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Migrating Agents to greener pastures

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This commit is contained in:
Viktor Klang 2013-01-23 02:06:49 +01:00
parent 13b1324509
commit 9522add9b7
9 changed files with 396 additions and 444 deletions
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2
akka-actor-tests/src/test/scala/akka/actor/dispatch/ActorModelSpec.scala
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@ -425,7 +425,7 @@ abstract class ActorModelSpec(config: String) extends AkkaSpec(config) with Defa
Thread.getAllStackTraces().asScala foreach {
case (thread, stack) ⇒
println(s"$thread:")
stack foreach (s => println(s"\t$s"))
stack foreach (s ⇒ println(s"\t$s"))
}
}
assert(Await.result(f1, remaining) === "foo")

40
akka-actor-tests/src/test/scala/akka/dispatch/ExecutionContextSpec.scala
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@ -4,6 +4,7 @@ import java.util.concurrent.{ ExecutorService, Executor, Executors }
import java.util.concurrent.atomic.AtomicInteger
import scala.concurrent._
import akka.testkit.{ TestLatch, AkkaSpec, DefaultTimeout }
import akka.util.SerializedSuspendableExecutionContext
@org.junit.runner.RunWith(classOf[org.scalatest.junit.JUnitRunner])
class ExecutionContextSpec extends AkkaSpec with DefaultTimeout {
@ -81,4 +82,43 @@ class ExecutionContextSpec extends AkkaSpec with DefaultTimeout {
Await.ready(latch, timeout.duration)
}
}
"A SerializedSuspendableExecutionContext" must {
"be suspendable and resumable" in {
val sec = SerializedSuspendableExecutionContext(1)(ExecutionContext.global)
val counter = new AtomicInteger(0)
def perform(f: Int ⇒ Int) = sec execute new Runnable { def run = counter.set(f(counter.get)) }
perform(_ + 1)
perform(x ⇒ { sec.suspend(); x * 2 })
awaitCond(counter.get == 2)
perform(_ + 4)
perform(_ * 2)
sec.resume()
awaitCond(counter.get == 12)
perform(_ * 2)
awaitCond(counter.get == 24)
sec.isEmpty must be === true
}
"execute 'throughput' nmber of tasks per sweep" in {
val submissions = new AtomicInteger(0)
val counter = new AtomicInteger(0)
val underlying = new ExecutionContext {
override def execute(r: Runnable) { submissions.incrementAndGet(); ExecutionContext.global.execute(r) }
override def reportFailure(t: Throwable) { ExecutionContext.global.reportFailure(t) }
}
val throughput = 25
val sec = SerializedSuspendableExecutionContext(throughput)(underlying)
sec.suspend()
def perform(f: Int ⇒ Int) = sec execute new Runnable { def run = counter.set(f(counter.get)) }
val total = 1000
1 to total foreach { _ ⇒ perform(_ + 1) }
sec.size() must be === total
sec.resume()
awaitCond(counter.get == total)
submissions.get must be === (total / throughput)
sec.isEmpty must be === true
}
}
}

81
akka-actor/src/main/scala/akka/util/SerializedSuspendableExecutionContext.scala Normal file
View file

@ -0,0 +1,81 @@
package akka.util
import java.util.concurrent.ConcurrentLinkedQueue
import java.util.concurrent.atomic.AtomicInteger
import scala.concurrent.ExecutionContext
import scala.util.control.NonFatal
import scala.annotation.{ tailrec, switch }
private[akka] object SerializedSuspendableExecutionContext {
final val Off = 0
final val On = 1
final val Suspended = 2
def apply(batchSize: Int)(implicit context: ExecutionContext): SerializedSuspendableExecutionContext =
new SerializedSuspendableExecutionContext(batchSize)(context match {
case s: SerializedSuspendableExecutionContext ⇒ s.context
case other ⇒ other
})
}
/**
* This `ExecutionContext` allows to wrap an underlying `ExecutionContext` and provide guaranteed serial execution
* of tasks submitted to it. On top of that it also allows for *suspending* and *resuming* processing of tasks.
*
* WARNING: This type must never leak into User code as anything but `ExecutionContext`
*
* @param throughput maximum number of tasks to be executed in serial before relinquishing the executing thread.
* @param context the underlying context which will be used to actually execute the submitted tasks
*/
private[akka] final class SerializedSuspendableExecutionContext(throughput: Int)(val context: ExecutionContext)
extends ConcurrentLinkedQueue[Runnable] with Runnable with ExecutionContext {
import SerializedSuspendableExecutionContext._
require(throughput > 0, s"SerializedSuspendableExecutionContext.throughput must be greater than 0 but was $throughput")
private final val state = new AtomicInteger(0)
@tailrec private final def addState(newState: Int): Boolean = {
val c = state.get;
state.compareAndSet(c, c | newState) || addState(newState)
}
@tailrec private final def remState(oldState: Int) {
val c = state.get
if (state.compareAndSet(c, c & ~oldState)) attach() else remState(oldState)
}
/**
* Resumes execution of tasks until `suspend` is called,
* if it isn't currently suspended, it is a no-op.
