Indeed, playground share seems flaky today.

Per https://cs.opensource.google/go/x/playground/+/master:share.go;l=55;drc=bb2a4ed2d77c5ebb58ace5e1466acec69a729a68, I believe this should only happen if r.Header.Get("X-AppEngine-Country") == "CN". Hmm.

Just as a data point, this seems to be pretty consistently happening to me today on the current live Playground version, from the UK. (And other IP-based geolocation services don't seem to think I'm in China.)

I'm observing the same issue from a French IP address.

Same problem with German IP (207.154.221.x). Both sharing and loading shared snippets does not work:

POST https://go.dev/_/share
451 (Unavailable For Legal Reasons)

GET https://go.dev/_/share?id=YJeYpEjdBF
451 (Unavailable For Legal Reasons)

The problem is not intermittent for me. Sharing stopped working completely yesterday.

Thanks for the reports. This is indeed now happening on each request, and affects website visitors in the US and many other locations. Only snippet loading and sharing is affected, other parts of the Go Playground work okay.

I've updated the issue and pinned it for visibility, but it's unlikely someone will have a chance to look into it until after the weekend.

I got the same issue. I host a frontend for Go Playground - https://goplay.tools which is hosted in the US and get 451 Unavailable For Legal Reasons on each share call.

The same occurs from Polish, Ukrainian and French IPs.

I looked into this briefly today. It appears that one of the internal IPs used for proxied traffic from the go.dev frontend to the playground backend was briefly categorized as CN, causing these spurious failures.

I think the IP in question has since been recategorized as US, but it will probably take several more days for that to propagate. Additionally, go.dev has its own mechanism for handling CN-based traffic, so this check on internal IPs is both pointless and unnecessary. We should remove it for proxied traffic, though we still need it for direct traffic to the playground backend.

Unfortunately, due to the timing around the holiday weekend in the US, we're unlikely to be able to mitigate this until Tuesday at the earliest. It may resolve naturally before then. In the meantime, if you're up for a blast from the past, the old frontend is still available at https://play-dot-golang-org.appspot.com/.

So the sharing feature has been down since Friday, and as of Tuesday, it still appears to be unresolved.

Understanding that the team doesn't work on weekends, I'm concerned about the length of downtime for such a critical component.

Could we get an update on the expected timeline for a fix?

Change https://go.dev/cl/556096 mentions this issue: cmd/golangorg/testdata: comment out playground snippet tests

@nalgeon the Go team is primarily based in the US, where Monday was a holiday. We're working on this now.

Change https://go.dev/cl/556157 mentions this issue: share: hard-code an allow list of IP prefixes for proxied traffic

Change https://go.dev/cl/556195 mentions this issue: share: use forwarded IP for geoIP prefix allow list comparison

Update for today: the above CLs temporarily mitigate the problem by allow listing several Google IP prefixes that have been observed to follow the problematic pattern: a transient recategorization as CN in early January, since reverted back to US. This short list covers all the traffic we've seen over the past week, and playground snippet sharing seems to be working again. However, there's no guarantee that this list will remain valid.

We're still pursuing several more permanent fixes.

Change https://go.dev/cl/556315 mentions this issue: share: remove the allowShare guard

This is mitigated and now @findleyr is actively working on a longer term solution. Unpinning.