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cache.go
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cache.go
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package yolosvc
import (
"bytes"
"encoding/gob"
"hash/fnv"
"net/http"
"net/http/httptest"
"net/url"
"sort"
"strings"
cache "github.com/patrickmn/go-cache"
"go.uber.org/zap"
)
// this cache middleware was inspired by https://github.com/victorspringer/http-cache
func cacheMiddleware(next http.Handler, c *cache.Cache, logger *zap.Logger) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.Method == http.MethodGet {
err := func() error {
sortURLParams(r.URL)
h := fnv.New64a()
key := string(h.Sum([]byte(r.URL.String())))
res, found := c.Get(key)
if found {
var response cached
dec := gob.NewDecoder(bytes.NewReader(res.([]byte)))
err := dec.Decode(&response)
if err != nil {
return err
}
for k, v := range response.Header {
w.Header().Set(k, strings.Join(v, ","))
}
_, err = w.Write(response.Value)
return err
}
rec := httptest.NewRecorder()
next.ServeHTTP(rec, r)
result := rec.Result()
defer result.Body.Close()
statusCode := result.StatusCode
value := rec.Body.Bytes()
if statusCode < 400 {
response := cached{
Value: value,
Header: result.Header,
}
var b bytes.Buffer
enc := gob.NewEncoder(&b)
err := enc.Encode(&response)
if err != nil {
return err
}
c.Set(key, b.Bytes(), cache.DefaultExpiration)
}
for k, v := range result.Header {
w.Header().Set(k, strings.Join(v, ","))
}
w.WriteHeader(statusCode)
_, err := w.Write(value)
return err
}()
if err != nil {
logger.Warn("caching error", zap.Error(err))
} else {
return
}
}
next.ServeHTTP(w, r)
})
}
type cached struct {
Value []byte
Header http.Header
}
func sortURLParams(u *url.URL) {
params := u.Query()
for _, param := range params {
sort.Slice(param, func(i, j int) bool {
return param[i] < param[j]
})
}
u.RawQuery = params.Encode()
}