tone down error logging in IO layer, see #3386

* Made defaultDecider available in SupervisorStrategy,
  turned out that I didn't need it but I think it could be
  good anyway, e.g.
  override def supervisorStrategy = OneForOneStrategy(
    enableLogging = false)(SupervisorStrategy.defaultDecider)
* Verified the following scenarios:
  - client connection failure
  - server bind failure
  - kill client (peer closed)
  - kill server (peer closed)

akka-actor-tests/src/test/scala/akka/io/TcpConnectionSpec.scala

@@ -527,14 +527,12 @@ class TcpConnectionSpec extends AkkaSpec("""
       run {
         localServerChannel.accept()
 
-        EventFilter.warning(pattern = "registration timeout", occurrences = 1) intercept {
         selector.send(connectionActor, ChannelConnectable)
         userHandler.expectMsg(Connected(serverAddress, clientSideChannel.socket.getLocalSocketAddress.asInstanceOf[InetSocketAddress]))
 
         verifyActorTermination(connectionActor)
       }
     }
-    }
 
     "close the connection when user handler dies while connecting" in new UnacceptedConnectionTest {
       run {

akka-actor-tests/src/test/scala/akka/io/TcpIntegrationSpec.scala

@@ -4,6 +4,7 @@
 
 package akka.io
 
+import scala.concurrent.duration._
 import akka.testkit.AkkaSpec
 import akka.util.ByteString
 import Tcp._
@@ -32,9 +33,7 @@ class TcpIntegrationSpec extends AkkaSpec("""
 
     "properly handle connection abort from one side" in new TestSetup {
       val (clientHandler, clientConnection, serverHandler, serverConnection) = establishNewClientConnection()
-      EventFilter[IOException](occurrences = 1) intercept {
       clientHandler.send(clientConnection, Abort)
-      }
       clientHandler.expectMsg(Aborted)
       serverHandler.expectMsgType[ErrorClosed]
       verifyActorTermination(clientConnection)

akka-actor/src/main/scala/akka/actor/FaultHandling.scala

@@ -145,20 +145,27 @@ object SupervisorStrategy extends SupervisorStrategyLowPriorityImplicits {
 
   /**
    * When supervisorStrategy is not specified for an actor this
-   * is used by default. The child will be stopped when
-   * [[akka.actor.ActorInitializationException]] or [[akka.ActorKilledException]]
-   * is thrown. It will be restarted for other `Exception` types.
-   * The error is escalated if it's a `Throwable`, i.e. `Error`.
+   * is used by default. OneForOneStrategy with decider defined in
+   * [[#defaultDecider]].
    */
   final val defaultStrategy: SupervisorStrategy = {
-    def defaultDecider: Decider = {
+    OneForOneStrategy()(defaultDecider)
+  }
+
+  /**
+   * When supervisorStrategy is not specified for an actor this
+   * [[Decider]] is used by default in the supervisor strategy.
+   * The child will be stopped when [[akka.actor.ActorInitializationException]],
+   * [[akka.ActorKilledException]], or [[akka.actor.DeathPactException]] is
+   * thrown. It will be restarted for other `Exception` types.
+   * The error is escalated if it's a `Throwable`, i.e. `Error`.
+   */
+  final def defaultDecider: Decider = {
     case _: ActorInitializationException ⇒ Stop
     case _: ActorKilledException         ⇒ Stop
     case _: DeathPactException           ⇒ Stop
     case _: Exception                    ⇒ Restart
   }
-    OneForOneStrategy()(defaultDecider)
-  }
 
   /**
    * This strategy resembles Erlang in that failing children are always

akka-actor/src/main/scala/akka/io/SelectionHandler.scala

@@ -168,7 +168,7 @@ private[io] object SelectionHandler {
           def tryRun(): Unit = {
             // thorough 'close' of the Selector
             @tailrec def closeNextChannel(it: JIterator[SelectionKey]): Unit = if (it.hasNext) {
-              try it.next().channel.close() catch { case NonFatal(e) ⇒ log.error(e, "Error closing channel") }
+              try it.next().channel.close() catch { case NonFatal(e) ⇒ log.debug("Error closing channel: {}", e) }
               closeNextChannel(it)
             }
             try closeNextChannel(selector.keys.iterator)
@@ -246,7 +246,24 @@ private[io] class SelectionHandler(settings: SelectionHandlerSettings) extends A
   override def postStop(): Unit = registry.shutdown()
 
   // we can never recover from failures of a connection or listener child
-  override def supervisorStrategy = SupervisorStrategy.stoppingStrategy
+  // and log the failure at debug level
+  override def supervisorStrategy = {
+    def stoppingDecider: SupervisorStrategy.Decider = {
+      case _: Exception ⇒ SupervisorStrategy.Stop
+    }
+    new OneForOneStrategy()(stoppingDecider) {
+      override protected def logFailure(context: ActorContext, child: ActorRef, cause: Throwable,
+                                        decision: SupervisorStrategy.Directive): Unit =
+        try {
+          val logMessage = cause match {
+            case e: ActorInitializationException if e.getCause ne null ⇒ e.getCause.getMessage
+            case e ⇒ e.getMessage
+          }
+          context.system.eventStream.publish(
+            Logging.Debug(child.path.toString, classOf[SelectionHandler], logMessage))
+        } catch { case NonFatal(_) ⇒ }
+    }
+  }
 
