Enum Command 

pub enum Command {
    Pause,
    Resume,
    ExitWithSuccess,
    Quit,
    Nudge,
}

Commands are messages that can be send to control the behavior of an actor.

They are similar to UNIX signals.

They are treated with a higher priority than regular actor messages.

Variants

Pause

Temporarily pauses the actor. A paused actor only checks on its high priority channel and still shows “progress”. It appears as healthy to the supervisor.

Scheduled message are still processed.

Semantically, it is similar to SIGSTOP.

Resume

Resume a paused actor. If the actor was not paused this command has no effects.

Semantically, it is similar to SIGCONT.

ExitWithSuccess

Stops the actor with a success exit status code.

Upstream actors that terminates should send the ExitWithSuccess command to downstream actors to inform them that there are no more incoming messages.

It is similar to Quit, except for the resulting exit status.

Quit

Asks the actor to gracefully shutdown.

The actor will stop processing messages and its finalize function will be called.

The exit status is then ActorExitStatus::Quit.

This is the equivalent of sending SIGINT/Ctrl-C to a process.

Nudge

Nudging is a No-op message.

Its only effect is to wake-up actors that are stuck waiting for a message.

This is useful to kill actors properly or for tests. Actors stuck waiting for a message do not have any timeout to check for their killswitch signal.

Note: Historically, actors used to have a timeout, then the wake up logic worked using a Kill command. However, after the introduction of supervision, it became common to recycle a mailbox.

After a panic for instance, the supervisor of an actor might kill it by activating its killswitch and sending a Kill message.

The respawned actor would receive its predecessor mailbox and possibly end up process a Kill message as its first message.

Trait Implementations

impl Debug for Command

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.