+var lockTidyInterval = time.Minute * 10
+
+// Lock the specified collection for reading or writing. Caller must
+// call Unlock() on the returned Locker when the operation is
+// finished.
+func (h *handler) collectionLock(collectionID string, writing bool) sync.Locker {
+ h.lockMtx.Lock()
+ defer h.lockMtx.Unlock()
+ if time.Since(h.lockTidied) > lockTidyInterval {
+ // Periodically delete all locks that aren't in use.
+ h.lockTidied = time.Now()
+ for id, locker := range h.lock {
+ if locker.TryLock() {
+ locker.Unlock()
+ delete(h.lock, id)
+ }
+ }
+ }
+ locker := h.lock[collectionID]
+ if locker == nil {
+ locker = new(sync.RWMutex)
+ if h.lock == nil {
+ h.lock = map[string]*sync.RWMutex{}
+ }
+ h.lock[collectionID] = locker
+ }
+ if writing {
+ locker.Lock()
+ return locker
+ } else {
+ locker.RLock()
+ return locker.RLocker()
+ }
+}
+