@Horusiath no offence taken, the app is indeed pretty complex, its an enterprise service bus. The app may load multiple projects and these projects should never be allowed to share instances like repositories, database connections, services etc. so each project has their own ninject container. Right now some services which do work in different threads have locks which i want to replace with actors and message passing
there are a LOT of services, and i can't rewrite everything at once. So i want to create a migration path which may not look pretty in the beginning, but i can then slowly refactor everything to akka actors
@Horusiath I am still at actor pattern, my current problem is that before i had the same state-model-type for the AR-state and for the read-model. Now i am changing that the AR is using his own State-type. The problem is that the Sender of the create-command shouled be informed with the newly created read-model. I have the idea, to pass a non-persitent event to the EventBus so that the ReadModelProjector can tell the Sender of the create command the entity
But it seams wrong
@Zetanova the view side of persistence plugin is lacking some features. That's why it was obsoleted on the jvm side in favor of persistence queries (which we will probably done too, once streams and persistence query will be ported). Btw. this idea with using third mediator seems neat to overcome current limitations.
@Horusiath readmodel generation is working good, the batching is easy and working well. The buffer of events will be flushed on MaxEventCount and Timeout in a single actor for each AR-type. The events are then grouped by Id and each group is processed by the normal Read-Modify-Update CRUD pattern.
triggered by a special event, I could send the readed read-model back to a requestor,
The other option would be the normal one that the client is generating the read-model internaly on client-side and sends only the create-command, without getting the model back.
but then there is a lag, where one client-component has the read-model and maybe an other need it to be created on the read-side (some query)
@OnamChilwan you could do so, ie. by passing children
Props through actor's constructor (this is done in few cases) or as part of some message to be send at some point in time. But if those are making a solution too complex, then it's a warning, that maybe a hierarchy of actors should be changed or maybe they are so tightly coupled, that they should be tested as one.
If you block a receive handler. Then it will 'block' a thread on the threadpool. (if it will actually block/lock the thread that was running at that time, depends on your code ofcourse, if your doing async await things, it might not)
but if your doing a query, and it deadlocks, wont your dbdriver throw an exception of some kind ?
either way, there is no magic code in the Akka.Net dispatchers that prevents these kind of problems. It needs to adhere to the normal set of rules regarding the TPL like anything else.
Akka.net makes concurrency easier to implement, and prevents alot of the pitfalls that come with the territory. But its not perfect ;) (nothing is)
This feels kinda ugly
while (Context.GetChildren().Any(x => x.GetType() == typeof (Account)))
Is there a good way to 'monitor' for a deadlock in cases like this? Perhaps configuring the dispatcher's deadlines
then I wouldn't have this complex graceful shutdown problem
i have to cut off incoming messages and lets everything passivate, it shouldn't be hard but it is tricky to keep it simple and foolproof
@Horusiath, I've been trying Akka.Streams, and I have couple of questions. For example I have this Scala code
override def eventsByTag(tag: String, offset: Long = 0L): Source[EventEnvelope, NotUsed] = {
Source.actorPublisher[EventEnvelope](EventsByTagPublisher.props(tag, offset, Long.MaxValue,
refreshInterval, maxBufSize, writeJournalPluginId)).mapMaterializedValue(_ ⇒ NotUsed)
.named("eventsByTag-" + URLEncoder.encode(tag, ByteString.UTF_8))
}1) What should I use, instead of NotUsed? Unit/Unit.Instanse or something else?
2) I should return Source<EventEnvelope, Unit>, but method "Named" returns IGraph<SourceShape<EventEnvelope>, NotUsed>. How to convert SourceShape<T> to T?
2 Use Source.FromGraph to cast the graph back into a source
@Horusiath Playing with Sharding, I just encountered the following: 2 nodes up, both hosting a region, both processing shard messages. One node leaves cluster, after a few seconds I restart it, it joins the cluster again, but it doesn't receive any shards. The node that didn't shut down keeps on processing all the messages for the entities. So it seems the rebalancing of the shards to the rebooted region doesn't happen?
in case when the difference between number of shards on two machines is too small