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> The actor model is asynchronous by definition For sure the independent execution of the actors internal logic is a fundamental property of an actor system. H

> The actor model is asynchronous by definition For sure the independent execution of the actors internal logic is a fundamental property of an actor system. However I think communication APIs between actors don't have to be asynchronous by definition: In Akka they are, because blocking threads woul kill the performance. In Erlang synchronous communication between actors works fine. The C# Orleans framework also favors "synchronous" communication - yes, actor communication returns Task<T> results which can be awaited, so it's async unter the hood - but I consider that an implementation detail). Pony in contrast leans to purely async APIs. There's no way to actively wait for a response from another actor. The advantage is that deadlocks are not possible at all, whereas with synchronous actor communication you can deadlock when 2 actors are waiting upon each other. The drawback are callbacks and the need to model everything as a state machine.

klibertp 10y ago
> In Erlang synchronous communication between actors works fine. There is no such thing as synchronous communication in Erlang! When coding in Erlang you better remember this. The primitive operation in Erlang is the async message send and that's it. Sync messages are built on top of async send, blocking receive blocks and a lot of overhead involving linking and monitoring (because the process you're sending to may die before the message arrives or before it can send the response). All this is handled by gen_somethings (`gen_server:call` does this, for example), but sync messages are not the basic primitive in Erlang. They may work, but they are not trivially implemented - I know, I tried working without OTP for a while. I reimplemented a lot of edge-cases handling in my project back then and when I finally checked library sources I was shocked to learn that it was still less than a half of what was needed...
- Matthias247 10y ago
  I wrote synchronous communication, with which I meant the combination of a sending a request message and do a blocking wait for a response message. I'm aware that the pure message sending in Erlang is async. What I intended to highlight is that the "do a blocking wait for a response" part is possible in Erlang, but not in Pony or Akka (yes, you can do it in Akka, but it's not recommended for performance reasons).

klibertp 10y ago

> In Erlang synchronous communication between actors works fine. There is no such thing as synchronous communication in Erlang! When coding in Erlang you better remember this. The primitive operation in Erlang is the async message send and that's it. Sync messages are built on top of async send, blocking receive blocks and a lot of overhead involving linking and monitoring (because the process you're sending to may die before the message arrives or before it can send the response). All this is handled by gen_somethings (`gen_server:call` does this, for example), but sync messages are not the basic primitive in Erlang. They may work, but they are not trivially implemented - I know, I tried working without OTP for a while. I reimplemented a lot of edge-cases handling in my project back then and when I finally checked library sources I was shocked to learn that it was still less than a half of what was needed...

Matthias247 10y ago
I wrote synchronous communication, with which I meant the combination of a sending a request message and do a blocking wait for a response message. I'm aware that the pure message sending in Erlang is async. What I intended to highlight is that the "do a blocking wait for a response" part is possible in Erlang, but not in Pony or Akka (yes, you can do it in Akka, but it's not recommended for performance reasons).