https://github.com/prx/dovetail-cdn-viewer-request
CloudFront Function handling Dovetail CDN viewer requests
https://github.com/prx/dovetail-cdn-viewer-request
Last synced: over 1 year ago
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CloudFront Function handling Dovetail CDN viewer requests
- Host: GitHub
- URL: https://github.com/prx/dovetail-cdn-viewer-request
- Owner: PRX
- License: agpl-3.0
- Created: 2021-05-17T16:48:52.000Z (about 5 years ago)
- Default Branch: main
- Last Pushed: 2024-08-30T15:40:37.000Z (almost 2 years ago)
- Last Synced: 2025-02-02T09:31:11.565Z (over 1 year ago)
- Language: JavaScript
- Homepage: https://dovetail.prx.org
- Size: 238 KB
- Stars: 0
- Watchers: 8
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Dovetail CDN Viewer Request
[CloudFront Function](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/cloudfront-functions.html)
to verify and normalize all requests to the [Dovetail CDN](https://github.com/PRX/Infrastructure/tree/main/cdn/dovetail-cdn).
This function is tied to the CloudFront `viewer-request` event, verifies the
request, redirects old/expired urls, and normalizes the requested paths.
## Configuration
As this is a CloudFront Function, you must hardcode everything instead of any
configurations. That said, we use a [Custom::CodeFetcher](https://github.com/PRX/Infrastructure/tree/main/cdn/dovetail-cdn) and a bit of python in CloudFormation to replace values at deploy time.
- `` - the scheme, domain, and optional path to
redirect requests back to if your url `?exp=` is expired.
## Usage
### Inputs
The lambda is invoked with a CloudFront Function [viewer-request event](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/functions-event-structure.html#functions-event-structure-request)
_(which is **NOT** the same as an edge function viewer-request event!!!)_ of the
structure:
```js
{
"request": {
"method": "GET",
"uri": "////filename.mp3",
"querystring": {
"exp": { "value": "99999999" },
"force": { "value": "1" }
}
}
}
```
The `uri` may also optionally include a `` token, to indicate this came
from a non-default feed (such as "adfree"):
```
"uri": "/////filename.mp3"
```
AND the `uri` may also also optionally start with an `` token,
to indicate which "stack" the Dovetail Router redirect originated from. This
will tie the CloudFront behavior + realtime-logs to that specific dovetail
stack within a region, for analytics processing. This token must start with a
lowercase character, not a number.
The `exp` is a (currently optional) epoch seconds timestamp, when this url will
no longer be valid and must be redirected back for a newer arrangement.
The `force` param optionally forces an edge-server cache miss, so we have to go
all the way down through the origin-request and arranger lambdas to restitch.
### Work
1. Check that the `uri` looks valid, and 404 right away on unknown paths.
2. Verify that the `?exp=` param is still valid. If the url has
expired, redirect back to `EXPIRED_REDIRECT_PREFIX` for a new redirect.
3. Normalize `uri` so that we don't make a bunch of redundant requests for the
same `arrangement_digest`. The [dovetail-cdn-origin-request](https://github.com/PRX/dovetail-cdn-origin-request)
expects `///` ... so rewrite to that.
4. If we're `?force`-ing, append a random `/random-` string to
the request `uri`. The CloudFront edge server will not have that full path
cached, so the request will fall through to origin-requesting.
5. Return the rewritten request.
### Error Handling
This function is very simple, and generally should never error. But if it did,
the user would just get a 500.
## Development
Tests can only be run locally. And since this is a CloudFront Function, it's not
really modern javascript, so you can't do any real linting and your syntax is
limited. But `prettier` is installed, so at least use that!
```sh
nvm use
yarn
npm test
# lint things up before committing
npm run lint
```
## Deploying
This function's code is pulled directly from Github via our Infrastructure
[Custom::CodeFetcher](https://github.com/PRX/Infrastructure/blob/master/cdn/dovetail3-cdn.yml).
You will need to change the `Cycle` param and redeploy the stack to pick up any
code changes here.
## License
[AGPL License](https://www.gnu.org/licenses/agpl-3.0.html)