SHA256
54 lines
2.9 KiB
Markdown
54 lines
2.9 KiB
Markdown
# CloudFront
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## What is it?
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[[_CloudFront|CloudFront]] is a CDN. It can be used for:
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- Static & Dynamic content
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- Video Streaming
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- Web Sockets
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## Benefits
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- [[_CloudFront|CloudFront]] can be fronted with [[AWS WAF]] for OWASP's top 10 protection.
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- [[_CloudFront|CloudFront]] can stream [[Videos On Demand]] using [[ISS Microsoft Smooth Streaming]]
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## Core components
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**Origin**: Location where all original files are located. Examples include: S3, EC2, ELB, Route53.
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**Edge Locations**: Compute located strategically close to end users.
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**Regional Caches**: Compute located in board geographical locations to speed up requests for edge locations.
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**Distribution**: A collection of Edge locations and Regional Cache that defines how cached content should behave.
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## Stages where [[Lambda@Edge]] and [[CloudFront Functions]] can trigger
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The order that the functions trigger within CloudFront is:
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| Order | Stage | L@E | CF Fns | Description | Example Use Cases |
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|--|---|---|---|---|--|
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| 1 | Viewer Request | ✔️ | ✔️ | When CloudFront receives a request from the viewer. | Redirection (`HTTP` -> `HTTPS`), Cookie Inspection for Auth, Modify Headers for A/B Testing |
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| 2 | Origin Request | ✔️ | ❌ | Before CloudFront forwards the request to the origin. | Add security headers (CSP/HSTS), set cookies for client side tracking, customise error messages |
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| 3 | Origin Response | ✔️ | ❌ | After CloudFront receives the request from the origin. | Rewrite URLs for SEO or routing, inject headers for origin authentication, selective content serving based on user agent (desktop/mobile mode). |
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| 4 | Viewer Response | ✔️ | ✔️ | Before CloudFront returns the response to the viewer. | Modify headers to control caching, update URLs in HTML for versioning, customise error responses from origin. |
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```mermaid
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sequenceDiagram
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participant Viewer
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participant Edge
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participant Origin
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Viewer->>Edge: Viewer Request
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Edge->>Origin: Origin Request
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Origin->>Edge: Origin Response
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Edge->>Viewer: Viewer Response
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```
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## Difference between [[Lambda@Edge]] and [[CloudFront Functions]]
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| | CF Fns | L@E |
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|---|---|---|
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| Programming Languages | JavaScript (ECMAScript 5.1) | Node.JS and Python |
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| Event Sources | Viewer only | Viewer and Origin |
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| Scale | +10,000,000 requests/s | 10,000 requests/s/Region |
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| Function Duration | Submilisecond | Up to 5s (Viewer) / Up to 30s (Origin) |
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| Max Memory | 2MB | 128MB-3,008MB |
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| Max Bundle Size | 10KB | 1MB (Viewer) / 50MB (Origin) |
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| Network, File System, and Request Body Access | ❌ | ✔️ |
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| Access to geolocation | ✔️ | ❌ (Viewer request) / ✔️ (Origin request & response, Viewer response) |
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| Can build/test entirely within CloudFront | ✔️ | ❌ |
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| Functions logging and metrics | ✔️ | ✔️ |
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| Pricing | Cheaper. Free tier available; charged pre request. | More expensive. Charged per request & function duration. |
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