Thumbnails don't work locally or on staging

[sophiamersmann]

Description

Grapher thumbnails only work once, then fail on subsequent hits with a 500 error.

Sorry about the pic. Can't copy in tmux.

Steps to reproduce

1. Go to any staging site, e.g. http://staging-site-sophia/grapher/income-share-distribution-before-tax-wid.svg
2. Refresh

Additional context

Martin wrote on Slack: "After a quick Google search, it seems like we shouldn’t be setting the headers directly in functions/_common/reusableHandlers.ts and instead treat them as immutable when it’s a response from native fetch. See related fix in Remix."

[danyx23]

Martin investigated some more and thinks it might instead be related to this issue in itty-router

[danyx23]

@sophiamersmann is this blocking you and/or does this happen in prod? We are triaging this now assuming that neither is the case - if this assumption is wrong then this might be even essential

[sophiamersmann]

@danyx23 It's not happening in prod, but I do have a PR up that is difficult to test because of this bug. I also eventually want to add thumbnails for chart views, which would also be a lot easier if this bug didn't make testing difficult.

[danyx23]

@ikesau do you feel comfortable debugging this this week or early next? Or do you think someone else would be better suited?

[ikesau]

Yeah! Happy to take this on 🙂