Work on the caching logic, for now turn it off to reduce memory usage

README.md

@@ -10,3 +10,10 @@ TODOs
 - make a cronjob to automatically renew the certificate
 - add a header bar and make the footer look a little nicer
 - do cool stuff so I can post about it here I guess
+
+Migration notes for myself
+- copy this server over (`git clone ...` plus copying auth keys)
+- run install script to set iptable rules
+- copy repositories over (`./gogs backup` to generate, copy over, etc)
+- rerun certbot with google-dns plugin (and copy DNS secret over, or regenerate)
+- fix DNS links

cache.go

@@ -2,10 +2,43 @@ package main
 
 import (
 	"net/http"
+	"runtime"
+	"unsafe"
 )
 
+type realCacheEntry struct {
+	r     Response
+	cache map[string]cacheEntry
+	key   string
+}
+
+// store a pointer to the real cache entry as an int here
+// so that the garbage collector can collect it if needed
 type cacheEntry struct {
-	r Response
+	p uintptr
+	//r Response
+}
+
+func (e cacheEntry) access() *Response {
+	ptr := unsafe.Pointer(e.p)
+	entry := (*realCacheEntry)(ptr)
+	return &entry.r
+}
+
+func addEntry(cache map[string]cacheEntry, s string, r Response) cacheEntry {
+	entry := new(realCacheEntry)
+	entry.r = r
+	entry.cache = cache
+	entry.key = s
+
+	cache[s] = cacheEntry{
+		p: (uintptr)(unsafe.Pointer(entry)),
+	}
+	runtime.SetFinalizer(entry, func(e *realCacheEntry) {
+		delete(e.cache, e.key)
+	})
+
+	return cache[s]
 }
 
 func Cache(h http.Handler) http.Handler {
@@ -18,9 +51,12 @@ func Cache(h http.Handler) http.Handler {
 			return
 		}
 
+		// NOTE: not threadsafe, TODO fix that
 		entry, exists := c[r.URL.String()]
 		if exists {
-			entry.r.WriteResponse(rw)
+			// NOTE: the finalizer can theoretically execute between the map read
+			// and here
+			entry.access().WriteResponse(rw)
 		} else {
 			rc := ResponseCollector{}
 			// copy request in case they modify it
@@ -28,7 +64,7 @@ func Cache(h http.Handler) http.Handler {
 			h.ServeHTTP(&rc, &req)
 			resp := rc.CollectResponse()
 			if resp.Code == 200 {
-				c[r.URL.String()] = cacheEntry{resp}
+				addEntry(c, r.URL.String(), resp)
 			}
 			resp.WriteResponse(rw)
 		}

main.go

@@ -189,7 +189,7 @@ func startServer(srv *http.Server) {
 	serveMux.HandleFunc("/", rootHandler)
 	//serveMux.Handle("/certbot/", http.StripPrefix("/certbot/", http.FileServer(http.Dir("./certbot-tmp"))))
 	serveMux.Handle("/gfm/", http.StripPrefix("/gfm", http.FileServer(gfmstyle.Assets)))
-	serveMux.Handle("/resize/", Cache(Resize(640, http.StripPrefix("/resize", http.FileServer(http.Dir("static/"))))))
+	serveMux.Handle("/resize/", Resize(640, http.StripPrefix("/resize", http.FileServer(http.Dir("static/")))))
 	if webhookKey != nil {
 		log.Print("web hook found")
 		serveMux.HandleFunc("/update", func(w http.ResponseWriter, r *http.Request) {