Does playframework release memory after a certain time?

Question

I am new to Play Framework. I having been running Play Framework 2.7.x in production mode. Actually in the most simple code:

package controllers

import javax.inject._
import play.api._
import play.api.mvc._


@Singleton
class HomeController @Inject()(cc: ControllerComponents) extends   AbstractController(cc) {


def index() = Action { implicit request: Request[AnyContent] =>
Ok(views.html.index())
}
}

Going to run I noticed that for each request it increased more memory usage. It increased and increased. At a stage with the increase of request incoming the memory using by the app reached at 1Gb. I stopped sending request, but I noticed that the app is not releasing any memory.

My question is - will this app release it's occupied memory and is there any way of doing that without restarting the app?

Answer 1

Play Framework runs on the Java Virtual Machine (JVM). JVM usually does not release memory back to the operating system. The memory can be released but it's a rare thing e.g. Java 12 introduced JEP 346: Promptly Return Unused Committed Memory from G1 but I'm not sure this would be useful for a small 1 GB heap.

JVM is usually configured to have an upper memory consumption limit and will stay under it or throw a variety of OutOfMemoryError when that's not possible. You should configure the JVM so it has an acceptable memory limit for your server and let the GC do the work.