bhale
commented
3 years ago I still think it would be helpful to allow for a JavaScript app hosted on a different TLD to access the functions in OpenFaas, however I did some more work today and managed to package my NextJS app in a way that it could be run along side my other functions with a FunctionsIngress. That is a good feature - I plan to write a template for NextJS and blog post on what I did soon.
My actions before raising this issue
I have read a lot of prior issues and documentation on how to work around CORS issues with functions in OpenFaas. For my backend sync functions, I have modified the templates slightly (python3-flask) to support an OPTIONS call to the backend in the CORS preflight check. A preflight check by calling with OPTIONS verb is done on POST, not on GET, so in the GET handler I can simply modify the flask response to include the CORS headers. To enable POST, you must have the extra step of making the app support an OPTIONS call, which the template does not.
(https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request)
However, I was unable to resolve the issue for async-functions, since the HTTP request is fully managed by OpenFaas and hands it off to my function over NATS. I attempted to add the headers using the annotations available from ingress-nginx, but I believe OpenFaas is rejecting the OPTIONS request of the preflight check. The response code is 405.
Expected Behaviour
There should be an annotation, config map, helm values or otherwise that instructs the OpenFaas async functions handler to support returning CORS headers and supporting a valid 200 response to an OPTIONS request so that subsequent posts can be made. Ideally this would apply to sync endpoints as well, but there is a lot of OPTIONS-unfriendly stuff that lives in the templates as well. I would be happy to make a PR for some of the python ones if this is desirable.
Current Behaviour
OpenFaas async handler has no support for adding CORS headers, and rejects OPTIONS requests.
Steps to Reproduce (for bugs)
Context
I am attempting to build APIs that could be consumed by others, including myself during development. I would like to deploy my JS frontend at a provider such as Netlify or Vercel and have it access my openfaas functions for dynamic content at runtime.
Your Environment
faas-cli version):CLI: commit: c12d57c39ac4cc6eef3c9bba2fb45113d882432f version: 0.12.14
Gateway uri: http://faas.bhale.dev version: 0.20.1 sha: 7b6cc60bd9865852cd11c98d4420752815052918 commit: Fix Invocation count wrong for multiple namespace
Provider name: faas-netes orchestration: kubernetes version: 0.12.8 sha: e88c54c3854614fe02809c6931d544f74d64c6f0 Your faas-cli version (0.12.14) may be out of date. Version: 0.12.19 is now available on GitHub.
Next steps
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