Implement delete-q! function to delete a single queue

This function lets the client delete an individual named queue. It is
useful for deleting corrupted queue files (such as that get created
when the disk fills up).

Closes: clj-commons#17

src/durable_queue.clj

@@ -433,6 +433,8 @@
   (^:private mark-retry! [_ q-name])
   (delete! [_]
     "Deletes all files associated with the queues.")
+  (delete-q! [_ q-name]
+    "Deletes all files associated with a queue.")
   (stats [_]
     "Returns a map of queue names onto information about the immediate state of the queue.")
   (fsync [_]
@@ -496,9 +498,7 @@
 
      (.mkdirs (io/file directory))
 
-     (let [
-
-           queue (memoize (fn [_] (LinkedBlockingQueue. (int max-queue-size))))
+     (let [queue (memoize (fn [_] (LinkedBlockingQueue. (int max-queue-size))))
            queue-name->files (directory->queue-name->slab-files directory)
 
            ;; core state stores
@@ -631,6 +631,16 @@
                (unmap s)
                (delete-slab s)))
 
+           (delete-q! [this q-name]
+             (let [q-name (munge (name q-name))]
+               (doseq [s (get @queue-name->slabs q-name)]
+                 (unmap s)
+                 (delete-slab s))
+               (.clear (queue q-name))
+               (swap! queue-name->stats assoc q-name nil)
+               (swap! queue-name->slabs assoc q-name nil)
+               (swap! queue-name->current-slab assoc q-name nil)))
+
            (fsync [_]
              (doseq [slab (->> @queue-name->slabs vals (apply concat))]
                (sync! slab)))