I then open sourced it in Jan 2013 in what was then named Camlistore (now Perkeep) in https://github.com/perkeep/perkeep/commit/6f9f0bdda9c9c1f147... d

And later I put it in https://pkg.go.dev/github.com/golang/groupcache/singleflight (groupcache was written for dl.google.com)

And a private copy in Go's net package in Jun 2013: https://github.com/golang/go/commit/61d3b2db6292581fc07a3767...

It later moved to golang.org/x/net, and later to the Go standard library (well, internal: https://pkg.go.dev/internal/singleflight)

We now even have a copy with generics in Tailscale's tree at https://pkg.go.dev/tailscale.com/util/singleflight

So many variants of that code :)

That being said, singleflight is a fantastic library and pattern that helps so much with p95 latency. It's a little noisy code-wise, but if you use it in the right places the gains are huge.

Also, totally agree with the below comment that recommends janos/singleflight -- start there, but most of the critical projects at my company, AuthZed, have reimplementations with tailored semantics.

https://github.com/janos/singleflight

Any suitable examples? In the linked posts it gives querying weather service as an example but still uses a cache. Even with a normal concurrent request to a single function, a caching layer can be added before it makes any external request. Or am I misunderstanding this use case?