mirror of
https://github.com/ClusterCockpit/cc-backend
synced 2024-12-26 13:29:05 +01:00
121 lines
3.2 KiB
Go
121 lines
3.2 KiB
Go
package lrucache
|
|
|
|
import (
|
|
"bytes"
|
|
"net/http"
|
|
"strconv"
|
|
"time"
|
|
)
|
|
|
|
// HttpHandler is can be used as HTTP Middleware in order to cache requests,
|
|
// for example static assets. By default, the request's raw URI is used as key and nothing else.
|
|
// Results with a status code other than 200 are cached with a TTL of zero seconds,
|
|
// so basically re-fetched as soon as the current fetch is done and a new request
|
|
// for that URI is done.
|
|
type HttpHandler struct {
|
|
cache *Cache
|
|
fetcher http.Handler
|
|
defaultTTL time.Duration
|
|
|
|
// Allows overriding the way the cache key is extracted
|
|
// from the http request. The defailt is to use the RequestURI.
|
|
CacheKey func(*http.Request) string
|
|
}
|
|
|
|
var _ http.Handler = (*HttpHandler)(nil)
|
|
|
|
type cachedResponseWriter struct {
|
|
w http.ResponseWriter
|
|
statusCode int
|
|
buf bytes.Buffer
|
|
}
|
|
|
|
type cachedResponse struct {
|
|
headers http.Header
|
|
statusCode int
|
|
data []byte
|
|
fetched time.Time
|
|
}
|
|
|
|
var _ http.ResponseWriter = (*cachedResponseWriter)(nil)
|
|
|
|
func (crw *cachedResponseWriter) Header() http.Header {
|
|
return crw.w.Header()
|
|
}
|
|
|
|
func (crw *cachedResponseWriter) Write(bytes []byte) (int, error) {
|
|
return crw.buf.Write(bytes)
|
|
}
|
|
|
|
func (crw *cachedResponseWriter) WriteHeader(statusCode int) {
|
|
crw.statusCode = statusCode
|
|
}
|
|
|
|
// Returns a new caching HttpHandler. If no entry in the cache is found or it was too old, `fetcher` is called with
|
|
// a modified http.ResponseWriter and the response is stored in the cache. If `fetcher` sets the "Expires" header,
|
|
// the ttl is set appropriately (otherwise, the default ttl passed as argument here is used).
|
|
// `maxmemory` should be in the unit bytes.
|
|
func NewHttpHandler(maxmemory int, ttl time.Duration, fetcher http.Handler) *HttpHandler {
|
|
return &HttpHandler{
|
|
cache: New(maxmemory),
|
|
defaultTTL: ttl,
|
|
fetcher: fetcher,
|
|
CacheKey: func(r *http.Request) string {
|
|
return r.RequestURI
|
|
},
|
|
}
|
|
}
|
|
|
|
// gorilla/mux style middleware:
|
|
func NewMiddleware(maxmemory int, ttl time.Duration) func(http.Handler) http.Handler {
|
|
return func(next http.Handler) http.Handler {
|
|
return NewHttpHandler(maxmemory, ttl, next)
|
|
}
|
|
}
|
|
|
|
// Tries to serve a response to r from cache or calls next and stores the response to the cache for the next time.
|
|
func (h *HttpHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
|
|
if r.Method != http.MethodGet {
|
|
h.ServeHTTP(rw, r)
|
|
return
|
|
}
|
|
|
|
cr := h.cache.Get(h.CacheKey(r), func() (interface{}, time.Duration, int) {
|
|
crw := &cachedResponseWriter{
|
|
w: rw,
|
|
statusCode: 200,
|
|
buf: bytes.Buffer{},
|
|
}
|
|
|
|
h.fetcher.ServeHTTP(crw, r)
|
|
|
|
cr := &cachedResponse{
|
|
headers: rw.Header().Clone(),
|
|
statusCode: crw.statusCode,
|
|
data: crw.buf.Bytes(),
|
|
fetched: time.Now(),
|
|
}
|
|
cr.headers.Set("Content-Length", strconv.Itoa(len(cr.data)))
|
|
|
|
ttl := h.defaultTTL
|
|
if cr.statusCode != http.StatusOK {
|
|
ttl = 0
|
|
} else if cr.headers.Get("Expires") != "" {
|
|
if expires, err := http.ParseTime(cr.headers.Get("Expires")); err == nil {
|
|
ttl = time.Until(expires)
|
|
}
|
|
}
|
|
|
|
return cr, ttl, len(cr.data)
|
|
}).(*cachedResponse)
|
|
|
|
for key, val := range cr.headers {
|
|
rw.Header()[key] = val
|
|
}
|
|
|
|
cr.headers.Set("Age", strconv.Itoa(int(time.Since(cr.fetched).Seconds())))
|
|
|
|
rw.WriteHeader(cr.statusCode)
|
|
rw.Write(cr.data)
|
|
}
|