mirror of https://github.com/jlelse/GoBlog
75 lines
2.2 KiB
Go
75 lines
2.2 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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"time"
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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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cacheTime, header, body := getCache(path, r.Context())
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if cacheTime == 0 {
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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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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, recorder.Header(), recorder.Body.Bytes())
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}
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return
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} else {
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expiresTime := time.Unix(cacheTime+appConfig.cache.expiration, 0).Format(time.RFC1123)
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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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w.Header().Set("Expires", expiresTime)
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w.Header().Set("GoBlog-Cache", "HIT")
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_, _ = w.Write(body)
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}
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} else {
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next.ServeHTTP(w, r)
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}
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})
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}
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func getCache(path string, context context.Context) (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, header map[string][]string, body []byte) {
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now := time.Now().Unix()
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headerBytes, _ := json.Marshal(header)
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startWritingToDb()
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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-appConfig.cache.expiration)
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_, _ = tx.Exec("insert or replace into cache (path, time, header, body) values (?, ?, ?, ?);", path, now, headerBytes, body)
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_ = tx.Commit()
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finishWritingToDb()
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}
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