Thank You .
So in case 1 , you are recommending the child to send a message to
controller when it gets a leave message .
The map(IP->actor) is maintained by controller .Controller will remove the
child from map and kill the child ?
Since controller is processing messages one by one there will not be any
inconsistency ?
Please let me know whether my understanding is right .
On Thu, Apr 14, 2016 at 5:30 AM, Michael Frank <syntaxjoc...@gmail.com>
wrote:
> I can think of two solutions.
>
> 1. in your controller actor, maintain a separate mapping of
> "networkdevice_IP" -> ActorRef. when you create a new child actor, don't
> give it a name, let akka pick a random unique name, then add the mapping.
> when routing messages to the child, instead of using getChild(), look up
> the actor ref in your map. when a child leaves, remove it from the map
> immediately, then stop it asynchronously by sending the 'leave' message.
>
> 2. in your controller actor, track child actors which are leaving, and
> stash messages destined to these actors until you receive termination
> confirmation. you could again keep a mapping of "networkdevice_IP" ->
> ActorRef, but this mapping would only hold actors which are leaving. when
> you receive a message for a child, first check if the child is leaving: if
> so stash() the message. if the child is not in the leaving map, if the
> child exists, send the message to it. if the child doesn't exist, create
> it. when a child is leaving, put a watch on the child using
> context.watch(), add the child name to the leaving map, then send the
> 'leave' message to the actor. when you receive the deathwatch Terminated()
> message, call unstashAll() to flush any stashed messages.
>
> i have used the first solution many times, its quick and easy. solution
> two is applicable however if you are modeling a resource which cannot have
> two separate incarnations running at the same time.
>
> -Michael
>
>
> On 04/13/16 01:15, Mahesh Govind wrote:
>
> Dear Experts ,
>
>
> Could you please help me with a right design choice for the following
> scenario.
>
>
>
> *Use case * : 1000's of Network device are controlled by a network .
>
>
>
> - Network devices will join and leave the network by sending *Join*
> and *Leave* messages respectively to the network controller.
>
> *Joining scenario*
>
> - When controller get a *Join* message from a network device ,
> - it will check whether an FSM actor exists for that network device by
> calling getContext().getChild("networkdevice_IP").
> - "networkdevice_IP" is used to identify the actor.
> - if the child lookup returns null , a new FSMActor will be spawned
> and join message is processed by the new FSMActor
>
>
> * Leaving scenario*
>
> - Network device will send a *Leave* message to the controller
> - controller will do getContext().getChild("networkdevice_IP") and get
> the right FSMActor.
> - sends “*leave* message" to this actor.
> - While processing Leave message , FSM actor will terminate itself by
> calling stop() .
>
>
> *Complication*
>
> - Now there is a possibility that while the stop() is being processed
> by FSMActor , a new Join may come from same network device
> (networkdevice_IP).
> - Since stop() is asynchronous getContext().getChild(network device)
> will still return the FSMActor (networkdevice_IP) , but if we send message
> to this actor , the message will go to DeadMessages.
> -
>
> *Design question .*
>
> - How to handle such scenario using AKKA ? So that we will not
> return a stale Actor using getContext().getChild()
> - [one possiblity might be to leave this corner scenario and let the
> network protocol to handle this with retransmission .But if retransmission
> is not there what to do ?]
>
> With thanks and regards
> Mahesh
>
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