* This operation is idempotent.
*/
final def resume(): Unit = remState(Suspended)
/**
* Suspends execution of tasks until `resume` is called,
* this operation is idempotent.
*/
final def suspend(): Unit = addState(Suspended)
final def run(): Unit = {
@tailrec def run(done: Int): Unit =
if (done < throughput && state.get == On) {
poll() match {
case null ⇒ ()
case some ⇒
try some.run() catch { case NonFatal(t) ⇒ context reportFailure t }
run(done + 1)
}
}
try run(0) finally remState(On)
}
final def attach(): Unit = if (!isEmpty && state.compareAndSet(Off, On)) context execute this
override final def execute(task: Runnable): Unit = try add(task) finally attach()
override final def reportFailure(t: Throwable): Unit = context reportFailure t
override final def toString: String = (state.get: @switch) match {
case 0 ⇒ "Off"
case 1 ⇒ "On"
case 2 ⇒ "Off & Suspended"
case 3 ⇒ "On & Suspended"
}
}

213
akka-agent/src/main/scala/akka/agent/Agent.scala
View file

@ -7,23 +7,17 @@ package akka.agent
import akka.actor._
import akka.japi.{ Function ⇒ JFunc, Procedure ⇒ JProc }
import akka.pattern.ask
import akka.util.Timeout
import scala.concurrent.stm._
import scala.concurrent.{ ExecutionContext, Future, Promise, Await }
import scala.concurrent.duration.{ FiniteDuration, Duration }
/**
* Used internally to send functions.
*/
private[akka] case class Update[T](function: T ⇒ T)
private[akka] case class Alter[T](function: T ⇒ T)
private[akka] case object Get
import akka.util.{ SerializedSuspendableExecutionContext, Timeout }
import util.Try
/**
* Factory method for creating an Agent.
*/
object Agent {
def apply[T](initialValue: T)(implicit system: ActorSystem) = new Agent(initialValue, system, system)
def apply[T](initialValue: T)(implicit context: ExecutionContext) = new Agent(initialValue, context)
}
/**
@ -96,14 +90,13 @@ object Agent {
* agent4.close
* }}}
*/
class Agent[T](initialValue: T, refFactory: ActorRefFactory, system: ActorSystem) {
class Agent[T](initialValue: T, context: ExecutionContext) {
private val ref = Ref(initialValue)
private val updater = refFactory.actorOf(Props(new AgentUpdater(this, ref))).asInstanceOf[InternalActorRef] //TODO can we avoid this somehow?
def this(initialValue: T, system: ActorSystem) = this(initialValue, system, system)
private val updater = SerializedSuspendableExecutionContext(10)(context)
/**
* Read the internal state of the agent.
* Java API
*/
def get(): T = ref.single.get
@ -113,22 +106,44 @@ class Agent[T](initialValue: T, refFactory: ActorRefFactory, system: ActorSystem
def apply(): T = get
/**
* Dispatch a function to update the internal state.
* Dispatch a new value for the internal state. Behaves the same
* as sending a function (x => newValue).
*/
def send(f: T ⇒ T): Unit = {
def dispatch = updater ! Update(f)
Txn.findCurrent match {
case Some(txn) ⇒ Txn.afterCommit(status ⇒ dispatch)(txn)
case _ ⇒ dispatch
}
}
def send(newValue: T): Unit = withinTransaction(new Runnable { def run = ref.single.update(newValue) })
/**
* Dispatch a function to update the internal state.
* In Java, pass in an instance of `akka.dispatch.Mapper`.
*/
def send(f: T ⇒ T): Unit = withinTransaction(new Runnable { def run = ref.single.transform(f) })
/**
* Dispatch a function to update the internal state but on its own thread.
* This does not use the reactive thread pool and can be used for long-running
* or blocking operations. Dispatches using either `sendOff` or `send` will
* still be executed in order.
* In Java, pass in an instance of `akka.dispatch.Mapper`.
*/
def sendOff(f: T ⇒ T)(implicit ec: ExecutionContext): Unit = withinTransaction(
new Runnable {
def run =
try updater.suspend() finally ec.execute(new Runnable { def run = try ref.single.transform(f) finally updater.resume() })
})
/**
* Dispatch an update to the internal state, and return a Future where
* that new state can be obtained.
* In Java, pass in an instance of `akka.dispatch.Mapper`.
*/
def alter(newValue: T): Future[T] = alter(_ ⇒ newValue)
/**
* Dispatch a function to update the internal state, and return a Future where
* that new state can be obtained within the given timeout.
* that new state can be obtained.
* In Java, pass in an instance of `akka.dispatch.Mapper`.
*/
def alter(f: T ⇒ T)(implicit timeout: Timeout): Future[T] = {
def dispatch = ask(updater, Alter(f)).asInstanceOf[Future[T]]
def alter(f: T ⇒ T): Future[T] = {
def dispatch = Future(ref.single.transformAndGet(f))(updater)
Txn.findCurrent match {
case Some(txn) ⇒
val result = Promise[T]()
@ -138,162 +153,56 @@ class Agent[T](initialValue: T, refFactory: ActorRefFactory, system: ActorSystem
}
}
/**
* Dispatch a new value for the internal state. Behaves the same
* as sending a function (x => newValue).
