Documentation

Configuring the internal Akka system

Play 2.0 uses an internal Akka Actor system to handle request processing. You can configure it in your application application.conf configuration file.

Action invoker actors

The action invoker Actors are used to execute the Action code. To be able to execute several Actions concurrently we are using several of these Actors managed by a Round Robin router. These actors are stateless.

These action invoker Actors are also used to retrieve the body parser needed to parse the request body. Because this part waits for a reply (the BodyParser object to use), it will fail after a configurable timeout.

Action invoker actors are run by the actions-dispatcher dispatcher.

Promise invoker actors

The promise invoker Actors are used to execute all asynchronous callback needed by Promise. Several Actors must be available to execute several Promise callbacks concurrently. These actors are stateless.

Promise invoker actors are run by the promises-dispatcher dispatcher.

WebSockets agent actors

Each WebSocket connection state is managed by an Agent actor. A new actor is created for each WebSocket, and is killed when the socket is closed. These actors are statefull.

WebSockets agent actors are run by the websockets-dispatcher dispatcher.

Default configuration

Here is the reference configuration used by Play 2.0 if you don’t override it. Adapt it according your application needs.

play {
    
    akka {
        event-handlers = ["akka.event.slf4j.Slf4jEventHandler"]
        loglevel = WARNING
        
        actor {
            
            deployment {

                /actions {
                    router = round-robin
                    nr-of-instances = 24
                }

                /promises {
                    router = round-robin
                    nr-of-instances = 24
                }

            }
            
            retrieveBodyParserTimeout = 1 second
            
            actions-dispatcher = {
                fork-join-executor {
                    parallelism-factor = 1.0
                    parallelism-max = 24
                }
            }

            promises-dispatcher = {
                fork-join-executor {
                    parallelism-factor = 1.0
                    parallelism-max = 24
                }
            }

            websockets-dispatcher = {
                fork-join-executor {
                    parallelism-factor = 1.0
                    parallelism-max = 24
                }
            }

            default-dispatcher = {
                fork-join-executor {
                    parallelism-factor = 1.0
                    parallelism-max = 24
                }
            }
            
        }
        
    }
    
}