vary should be set to 'Accept' in the response header

[omrisiri]

When enabling webp we need to return vary: 'Accept' header rather than take it from the request headers since it doesn't exist there and will throw an exception

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[timkelty]

I'm trying to get AUTO_WEBP to work…https://github.com/thumbor/thumbor/wiki/Configuration#auto_webp

Is there an update on this issue or a reason it isn't merged in? @omrisiri @gsingh04

[timkelty]

@omrisiri Were you able to get this working (AUTO_WEBP)?

I merged tested this PR, and confirmed it does work when you access the API directly (when setting AUTO_WEBP), but doesn't work through the cloudfront url.

Example:

Request png w/ accept header, directly from api: get back webp

❯ curl -I --header "accept: image/webp,image/*,*/*;q=0.8" "https://i308nq9jlf.execute-api.us-east-1.amazonaws.com/image/950x950/test.png"
HTTP/2 200
content-type: image/webp
content-length: 111482

Request png w/ accept header, from cloudfront url: get back png:

❯ curl -I --header "accept: image/webp,image/*,*/*;q=0.8" "https://ds3bnhnnjgxql.cloudfront.net/950x950/test.png"
HTTP/2 200
content-type: image/png
content-length: 241881

[omrisiri]

In order for this to work with cloudfront you will need to whitelist the Accept header in the behaviors tab in the distribution settings

[timkelty]

@omrisiri I actually just ended up uncommenting these lines: https://github.com/awslabs/serverless-image-handler/blob/50856dc17ea7671829f3f940ae27f3a35807b59f/deployment/serverless-image-handler.template#L475-L479

See #32

[jainraj]

@omrisiri We don't need to change anything here. If we forward the headers from cloudfront (https://aws.amazon.com/premiumsupport/knowledge-center/configure-cloudfront-to-forward-headers/ choose accept instead of host), this will work as it is. And I think we will have to forward the headers anyway since the thumbor needs to know the header value.

[timkelty]

@jainraj @omrisiri I've configured cloudfront to forward the Accept header, which works, but throws an error when you pass a format filter, eg: https://dlywxk1dfco56.cloudfront.net/Uz-eU0TnL0X_2ZbKHeCc1-lVyfs=/716x716/filters:focal(839x839:841x841):format(jpeg):quality(61):sharpen(0.5,0.5,true)/development.craftcms.stealthmonitoring/headshots/Rob-Cherun.jpg

[jainraj]

Request the moderators to close the PR and add in documentation that we will need to forward ACCEPT header in CloudFront for AUTO_WEBP to work as expected

[timkelty]

I can verify @jainraj's solution works. Shouldn't we add the Accepts whitelist header to the cloudfront dist as part of the default configuration?

[timkelty]

Just came across an issue using @jainraj's solution (adding the Accept header to whitelist). It throws an error when you try to set the format via the format() filter. I end up with an error like:

[ERROR]	2019-05-08T17:32:50.341Z	43028d25-8143-4d69-90f2-550e86bbc35a	lambda_handler trace: Traceback (most recent call last):
File "/var/task/image_handler/lambda_function.py", line 338, in lambda_handler
result = call_thumbor(event)
File "/var/task/image_handler/lambda_function.py", line 317, in call_thumbor
return process_thumbor_responde(thumbor_response, vary)
File "/var/task/image_handler/lambda_function.py", line 287, in process_thumbor_responde
vary = thumbor_response.headers['vary']
File "/var/task/requests/structures.py", line 52, in __getitem__
return self._store[key.lower()][1]
KeyError: 'vary'

[shsenior]

Resolved with v4.0.0