CODEWITHSUNDEEP
scalaasynchronousakka
Ivan Voroshilin
Ivan Voroshilin

Reputation: 5409

Akka: what is the reason of processing messages one at a time in an Actor?

It is said:

Akka ensures that each instance of an actor runs in its own lightweight thread and that messages are processed one at a time.

Can you please explain what is the reason of processing messages one at a time in an Actor?

Upvotes: 8

Views: 1681

Answers (1)

Konrad 'ktoso' Malawski
Konrad 'ktoso' Malawski

Reputation: 13130

This way we can guarantee thread safety inside an Actor.

Because an actor will only ever handle one message at any given time, we can guarantee that accessing the actor's local state is safe to access, even though the Actor itself may be switching Threads which it is executing on. Akka guarantees that the state written while handling message M1 are visible to the Actor once it handles M2, even though it may now be running on a different thread (normally guaranteeing this kind of safety comes at a huge cost, Akka handles this for you).

It also originates from the original Actor model description, which is an concurrency abstraction, described as actors who can only one by one handle messages and respond to these by performing one of these actions: send other messages, change it's behaviour or create new actors.

Upvotes: 14

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