Concurrent computing in Julia with actors.

Actors implements the Actor Model of computation:

An actor ... in response to a message it receives, can concurrently:

• send a finite number of messages to other actors;
• create a finite number of new actors;
• designate the behavior to be used for the next message it receives.

Actors make(s) concurrency easy to understand and reason about and integrate(s) well with Julia's multi-threading and distributed computing. It provides an API for writing reactive applications, that are:

• responsive: react to inputs and events,
• message-driven: rely on asynchronous message-passing,
• resilient: can cope with failures,
• elastic: can distribute load over multiple threads and workers.

The following example defines two behavior functions: greet and hello and spawns two actors with them. sayhello will forward a message to greeter, get a greeting string back and deliver it as a result:

julia> using Actors

julia> import Actors: spawn

julia> greet(greeting, msg) = greeting*", "*msg*"!" # a greetings server
greet (generic function with 1 method)

julia> hello(greeter, to) = request(greeter, to)    # a greetings client
hello (generic function with 1 method)

julia> greeter = spawn(greet, "Hello")              # start the server with a greet string
Link{Channel{Any}}(Channel{Any}(sz_max:32,sz_curr:0), 1, :default)

julia> sayhello = spawn(hello, greeter)             # start the client with a link to the server
Link{Channel{Any}}(Channel{Any}(sz_max:32,sz_curr:0), 1, :default)

julia> request(sayhello, "World")                   # request the client
"Hello, World!"

julia> request(sayhello, "Kermit")
"Hello, Kermit!"

Please look into the manual for more information and more serious examples.

Actors is part of the Julia GitHub group JuliaActors. Please join!

• Oliver Schulz (until v0.1, Oct 2017)
• Paul Bayer (rewrite since v0.1.1, Nov 2020)

MIT