These are chat archives for akkadotnet/akka.net

3rd
Aug 2018
lujunjie
@LosCaesar_gitlab
Aug 03 2018 03:00
I want to know how to implement some actors to form a ring and make multiple rounds of messaging?Thanks
Vasily Kirichenko
@vasily-kirichenko
Aug 03 2018 07:46
@Horusiath I need to "ask" an actor outside actor system (it's a call from Fable.Remoting). I have only IActorRef<'a> on which I can call <?, but it's untyped. You suggest to pass an IActorRef<> to receive response, but where can I get one?
Bartosz Sypytkowski
@Horusiath
Aug 03 2018 07:48
@vasily-kirichenko this is what ask overload I give you a link to is all about (instead of message it takes message factory which takes temporary callback address as a param). But it's not exposed directly in Akkling yet
Vasily Kirichenko
@vasily-kirichenko
Aug 03 2018 08:42
@Horusiath thanks. We need to add it to Akkling.
Stijn Herreman
@stijnherreman
Aug 03 2018 09:16
When actor A sends a message to actor B, and B is supposed to reply to A with some data, how do I inform A of a failure in one of B's children? This cannot be done with a supervisor strategy it seems? The goal is to let A know it should stop its process and shut down, logging a failure somewhere.
Stijn Herreman
@stijnherreman
Aug 03 2018 09:26
Maybe I need to clarify a bit. B is a supervisor that Forwards messages to children. Failure in children is escalated to B, so I'm looking for a way to have B Tell A about the failure.
Vasily Kirichenko
@vasily-kirichenko
Aug 03 2018 09:26
@stijnherreman You can watch an actor.
Stijn Herreman
@stijnherreman
Aug 03 2018 09:28
@vasily-kirichenko Thanks, I'll take a look
Vagif Abilov
@object
Aug 03 2018 10:14
I wonder what would be the best way to investigate timeout problems with SqlServer adapter. Recovery of persistent actors in our system sometimes fail with timeout exception. When we traced low-level db activities we found that sometimes INSERT into EventJournal doesn't return for a long time (example: 42 seconds), and it blocks SELECT from the same PersistentId. Such long time on INSERT doesn't make sense, but we are using BatchingJournal. Can this be part of the problem? /cc @Horusiath
Vasily Kirichenko
@vasily-kirichenko
Aug 03 2018 10:23
select (nolock)?
Vagif Abilov
@object
Aug 03 2018 10:25
We don't do these SELECTs.
It's all Akka EventJournal adapter
this one? :)
Vagif Abilov
@object
Aug 03 2018 10:51
Yes. Temporarily switched from Batching to non-batching journal. No difference
Bartosz Sypytkowski
@Horusiath
Aug 03 2018 11:01
@object you can relax isolation level of your transactions using isolation-level config
there are also max-batch-size, max-buffer-size and max-concurrent-operations
Bartosz Sypytkowski
@Horusiath
Aug 03 2018 11:07
it works like that: batching journal buffers incoming write requests (the max size of that buffer is max-buffer-size=500000, after that size is reached any more writes will be denied until buffer will be freed). These writes are picked into batches (up to max-batch-size=100) and every batch is essentially a single db request - keep in mind that if you store mutliple events in a single Persist request, they all count as 1 atomic write.
last, since db requests are asynchronous by default, we don't call them one by one. Instead we execute many of them up to a given concurrency limit (max-concurrent-operations=64). keep in mind, that every operation uses separate db connection - ADO.NET is pooling them and afaik pool size is 100 by default.
Bartosz Sypytkowski
@Horusiath
Aug 03 2018 11:12
also max concurrency limit is specific to batching journal, not shared with snapshot store, but they still use the same ADO.NET pool given the same connection string. So they can compete for connections in the pool. If you want a separate pool for snapshot store you can specify a different connection string for it - if I remember correctly ADO.NET allocates connection pools based on connection string matching
Vasily Kirichenko
@vasily-kirichenko
Aug 03 2018 11:24
@Horusiath It seems you don't use bulk insert, why?
Vagif Abilov
@object
Aug 03 2018 11:35
Tried different isolation levels, no difference.