*/
def send(newValue: T): Unit = send(_ ⇒ newValue)
/**
* Dispatch a new value for the internal state. Behaves the same
* as sending a function (x => newValue).
*/
def update(newValue: T): Unit = send(newValue)
/**
* Dispatch a function to update the internal state but on its own thread.
* This does not use the reactive thread pool and can be used for long-running
* or blocking operations. Dispatches using either `sendOff` or `send` will
* still be executed in order.
*/
def sendOff(f: T ⇒ T)(implicit ec: ExecutionContext): Unit = {
send((value: T) ⇒ {
suspend()
Future(ref.single.transformAndGet(f)).andThen({ case _ ⇒ resume() })
value
})
}
/**
* Dispatch a function to update the internal state but on its own thread,
* and return a Future where that new state can be obtained within the given timeout.
* and return a Future where that new state can be obtained.
* This does not use the reactive thread pool and can be used for long-running
* or blocking operations. Dispatches using either `alterOff` or `alter` will
* still be executed in order.
* In Java, pass in an instance of `akka.dispatch.Mapper`.
*/
def alterOff(f: T ⇒ T)(implicit timeout: Timeout, ec: ExecutionContext): Future[T] = {
def alterOff(f: T ⇒ T)(implicit ec: ExecutionContext): Future[T] = {
val result = Promise[T]()
send((value: T) ⇒ {
suspend()
result completeWith Future(ref.single.transformAndGet(f)).andThen({ case _ ⇒ resume() })
value
withinTransaction(new Runnable {
def run = {
updater.suspend()
result completeWith Future(try ref.single.transformAndGet(f) finally updater.resume())
}
})
result.future
}
private final def withinTransaction(run: Runnable): Unit = {
def dispatch = updater.execute(run)
Txn.findCurrent match {
case Some(txn) ⇒ Txn.afterCommit(status ⇒ dispatch)(txn)
case _ ⇒ dispatch
}
}
/**
* A future to the current value that will be completed after any currently
* queued updates.
*/
def future(implicit timeout: Timeout): Future[T] = (updater ? Get).asInstanceOf[Future[T]] //Known to be safe
/**
* Gets this agent's value after all currently queued updates have completed.
*/
def await(implicit timeout: Timeout): T = Await.result(future, timeout.duration)
def future(): Future[T] = Future(ref.single.get)(updater)
/**
* Map this agent to a new agent, applying the function to the internal state.
* Does not change the value of this agent.
* In Java, pass in an instance of `akka.dispatch.Mapper`.
*/
def map[B](f: T ⇒ B): Agent[B] = Agent(f(get))(system)
def map[B](f: T ⇒ B): Agent[B] = Agent(f(get))(updater)
/**
* Flatmap this agent to a new agent, applying the function to the internal state.
* Does not change the value of this agent.
* In Java, pass in an instance of `akka.dispatch.Mapper`.
*/
def flatMap[B](f: T ⇒ Agent[B]): Agent[B] = f(get)
/**
* Applies the function to the internal state. Does not change the value of this agent.
* In Java, pass in an instance of `akka.dispatch.Foreach`.
*/
def foreach[U](f: T ⇒ U): Unit = f(get)
/**
* Suspends processing of `send` actions for the agent.
*/
def suspend(): Unit = updater.suspend()
/**
* Resumes processing of `send` actions for the agent.
*/
def resume(): Unit = updater.resume(causedByFailure = null)
/**
* Closes the agents and makes it eligible for garbage collection.
* A closed agent cannot accept any `send` actions.
*/
def close(): Unit = updater.stop()
// ---------------------------------------------
// Support for Java API Functions and Procedures
// ---------------------------------------------
/**
* Java API:
* Dispatch a function to update the internal state.
*/
def send(f: JFunc[T, T]): Unit = send(x ⇒ f(x))
/**
* Java API
* Dispatch a function to update the internal state, and return a Future where that new state can be obtained
* within the given timeout
*/
def alter(f: JFunc[T, T], timeout: FiniteDuration): Future[T] = alter(x ⇒ f(x))(timeout)
/**
* Java API:
* Dispatch a function to update the internal state but on its own thread.
* This does not use the reactive thread pool and can be used for long-running
* or blocking operations. Dispatches using either `sendOff` or `send` will
* still be executed in order.
*/
def sendOff(f: JFunc[T, T], ec: ExecutionContext): Unit = sendOff(x ⇒ f(x))(ec)
/**
* Java API:
* Dispatch a function to update the internal state but on its own thread,
* and return a Future where that new state can be obtained within the given timeout.
* This does not use the reactive thread pool and can be used for long-running
* or blocking operations. Dispatches using either `alterOff` or `alter` will
* still be executed in order.
