I'm new to Play and Scala. I'm trying to build an Application using Play and Scala. I need to make post call internally to get data from my server. But this should be synchronous. After getting the data from this post request, I need to send that data to front end. I've seen many resources but all are asynchronous. Please help me.
I'm fetching data from DB and then should return the data as response.
DB is at remote server not in the hosted server.
I think you should not block anyway.
def action = Action.async {
WS.url("some url")
.post(Json.toJson(Map("query"->query)))
.map { response =>
val jsonResponse = response.json
// in this place you have your response from your call
// now just do whatever you need to do with it,
// in this example I will return it as `Ok` result
Ok(jsonResponse)
}
}
Just map the result of your call and modify it staying in context of Future and use Action.async that takes a Future.
If you really want to block use Await.result(future, 5 seconds), importing
import scala.concurrent.duration._
import scala.concurrent.Await
See docs for Await here
All requests are asynchronous but nothing prevents you from waiting the response with await in your code.
val response = await(yourFutureRequest).body
The line written above will block until the future has finished.
Related
[EDITED: I realized after reading response that I oversimplified my question.]
I am new to Locust and not sure how to solve this problem.
I have function (call it "get_doc") that is passed a locust.HttpSession() and uses it to issue an HTTP request. It gets the response and parses it, returning it up several layers of call. One of these higher-level calls looks at the returned, parsed document to decide if the response was what was expected or not. If not, I want Locust to mark the request/response as failed. A code sketch would be:
class MyUser (HttpUser):
#task
def mytask(self):
behavior1 (self.client)
def bahavior1(session):
doc = get_doc(session, url1)
if not doc_ok (doc):
??? how to register a failure with Locust here...
doc2 = get_doc(session, url2)
...
def get_doc(http_session, url):
page = http_session.get(url)
doc = parse (page)
return doc
There may be several behavior[n] functions and several Locust users calling them.
A constraint is that I would like to keep Locust-specific stuff out of bahavior1() so that I can call it with an ordinary Requests session. I have tried to do something like this in get_doc() (the catch_response parameter and success/fail stuff is actually conditionalized on 'session' being an HttpSession object):
def get_doc (session, meth, url):
resp = session.request (meth, url, catch_response=True)
doc = parse (resp.content)
doc.logfns = resp.success, resp.failure
return doc
and then in behavior1() or some higher up-chain caller I can
doc.logfns[1]("Document not as expected")
or
doc.logfns[0] # Looks good!
Unfortunately this is not working; the calls to them produce no errors but Locust doesn't seem to record any successes or failures either. I am not sure if it should work or I bungled something in my code. Is this feasible? Is there a better way?
You can make get_doc a context manager, call .get with catch_response=True and yield instead of return inside it. Similar to how it is done here: https://github.com/SvenskaSpel/locust-plugins/blob/2cbbdda9ae37b6cbb0a11cf69aca80b164198aec/locust_plugins/users/rest.py#L22
And then use it like this
def mytask(self):
with get_doc(self.client, url) as doc:
if not doc_ok(doc):
doc.failure(”doc was not ok :(”)
If you want, you can add the parsed doc as a field on the response before yielding in your doc function, or call doc.failure() inside doc_ok.
I am trying to do asynchronous http calls with akka streams.
This is what I tried.
Source(listEndpoints)
.mapAsync(20)(endpoint => Future(Await.result(request(HttpMethods.POST, endpoint, List(authHeader)), timeout)))
.runWith(Sink.seq[HttpResponse])
I am using akka-http within the request method and it returns Future[HttpResponse]
I think I am abusing Future here. The code above would give me a Future[List[HttpResponse]] and I have to use Await again to get a List[HttpResponse]. Is there a more elegant way to timeout functions within mapAsync?
Assuming your request method at some point does
Http().singleRequest
to get a Future[HttpResponse], you can pass a timeout for the request through:
// inside def request(...), will probably need to add a timeout argument here
val request = ??? // Build the HttpRequest
Http().singleRequest(
request = request,
settings = ConnectionPoolSettings.default.withMaxConnectionLifetime(timeout)
Then your stream would just be
Source(listEndpoints)
.mapAsync(request(...))
