Thank you
On Thu, Apr 14, 2016 at 10:19 PM, Michael Frank <[email protected]>
wrote:
> reply inline. hopefully this makes my solution more clear.
>
> -Michael
>
> On 04/14/16 02:37, Mahesh Govind wrote:
>
> Thank You .
>
> So in case 1 , you are recommending the child to send a message to
> controller when it gets a leave message .
>
>
> no. i would use the same message flow as you described in your original
> email. the only change i would make is instead of:
>
> "controller will do getContext().getChild("networkdevice_IP") and get the
> right FSMActor."
>
> i would instead get the child ActorRef by consulting the map, then
> immediately remove the child from the map. by 'immediately' i mean remove
> the child from the map in this iteration of the actor receive loop. since
> actors process their messages synchronously, there is no chance of
> inconsistency.
>
> The map(IP->actor) is maintained by controller .Controller will remove the
> child from map and kill the child ?
>
>
> yes.
>
> Since controller is processing messages one by one there will not be any
> inconsistency ?
>
>
> yes.
>
>
>
> Please let me know whether my understanding is right .
>
>
>
>
> On Thu, Apr 14, 2016 at 5:30 AM, Michael Frank <[email protected]>
> 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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