*/
def alterOff(f: JFunc[T, T], timeout: FiniteDuration, ec: ExecutionContext): Unit = alterOff(x ⇒ f(x))(Timeout(timeout), ec)
/**
* Java API:
* Map this agent to a new agent, applying the function to the internal state.
* Does not change the value of this agent.
*/
def map[B](f: JFunc[T, B]): Agent[B] = Agent(f(get))(system)
/**
* Java API:
* Flatmap this agent to a new agent, applying the function to the internal state.
* Does not change the value of this agent.
*/
def flatMap[B](f: JFunc[T, Agent[B]]): Agent[B] = f(get)
/**
* Java API:
* Applies the function to the internal state. Does not change the value of this agent.
*/
def foreach(f: JProc[T]): Unit = f(get)
}
/**
* Agent updater actor. Used internally for `send` actions.
*
* INTERNAL API
*/
private[akka] class AgentUpdater[T](agent: Agent[T], ref: Ref[T]) extends Actor {
def receive = {
case u: Update[_] ⇒ update(u.function.asInstanceOf[T ⇒ T])
case a: Alter[_] ⇒ sender ! update(a.function.asInstanceOf[T ⇒ T])
case Get ⇒ sender ! agent.get
case _ ⇒
}
def update(function: T ⇒ T): T = ref.single.transformAndGet(function)
}
}

52
akka-agent/src/test/scala/akka/agent/AgentSpec.scala
View file

@ -18,7 +18,7 @@ class CountDownFunction[A](num: Int = 1) extends Function1[A, A] {
class AgentSpec extends AkkaSpec {
implicit val timeout = Timeout(5.seconds.dilated)
import system.dispatcher
"Agent" must {
"update with send dispatches in order sent" in {
val countDown = new CountDownFunction[String]
@ -31,36 +31,29 @@ class AgentSpec extends AkkaSpec {
countDown.await(5 seconds)
agent() must be("abcd")
agent.close()
}
"maintain order between send and sendOff" in {
val countDown = new CountDownFunction[String]
val l1, l2 = new CountDownLatch(1)
import system.dispatcher
val l1, l2 = new TestLatch(1)
val agent = Agent("a")
agent send (_ + "b")
agent.sendOff((s: String) ⇒ { l1.countDown; l2.await(5, TimeUnit.SECONDS); s + "c" })
l1.await(5, TimeUnit.SECONDS)
agent.sendOff((s: String) ⇒ { l1.countDown; Await.ready(l2, timeout.duration); s + "c" })
Await.ready(l1, timeout.duration)
agent send (_ + "d")
agent send countDown
l2.countDown
countDown.await(5 seconds)
agent() must be("abcd")
agent.close()
}
"maintain order between alter and alterOff" in {
import system.dispatcher
val l1, l2 = new CountDownLatch(1)
val l1, l2 = new TestLatch(1)
val agent = Agent("a")
val r1 = agent.alter(_ + "b")
val r2 = agent.alterOff((s: String) ⇒ { l1.countDown; l2.await(5, TimeUnit.SECONDS); s + "c" })
l1.await(5, TimeUnit.SECONDS)
val r2 = agent.alterOff(s ⇒ { l1.countDown; Await.ready(l2, timeout.duration); s + "c" })
Await.ready(l1, timeout.duration)
val r3 = agent.alter(_ + "d")
val result = Future.sequence(Seq(r1, r2, r3)).map(_.mkString(":"))
l2.countDown
@ -68,18 +61,16 @@ class AgentSpec extends AkkaSpec {
Await.result(result, 5 seconds) must be === "ab:abc:abcd"
agent() must be("abcd")
agent.close()
}
"be immediately readable" in {
val countDown = new CountDownFunction[Int]
val readLatch = new CountDownLatch(1)
val readLatch = new TestLatch(1)
val readTimeout = 5 seconds
val agent = Agent(5)
val f1 = (i: Int) ⇒ {
readLatch.await(readTimeout.length, readTimeout.unit)
Await.ready(readLatch, readTimeout)
i + 5
}
agent send f1
@ -90,15 +81,12 @@ class AgentSpec extends AkkaSpec {
countDown.await(5 seconds)
read must be(5)
agent() must be(10)
agent.close()
}
"be readable within a transaction" in {
val agent = Agent(5)
val value = atomic { t ⇒ agent() }
value must be(5)
agent.close()
}
"dispatch sends in successful transactions" in {
@ -112,8 +100,6 @@ class AgentSpec extends AkkaSpec {
countDown.await(5 seconds)
agent() must be(10)
agent.close()
}
"not dispatch sends in aborted transactions" in {
@ -132,8 +118,6 @@ class AgentSpec extends AkkaSpec {
countDown.await(5 seconds)
agent() must be(5)
agent.close()
}
"be able to return a 'queued' future" in {
@ -142,8 +126,6 @@ class AgentSpec extends AkkaSpec {
agent send (_ + "c")
Await.result(agent.future, timeout.duration) must be("abc")
agent.close()
}
"be able to await the value after updates have completed" in {
@ -151,9 +133,7 @@ class AgentSpec extends AkkaSpec {
agent send (_ + "b")
agent send (_ + "c")
agent.await must be("abc")
agent.close()
Await.result(agent.future, timeout.duration) must be("abc")
}
"be able to be mapped" in {
@ -162,9 +142,6 @@ class AgentSpec extends AkkaSpec {
agent1() must be(5)
agent2() must be(10)
agent1.close()
agent2.close()
}
"be able to be used in a 'foreach' for comprehension" in {
@ -176,8 +153,6 @@ class AgentSpec extends AkkaSpec {
}
result must be(3)
agent.close()
}
"be able to be used in a 'map' for comprehension" in {
@ -186,9 +161,6 @@ class AgentSpec extends AkkaSpec {
agent1() must be(5)
agent2() must be(10)
agent1.close()
agent2.close()
}
"be able to be used in a 'flatMap' for comprehension" in {
@ -203,10 +175,6 @@ class AgentSpec extends AkkaSpec {
agent1() must be(1)
agent2() must be(2)
agent3() must be(3)
agent1.close()
agent2.close()
agent3.close()
}
}
}

121
akka-docs/rst/java/agents.rst
View file

@ -15,77 +15,35 @@ functions that are asynchronously applied to the Agent's state and whose return
value becomes the Agent's new state. The state of an Agent should be immutable.
