diff --git a/db/src/tx_observer.rs b/db/src/tx_observer.rs
index 9d4fa3e7..d2011294 100644
--- a/db/src/tx_observer.rs
+++ b/db/src/tx_observer.rs
@@ -49,27 +49,10 @@ impl TxObserver {
     }
 }
 
-pub trait CommandClone {
-    fn clone_box(&self) -> Box<Command + Send>;
+pub trait Command {
+    fn execute(&mut self);
 }
 
-impl<T> CommandClone for T where T: 'static + Command + Clone + Send {
-    fn clone_box(&self) -> Box<Command + Send> {
-        Box::new(self.clone())
-    }
-}
-
-pub trait Command: CommandClone {
-    fn execute(&self);
-}
-
-impl Clone for Box<Command + Send> {
-    fn clone(&self) -> Box<Command + Send> {
-        self.clone_box()
-    }
-}
-
-#[derive(Clone)]
 pub struct NotifyTxObserver {
     key: String,
     reports: Vec<Arc<TxReport>>,
@@ -87,22 +70,21 @@ impl NotifyTxObserver {
 }
 
 impl Command for NotifyTxObserver {
-    fn execute(&self) {
+    fn execute(&mut self) {
         self.observer.upgrade().map(|o| o.notify(&self.key, &self.reports));
     }
 }
 
-#[derive(Clone)]
 pub struct AsyncBatchExecutor {
     commands: Vec<Box<Command + Send>>,
 }
 
 impl Command for AsyncBatchExecutor {
-    fn execute(&self) {
+    fn execute(&mut self) {
         // need to clone to move to a new thread.
-        let command_queue = self.commands.clone();
+        let command_queue = ::std::mem::replace(&mut self.commands, Vec::new());
         thread::spawn (move ||{
-            for command in command_queue.iter() {
+            for mut command in command_queue.into_iter() {
                 command.execute();
             }
         });
@@ -121,7 +103,8 @@ impl TxObservationService {
             command_queue: Vec::new(),
         }
     }
-    // For testing purposes
+
+    // For testing purposes.
     pub fn is_registered(&self, key: &String) -> bool {
         self.observers.contains_key(key)
     }
@@ -157,10 +140,9 @@ impl TxObservationService {
     }
 
     pub fn run(&mut self) {
-        for command in self.command_queue.iter() {
+        let command_queue = ::std::mem::replace(&mut self.command_queue, Vec::new());
+        for mut command in command_queue.into_iter() {
             command.execute();
         }
-
-        self.command_queue.clear();
     }
 }