WIP, but this is going to become my new blog CMS
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 

167 lines
4.4 KiB

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