.runWith(Sink.seq[HttpResponse])
and you'd only need to Await at the "end of the world" for the Future[List[HttpResponse]] to complete.
You can also change the default max connection lifetime with akka.http.host-connection-pool.max-connection-lifetime in application.conf
I have found an [example][1] where akka-http is used with Source.single to make a request. Now I'd like to use Source.tick to implement polling requests which are execute every X seconds like this:
import akka.http.scaladsl.model._
import scala.concurrent.duration._
val request: HttpRequest = RequestBuilding.Get(Uri("http://api.someSite.com"))
val source: Source[HttpRequest, Cancellable] = Source.tick(1.seconds, 1.seconds, request)
val sourceWithDest = source.via(Http().superPool())
However, I get a compile error in the last line which I cant resolve(Type mismatch). Any ideas on what I am doing wrong or suggestions for alternatives?
[1]: https://gist.github.com/steinybot/a1f79fe9a67693722164
As per the docs:
The Flow returned by Http().superPool(...) is very similar to the one
from the Host-Level Client-Side API, so the Using a Host Connection
Pool section also applies here.
And then
The “pool client flow” returned by
Http().cachedHostConnectionPool(...) has the following type:
Flow[(HttpRequest, T), (Try[HttpResponse], T), HostConnectionPool]
This is to give client-side code the possibility to implement some logic to match the original requests to the corresponding response. Assuming you don't need this kind of behaviour in your case, you can always proceed by appending NotUsed to your request before feeding it to the pool flow. E.g.
val sourceWithDest: Source[Try[HttpResponse], Cancellable] =
source.map(req ⇒ (req, NotUsed)).via(Http().superPool[NotUsed]()).map(_._1)
I'm developing an application using Play framework in scala. I have to handle the below use case in my application.
For a particular request from the browser to the play server the Play server should make an http request to some external server (for Eg: somesite.com) and send the response from this request back to the web browser.
I have written the below code to send the request to external serever in the controller.
val holder = WS.url("http://somesite.com")
val futureResponse = holder.get
Now how do I send back the response recieved from "somesite.com" back to the browser?
There's an example in the Play documentation for WS, under Using in a controller; I've adapted it to your scenario:
def showSomeSiteContent = Action.async {
WS.url("http://somesite.com").get().map { response =>
Ok(response.body)
}
}
The key thing to note is the idiomatic use of map() on the Future that you get back from the get call - code inside this map block will be executed once the Future has completed successfully.
The Action.async "wrapper" tells the Play framework that you'll be returning a Future[Response] and that you want it to do the necessary waiting for things to happen, as explained in the Handling Asynchronous Results documentation.
You may also be interested in dynamically returning the status and content type:
def showSomeSiteContent = Action.async {
WS.url("http://somesite.com").get().map { response =>
Status(response.status)(response.body).as(response.ahcResponse.getContentType)
}
}
Dynamic status could help if the URL/service you call fails to answer correctly.
Dynamic content type can be handy if your URL/service can return different content HTML/XML... depending on some dynamic parameter.
In my play framework 2 application I'd like to have a log message with the request, response, and some details about the response - such as the number of search results returned from an external web call.
What I have now is a filter like this:
object AccessLog extends Filter {
import play.api.mvc._
import play.api.libs.concurrent.Execution.Implicits._
def apply(next: RequestHeader => Future[SimpleResult])(request: RequestHeader): Future[SimpleResult] = {
val result = next(request)
result map { r =>
play.Logger.info(s"Request: ${request.uri} - Response: ${r.header.status}")
}
result
}
}
At the point of logging, I've alread converted my classes into json, so it seems wasteful to parse the json back into objects so I can log information about it.
Is it possible to compute the number of search results earlier in the request pipeline, maybe into a dictionary, and pull them out when I log the message here?
I was looking at flash, but don't want the values to be sent out in a cookie at any cost. Maybe I can clear the flash instead. Buf if there's a more suitable way I'd like to see that.
This is part of a read-only API that does not involve user accounts or sessions.
You could try using the play.api.cache.Cache object if you can come up with a reproducible unique request identifier. Once you have logged your request, you can remove it from the Cache.