mirror of https://github.com/jlelse/GoBlog
121 lines
3.6 KiB
Go
121 lines
3.6 KiB
Go
package main
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import (
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"context"
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"encoding/json"
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"net/http"
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"net/http/httptest"
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"net/url"
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"sync"
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"time"
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)
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var cacheMutexes map[string]*sync.Mutex
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func initCache() {
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cacheMutexes = map[string]*sync.Mutex{}
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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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requestURL, _ := url.ParseRequestURI(r.RequestURI)
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path := slashTrimmedPath(r)
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if appConfig.Cache.Enable &&
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// check bypass query
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!(requestURL != nil && requestURL.Query().Get("cache") == "0") {
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// Check cache mutex
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if cacheMutexes[path] == nil {
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cacheMutexes[path] = &sync.Mutex{}
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}
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// Lock mutex - prevents multiple new renderings
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cacheMutexes[path].Lock()
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// Get cache
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cacheTime, header, body := getCache(r.Context(), path)
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if cacheTime == 0 {
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// No cache available
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recorder := httptest.NewRecorder()
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next.ServeHTTP(recorder, r)
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// copy values from recorder
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code := recorder.Code
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// send response
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for k, v := range recorder.Header() {
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w.Header()[k] = v
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}
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now := time.Now()
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setCacheHeaders(w, now.Format(time.RFC1123), time.Unix(now.Unix()+appConfig.Cache.Expiration, 0).Format(time.RFC1123))
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w.Header().Set("GoBlog-Cache", "MISS")
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w.WriteHeader(code)
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_, _ = w.Write(recorder.Body.Bytes())
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// Save cache
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if code == http.StatusOK {
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saveCache(path, now, recorder.Header(), recorder.Body.Bytes())
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}
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cacheMutexes[path].Unlock()
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return
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}
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cacheMutexes[path].Unlock()
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cacheTimeString := time.Unix(cacheTime, 0).Format(time.RFC1123)
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expiresTimeString := time.Unix(cacheTime+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 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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w.Header().Set("GoBlog-Cache", "HIT")
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// write cached body
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_, _ = w.Write(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 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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func getCache(context context.Context, path string) (creationTime int64, header map[string][]string, body []byte) {
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var headerBytes []byte
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allowedTime := time.Now().Unix() - appConfig.Cache.Expiration
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row := appDb.QueryRowContext(context, "select COALESCE(time, 0), header, body from cache where path=? and time>=?", path, allowedTime)
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_ = row.Scan(&creationTime, &headerBytes, &body)
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header = make(map[string][]string)
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_ = json.Unmarshal(headerBytes, &header)
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return
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}
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func saveCache(path string, now time.Time, header map[string][]string, body []byte) {
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headerBytes, _ := json.Marshal(header)
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startWritingToDb()
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defer finishWritingToDb()
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tx, err := appDb.Begin()
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if err != nil {
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return
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}
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_, _ = tx.Exec("delete from cache where time<?;", now.Unix()-appConfig.Cache.Expiration)
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_, _ = tx.Exec("insert or replace into cache (path, time, header, body) values (?, ?, ?, ?);", path, now.Unix(), headerBytes, body)
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_ = tx.Commit()
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}
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func purgeCache(path string) {
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startWritingToDb()
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defer finishWritingToDb()
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tx, err := appDb.Begin()
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if err != nil {
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return
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}
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_, _ = tx.Exec("delete from cache where path=?", path)
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_ = tx.Commit()
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}
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