cf

CloudFront/_CloudFront.md

@@ -5,17 +5,19 @@
 - Video Streaming
 - Web Sockets
 
-## Benefits
+### Benefits
 - [[_CloudFront|CloudFront]] can be fronted with [[AWS WAF]] for OWASP's top 10 protection.
 - [[_CloudFront|CloudFront]] can stream [[Videos On Demand]] using [[ISS Microsoft Smooth Streaming]]
 
-## Core components
+### Core components
 **Origin**: Location where all original files are located. Examples include: S3, EC2, ELB, Route53.
 **Edge Locations**: Compute located strategically close to end users.
 **Regional Caches**: Compute located in board geographical locations to speed up requests for edge locations.
-**Distribution**: A collection of Edge locations and Regional Cache that defines how cached content should behave. 
+**Distribution**: A collection of Edge locations and Regional Cache that defines how cached content should behave.
+
+## Running Code
   
-## Stages where [[Lambda@Edge]] and [[CloudFront Functions]] can trigger
+### Stages where [[Lambda@Edge]] and [[CloudFront Functions]] can trigger
 The order that the functions trigger within CloudFront is:
 | Order | Stage | L@E | CF Fns |  Description | Example Use Cases |
 |--|---|---|---|---|--|
@@ -36,7 +38,7 @@ sequenceDiagram
     Edge->>Viewer: Viewer Response
 ```
 
-## Difference between [[Lambda@Edge]] and [[CloudFront Functions]]
+### Difference between [[Lambda@Edge]] and [[CloudFront Functions]]
 |   |  CF Fns |  L@E |
 |---|---|---|
 |  Programming Languages |  JavaScript (ECMAScript 5.1) |  Node.JS and Python |
@@ -51,3 +53,43 @@ sequenceDiagram
 |  Functions logging and metrics |  ✔️ |  ✔️ |
 |  Pricing |  Cheaper. Free tier available; charged pre request. |  More expensive. Charged per request & function duration. |
 
+## CloudFront Origin
+It's the source where CloudFront will send requests.
+
+### CloudFront Origin Groups
+It allows you to group a **primary** and **secondary origin** together as a destination for requests to enable high availability and fault tolerance.
+
+The **Primary Origin** is where **all** the requests will be sent.
+The **Secondary Origin** is where the requests will be sent if the **Primary Origin** is **not available**. It will act like a **failover** origin.
+
+The **failover** criteria is based on **HTTP Status Codes**: 400, 403, 404, 416, 500, 502, 503, 504.
+
+CloudFront will failover on: `GET`, `HEAD`, and `OPTION` requests.
+CloudFront will NOT failover on: `PUT`, `POST`, `PATCH`, and `DELETE`.
+
+## CloudFront Caching Policy
+### Cache Key
+The **Cache Key** is a unique identifier for every object in the cache and determines whether a viewer request results in a cache hit.
+A cache hit occurs when a viewer request generates the same **Cache Key** as a prior request and the object for that cache key is in the edge location's cache.
+The more people hit the cache, the better the application performance will be.
+
+### Cache Policy
+A **Cache Policy** determines the **Cache Key**.
+
+AWS has managed **Cache Policies** for use:
+- `Amplify`
+- `CachingDisabled`
+- `CachingOptimized`
+- `CachingOptimizedForUncompressedObjects`
+- `Elemental-MediaPackage`
+
+You can make your own **Caching Policy**:
+- **TTL Settings**:
+    - **Minimum** / **Maximum** **TTL**: min / max time to hold the file in the cache.
+    - **Default TTL**: default time to hold a file in the cache.
+
+- **Cache Key Settings**:
+    - **Headers**: which headers are a part of the **Cache Key**.
+    - **Cookies**: which cookies are a part of the **Cache Key**.
+    - **Query String**: which query string parameters are a part of the **Cache Key**.
+    - **Compression Support**: What compression format is part of the **Cache Key**.