val value = authenticateUser
private def authenticateUser = {
val holder = WS.url(platformUrl + "/userApi/auth/login?username=testuser&password=testPass")
val res = holder.post(Results.EmptyContent()).onComplete {
case Success(response) => response.cookies.map{cookie => println(cookie.value.get)}
case Failure(errors) => println("")
// The `Future` failed.
}
}
How to return cookie.value.get from authenticateUser method?
First of all, you seem to have many cookies, so it's not clear, the value of which one you want to return.
More importantly, you should not actually return the value itself. The idea is to return the Future, that can be further transformed downstream:
def authenticateUser = WS.url(..)
.post(Results.EmptyContent)
.map { _.cookies }
.map { _.find(_.name == "Auth").flatMap(_.value).getOrElse("") }
Now, somewhere downstream, you can have something like:
def serve(request: Request): Future[Response] = authenticateUser
.map { user =>
serveRequest(user, request)
}.map { result => makeResponse(result) }
I don't know the specifics of Play, so, consider the Request/Response stuff "pseudocode", but the basic idea is that your entire processing should be a chain of Future transformations. The general rule is to never block the service thread.
Related
Because I do some "complex" operations, I think my Actor became asyncronous. The main problem I think is that I use Await.result inside the method which return responses.
actor:
def process(subscribers: Set[ActorRef]): Receive = {
case Join(ref) => context become process(subscribers + ref)
case Leave(ref) => context become process(subscribers - ref)
case Push(request) =>
val filteredSubscribers = (subscribers - sender())
.filter(s => exists(s, request)) // just some actor filters
filteredSubscribers.foreach { subscriber =>
// here I have a Map with each actor requests
val actorOptions = getActorOptions(subscriber)
subscriber ? getResponse(actorOptions, request)
}
}
The problem is inside getResponse (I think).
getResponse(actorOptions: JsValue, request: SocketRequest): JsValue = {
(actorOptions \ "dashboardId").asOpt[Int] match {
case Some(id) => {
val response = widgetsService.getByDashboadId(id) map { widgets =>
val widgetsResponse: List[Future[String]] = widgets.map(w => {
widgetsService.getDataById(w.id) map {
data => s"""{ "widgetId": ${w.id}, "data": $data }"""
}
})
var responses: List[String] = List.empty
widgetsResponse.foreach(f => {
f.onComplete {
case Success(value) => responses = value :: responses
case Failure(e) => println(s"Something happened: ${e.getMessage}")
}
})
// first time when I use Await.result
// used to populate the responses list with data from all futures
Await.result(Future.sequence(widgetsResponse), Duration.Inf)
Json.parse(s"""{
"dashboardId": $id,
"widgets": [${response.mkString(", ")}]
}""".stripMargin)
}
// second time when I use Await.result
// used to return a JsValue instead of a Future[JsValue]
Await.result(response, Duration.Inf)
}
case None => buildDefaultJson // return default json value, unimportant for this example
}
}
Due of that, In frontend, if I have 2 sockets clients, the response for the second will be send only after first.
I found that I can obtain a "fake" increase of performance if I embrance the getResponse in a future inside of my Actor.
filteredSubscribers.foreach { subscriber =>
val actorOptions = getActorOptions(subscriber)
Future(subscriber ? getResponse(actorOptions, request))
}
So, for both subscribers the action will be started in same time, but when the first will reach the Await.result, the second will be locked until first is done.
I need to avoid using Await.result there, but I don't know how to get the results of a list of futures, without using for-comprehension (because is a dynamically list) for first time where I use it.
Because Akka ask operator (?) return a Future[Any], I tried that my getResponse method to return directly a JsValue to be mapped then in Future[JsValue]. If I remove the second Await.result and my method will return Future[JsValue], then the actor will return a Future[Future[JsValue]] which I don't think is too right.
After some more researches and solutions found on so, my code become:
Future.sequence(widgetsResponse) map { responses =>
Json.parse(
s"""
|{
|"dashboardId": $id,
|"tableSourceId": $tableSourceId,
|"widgets": [ ${responses.mkString(", ")}]
|}""".stripMargin
)
}
getResponse returns a Future[JsValue] now, removing both Await.result cases, and actor case become:
filteredSubscribers.foreach { subscriber =>
val actorOptions = getActorOptions(subscriber)
getResponse(actorOptions, request) map { data =>
subscriber ? data
}
}
I don't know why, still have a synchronous behavior. Damn, this can be due of my subscribers type: Set[ActorRef]? I tried to use parallel foreach and this looks like solving my problem:
filteredSubscribers.par.foreach { subscriber =>
val actorOptions = getActorOptions(subscriber)
getResponse(actorOptions, request) map { data =>
subscriber ? data
}
}
I have a method that returns a Future[Boolean] in a Play controller and i want to evaluate that using async but i can't seem to get it to compile.