While updates to Agents are asynchronous, the state of an Agent is always
immediately available for reading by any thread (using ``get``) without any
messages.
immediately available for reading by any thread (using ``get``) without any messages.
Agents are reactive. The update actions of all Agents get interleaved amongst
threads in a thread pool. At any point in time, at most one ``send`` action for
threads in an ``ExecutionContext``. At any point in time, at most one ``send`` action for
each Agent is being executed. Actions dispatched to an agent from another thread
will occur in the order they were sent, potentially interleaved with actions
dispatched to the same agent from other sources.
dispatched to the same agent from other threads.
If an Agent is used within an enclosing transaction, then it will participate in
that transaction. Agents are integrated with the STM - any dispatches made in
that transaction. Agents are integrated with Scala STM - any dispatches made in
a transaction are held until that transaction commits, and are discarded if it
is retried or aborted.
Creating and stopping Agents
Creating Agents
============================
Agents are created by invoking ``new Agent(value, system)`` passing in the
Agent's initial value and a reference to the ``ActorSystem`` for your
application. An ``ActorSystem`` is required to create the underlying Actors. See
:ref:`actor-systems` for more information about actor systems.
Here is an example of creating an Agent:
Agents are created by invoking ``new Agent<ValueType>(value, executionContext)`` – passing in the Agent's initial
value and providing an ``ExecutionContext`` to be used for it:
.. includecode:: code/docs/agent/AgentDocTest.java
:include: import-system,import-agent
:include: import-agent,create
:language: java
.. includecode:: code/docs/agent/AgentDocTest.java#create
:language: java
An Agent will be running until you invoke ``close`` on it. Then it will be
eligible for garbage collection (unless you hold on to it in some way).
.. includecode:: code/docs/agent/AgentDocTest.java#close
:language: java
Updating Agents
===============
You update an Agent by sending a function that transforms the current value or
by sending just a new value. The Agent will apply the new value or function
atomically and asynchronously. The update is done in a fire-forget manner and
you are only guaranteed that it will be applied. There is no guarantee of when
the update will be applied but dispatches to an Agent from a single thread will
occur in order. You apply a value or a function by invoking the ``send``
function.
.. includecode:: code/docs/agent/AgentDocTest.java#import-function
:language: java
.. includecode:: code/docs/agent/AgentDocTest.java#send
:language: java
You can also dispatch a function to update the internal state but on its own
thread. This does not use the reactive thread pool and can be used for
long-running or blocking operations. You do this with the ``sendOff``
method. Dispatches using either ``sendOff`` or ``send`` will still be executed
in order.
.. includecode:: code/docs/agent/AgentDocTest.java#send-off
:language: java
Reading an Agent's value
========================
Agents can be dereferenced (you can get an Agent's value) by calling the get
method:
Agents can be dereferenced (you can get an Agent's value) by invoking the Agent
with ``get()`` like this:
.. includecode:: code/docs/agent/AgentDocTest.java#read-get
:language: java
@ -94,15 +52,58 @@ Reading an Agent's current value does not involve any message passing and
happens immediately. So while updates to an Agent are asynchronous, reading the
state of an Agent is synchronous.
You can also get a ``Future`` to the Agents value, that will be completed after the
currently queued updates have completed:
Awaiting an Agent's value
=========================
It is also possible to read the value after all currently queued sends have
completed. You can do this with ``await``:
.. includecode:: code/docs/agent/AgentDocTest.java#import-timeout
.. includecode:: code/docs/agent/AgentDocTest.java
:include: import-future,read-future
:language: java
.. includecode:: code/docs/agent/AgentDocTest.java#read-await
See :ref:`futures-java` for more information on ``Futures``.
