actor-framework/chat

CAF: The C++ Actor Framework

Farafonov Alexey

@farafonov-alexey

Hello all. What is the proper syntax of this 0.17 block

self->attach_functor([=](const caf::error& reason) {
    if (reason.category() == atom_constant<atom("exit")>::value) {
    ...

in caf 0.18?

Dominik Charousset

@Neverlord

category gives you a type ID in 0.18, so you'd need to compare against the ID of the atom. Something like reason.category() == type_id_v<my_atom>.

Farafonov Alexey

@farafonov-alexey

Well I think this exit atom was inner caf.

type_id_v<exit>?

Dominik Charousset

@Neverlord

At least on 0.18 I can't find an 'exit' atom: https://github.com/actor-framework/actor-framework/blob/master/libcaf_core/caf/type_id.hpp#L428

Isn't this code supposed to check whether the error is an exit_reason?

Then that'd be just category() == type_id_v<exit_reason>.

Farafonov Alexey

@farafonov-alexey

That's code snippet inside caf 0.17 broker, where we trying to determing caf::error category in attach_functor and do smth if this is exit

Isn't this code supposed to check whether the error is an exit_reason?

Yes. Thank you!

Dominik Charousset

@Neverlord

👍

Farafonov Alexey

@farafonov-alexey

Get this compile error. Couldn't find out what is wrong. I'm not using caf::byte btw.

[build] ...MSVC\14.28.29333\include\xmemory(701,82): error C2440: 'initializing': cannot convert from 'const caf::byte' to '_Objty'
[build]           with
[build]           [
[build]               _Objty=unsigned char
[build]           ]

Farafonov Alexey

@farafonov-alexey

Figured out the cause of error new_data_msg.buf has custom type byte_buffer, that is vector of caf::byte

Quang Huy Nguyen

@Qhuy1605_twitter

did you do ./configure --prefix=$PWD/build in the beginning?

Hi, i have tried but this error still occurs :(

Dominik Charousset

@Neverlord

Can you share what steps you've taken? Git checkout, configure arguments, etc. The CMake output looks weird, like something messed with the folders.

Dominik Charousset

@Neverlord

Maybe just deleting the build directory and doing a clean build would already help.

Quang Huy Nguyen

@Qhuy1605_twitter

Can you share what steps you've taken? Git checkout, configure arguments, etc. The CMake output looks weird, like something messed with the folders.

Hi Dominik, i just downloaded the source code from git, and ran ./configure without arguments (like the document on git).

Quang Huy Nguyen

@Qhuy1605_twitter

Nevermind, i have already fixed it. Thank you!

ferjif

@ferjif

Hey. I was searching on logging in caf but couldn't find any examples. not even in the examples folder of caf's github. can anyone help me on how to do it

Dominik Charousset

@Neverlord

You basically need to build CAF with logging enabled. Either by passing --log-level=... to the configure script or by setting CAF_LOG_LEVEL directly when using CMake. Maybe this article here is of some use: https://www.cafcademy.com/gems/indenting-trace-logs

Christian C.

@DrDeadbrain

Hey I have a question about Message Handling when using Group Communication. Do all group member have to handle all messages that are published inside the group? At the moment I'm only have returns for messages that I want to handle with the specific group member but I'm getting a lot of unexpected message errors that seem to terminate my members.
If I have to handle every message what is the best way to handle them without publishing a new message to the group?
Thanks in advance

Dominik Charousset

@Neverlord

Yes, all subscribers have to handle all messages on the group. If you respond to a group message, everyone in the groups receives the response. You can either add matching handlers to all subscribers or add a default handler to silently discard messages you didn't expect. But beware of the risk, since doing this can lead to very hard-to-debug errors down the road.

Christian C.

@DrDeadbrain

Alright. Thanks for your fast reply!

Cem Degirmenci

@sputnikcem_twitter

is it possible to do something like .add<std::map<int,std::vector<int>>>(port_list, "port-list,p", "portlist"); in the config?

I get some empty list but don't know if I do something wrong or if it is not possible at all

Cem Degirmenci

@sputnikcem_twitter

ah my mistake, we need curly braces for the map

in the configuration file

ferjif

@ferjif

Hey Guys

I recently updated my caf from 0.17.6 to 0.18.5

then realized that custom atoms cause core dump

i searched every where but nothing comes up

Noir

@josephnoir

The atom implementation changed with 0.18. The "Atoms" section in the manual explains how to use them: https://actor-framework.readthedocs.io/en/stable/MessageHandlers.html#atoms They are defined in the type id block of your application. (Don't forget to load it, e.g., like this).

Yifei Yang

@Yifei-yang7

Hey I also updated from 0.17.6 to 0.18.5, and found caf::message_view is not an api anymore, may I know its alternative?

Dominik Charousset

@Neverlord

@Yifei-yang7 there isn't an analog in the new implementation since the entire type_erased_tuple-API has been cut out.

Yifei Yang

@Yifei-yang7

got it, thx! Is it possible to remote_spawn actors with detached option? Is it achievable by adding it into make_massage()?

Yifei Yang

@Yifei-yang7

or is it possible to change the api of add_actor_type to let spawn_option in? cause I found add_actor_type specifies no_spawn_option internally

Dominik Charousset

@Neverlord

The message only wraps the constructor arguments. Doesn't seem like there's an API for that at the moment.

Feel free to make a feature request on GitHub. :)

Yifei Yang

@Yifei-yang7

Thanks! I will make one for that. :)

Dominik Charousset

@Neverlord

👍

Rich Henry

@phaistos

im having the same issue as @ferjif above, i core dump whenever i try to use an atom defined with the new API, im following the pattern in the documentation

Dominik Charousset

@Neverlord

Are you passing your type IDs to CAF_MAIN or call init_global_meta_objects?

Here's a longer answer to a similar issue: https://stackoverflow.com/questions/70353846/segmentation-faults-when-testing-typed-actors-with-custom-atoms

Rich Henry

@phaistos

fixed, thanks a lot

i didnt see any discussion of that method, or the passing of arguments in the docs, but i didnt read them very closely either

and on closer inspection i see it

Dominik Lohmann

@dominiklohmann

If I have an actor behavior that takes a parameter by reference, would it theoretically be safe to store that reference elsewhere if I also manually keep a reference count to the current message as long as I keep the reference? How would I go about getting a strong reference to the current message from a "self" pointer?

Dominik Charousset

@Neverlord

self->current_mailbox_element()-> payload gives you the message in a handler. Keeping a reference/pointer into that message is only safe for read-only access because you otherwise break COW (changing a tuple with ref count > 1).

Dominik Lohmann

@dominiklohmann

It is for read-only access purposes, thanks! Not sure if you've seen my discussion comment regarding coroutines w/ CAF result (open to chat about it any time!), but I kind of need to extend the current message lifetime until the coroutine frame is destroyed because by-reference function parameters are only stored by-reference in the coroutine frame.

Dominik Charousset

@Neverlord

I've seen the notification, I'll get back to that if I can make the time. Are you still on 0.17? In that case it's a bit more complicated. Because in 0.17 CAF can fuse the content into the mailbox element itself. You could do something like self->current_mailbox_element()->move_content_to_message() to have something to hold onto.

But that of course invalidates the original reference.

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