Interrupt

Source and Output

"""Example: interrupting a process mid-execution."""

from asimpy import Environment, Interrupt, Process
from _util import example

JOB_DURATION = 10  # how long the worker's job takes if uninterrupted
INTERRUPT_AT = 4  # tick at which the manager interrupts the worker


class Worker(Process):
    async def run(self):
        self._env.log("worker", "start job")
        try:
            await self.timeout(JOB_DURATION)
            self._env.log("worker", "finish job")
        except Interrupt as exc:
            elapsed = self.now - 0  # worker started at t=0
            self._env.log(
                "worker", f"interrupted: {exc.cause} (worked {elapsed} ticks)"
            )


class Manager(Process):
    def init(self, worker):
        self._worker = worker

    async def run(self):
        await self.timeout(INTERRUPT_AT)
        self._env.log("manager", "sending interrupt")
        self._worker.interrupt("stop and report")


def main():
    env = Environment()
    # Manager needs a reference to Worker, so Worker must be created first.
    worker = Worker(env)
    Manager(env, worker)
    env.run()
    return env


if __name__ == "__main__":
    example(main)

Key Points

1. process.interrupt(cause) throws an Interrupt exception into the target process at its current await point. cause can be any Python object.

2. The process must catch Interrupt. An uncaught interrupt terminates the process and re-raises the exception.

3. The worker's await self.timeout(JOB_DURATION) is cancelled when the interrupt arrives at t=4. Execution resumes at the except Interrupt block, not after the await.

4. interrupt() has no effect if the target process has already finished.

Check for Understanding

What would happen if the manager called self._worker.interrupt(...) at t=10, which is after JOB_DURATION=10 would have elapsed? Would the worker log "finish job" or "interrupted"?