   def spawnChildWithCapacityProtection(cmd: WorkerForCommand, retriesLeft: Int): Unit = {
     if (TraceLogging) log.debug("Executing [{}]", cmd)
@@ -258,7 +275,7 @@ private[io] class SelectionHandler(settings: SelectionHandlerSettings) extends A
       if (MaxChannelsPerSelector > 0) context.watch(child) // we don't need to watch if we aren't limited
     } else {
       if (retriesLeft >= 1) {
-        log.warning("Rejecting [{}] with [{}] retries left, retrying...", cmd, retriesLeft)
+        log.debug("Rejecting [{}] with [{}] retries left, retrying...", cmd, retriesLeft)
         context.parent forward Retry(cmd, retriesLeft - 1)
       } else {
         log.warning("Rejecting [{}] with no retries left, aborting...", cmd)

akka-actor/src/main/scala/akka/io/TcpConnection.scala

@@ -65,7 +65,7 @@ private[io] abstract class TcpConnection(val tcp: TcpExt, val channel: SocketCha
     case ReceiveTimeout ⇒
       // after sending `Register` user should watch this actor to make sure
       // it didn't die because of the timeout
-      log.warning("Configured registration timeout of [{}] expired, stopping", RegisterTimeout)
+      log.debug("Configured registration timeout of [{}] expired, stopping", RegisterTimeout)
       context.stop(self)
   }
 

akka-actor/src/main/scala/akka/io/TcpListener.scala

@@ -59,7 +59,7 @@ private[io] class TcpListener(selectorRouter: ActorRef,
     } catch {
       case NonFatal(e) ⇒
         bindCommander ! bind.failureMessage
-        log.error(e, "Bind failed for TCP channel on endpoint [{}]", bind.localAddress)
+        log.debug("Bind failed for TCP channel on endpoint [{}]: {}", bind.localAddress, e)
         context.stop(self)
     }
 
@@ -79,7 +79,7 @@ private[io] class TcpListener(selectorRouter: ActorRef,
       log.warning("Could not register incoming connection since selector capacity limit is reached, closing connection")
       try socketChannel.close()
       catch {
-        case NonFatal(e) ⇒ log.error(e, "Error closing channel")
+        case NonFatal(e) ⇒ log.debug("Error closing socket channel: {}", e)
       }
 
     case Unbind ⇒
@@ -95,7 +95,7 @@ private[io] class TcpListener(selectorRouter: ActorRef,
       if (limit > 0) {
         try channel.accept()
         catch {
-          case NonFatal(e) ⇒ { log.error(e, "Accept error: could not accept new connection due to {}", e); null }
+          case NonFatal(e) ⇒ { log.error(e, "Accept error: could not accept new connection"); null }
         }
       } else null
     if (socketChannel != null) {
@@ -115,7 +115,7 @@ private[io] class TcpListener(selectorRouter: ActorRef,
         channel.close()
       }
     } catch {
-      case NonFatal(e) ⇒ log.error(e, "Error closing ServerSocketChannel")
+      case NonFatal(e) ⇒ log.debug("Error closing ServerSocketChannel: {}", e)
     }
   }
 }

akka-actor/src/main/scala/akka/io/UdpConnection.scala

@@ -41,8 +41,8 @@ private[io] class UdpConnection(udpConn: UdpConnectedExt,
       datagramChannel.connect(remoteAddress)
     } catch {
       case NonFatal(e) ⇒
-        log.error(e, "Failure while connecting UDP channel to remote address [{}] local address [{}]",
-          remoteAddress, localAddress.map { _.toString }.getOrElse("undefined"))
+        log.debug("Failure while connecting UDP channel to remote address [{}] local address [{}]: {}",
+          remoteAddress, localAddress.getOrElse("undefined"), e)
         commander ! CommandFailed(connect)
         context.stop(self)
     }
@@ -126,7 +126,7 @@ private[io] class UdpConnection(udpConn: UdpConnectedExt,
       log.debug("Closing DatagramChannel after being stopped")
       try channel.close()
       catch {
-        case NonFatal(e) ⇒ log.error(e, "Error closing DatagramChannel")
+        case NonFatal(e) ⇒ log.debug("Error closing DatagramChannel: {}", e)
       }
     }
 }

akka-actor/src/main/scala/akka/io/UdpListener.scala

@@ -49,7 +49,7 @@ private[io] class UdpListener(val udp: UdpExt,
     } catch {
       case NonFatal(e) ⇒
         bindCommander ! CommandFailed(bind)
-        log.error(e, "Failed to bind UDP channel to endpoint [{}]", bind.localAddress)
+        log.debug("Failed to bind UDP channel to endpoint [{}]: {}", bind.localAddress, e)
         context.stop(self)
     }
 
@@ -99,7 +99,7 @@ private[io] class UdpListener(val udp: UdpExt,
       log.debug("Closing DatagramChannel after being stopped")
       try channel.close()
       catch {
-        case NonFatal(e) ⇒ log.error(e, "Error closing DatagramChannel")
+        case NonFatal(e) ⇒ log.debug("Error closing DatagramChannel: {}", e)
       }
     }
   }

akka-actor/src/main/scala/akka/io/UdpSender.scala

@@ -41,7 +41,7 @@ private[io] class UdpSender(val udp: UdpExt,
     log.debug("Closing DatagramChannel after being stopped")
     try channel.close()
     catch {
-      case NonFatal(e) ⇒ log.error(e, "Error closing DatagramChannel")
+      case NonFatal(e) ⇒ log.debug("Error closing DatagramChannel: {}", e)
     }
   }
 }