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POMy http request becomes null inside an Akka future
 

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    <p>My server application uses Scalatra, with json4s, and Akka.</p> <p>Most of the requests it receives are POSTs, and they return immediately to the client with a fixed response. The actual responses are sent asynchronously to a server socket at the client. To do this, I need to <code>getRemoteAddr</code> from the http request. I am trying with the following code:</p> <pre><code>case class MyJsonParams(foo:String, bar:Int) class MyServices extends ScalatraServlet { implicit val formats = DefaultFormats post("/test") { withJsonFuture[MyJsonParams]{ params =&gt; // code that calls request.getRemoteAddr goes here // sometimes request is null and I get an exception println(request) } } def withJsonFuture[A](closure: A =&gt; Unit)(implicit mf: Manifest[A]) = { contentType = "text/json" val params:A = parse(request.body).extract[A] future{ closure(params) } Ok("""{"result":"OK"}""") } } </code></pre> <p>The intention of the <code>withJsonFuture</code> function is to move some boilerplate out of my route processing.</p> <p>This sometimes works (prints a non-null value for <code>request</code>) and sometimes <code>request</code> is null, which I find quite puzzling. I suspect that I must be "closing over" the <code>request</code> in my future. However, the error also happens with controlled test scenarios when there are no other requests going on. I would imagine <code>request</code> to be immutable (maybe I'm wrong?)</p> <p>In an attempt to solve the issue, I have changed my code to the following:</p> <pre><code>case class MyJsonParams(foo:String, bar:Int) class MyServices extends ScalatraServlet { implicit val formats = DefaultFormats post("/test") { withJsonFuture[MyJsonParams]{ (addr, params) =&gt; println(addr) } } def withJsonFuture[A](closure: (String, A) =&gt; Unit)(implicit mf: Manifest[A]) = { contentType = "text/json" val addr = request.getRemoteAddr() val params:A = parse(request.body).extract[A] future{ closure(addr, params) } Ok("""{"result":"OK"}""") } } </code></pre> <p>This seems to work. However, I really don't know if it is still includes any bad concurrency-related programming practice that could cause an error in the future ("future" meant in its most common sense = what lies ahead :).</p>
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