On Friday, 18 March 2016 08:59:14 UTC+11, Rafał Krzewski wrote:
>
> Are you sure you are approaching the problem from the best angle? Akka
> gives you a guarantee that the execution of actor code is single threaded,
> so each time a message is processed, the code has an "exclusive lock" on
> the actor's internal state (quotation marks because there is actually no
> lock involved, just smart thread scheduling).
>
> Does your writer need to exchange several messages with the target actor,
> and the messages from readers should not be processed over the duration of
> that conversation? In such case, you should be able to implement it with
> little effort using become [1] and Stash [2]. For extra style points, you
> can use FSM [3] :) Just watch out for unbounded mailboxes when using Stash!
> Stashing large number of messages may exhaust heap space.
>
Stash is perfect for this use case. We use it to implement write
transactions in CurioDB (https://github.com/stephenmcd/curiodb)
- Each command an actor receives is read or write, and has its own
transaction ID
- When a write command is received and there's no current transaction, we
store the transaction ID as the current transaction
- When a write command is received and there is a current transaction ID,
we stash the command
- Once the transaction is finished, remove the transaction ID, and unstash
all previously stashed commands to be replayed
- Read commands can always read, no stash-base-lock needed
>
> Cheers,
> Rafał
>
> [1] http://doc.akka.io/docs/akka/2.4.2/scala/actors.html#Become_Unbecome
> [2] http://doc.akka.io/docs/akka/2.4.2/scala/actors.html#Stash
> [3] http://doc.akka.io/docs/akka/2.4.2/scala/fsm.html
>
> W dniu czwartek, 17 marca 2016 16:52:47 UTC+1 użytkownik neel choudhury
> napisał:
>>
>> I want to implement the famous reader writer model using actor model. We
>> can have multiple reader reading but only one writer can write. Also when a
>> writer writes no reader can read and vice versa.
>>
>> To solve this problem i thought of using a superviser actor which
>> maintains a set for reader actors and a queue for writer actors. Now a
>> writer can be dequeued and start writing when the set for readers are
>> empty. Also when the writer completes all reader actors from the set can
>> start reading.
>>
>> Can we have a better problem of solving this famous problem using actor
>> model?
>>
>> Also is this model better than the original reader writer problem soved
>> using read or write locks?
>>
>
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