mirror of https://github.com/jlelse/GoBlog
127 lines
3.0 KiB
Go
127 lines
3.0 KiB
Go
package main
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import (
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"io/ioutil"
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"net/http"
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"net/http/httptest"
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"sync"
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"time"
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"golang.org/x/sync/singleflight"
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)
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var (
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cacheGroup singleflight.Group
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cacheMap = map[string]*cacheItem{}
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cacheMutex = &sync.RWMutex{}
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)
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func initCache() {
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go func() {
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for {
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// GC the entries every 60 seconds
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time.Sleep(60 * time.Second)
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cacheMutex.Lock()
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for key, item := range cacheMap {
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if item.expired() {
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delete(cacheMap, key)
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}
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}
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cacheMutex.Unlock()
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}
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}()
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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") {
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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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// log.Println(string(cache.body))
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cacheTimeString := time.Unix(cache.creationTime, 0).Format(time.RFC1123)
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expiresTimeString := time.Unix(cache.creationTime+appConfig.Cache.Expiration, 0).Format(time.RFC1123)
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// check conditional request
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ifModifiedSinceHeader := r.Header.Get("If-Modified-Since")
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if ifModifiedSinceHeader != "" && ifModifiedSinceHeader == cacheTimeString {
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setCacheHeaders(w, cacheTimeString, expiresTimeString)
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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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// 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, cacheTimeString, expiresTimeString)
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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, cacheTimeString string, expiresTimeString string) {
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w.Header().Set("Cache-Control", "public")
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w.Header().Set("Last-Modified", cacheTimeString)
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w.Header().Set("Expires", expiresTimeString)
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}
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type cacheItem struct {
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creationTime int64
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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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return c.creationTime < time.Now().Unix()-appConfig.Cache.Expiration
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}
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func getCache(key string, next http.Handler, r *http.Request) *cacheItem {
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cacheMutex.RLock()
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item, ok := cacheMap[key]
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cacheMutex.RUnlock()
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if !ok || item.expired() {
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// No cache available
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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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item = &cacheItem{
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creationTime: time.Now().Unix(),
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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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cacheMutex.Lock()
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cacheMap[key] = item
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cacheMutex.Unlock()
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}
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return item
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}
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func purgeCache() {
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cacheMutex.Lock()
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cacheMap = map[string]*cacheItem{}
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cacheMutex.Unlock()
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}
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