CODEWITHSUNDEEP
multithreadingscalafuture
Incerteza
Incerteza

Reputation: 34934

Repeat asynchronous requests to the server

What I want to do is repeat GET requests to a server asynchronously over and over again so that I can synchronize the local data with the remote one. I'd like to do this by using Futures without involving akka because I just want to understand the basic idea of how to do that at the lower level. No async and await preferably either because they are kind of the high level functions for Futures and Promises, thus I'd like to use Futures and Promises themselves.

So this is my functions:

def sendHttpRequestToServer(): String = { ... }

def send: Unit = {
  val f = future { sendHttpRequestToServer() }
  f onComplete {
    case Success(x) => 
      processResult(x)      // do something with result "x"
      send                  // delay if needed and send the request again
    case onFailure(e) =>
      logException(e)
      send                  // send the request again
  }  
}

That's what I think it might be. How could I change it, is there any mistake in algorithm? Your thoughts.

UPDATE:

As I already know, futures are not designed for recurring tasks, only for one time ones. Therefore, they can't be used here. What do I use then?

Upvotes: 0

Views: 125

Answers (1)

wingedsubmariner
wingedsubmariner

Reputation: 13667

Your code has some issues with exception handling. If an exception is thrown in processResult or logException the send will no longer occur, breaking your loop. This exception will also not be logged. A better way is:

f.map(processResult).onFailure(logException)
f.onComplete(x => send())

This way the send still happens despite exceptions in processResult or logException, exceptions from processResult are logged, and the next send can begin intermediately while the results are still being processed. If you want to wait until processing is complete, you could do:

val f2 = f.map(processResult).recover { case e => logException(e) }
f2.onComplete(x => send())

Upvotes: 3

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