Sergey Antropoff
64 lines
2.0 KiB
Python
64 lines
2.0 KiB
Python
"""Explicit virtual-machine state machine."""
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from __future__ import annotations
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from dataclasses import dataclass
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from enum import StrEnum
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from app.simulation.clock import Clock
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class VmState(StrEnum):
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STOPPED = "stopped"
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STARTING = "starting"
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RUNNING = "running"
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PAUSING = "pausing"
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PAUSED = "paused"
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RESUMING = "resuming"
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STOPPING = "stopping"
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MIGRATING = "migrating"
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SNAPSHOTTING = "snapshotting"
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BACKING_UP = "backing_up"
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ERROR = "error"
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class InvalidTransitionError(ValueError):
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pass
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TRANSITIONS: dict[tuple[VmState, str], tuple[VmState, VmState]] = {
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(VmState.STOPPED, "start"): (VmState.STARTING, VmState.RUNNING),
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(VmState.RUNNING, "stop"): (VmState.STOPPING, VmState.STOPPED),
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(VmState.RUNNING, "pause"): (VmState.PAUSING, VmState.PAUSED),
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(VmState.PAUSED, "resume"): (VmState.RESUMING, VmState.RUNNING),
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(VmState.RUNNING, "migrate"): (VmState.MIGRATING, VmState.RUNNING),
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(VmState.STOPPED, "migrate"): (VmState.MIGRATING, VmState.STOPPED),
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(VmState.RUNNING, "snapshot"): (VmState.SNAPSHOTTING, VmState.RUNNING),
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(VmState.STOPPED, "snapshot"): (VmState.SNAPSHOTTING, VmState.STOPPED),
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(VmState.RUNNING, "backup"): (VmState.BACKING_UP, VmState.RUNNING),
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(VmState.STOPPED, "backup"): (VmState.BACKING_UP, VmState.STOPPED),
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}
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@dataclass(frozen=True, slots=True)
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class Transition:
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operation: str
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before: VmState
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intermediate: VmState
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after: VmState
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def plan_transition(state: VmState, operation: str) -> Transition:
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states = TRANSITIONS.get((state, operation))
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if states is None:
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raise InvalidTransitionError(f"cannot {operation} VM while it is {state}")
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return Transition(operation, state, states[0], states[1])
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async def execute_transition(
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state: VmState, operation: str, clock: Clock, duration_seconds: float
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) -> tuple[VmState, VmState]:
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transition = plan_transition(state, operation)
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await clock.sleep(duration_seconds)
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return transition.intermediate, transition.after
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