akkadotnet/akka.net

Port of Akka actors for .NET

Aaron Stannard

@Aaronontheweb

if there's a big backlog of messages sitting in front of it

Christian Duhard

@cduhard

yep

Aaron Stannard

@Aaronontheweb

then the likelihood of a timeout will be higher

Christian Duhard

@cduhard

this graceful shutdown is a lot harder than I anticipated

Aaron Stannard

@Aaronontheweb

what's the issue exactly?

Christian Duhard

@cduhard

coordinating everything

Aaron Stannard

@Aaronontheweb

one pattern I've used

and we use this inside the Remoting class for doing a simultaneous shutdown of all transports at once

is I'll build a list of IActorRefs that need to be shutdown

call graceful stop on all of them and build a Task<bool> []

Christian Duhard

@cduhard

my persistent actors need to passivate before I can shutdown a bunch of supporting actors

Aaron Stannard

@Aaronontheweb

then I'll call Task.WhenAll and log a warning if not all of those actors shutdown

ah, got it

yeah, it's tricky

Christian Duhard

@cduhard

i also have a tricky saga type thing in my persistent actors

Christian Duhard

@cduhard

                    var m = message as Shutdown;
                    while (Context.GetChildren().Any(x => x.GetType() == typeof (Account)))
                    {
                        Thread.Sleep(500);
                    }

that seems pretty ugly

Account is the persistent actor type

Bartosz Sypytkowski

@Horusiath

@cduhard belive me, you never want thread blocking in your actors logic. Like NEVER

Christian Duhard

@cduhard

i was more demoing the line of thinking. i have never ran that code

@Horusiath baby kittens are safe

Pavel Knorr

@knorrus

Hi guys! Observing strange issue with Akka persitence, my configuration looks like:
Akka.Persistence 1.0.6.17-beta
Akka.Persistence.PostgreSql 1.0.5.2-beta
In code I have following:
https://gist.github.com/knorrus/c2575fd893f6432d2ee15e2b1750b3b2
Shortly when sending something to journal everything is ok, but during recover, Inner field of de-serialized object is always null
Is there is a know issue?

Bartosz Sypytkowski

@Horusiath

@knorrus this is problem of:

Json.NET v7 being unable to correctly serialize/deserialize auto properties initialized with C# 6 syntax
Using JSON.NET at all as the default serializer for persistence ;)

Christian Duhard

@cduhard

are there other good options for json?

Pavel Knorr

@knorrus

@Horusiath I'm using Newtonsoft.Json 8.0.2

Bartosz Sypytkowski

@Horusiath

json.net v8 has fixed this issue, but you shouldn't relly on the default akka serializer for persistence - it was not created for that

@knorrus try public UserFile UserFile { get; private set; } to verify

Christian Duhard

@cduhard

@Horusiath what would you recommend to accomplish what my terrible thread.sleep example does?

Pavel Knorr

@knorrus

@Horusiath YOU SAVE MY DAY!

with private setter it works

Bartosz Sypytkowski

@Horusiath

@cduhard first you'd need a good way to recognize children of type Account - potentially you could use actor name for that. Then either send the account shutdown message to all children (and make only account able to handle it) or use selection to filter account children and send shutdown to them

Pavel Knorr

@knorrus

@Horusiath Which serializer should I use for persistence? Akka.Persistence comes with Json.Net by default

Bartosz Sypytkowski

@Horusiath

with account children recognized by name, you could easily count them and wait until all of them are dead

Christian Duhard

@cduhard

@Horusiath They already passivate on their own

@Horusiath I just need a way to wait until they are all terminated before starting shutdown of supporting actors and routers

Bartosz Sypytkowski

@Horusiath

@knorrus the major problem with the default serializer is that it may (and will be) changed in the future, while your persisted events format won't. You can always use your own serializer - depending on who you'll ask, there will be different responses. My favourite are schema-defined ones, like proto buf, flat buffers or MS Bond

@cduhard it's still better to do so asynchronously

Christian Duhard

@cduhard

@Horusiath i understand. How to do it async is the part I am having some trouble with. I was hoping to use built in mechanism rather that add a bunch of new message flow

Bartosz Sypytkowski

@Horusiath

@cduhard so you want to stop a parent once all of it's children of specific type will answer to stop request?

to11mtm

@to11mtm

@Horusiath : Wasn't the expectation that things would be moving to 'Wire'? Or has that changed?

Bartosz Sypytkowski

@Horusiath

@to11mtm yes, that's the plan

Christian Duhard

@cduhard

@Horusiath The AggregateCoordinator maintains many worker routers that are used by th persistent actors. They can't be stopped until all are passivated

to11mtm

@to11mtm

Would that be a fairly safe way to go as far as if our team was planning on setting up persistence now?

Christian Duhard

@cduhard

@Horusiath i need to order the shutdown -> PersistentActors -> All Other Children (can be in parallel)

i suppose I could start a timer when the Coordinator receives the Shutdown which is what the silly thread.sleep us trying to accomplish

Become(ShuttingDown) -> fire up timer, handle the timer message -> check for PersistentActors status, then shutdown remaining worker children

Bartosz Sypytkowski

@Horusiath

@to11mtm in general you should never allow third party library tell you what format it will use to store your data. What if something changes or you'll need to migrate your data to another solution? You should either specify message format by yourself or have some migration path for it - if I'm right after 1.5 we'll switch to Wire, but still you'll be able to use json.net serializer as an alternative, you'll just need to specify it explicitly. Also we'll probably provide some tips about how to write format migration scenarios.

Christian Duhard

@cduhard

i think that will work. see any flaws?

Bartosz Sypytkowski

@Horusiath

@cduhard what do you need timer for?

Christian Duhard

@cduhard

to check for non-terminated persistent actors

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