Updating Agents (send & alter)
==============================
You update an Agent by sending a function (``akka.dispatch.Mapper``) that transforms the current value or
by sending just a new value. The Agent will apply the new value or function
atomically and asynchronously. The update is done in a fire-forget manner and
you are only guaranteed that it will be applied. There is no guarantee of when
the update will be applied but dispatches to an Agent from a single thread will
occur in order. You apply a value or a function by invoking the ``send``
function.
.. includecode:: code/docs/agent/AgentDocTest.java
:include: import-function,send
:language: java
You can also dispatch a function to update the internal state but on its own
thread. This does not use the reactive thread pool and can be used for
long-running or blocking operations. You do this with the ``sendOff``
method. Dispatches using either ``sendOff`` or ``send`` will still be executed
in order.
.. includecode:: code/docs/agent/AgentDocTest.java
:include: import-function,send-off
:language: java
All ``send`` methods also have a corresponding ``alter`` method that returns a ``Future``.
See :ref:`futures-java` for more information on ``Futures``.
.. includecode:: code/docs/agent/AgentDocTest.java
:include: import-future,import-function,alter
:language: java
.. includecode:: code/docs/agent/AgentDocTest.java
:include: import-future,import-function,alter-off
:language: java
Transactional Agents
====================
If an Agent is used within an enclosing transaction, then it will participate in
that transaction. If you send to an Agent within a transaction then the dispatch
to the Agent will be held until that transaction commits, and discarded if the
transaction is aborted. Here's an example:
.. includecode:: code/docs/agent/AgentDocTest.java#transfer-example
:language: java

113
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@ -5,107 +5,112 @@ package docs.agent;
import static org.junit.Assert.*;
import scala.concurrent.ExecutionContext;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;
import akka.testkit.AkkaSpec;
//#import-system
import akka.actor.ActorSystem;
//#import-system
import scala.concurrent.Await;
import scala.concurrent.duration.Duration;
//#import-agent
import akka.agent.Agent;
import scala.concurrent.ExecutionContext;
import akka.agent.Agent;
import akka.dispatch.ExecutionContexts;
//#import-agent
//#import-function
import akka.japi.Function;
import akka.dispatch.Mapper;
//#import-function
//#import-timeout
import akka.util.Timeout;
import static java.util.concurrent.TimeUnit.SECONDS;
//#import-timeout
//#import-future
import scala.concurrent.Future;
//#import-future
public class AgentDocTest {
private static ActorSystem testSystem;
private static ExecutionContext ec;
@BeforeClass
public static void beforeAll() {
testSystem = ActorSystem.create("AgentDocTest", AkkaSpec.testConf());
ec = testSystem.dispatcher();
}
@AfterClass
public static void afterAll() {
testSystem.shutdown();
testSystem = null;
}
private static ExecutionContext ec = ExecutionContexts.global();
@Test
public void createAndClose() {
//#create
ActorSystem system = ActorSystem.create("app");
Agent<Integer> agent = new Agent<Integer>(5, system);
public void createAndRead() throws Exception {
//#create
ExecutionContext ec = ExecutionContexts.global();
Agent<Integer> agent = new Agent<Integer>(5, ec);
//#create
//#close
agent.close();
//#close
//#read-get
Integer result = agent.get();
//#read-get
system.shutdown();
//#read-future
Future<Integer> future = agent.future();
//#read-future
assertEquals(result, new Integer(5));
assertEquals(Await.result(future, Duration.create(5,"s")), new Integer(5));
}
@Test
public void sendAndSendOffAndReadAwait() {
Agent<Integer> agent = new Agent<Integer>(5, testSystem);
public void sendAndSendOffAndReadAwait() throws Exception {
Agent<Integer> agent = new Agent<Integer>(5, ec);
//#send
// send a value
agent.send(7);
// send a function
agent.send(new Function<Integer, Integer>() {
agent.send(new Mapper<Integer, Integer>() {
public Integer apply(Integer i) {
return i * 2;
}
});
//#send
Function<Integer, Integer> longRunningOrBlockingFunction = new Function<Integer, Integer>() {
Mapper<Integer, Integer> longRunningOrBlockingFunction = new Mapper<Integer, Integer>() {
public Integer apply(Integer i) {
return i * 1;
}
};
ExecutionContext theExecutionContextToExecuteItIn = ec;
//#send-off
// sendOff a function
agent.sendOff(longRunningOrBlockingFunction, ec);
agent.sendOff(longRunningOrBlockingFunction,
theExecutionContextToExecuteItIn);
//#send-off
//#read-await
Integer result = agent.await(new Timeout(5, SECONDS));
//#read-await
assertEquals(result, new Integer(14));
agent.close();
assertEquals(Await.result(agent.future(), Duration.create(5,"s")), new Integer(14));
}
@Test
public void readWithGet() {
Agent<Integer> agent = new Agent<Integer>(5, testSystem);
@Test
public void alterAndAlterOff() throws Exception {
Agent<Integer> agent = new Agent<Integer>(5, ec);
//#read-get
Integer result = agent.get();
//#read-get
//#alter
// alter a value
Future<Integer> f1 = agent.alter(7);
assertEquals(result, new Integer(5));
// alter a function (Mapper)
Future<Integer> f2 = agent.alter(new Mapper<Integer, Integer>() {
public Integer apply(Integer i) {
return i * 2;
}
});
//#alter
agent.close();
}
Mapper<Integer, Integer> longRunningOrBlockingFunction = new Mapper<Integer, Integer>() {
public Integer apply(Integer i) {
return i * 1;
}
};
ExecutionContext theExecutionContextToExecuteItIn = ec;
//#alter-off
// alterOff a function (Mapper)
Future<Integer> f3 = agent.alterOff(longRunningOrBlockingFunction,
theExecutionContextToExecuteItIn);
//#alter-off
assertEquals(Await.result(f3, Duration.create(5,"s")), new Integer(14));
}
}

60
akka-docs/rst/scala/agents.rst
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@ -19,10 +19,10 @@ immediately available for reading by any thread (using ``get`` or ``apply``)
without any messages.