The following will work:
def health = Action {
logger.info("Endpoint method: health")
val isHealthy = healthCheckService.checkDynamo()
val b: Boolean = Await.result(isHealthy, scala.concurrent.duration.Duration(5, "seconds"))
Ok(Json.toJson(HealthCheckResponse(b.toString)))
}
But i don't think i want that Await in there. So i'm trying things like this with no success:
def health =
Action.async {
Future {
logger.info("Endpoint method: health")
healthCheckService.checkDynamo() match {
case Future.successful(true) => Ok(Json.toJson("false"))
case false => Ok(Json.toJson("true"))
}
val r = healthCheckService.checkDynamo() match {
case true => Ok(Json.toJson("false"))
case false => Ok(Json.toJson("true"))
}
}
}
I can't even get those to compile to test them out.
Any suggestions?
Try this:
def health = Action.async {
healthCheckService.checkDynamo().map {
case true => Ok(Json.toJson("false"))
case false => Ok(Json.toJson("true"))
}
}
Let Play handle the awaiting for you under the hood. That is, Action.async accepts a Future, which checkDynamo() already returns. All you have to do is map it to the appropriate result.
With Futures you have to use combinators like map and flatMap to express the final value. For example:
Action.async {
healthCheckService.checkDynamo()
.map { result => // boolean
HealthCheckResponse(result.toString)
}
.map(Json.toJson(_))
.map(Ok(_))
}
(You can merge maps above to one map and construct the final Ok value there; it is more or less a matter of taste)
If you have, say, two async calls which you want to execute and return a result based on their results, you can use flatMap, which could be easily expressed using a for comprehension:
Action.async {
for {
result1 <- someService.someCall()
result2 <- anotherService.anotherCall(result1.someProperty)
finalResult = SomeFinalResultType(result1, result2)
} yield Ok(Json.toJson(finalResult))
}
If you are not familiar with futures, you might want to read some tutorial which explains their nature, how to combine them and how to get useful results from them, like this one: http://hello-scala.com/920-scala-futures.html
No need to pay attention to the purpose of the function here, it's only for demonstration:
def readAllByPersonOrFail(person: Person, otherPersonId: Long): Future[List[Person]] = {
val personSiblingsFuture: Future[List[Person]] = personSiblingsDomain.readAllByPersonId(person.id)
personSiblingsFuture.map { persons =>
persons.find(_.id == otherPersonId) match {
case Some(person) =>
person.isActive match {
case true => person
case false => throw new IllegalArgumentException("something inactive")
}
case None => throw new IllegalArgumentException("something wrong ehre")
}
}
personSiblingsFuture
}
I would like to return personSiblingsFuture above iff it validates (makes sure correct person is in the list and is active), otherwise throw the exception. I don't think the above code is doing the right thing as it is not existing upon failure.
Take a look at scala.concurrent.Future.map. This creates a new future, whose value is resolved by applying a function to the successful result of this future.
Note that here you're throwing away the resulting future you just created with .map() too.
There are a few areas to solve your problem, though you should question more deeply the use of exceptions with Futures. Scala provides concepts like Future, Option, and Try specifically to avoid throwing exceptions and have a clearer control flow.
Option 1, return the mapped future
In your funciton,
def func(...): Future[List[Person]] {
val personSiblingsFuture = ...;
personSiblingsFuture.map { persons =>
...
}
}
// note we're not returning personSiblingsFuture,
// but the mapped result
When someone actually tries to get the value of the future, e.g. by using .value, they might see an exception intead:
def main() {
val future = func(...); // this is fine
val my_list = future.value; // awaits Future, might throw here
}
Option 2, actually await the list and throw in the function
Returning a future that might throw is strange, it might be a bit easier if the you actually explicitly a had a function that might throw, e.g.
/** jsdoc describing function **/
def funcMightThrow(...): List[Person] {
val personSiblingsFuture = ...;
val personSiblings = personSiblingsFuture.value;
personSiblings.find(_.id == otherPersonId) match {
case Some(person) =>
person.isActive match {
case true => personSiblings
case false => throw new IllegalArgumentException("something inactive")
}
case None => throw new IllegalArgumentException("something wrong ehre")
}
}
Option 3, consider making return types more explicit
def func(...): Future[Try[List[Person]]] {
val personSiblingsFuture = ...;
personSiblingsFuture.map { persons =>
...
