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167 lines
4.4 KiB
167 lines
4.4 KiB
package main
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import (
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"bytes"
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"crypto/sha256"
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"fmt"
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"io"
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"io/ioutil"
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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/araddon/dateparse"
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lru "github.com/hashicorp/golang-lru"
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"golang.org/x/sync/singleflight"
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)
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const (
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cacheInternalExpirationHeader = "GoBlog-Expire"
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)
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var (
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cacheGroup singleflight.Group
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cacheLru *lru.Cache
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)
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func initCache() (err error) {
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cacheLru, err = lru.New(500)
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return
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}
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func cacheMiddleware(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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if appConfig.Cache.Enable &&
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// check method
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(r.Method == http.MethodGet || r.Method == http.MethodHead) &&
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// check bypass query
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!(r.URL.Query().Get("cache") == "0" || r.URL.Query().Get("cache") == "false") {
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key := cacheKey(r)
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// Get cache or render it
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cacheInterface, _, _ := cacheGroup.Do(key, func() (interface{}, error) {
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return getCache(key, next, r), nil
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})
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cache := cacheInterface.(*cacheItem)
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// copy cached headers
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for k, v := range cache.header {
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w.Header()[k] = v
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}
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setCacheHeaders(w, cache)
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// check conditional request
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if ifNoneMatchHeader := r.Header.Get("If-None-Match"); ifNoneMatchHeader != "" && ifNoneMatchHeader == cache.eTag {
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// send 304
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w.WriteHeader(http.StatusNotModified)
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return
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}
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if ifModifiedSinceHeader := r.Header.Get("If-Modified-Since"); ifModifiedSinceHeader != "" {
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t, err := dateparse.ParseAny(ifModifiedSinceHeader)
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if err == nil && t.After(cache.creationTime) {
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// send 304
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w.WriteHeader(http.StatusNotModified)
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return
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}
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}
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// set status code
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w.WriteHeader(cache.code)
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// write cached body
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_, _ = w.Write(cache.body)
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return
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}
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next.ServeHTTP(w, r)
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return
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})
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}
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func cacheKey(r *http.Request) string {
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return r.URL.String()
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}
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func setCacheHeaders(w http.ResponseWriter, cache *cacheItem) {
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w.Header().Set("ETag", cache.eTag)
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w.Header().Set("Last-Modified", cache.creationTime.UTC().Format(http.TimeFormat))
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if w.Header().Get("Cache-Control") == "" {
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if cache.expiration != 0 {
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w.Header().Set("Cache-Control", fmt.Sprintf("public,max-age=%d,stale-while-revalidate=%d", cache.expiration, cache.expiration))
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} else {
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w.Header().Set("Cache-Control", fmt.Sprintf("public,max-age=%d,s-max-age=%d,stale-while-revalidate=%d", appConfig.Cache.Expiration, appConfig.Cache.Expiration/3, appConfig.Cache.Expiration))
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}
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}
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}
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type cacheItem struct {
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expiration int
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creationTime time.Time
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eTag string
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code int
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header http.Header
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body []byte
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}
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func (c *cacheItem) expired() bool {
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if c.expiration != 0 {
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return time.Now().After(c.creationTime.Add(time.Duration(c.expiration) * time.Second))
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}
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return false
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}
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func getCache(key string, next http.Handler, r *http.Request) (item *cacheItem) {
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if lruItem, ok := cacheLru.Get(key); ok {
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item = lruItem.(*cacheItem)
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}
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if item == nil || item.expired() {
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// No cache available
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// Remove problematic headers
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r.Header.Del("If-Modified-Since")
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r.Header.Del("If-Unmodified-Since")
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r.Header.Del("If-None-Match")
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r.Header.Del("If-Match")
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r.Header.Del("If-Range")
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r.Header.Del("Range")
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// Record request
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recorder := httptest.NewRecorder()
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next.ServeHTTP(recorder, r)
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// Cache values from recorder
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result := recorder.Result()
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body, _ := ioutil.ReadAll(result.Body)
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_ = result.Body.Close()
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eTag := result.Header.Get("ETag")
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if eTag == "" {
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h := sha256.New()
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_, _ = io.Copy(h, bytes.NewReader(body))
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eTag = fmt.Sprintf("%x", h.Sum(nil))
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}
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lastMod := time.Now()
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if lm := result.Header.Get("Last-Modified"); lm != "" {
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if parsedTime, te := dateparse.ParseLocal(lm); te == nil {
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lastMod = parsedTime
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}
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}
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exp, _ := strconv.Atoi(result.Header.Get(cacheInternalExpirationHeader))
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// Remove problematic headers
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result.Header.Del(cacheInternalExpirationHeader)
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result.Header.Del("Accept-Ranges")
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result.Header.Del("ETag")
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result.Header.Del("Last-Modified")
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// Create cache item
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item = &cacheItem{
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expiration: exp,
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creationTime: lastMod,
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eTag: eTag,
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code: result.StatusCode,
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header: result.Header,
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body: body,
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}
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// Save cache
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cacheLru.Add(key, item)
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}
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return item
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}
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func purgeCache() {
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cacheLru.Purge()
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}
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func setInternalCacheExpirationHeader(w http.ResponseWriter, expiration int) {
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w.Header().Set(cacheInternalExpirationHeader, strconv.Itoa(expiration))
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}
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