Agents are reactive. The update actions of all Agents get interleaved amongst
threads in a thread pool. At any point in time, at most one ``send`` action for
threads in an ``ExecutionContext``. At any point in time, at most one ``send`` action for
each Agent is being executed. Actions dispatched to an agent from another thread
will occur in the order they were sent, potentially interleaved with actions
dispatched to the same agent from other sources.
dispatched to the same agent from other threads.
If an Agent is used within an enclosing transaction, then it will participate in
that transaction. Agents are integrated with Scala STM - any dispatches made in
@ -30,32 +30,33 @@ a transaction are held until that transaction commits, and are discarded if it
is retried or aborted.
Creating and stopping Agents
Creating Agents
============================
Agents are created by invoking ``Agent(value)`` passing in the Agent's initial
value:
value and providing an implicit ``ExecutionContext`` to be used for it, for these
examples we're going to use the default global one, but YMMV:
.. includecode:: code/docs/agent/AgentDocSpec.scala#create
Note that creating an Agent requires an implicit ``ActorSystem`` (for creating
the underlying actors). See :ref:`actor-systems` for more information about
actor systems. An ActorSystem can be in implicit scope when creating an Agent:
Reading an Agent's value
========================
.. includecode:: code/docs/agent/AgentDocSpec.scala#create-implicit-system
Agents can be dereferenced (you can get an Agent's value) by invoking the Agent
with parentheses like this:
Or the ActorSystem can be passed explicitly when creating an Agent:
.. includecode:: code/docs/agent/AgentDocSpec.scala#read-apply
.. includecode:: code/docs/agent/AgentDocSpec.scala#create-explicit-system
Or by using the get method:
An Agent will be running until you invoke ``close`` on it. Then it will be
eligible for garbage collection (unless you hold on to it in some way).
.. includecode:: code/docs/agent/AgentDocSpec.scala#read-get
.. includecode:: code/docs/agent/AgentDocSpec.scala#close
Reading an Agent's current value does not involve any message passing and
happens immediately. So while updates to an Agent are asynchronous, reading the
state of an Agent is synchronous.
Updating Agents
===============
Updating Agents (send & alter)
======================
You update an Agent by sending a function that transforms the current value or
by sending just a new value. The Agent will apply the new value or function
@ -75,37 +76,22 @@ in order.
.. includecode:: code/docs/agent/AgentDocSpec.scala#send-off
All ``send`` methods also have a corresponding ``alter`` method that returns a ``Future``.
See :ref:`futures-scala` for more information on ``Futures``.
Reading an Agent's value
========================
Agents can be dereferenced (you can get an Agent's value) by invoking the Agent
with parentheses like this:
.. includecode:: code/docs/agent/AgentDocSpec.scala#read-apply
Or by using the get method:
.. includecode:: code/docs/agent/AgentDocSpec.scala#read-get
Reading an Agent's current value does not involve any message passing and
happens immediately. So while updates to an Agent are asynchronous, reading the
state of an Agent is synchronous.
.. includecode:: code/docs/agent/AgentDocSpec.scala#alter
.. includecode:: code/docs/agent/AgentDocSpec.scala#alter-off
Awaiting an Agent's value
=========================
It is also possible to read the value after all currently queued sends have
completed. You can do this with ``await``:
.. includecode:: code/docs/agent/AgentDocSpec.scala#read-await
You can also get a ``Future`` to this value, that will be completed after the
You can also get a ``Future`` to the Agents value, that will be completed after the
currently queued updates have completed:
.. includecode:: code/docs/agent/AgentDocSpec.scala#read-future
See :ref:`futures-scala` for more information on ``Futures``.
