin Access Control (OAC) to restrict access to the bucket.

What happened?

The S3 Bucket Stack creates the bucket.

The Global CloudFront Stack needs the S3 bucket to configure the origin and apply the OAC.

When you enable the OAC, the CloudFront distribution automatically tries to update the S3 bucket policy to allow only its OAC access.

But the S3 bucket policy can’t be updated until the CloudFront distribution exists, and the CloudFront distribution can’t exist until the S3 bucket policy allows access.

This created a cyclic dependency:

1. CloudFront needs the S3 bucket to exist with permissions.

2. The S3 bucket needs CloudFront to exist with its OAC.

3. Both wait for each other and CloudFormation fails.

---

Second Setup (Three Stacks Approach)

You tried splitting it into three stacks to solve the dependency:

1. S3 Bucket Stack: Creates the bucket.

2. Global CloudFront Stack: Creates the CloudFront distribution but with a default public bucket access (no OAC initially).

3. S3 Origin Stack: Updates the CloudFront distribution to assign the OAC after the fact.

What happened here?

The Global CloudFront Stack creates a default configuration for the S3 bucket (public access).

The S3 Origin Stack then overrides this public access by assigning the OAC to CloudFront and tries to update the bucket policy.

But the S3 Origin Stack still faces dependency issues, because:

The S3 bucket's policy needs to allow the OAC, which is tied to the CloudFront distribution.

CloudFront depends on the S3 bucket, but now the S3 Origin Stack indirectly reintroduces the same cyclic dependency by trying to retroactively assign the OAC.

---

Third Setup (Proposed Solution)

The final solution uses the two stacks approach with a twist:

1. S3 Bucket Stack: Creates the S3 bucket but does not worry about policies during stack creation.

2. Global CloudFront Stack:

Creates the CloudFront distribution with the OAC.

Uses a custom Lambda function to update the bucket policy after the distribution and OAC are created.

---

Why Does This Work?

The key is using a Lambda function (custom resource) to handle the bucket policy update after all dependencies are resolved.

1. The S3 Bucket Stack is created first, and it does not depend on anything else. It just outputs the bucket name/ARN.

2. The Global CloudFront Stack is created second:

It creates the CloudFront distribution and OAC.

After the distribution and OAC are created, the stack triggers a Lambda function to update the bucket policy.

3. The Lambda function updates the bucket policy dynamically:

It gets the bucket name from the S3 Bucket Stack.

It gets the OAC ID from the CloudFront Stack.

It uses the AWS SDK to set the correct bucket policy, allowing access from the OAC.

Since the Lambda runs after the stacks are fully created, there’s no circular dependency. The bucket policy update is deferred until the CloudFront distribution and OAC exist.

---

Summary of the Three Approaches

1. Two Stacks (Initial Issue):

Directly tried to set the OAC in the CloudFront stack.

Failed because the S3 bucket policy tried to update itself before the CloudFront distribution existed, causing a cyclic dependency.

2. Three Stacks (Intermediate Attempt):

Tried to split the setup into three stacks.

Still faced the same issue because the S3 Origin Stack introduced a new cyclic dependency by attempting to assign the OAC and update the bucket policy after the CloudFront stack was created.

3. Final Solution (Custom Lambda):

Two stacks: S3 Bucket Stack + Global CloudFront Stack.

Used a Lambda function to update the bucket policy after all dependencies (bucket, CloudFront, OAC) were resolved.

No cyclic dependencies because the Lambda runs only after both stacks are deployed.

---

Explaining in Layman’s Terms

Think of the bucket and CloudFront distribution like two friends who need to coordinate:

1. The bucket says, “I can’t let anyone in unless I know who’s coming (OAC).”

2. The CloudFront distribution says, “I can’t create my key (OAC) unless the bucket lets me in.”

They end up in a stalemate, waiting for each other forever (cyclic dependency).

The final solution introduces a mediator (Lambda):

The mediator says, “Let’s first set up the bucket and CloudFront separately. Once both are ready, I’ll step in and fix the bucket’s policy so they can talk to each other.”

This way, both friends don’t depend on each other directly, and the mediator resolves their conflict afterward.

Let me know if you'd like me to clarify anything further!

[DAMSCROW]

Let me simplify the three-stack solution you tried and explain why it still led to issues in a layman’s perspective.

---

The Setup: Three Stacks

1. First Stack: S3 Bucket Stack

Creates the S3 bucket (the storage location).

This bucket initially has no restrictions, so anyone can technically access it.

2. Second Stack: Global CloudFront Stack

Creates the CloudFront distribution (the delivery system for your content).

By default, it is set up to allow public access to the S3 bucket (no restrictions like OAC at this stage).

3. Third Stack: S3 Origin Stack

The goal of this stack is to:

1. Assign an Origin Access Control (OAC) to the CloudFront distribution.

2. Restrict the S3 bucket policy so only this OAC can access the bucket.

3. Update the CloudFront distribution with these changes.

---

Why You Thought This Might Work

By splitting the process into three separate parts, you thought it would break the direct dependency between the bucket and the CloudFront distribution.

The idea was to:

1. Create the bucket first without worrying about restrictions (Stack 1).

2. Create CloudFront with public access (Stack 2).

3. Later, switch to restricted OAC access in a third step (Stack 3).

---

What Actually Happened

Even though the process was split, the S3 Origin Stack (Stack 3) introduced the same cyclic dependency indirectly. Here’s why:

1. Global CloudFront Stack (Stack 2) created the CloudFront distribution with public access.

This stack didn’t assign the OAC yet, so it was still allowing unrestricted access to the bucket.

2. S3 Origin Stack (Stack 3) tried to:

Assign the OAC to the CloudFront distribution.

Restrict the bucket policy to only allow access from this OAC.

The Issue

When the S3 Origin Stack tried to update the bucket policy, the same problem arose:

The bucket policy couldn’t be updated to restrict access to the OAC until the OAC and CloudFront distribution were fully configured.

The CloudFront distribution needed to access the bucket, but the bucket wasn’t ready because it required the OAC permissions.

Result: The same chicken-and-egg situation occurred, just in a more complicated form:

CloudFront (Stack 2) depended on the bucket policy from Stack 1.

The bucket policy (Stack 3) depended on the OAC created in Stack 2.

Even though the process was split into three steps, the S3 Origin Stack couldn’t solve the root dependency issue. The cyclic dependency still existed between the stacks.

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Explaining in Layman’s Terms

Imagine you’re building a house:

1. First Step (Stack 1): You build a door (S3 bucket).

It’s open to everyone for now.

2. Second Step (Stack 2): You build a security system (CloudFront distribution).

For now, the security system lets anyone through because it’s not fully configured yet.

3. Third Step (Stack 3): You try to lock the door so only the security system can let people in (OAC).

The Problem:

To lock the door, you need the security system fully set up (OAC).

But the security system needs access to the door to finish setting itself up.

Both the door and the security system end up waiting on each other, and nothing works properly.

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Why the Three-Stack Solution Failed

1. The third stack (S3 Origin Stack) tried to retroactively fix something that was inherently broken.

2. The cyclic dependency wasn’t solved because both the S3 bucket and CloudFront distribution still needed each other to complete their setup.

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Why the Final Solution Works

In the Lambda-based solution, you remove the dependency during stack creation by introducing a "helper" (the Lambda function).

The Lambda waits until everything is ready (both the bucket and CloudFront distribution exist) and then steps in to update the bucket policy.

This avoids the chicken-and-egg problem because the Lambda operates independently after the fact.

Let me know if you’d like further clarifications!