Adding support for being able to _not_ use ExecutionHandler by setting the poolsize to 0

akka-remote/src/main/resources/reference.conf

@@ -122,7 +122,8 @@ akka {
       # (I) Length in akka.time-unit how long core threads will be kept alive if idling
       execution-pool-keepalive = 60s
 
-      # (I) Size of the core pool of the remote execution unit
+      # (I) Size in number of threads of the core pool of the remote execution unit,
+      # set to 0 to disable the execution pool
       execution-pool-size = 4
 
       # (I) Maximum channel size, 0 for off

akka-remote/src/main/scala/akka/remote/netty/NettyRemoteSupport.scala

@@ -71,7 +71,7 @@ private[akka] class NettyRemoteTransport(_system: ExtendedActorSystem, _provider
      */
     def defaultStack(withTimeout: Boolean, isClient: Boolean): Seq[ChannelHandler] =
       (if (settings.EnableSSL) List(NettySSLSupport(settings, NettyRemoteTransport.this.log, isClient)) else Nil) :::
-        (if (withTimeout) List(timeout) else Nil) ::: msgFormat ::: authenticator ::: executionHandler :: Nil
+        (if (withTimeout) List(timeout) else Nil) ::: msgFormat ::: authenticator ::: executionHandler
 
     /**
      * Construct an IdleStateHandler which uses [[akka.remote.netty.NettyRemoteTransport]].timer.
@@ -95,13 +95,15 @@ private[akka] class NettyRemoteTransport(_system: ExtendedActorSystem, _provider
      * happen on a netty thread (that could be bad if re-sending over the network for
      * remote-deployed actors).
      */
-    val executionHandler = new ExecutionHandler(new OrderedMemoryAwareThreadPoolExecutor(
-      settings.ExecutionPoolSize,
-      settings.MaxChannelMemorySize,
-      settings.MaxTotalMemorySize,
-      settings.ExecutionPoolKeepalive.length,
-      settings.ExecutionPoolKeepalive.unit,
-      system.threadFactory))
+    val executionHandler = if (settings.ExecutionPoolSize != 0)
+      List(new ExecutionHandler(new OrderedMemoryAwareThreadPoolExecutor(
+        settings.ExecutionPoolSize,
+        settings.MaxChannelMemorySize,
+        settings.MaxTotalMemorySize,
+        settings.ExecutionPoolKeepalive.length,
+        settings.ExecutionPoolKeepalive.unit,
+        system.threadFactory)))
+    else Nil
 
     /**
      * Construct and authentication handler which uses the SecureCookie to somewhat

akka-remote/src/main/scala/akka/remote/netty/Settings.scala

@@ -73,7 +73,7 @@ private[akka] class NettySettings(config: Config, val systemName: String) {
   val ExecutionPoolKeepalive: Duration = Duration(getMilliseconds("execution-pool-keepalive"), MILLISECONDS)
 
   val ExecutionPoolSize: Int = getInt("execution-pool-size") match {
-    case sz if sz < 1 ⇒ throw new IllegalArgumentException("akka.remote.netty.execution-pool-size is less than 1")
+    case sz if sz < 0 ⇒ throw new IllegalArgumentException("akka.remote.netty.execution-pool-size is less than 0")
     case sz           ⇒ sz
   }