Add CoordinatedShutdown task (or document how) automatically in AkkaManagement.stop()

[helena]

For example, something like

val management = AkkaManagement(system) 

// call internalStart() where appropriate 
private def internalStart(): Future[Done] = { 
  import system.dispatcher 
  management.start().map { _ => 
    CoordinatedShutdown(system).addTask(CoordinatedShutdown.PhaseBeforeServiceUnbind, "stop-akka-http-management") { () => management.stop() } 
    Done 
  } 
} 

And clarify necessity of AkkaManagement.stop() in docs or once integrated, remove the section or explain it's done automatically.

[ignasi35]

The general recommendation wrt lifecycle management was for libraries (like Akka Management) to document recommended ways to handle the shutdown without actually doing the actual task registration.

This leaves users of the library or framework integrators the options to handle the lifecycle whichever way works best for them.

[helena]

It could be configurable - enable/disable with off by default.

[ignasi35]

It could be configurable - enable/disable with off by default.

I think this is counterintuitive. IMHO, having a coherent approach to lifecycle management in all libraries of the ecosystem is very helpful. Then, each library should consider the shutdown a first-level topic on their ref docs and start the page with a snippet registering the necessary tasks to fully shutdown each module on that library.

The main problem I have, as a Lagom maintainer, is that my usage of akka-management is specific to Lagom (and other users will have specific use cases). I also may have custom phases on the shutdown DAG of tasks. Then, if I want to use akka-management I have to disable some default behavior to, then, code it back with my specific needs.

[chbatey]

We should at the very least document that it is a good idea.

[ennru]

#650 added a link to how Lagom does it.