Stop all actors at once instead of stopping/joining threads sequentially

Change-Id: Iaf8c28a18cf041f162f98e769f6b42f344285811

src/lib.rs

@@ -621,6 +621,8 @@ impl Deref for System {
 impl SystemHandle {
     /// Stops all actors spawned by this system.
     pub fn shutdown(&self) -> Result<(), ActorError> {
+        let shutdown_start = Instant::now();
+
         let current_thread = thread::current();
         let current_thread_name = current_thread.name().unwrap_or("Unknown thread id");
         info!("Thread [{}] shutting down the actor system", current_thread_name);
@@ -656,18 +658,26 @@ impl SystemHandle {
         let err_count = {
             let mut registry = self.registry.lock();
             debug!("[{}] joining {} actor threads.", self.name, registry.len());
-            // Joining actors in the reverse order in which they are spawn.
+
+            // Stopping actors in the reverse order in which they were spawned.
+            // We send the Stop control message to all actors first so they can
+            // all shut down in parallel, so actors will be in the process of
+            // stopping when we join the threads below.
+            for entry in registry.iter_mut().rev() {
+                let actor_name = entry.name();
+
+                if let Err(e) = entry.control_addr().send(Control::Stop) {
+                    warn!("control channel is closed: {} ({})", actor_name, e);
+                }
+            }
+
             registry
                 .drain(..)
                 .rev()
                 .enumerate()
-                .filter_map(|(i, mut entry)| {
+                .filter_map(|(i, entry)| {
                     let actor_name = entry.name();
 
-                    if let Err(e) = entry.control_addr().send(Control::Stop) {
-                        warn!("control channel is closed: {} ({})", actor_name, e);
-                    }
-
                     match entry {
                         RegistryEntry::CurrentThread(_) => None,
                         RegistryEntry::BackgroundThread(_control_addr, thread_handle) => {
@@ -689,7 +699,7 @@ impl SystemHandle {
                 .count()
         };
 
-        info!("[{}] system finished shutting down.", self.name);
+        info!("[{}] system finished shutting down in {:?}", self.name, shutdown_start.elapsed());
 
         if let Some(callback) = self.callbacks.postshutdown.as_ref() {
             info!("[{}] calling post-shutdown callback.", self.name);