Prevents cache stampede https://en.wikipedia.org/wiki/Cache_stampede by only running a single data fetch operation per expired / missing key regardless of number of requests to that key.

import (
	"log/slog"
	"net/http"
	"time"
	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/go-chi/stampede"
	memcache "github.com/goware/cachestore-mem"
)
func main() {
	r := chi.NewRouter()
	r.Use(middleware.Logger)
	r.Use(middleware.Recoverer)
	r.Get("/", func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("index"))
	})
	cache, err := memcache.NewBackend(1000)
	if err != nil {
		panic(err)
	}
	cacheMiddleware := stampede.Handler(
		slog.Default(), cache, 5*time.Second,
		stampede.WithHTTPCacheKeyRequestHeaders([]string{"AuthorizatioN"}),
	)
	r.With(cacheMiddleware).Get("/cached", func(w http.ResponseWriter, r *http.Request) {
		// processing..
		time.Sleep(1 * time.Second)
		w.WriteHeader(200)
		w.Write([]byte("...hi"))
	})
	http.ListenAndServe(":3333", r)
}

• Requests passed through the stampede handler will be batched into a single request when there are parallel requests for the same endpoint/resource. This is also known as request coalescing.
• Parallel requests for the same endpoint / resource, will be just a single handler call and the remaining requests will receive the response of the first request handler.
• The response payload for the endpoint / resource will then be cached for up to ttl time duration for subequence requests, which offers further caching. You may also use a ttl value of 0 if you want the response to be as fresh as possible, and still prevent a stampede scenario on your handler.
• Security note: response headers will be the same for all requests, so make sure to not include anything sensitive or user specific. In the case you require user-specific stampede handlers, make sure you pass a custom keyFunc to the stampede.Handler and split the cache by an account's id. NOTE: we do avoid caching response headers for CORS, set-cookie and x-ratelimit.

See example for a variety of examples.

MIT