Transactional Agents
====================

158
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@ -7,54 +7,46 @@ import language.postfixOps
import akka.agent.Agent
import scala.concurrent.duration._
import akka.util.Timeout
import scala.concurrent.{ Await, ExecutionContext }
import akka.testkit._
import scala.concurrent.Future
class AgentDocSpec extends AkkaSpec {
"create and close" in {
"create" in {
//#create
import scala.concurrent.ExecutionContext.Implicits.global
import akka.agent.Agent
val agent = Agent(5)
//#create
//#close
agent.close()
//#close
}
"create with implicit system" in {
//#create-implicit-system
import akka.actor.ActorSystem
import akka.agent.Agent
"read value" in {
import scala.concurrent.ExecutionContext.Implicits.global
val agent = Agent(0)
implicit val system = ActorSystem("app")
{
//#read-apply
val result = agent()
//#read-apply
result must be === 0
}
{
//#read-get
val result = agent.get
//#read-get
result must be === 0
}
val agent = Agent(5)
//#create-implicit-system
agent.close()
system.shutdown()
}
"create with explicit system" in {
//#create-explicit-system
import akka.actor.ActorSystem
import akka.agent.Agent
val system = ActorSystem("app")
val agent = Agent(5)(system)
//#create-explicit-system
agent.close()
system.shutdown()
{
//#read-future
val future = agent.future
//#read-future
Await.result(future, 5 seconds) must be === 0
}
}
"send and sendOff" in {
val agent = Agent(0)
import system.dispatcher
val agent = Agent(0)(ExecutionContext.global)
//#send
// send a value
agent send 7
@ -64,70 +56,47 @@ class AgentDocSpec extends AkkaSpec {
agent send (_ * 2)
//#send
def longRunningOrBlockingFunction = (i: Int) ⇒ i * 1
def longRunningOrBlockingFunction = (i: Int) ⇒ i * 1 // Just for the example code
def someExecutionContext() = scala.concurrent.ExecutionContext.Implicits.global // Just for the example code
//#send-off
// the ExecutionContext you want to run the function on
implicit val ec = someExecutionContext()
// sendOff a function
agent sendOff (longRunningOrBlockingFunction)
agent sendOff longRunningOrBlockingFunction
//#send-off
val result = agent.await(Timeout(5 seconds))
result must be === 16
Await.result(agent.future, 5 seconds) must be === 16
}
"read with apply" in {
val agent = Agent(0)
"alter and alterOff" in {
val agent = Agent(0)(ExecutionContext.global)
//#alter
// alter a value
val f1: Future[Int] = agent alter 7
//#read-apply
val result = agent()
//#read-apply
// alter a function
val f2: Future[Int] = agent alter (_ + 1)
val f3: Future[Int] = agent alter (_ * 2)
//#alter
result must be === 0
}
def longRunningOrBlockingFunction = (i: Int) ⇒ i * 1 // Just for the example code
def someExecutionContext() = ExecutionContext.global // Just for the example code
"read with get" in {
val agent = Agent(0)
//#alter-off
// the ExecutionContext you want to run the function on
implicit val ec = someExecutionContext()
// alterOff a function
val f4: Future[Int] = agent alterOff longRunningOrBlockingFunction
//#alter-off
//#read-get
val result = agent.get
//#read-get
result must be === 0
}
"read with await" in {
val agent = Agent(0)
//#read-await
import scala.concurrent.duration._
import akka.util.Timeout
implicit val timeout = Timeout(5 seconds)
val result = agent.await
//#read-await
result must be === 0
}
"read with future" in {
val agent = Agent(0)
//#read-future
import scala.concurrent.Await
implicit val timeout = Timeout(5 seconds)
val future = agent.future
val result = Await.result(future, timeout.duration)
//#read-future
result must be === 0
Await.result(f4, 5 seconds) must be === 16
}
"transfer example" in {
//#transfer-example
import scala.concurrent.ExecutionContext.Implicits.global
import akka.agent.Agent
import scala.concurrent.duration._
import akka.util.Timeout
import scala.concurrent.stm._
def transfer(from: Agent[Int], to: Agent[Int], amount: Int): Boolean = {
@ -145,25 +114,25 @@ class AgentDocSpec extends AkkaSpec {
val to = Agent(20)
val ok = transfer(from, to, 50)
implicit val timeout = Timeout(5 seconds)
val fromValue = from.await // -> 50
val toValue = to.await // -> 70
val fromValue = from.future // -> 50
val toValue = to.future // -> 70
//#transfer-example
fromValue must be === 50
toValue must be === 70
Await.result(fromValue, 5 seconds) must be === 50
Await.result(toValue, 5 seconds) must be === 70
ok must be === true
}
"monadic example" in {
def println(a: Any) = ()
//#monadic-example
import scala.concurrent.ExecutionContext.Implicits.global
val agent1 = Agent(3)
val agent2 = Agent(5)
// uses foreach
var result = 0
for (value ← agent1) {
result = value + 1
}
for (value ← agent1)
println(value)
// uses map
val agent3 = for (value ← agent1) yield value + 1
@ -178,15 +147,8 @@ class AgentDocSpec extends AkkaSpec {
} yield value1 + value2
//#monadic-example
result must be === 4
agent3() must be === 4
agent4() must be === 4
agent5() must be === 8
agent1.close()
agent2.close()
agent3.close()
agent4.close()
agent5.close()
}
}