// successful case returns 'persons' (List[Person])
// fail cases return Failure(...) instead
}
} // return the mapped future
You can also return Try[List[Person]] rather than a Future[] of that, by using .value, which makes func a blocking function.
private class FutMemorizer[T](valid: T => Boolean)(f: () => Future[T]) {
private val ref = new AtomicReference[Promise[T]]
#scala.annotation.tailrec
final def get(): Future[T] = {
val nullableRef = ref.get()
val valid = checkPromise(ref.get())
if(valid) {
nullableRef.future
} else {
val p = Promise[T]
val success = ref.compareAndSet(nullableRef, p)
if(success) {
p.completeWith(f())
p.future
} else {
get()
}
}
}
private def checkPromise(nullable: Promise[T]) = {
nullable != null && {
nullable.future.value match {
case None => true // future is not complete all caller should wait
case Some(Success(v)) => valid(v)
case _ => false
}
}
}
}
I am implementing an Future memorizer that only cache a valid future value.
It must meet following requirements
Futures created by f never executed paralleled
get never return a invalid value (once invalid recall f() to reload)
Is my implementation correct ?
Is there a more functional or simpler way to do this (because I hardly prove correntness of mime)?
As far as I understand this is wrong:
p.completeWith(f())
The caller gets a future the value of which is (or will be sometimes) that of the future returned by f(), but it's not checked anywhere that this value satisfies or will satisfy valid(...); same for other callers that came while the resulting future returned by f() is in progress if it takes time. It's only when result of f() completes will the next caller probably start "fixing" it.
I would probably go about fixing this problem the following way (see the fixed method), with some stylistic changes:
class FutMemorizer[T](valid: T => Boolean)(f: () => Future[T]) {
private val ref = new AtomicReference[Future[T]]
#tailrec
final def get: Future[T] = {
val current = ref.get
if (current != null && isValid(current)) current
else {
val p = Promise[T]
val pf = p.future
if (ref.compareAndSet(current, pf)) {
p.completeWith(fixed(f))
pf
} else get
}
}
private def fixed(f: () => Future[T]): Future[T] =
f() flatMap { t =>
if (valid(t)) Future.successful(t) else fixed(f)
}
private def isValid(future: Future[T]) =
future.value match {
case None => true // future is not complete all caller should wait
case Some(Success(v)) => valid(v)
case _ => false
}
}
As for your question about a more functional way of doing it I guess f and valid having effects on the external state and basing their computations on it (which I guess is the point of having a memorizer with invalidation) would seriously hinder it.
Just find spray-cache already have this feature
I'm new to asynchronous programming. I read this tutorial http://danielwestheide.com/blog/2013/01/09/the-neophytes-guide-to-scala-part-8-welcome-to-the-future.html and was surprised by how effortless I can incorporate Future into the program. However, when I was using Future with Routing, the return type is kind of wrong.
get {
optionalCookie("commToken") {
case Some(commCookie) =>
val response = (MTurkerProgressActor ? Register).mapTo[..].map({...})
val result = Await.result(response, 5 seconds)
setCookie(HttpCookie("commToken", content = result._2.mturker.get.commToken)) {
complete(result._1, result._2.mturker.get)
}
case None => // ...
}
}
I really don't want to use Await (what's the point of asynchronous if I just block the thread and wait for 5 seconds?). I tried to use for-comprehension or flatMap and place the setCookie and complete actions inside, but the return type is unacceptable to Spray. For-comprehension returns "Unit", and flatMap returns a Future.
Since I need to set up this cookie, I need the data inside. Is Await the solution? Or is there a smatter way?
You can use the onSuccess directive:
get {
optionalCookie("commToken") { cookie =>
//....
val response = (MTurkerProgressActor ? Register).mapTo[..].map({...})
onSuccess(response) {
case (result, mTurkerResponse) =>
setCookie(HttpCookie("commToken", content = mTurkerResponse.mturker.get.commToken)) {
complete(result, mturkerResponse.mturker.get)
}
}
}
There's also onFailure and onComplete (for which you have to match on Success and Failure) See http://spray.io/documentation/1.2.1/spray-routing/future-directives/onComplete/
Also, instead of using get directly it's much more idiomatic to use map (I assume the mturker is an Option or something similar):
case (result, mTurkerResponse) =>
mTurkerResponse.mturker.map { mt =>
setCookie(HttpCookie("commToken", content = mt.commToken)) {
complete(result, mt)
}
}
You can also make a custom directive using this code -
case class ExceptionRejection(ex: Throwable) extends Rejection
protected def futureDirective[T](x: Future[T],
exceptionHandler: (Throwable) => Rejection = ExceptionRejection(_)) =
new Directive1[T] {
override def happly(f: (::[T, HNil]) => Route): Route = { ctx =>
x
.map(t => f(t :: HNil)(ctx))
.onFailure { case ex: Exception =>
ctx.reject(exceptionHandler(ex))
}
}
}
Example usage -
protected def getLogin(account: Account) = futureDirective(
logins.findById(account.id)
)
getAccount(access_token) { account =>
getLogin(account) { login =>
// ...
}
}