internal/short: stop using memcache

Cloud Datastore alone should be plenty fast enough for our redirects
and plenty high enough bandwidth for our traffic load.
Avoiding Memcache really means avoiding Redis, which makes
the admin.go.dev site work better, since I apparently didn't set up
the peering between the two projects correctly, and admin is not
deleting things from Redis as it should be. Redis seems like
premature optimization at this point, so disable it, in preparation
for deleting it entirely.

Change-Id: Icfa3a0668f944fac8dad3280eb24356234ff0fc2
Reviewed-on: https://go-review.googlesource.com/c/website/+/498635
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Russ Cox <rsc@golang.org>

internal/short/short.go

@@ -24,6 +24,10 @@ import (
 	"golang.org/x/website/internal/memcache"
 )
 
+// useMemcache controls whether to use Redis.
+// We are hoping to remove Redis entirely.
+const useMemcache = false
+
 const (
 	prefix  = "/s"
 	kind    = "Link"
@@ -72,7 +76,10 @@ func (h server) linkHandler(w http.ResponseWriter, r *http.Request) {
 	}
 
 	var link Link
-	if err := h.memcache.Get(ctx, cacheKey(key), &link); err != nil {
+	if useMemcache {
+		err = h.memcache.Get(ctx, cacheKey(key), &link)
+	}
+	if err != nil || !useMemcache {
 		k := datastore.NameKey(kind, key, nil)
 		err = h.datastore.Get(ctx, k, &link)
 		switch err {
@@ -84,12 +91,14 @@ func (h server) linkHandler(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "internal server error", http.StatusInternalServerError)
 			return
 		case nil:
-			item := &memcache.Item{
-				Key:    cacheKey(key),
-				Object: &link,
-			}
-			if err := h.memcache.Set(ctx, item); err != nil {
-				log.Printf("WARNING %q: %v", key, err)
+			if useMemcache {
+				item := &memcache.Item{
+					Key:    cacheKey(key),
+					Object: &link,
+				}
+				if err := h.memcache.Set(ctx, item); err != nil {
+					log.Printf("WARNING %q: %v", key, err)
+				}
 			}
 		}
 	}
@@ -156,9 +165,11 @@ func (h server) adminHandler(w http.ResponseWriter, r *http.Request) {
 		default:
 			http.Error(w, "unknown action", http.StatusBadRequest)
 		}
-		err := h.memcache.Delete(ctx, cacheKey(key))
-		if err != nil && err != memcache.ErrCacheMiss {
-			log.Printf("WARNING %q: %v", key, err)
+		if useMemcache {
+			err := h.memcache.Delete(ctx, cacheKey(key))
+			if err != nil && err != memcache.ErrCacheMiss {
+				log.Printf("WARNING %q: %v", key, err)
+			}
 		}
 	}