!per #3729 Journaling protocol optimization

- internal batching of individually received Persistent messages
- testing fault tolerance of Processor in presence of random
  * journaling failures
  * processing failures

akka-docs/rst/scala/code/docs/event/LoggingDocSpec.scala

@@ -60,14 +60,14 @@ object LoggingDocSpec {
       reqId += 1
       val always = Map("requestId" -> reqId)
       val perMessage = currentMessage match {
-        case r: Req => Map("visitorId" -> r.visitorId)
-        case _      => Map()
+        case r: Req ⇒ Map("visitorId" -> r.visitorId)
+        case _      ⇒ Map()
       }
       always ++ perMessage
     }
 
     def receive: Receive = {
-      case r: Req => {
+      case r: Req ⇒ {
         log.info(s"Starting new request: ${r.work}")
       }
     }
@@ -75,7 +75,6 @@ object LoggingDocSpec {
 
   //#mdc-actor
 
-
   //#my-event-listener
   import akka.event.Logging.InitializeLogger
   import akka.event.Logging.LoggerInitialized
@@ -117,7 +116,7 @@ object LoggingDocSpec {
 
 class LoggingDocSpec extends AkkaSpec {
 
-  import LoggingDocSpec.{MyActor, MdcActor, MdcActorMixin, Req}
+  import LoggingDocSpec.{ MyActor, MdcActor, MdcActorMixin, Req }
 
   "use a logging actor" in {
     val myActor = system.actorOf(Props[MyActor])

akka-docs/rst/scala/code/docs/persistence/PersistenceDocSpec.scala

@@ -18,15 +18,12 @@ trait PersistenceDocSpec {
 
     class MyProcessor extends Processor {
       def receive = {
-        case Persistent(payload, sequenceNr) ⇒ {
-          // message successfully written to journal
-        }
-        case PersistenceFailure(payload, sequenceNr, cause) ⇒ {
-          // message failed to be written to journal
-        }
-        case other ⇒ {
-          // message not written to journal
-        }
+        case Persistent(payload, sequenceNr) ⇒
+        // message successfully written to journal
+        case PersistenceFailure(payload, sequenceNr, cause) ⇒
+        // message failed to be written to journal
+        case other ⇒
+        // message not written to journal
       }
     }
     //#definition
@@ -109,18 +106,16 @@ trait PersistenceDocSpec {
       val channel = context.actorOf(Channel.props(), name = "myChannel")
 
       def receive = {
-        case p @ Persistent(payload, _) ⇒ {
+        case p @ Persistent(payload, _) ⇒
           channel ! Deliver(p.withPayload(s"processed ${payload}"), destination)
-        }
       }
     }
 
     class MyDestination extends Actor {
       def receive = {
-        case p @ ConfirmablePersistent(payload, _) ⇒ {
+        case p @ ConfirmablePersistent(payload, _) ⇒
           println(s"received ${payload}")
           p.confirm()
-        }
       }
     }
     //#channel-example
@@ -135,7 +130,7 @@ trait PersistenceDocSpec {
       //#channel-id-override
 
       def receive = {
-        case p @ Persistent(payload, _) ⇒ {
+        case p @ Persistent(payload, _) ⇒
           //#channel-example-reply
           channel ! Deliver(p.withPayload(s"processed ${payload}"), sender)
           //#channel-example-reply
@@ -144,8 +139,7 @@ trait PersistenceDocSpec {
           //#resolve-destination
           //#resolve-sender
           channel forward Deliver(p, destination, Resolve.Sender)
-          //#resolve-sender
-        }
+        //#resolve-sender
       }
     }
 
@@ -175,15 +169,13 @@ trait PersistenceDocSpec {
       startWith("closed", 0)
 
       when("closed") {
-        case Event(Persistent("open", _), counter) ⇒ {
+        case Event(Persistent("open", _), counter) ⇒
           goto("open") using (counter + 1) replying (counter)
-        }
       }
 
       when("open") {
-        case Event(Persistent("close", _), counter) ⇒ {
+        case Event(Persistent("close", _), counter) ⇒
           goto("closed") using (counter + 1) replying (counter)
-        }
       }
     }
     //#fsm-example
@@ -239,7 +231,7 @@ trait PersistenceDocSpec {
     val system = ActorSystem("example")
     val processor = system.actorOf(Props[MyProcessor])
 
-    processor ! PersistentBatch(Vector(Persistent("a"), Persistent("b")))
+    processor ! PersistentBatch(List(Persistent("a"), Persistent("b")))
     //#batch-write
     system.shutdown()
   }

akka-docs/rst/scala/code/docs/persistence/PersistencePluginDocSpec.scala

@@ -23,6 +23,9 @@ import akka.persistence.snapshot._
 object PersistencePluginDocSpec {
   val config =
     """
+      //#max-batch-size
+      akka.persistence.journal.max-batch-size = 200
+      //#max-batch-size
       //#journal-config
       akka.persistence.journal.leveldb.dir = "target/journal"
       //#journal-config
@@ -69,8 +72,7 @@ class PersistencePluginDocSpec extends WordSpec {
 }
 
 class MyJournal extends AsyncWriteJournal {
-  def writeAsync(persistent: PersistentRepr): Future[Unit] = ???
-  def writeBatchAsync(persistentBatch: Seq[PersistentRepr]): Future[Unit] = ???
+  def writeAsync(persistentBatch: Seq[PersistentRepr]): Future[Unit] = ???
   def deleteAsync(processorId: String, fromSequenceNr: Long, toSequenceNr: Long, permanent: Boolean): Future[Unit] = ???
   def confirmAsync(processorId: String, sequenceNr: Long, channelId: String): Future[Unit] = ???
   def replayAsync(processorId: String, fromSequenceNr: Long, toSequenceNr: Long)(replayCallback: (PersistentRepr) ⇒ Unit): Future[Long] = ???