forked from Ivasoft/opds-proxy
0f0540549d
Kobo eReaders have a buggy browser that makes 2 requests for the same HTTP resource when you click a link. This change ensures that requests within a certain time frame from the same IP, for the same path / query params will only be executed a single time. We record the http request response and replay it for the second request. If we get 2 simultaneous requests, we use the sync/singleflight library to ensure only the first request is actually processed. The second waits for the shared result of the first. This probably adds latency since some requests are blocked while we determine if we already have a cache entry, but for a simple service like this I don't think it matters.
54 lines
1.4 KiB
Go
54 lines
1.4 KiB
Go
package debounce
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import (
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"crypto/md5"
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"encoding/hex"
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"net"
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"net/http"
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"net/http/httptest"
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"strconv"
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"time"
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"github.com/evan-buss/opds-proxy/internal/cache"
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"golang.org/x/sync/singleflight"
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)
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func NewDebounceMiddleware(debounce time.Duration) func(next http.HandlerFunc) http.HandlerFunc {
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responseCache := cache.NewCache[httptest.ResponseRecorder](cache.CacheConfig{CleanupInterval: time.Second, TTL: debounce})
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singleflight := singleflight.Group{}
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return func(next http.HandlerFunc) http.HandlerFunc {
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return func(w http.ResponseWriter, r *http.Request) {
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ip, _, _ := net.SplitHostPort(r.RemoteAddr)
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hash := md5.Sum([]byte(ip + r.URL.Path + r.URL.RawQuery))
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key := string(hex.EncodeToString(hash[:]))
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if entry, exists := responseCache.Get(key); exists {
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w.Header().Set("X-Debounce", "true")
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writeResponse(entry, w)
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return
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}
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rw, _, shared := singleflight.Do(key, func() (interface{}, error) {
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rw := httptest.NewRecorder()
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next(rw, r)
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return rw, nil
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})
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recorder := rw.(*httptest.ResponseRecorder)
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responseCache.Set(key, recorder)
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w.Header().Set("X-Shared", strconv.FormatBool(shared))
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writeResponse(recorder, w)
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}
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}
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}
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func writeResponse(rec *httptest.ResponseRecorder, w http.ResponseWriter) {
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for k, v := range rec.Header() {
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w.Header()[k] = v
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}
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w.WriteHeader(rec.Code)
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w.Write(rec.Body.Bytes())
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}
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