Bartosz Sypytkowski
@Horusiath
Aug 03 2018 11:36
@vasily-kirichenko I wanted to, just haven't got time to implement it. Current implementation was more inline with the one, that already existed before, so I wanted to be sure that it could work as drop-in replacement without breaking things. Tbh, if akka.persistence was implemented on top of streams, batching journal and normal one would probably differ only with the stage in between performing the batch operation.
Vasily Kirichenko
@vasily-kirichenko
Aug 03 2018 11:44
Yeah, I see.
Jay DeBoer
@jaydeboer
Aug 03 2018 11:55
@Danthar Thanks, I was reading the docs, other docs, that were not as clear. Thanks for that link, that really helped explain it. :)
mikeprag
@mikeprag
Aug 03 2018 13:35
Hi All...I have implemented Akka.NET in a dispatcher / worker pattern to distribute load across multiple machines for a job processing system. On the remote machines I have a service running with Akka workers waiting to accept remote requests. When the worker (actor) is created, it instantiates a type using Assembly.LoadFrom - the location to load the dll is passed as part of the worker creation request. Then, requests to process an xml data file are sent to the worker actors which should use the assembly that was instantiated when the worker was created to process the data. My main dispatcher works with batches of data (a job) and in between jobs, stops the remote workers. When a new job is created, it creates new workers to process the job. This is working fine however on subsequent jobs, where the source .dll has changed, it seems that the old .dll is being used instead of the new one. On each new job, the dispatcher first pulls the assets (dll and other files) to a new file share where the worker should load it from and I can see from my logs that the new worker is using the correct location however the results are showing its using the .dll from a previous job (worker). I am creating my actors with a unique name and I thought this would give some isolation as new, unique workers would be created. What am I missing that the remote process is re-using workers or the .dll. I know something is not quite right as the remote service has a lock on the .dll even after its finished and the workers have been stopped as when I come to delete the assets in the shared folder, I'm unable to until I shut down the remote service. Sorry for the long winded description - Any ideas?
Stijn Herreman
@stijnherreman
Aug 03 2018 13:41
@mikeprag You cannot unload an assembly once it's been loaded, nor can you reload it. You need to create a new AppDomain if you want to do that.
mikeprag
@mikeprag
Aug 03 2018 13:57
Hi Stijn....Thanks for the quick response....I thought (clearly incorrectly) that multiple actors would have separate AppDomains but I guess this is not the case. Is there anyway in the Akka config to have workers created in separate AppDomains so I can 'config' out this issue or do I need to write this into my worker?
Stijn Herreman
@stijnherreman
Aug 03 2018 14:03
I think this is something you need to write yourself, but I'm not sure. Others with more experience might be able to confirm that.
mikeprag
@mikeprag
Aug 03 2018 14:12
@stijnherreman - Thanks. I guess it wouldn't be too hard to create an AppDomain to execute on. Is this just a general issue / thing to bear in mind with Akka that if you change any of the binaries for execution, you would have to restart the remote host process every time? Does anyone know of a way to do this from Akka config? Is this something to do with the Akka dispatcher?
Vagif Abilov
@object
Aug 03 2018 14:50
@mikeprag It doesn't sound like running actors in separate AppDomains fit well actors nature. Actors have very small footprint (few hundred bytes), they don't have allocated threads, they just borrow threads to process messages. AFAIK an AppDomain drags a memory footprint of at megabytes, not even kilobytes (didn't find any figures but will be very surprised if it's below 1 meg). This shouldn't stop you from creating additional domains, but I think you need to do it outside actor system.
PinkyBrain
@PinkyBrain_gitlab
Aug 03 2018 22:46
what's the right pattern for implementing throttling functionality with actors? I would like to have an actor receive a message with a collection of things to process, and it would create a new actor to process each one, and it should be able to limit the number of outstanding operations (child actors who have not replied yet)
if I understand correctly the one message at a time promise, once this actor receives the message with the collection of items to process and starts creating child actors, how will it know that one of these child actors has replied, if it can't process that reply message until it's finished processing the one with the collection of items?
would I need to use pipeTo? would it be safe to have a mutable property in that parent actor keeping track of the number of outstanding child actors, or can I get this from akka itself?