Add per-item ttl in store

cmd/eokvin/http.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"net/http"
 	"strings"
+	"time"
 
 	"golang.org/x/crypto/acme/autocert"
 )
@@ -135,26 +136,56 @@ func redirectToCanonicalHost(w http.ResponseWriter, r *http.Request) {
 
 // newHandler is an http.Handler that creates a new item in the urlStore store.
 var newHandler http.HandlerFunc = func(w http.ResponseWriter, r *http.Request) {
+	var serverError = func(err error) {
+		w.WriteHeader(http.StatusInternalServerError)
+		log.Println("error creating short url:", err.Error())
+		if _, err = w.Write([]byte(`{"error":"internal error"}`)); err != nil {
+			log.Println("error writing response:", err.Error())
+		}
+	}
+
+	var badRequest = func(message string) {
+		b, err := json.Marshal(map[string]string{"error": message})
+		if err != nil {
+			serverError(err)
+			return
+		}
+		w.WriteHeader(http.StatusBadRequest)
+		if _, err = w.Write(b); err != nil {
+			log.Println("error writing response:", err.Error())
+		}
+	}
+
 	link := r.PostFormValue("url")
 	if len(link) == 0 {
-		w.WriteHeader(http.StatusBadRequest)
+		badRequest("url cannot be blank")
 		return
 	}
+	ttl := urlStore.ttl
+	s := r.PostFormValue("ttl")
+	if len(s) > 0 {
+		var err error
+		if ttl, err = time.ParseDuration(s); err != nil {
+			badRequest("invalid value given for ttl")
+			return
+		}
+	}
+
 	k, err := urlStore.newItemID()
 	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
+		serverError(err)
 		return
 	}
 	urlStore.mu.Lock()
-	urlStore.entries[k] = newItem(link)
+	urlStore.entries[k] = newItem(link, ttl)
 	urlStore.mu.Unlock()
-	b, err := json.Marshal(map[string]string{"short-url": canonicalHost + "/" + k.String()})
+	b, err := json.Marshal(
+		map[string]string{
+			"short-url": canonicalHost + "/" + k.String(),
+			"expires": time.Now().Add(ttl).Format("2006-01-02T15:04:05-0700"),
+		})
 	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		_, err = fmt.Fprintf(w, `{"error": "%s"}\n`, strings.Replace(err.Error(), `"`, `'`, -1))
-		if err != nil {
-			log.Println("error writing response:", err.Error())
-		}
+		serverError(err)
 		return
 	}
 	w.WriteHeader(http.StatusCreated)

cmd/eokvin/store.go

@@ -22,11 +22,17 @@ func (c itemID) String() string {
 type item struct {
 	value string
 	insertedAt time.Time
+	ttl time.Duration
 }
 func (c item) String() string {
 	return c.value
 }
 
+// newItem initializes a new url store item with a TTL.
+func newItem(s string, ttl time.Duration) item {
+	return item{value: s, insertedAt: time.Now(), ttl: ttl}
+}
+
 // A store is an in-memory data store with expiring items.
 type store struct {
 	mu sync.RWMutex
@@ -57,7 +63,12 @@ func (cch *store) newItemID() (itemID, error) {
 
 // isExpired returns true if the given item is expired.
 func (cch *store) isExpired(c item) bool {
-	return c.insertedAt.Before(time.Now().Add(-1 * cch.ttl))
+	ttl := c.ttl
+	if ttl == 0 {
+		// fallback to the stores configured ttl
+		ttl = cch.ttl
+	}
+	return c.insertedAt.Before(time.Now().Add(-1 * ttl))
 }
 
 // expiredItemReaper deletes expired entries from the store at regular
@@ -66,6 +77,8 @@ func (cch *store) expiredItemReaper() error {
 	for {
 		select {
 		case <-time.After(30 * time.Second):
+			// make a list of items that need to be deleted, but avoid
+			// fully locking the entries map.
 			var del []itemID
 			cch.mu.RLock()
 			for k, v := range cch.entries {
@@ -77,6 +90,8 @@ func (cch *store) expiredItemReaper() error {
 			if len(del) == 0 {
 				continue
 			}
+			// with at least one entry to delete, obtain a full write lock
+			// and make the modifications in a loop.
 			cch.mu.Lock()
 			for _, k := range del {
 				delete(cch.entries, k)
@@ -85,9 +100,3 @@ func (cch *store) expiredItemReaper() error {
 		}
 	}
 }
-
-// newItem initializes a new item.
-func newItem(s string) item {
-	return item{value: s, insertedAt: time.Now()}
-}
-