107 lines
3.5 KiB
Python
107 lines
3.5 KiB
Python
"""MazeNET topology status state machine.
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Seven states — six active in v1. ``degraded`` is schema-reserved for the
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future Healer worker and has no transitions into it from v1 code paths.
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"""
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from __future__ import annotations
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class TopologyStatus:
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PENDING = "pending"
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DEPLOYING = "deploying"
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ACTIVE = "active"
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DEGRADED = "degraded"
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FAILED = "failed"
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TEARING_DOWN = "tearing_down"
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TORN_DOWN = "torn_down"
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ALL: frozenset[str] = frozenset(
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{PENDING, DEPLOYING, ACTIVE, DEGRADED, FAILED, TEARING_DOWN, TORN_DOWN}
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)
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# Directed transitions. torn_down is terminal. degraded is unreachable
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# in v1 (Healer would be the only writer), but its outbound edges stay
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# defined so when Healer lands the state machine already accepts them.
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_LEGAL: dict[str, frozenset[str]] = {
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TopologyStatus.PENDING: frozenset(
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{TopologyStatus.DEPLOYING, TopologyStatus.TORN_DOWN}
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),
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TopologyStatus.DEPLOYING: frozenset(
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{
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TopologyStatus.ACTIVE,
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TopologyStatus.FAILED,
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TopologyStatus.DEGRADED,
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TopologyStatus.TEARING_DOWN,
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}
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),
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TopologyStatus.ACTIVE: frozenset(
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{TopologyStatus.DEGRADED, TopologyStatus.TEARING_DOWN}
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),
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TopologyStatus.DEGRADED: frozenset(
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{TopologyStatus.ACTIVE, TopologyStatus.TEARING_DOWN}
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),
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TopologyStatus.FAILED: frozenset({TopologyStatus.TEARING_DOWN}),
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TopologyStatus.TEARING_DOWN: frozenset(
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{TopologyStatus.TORN_DOWN, TopologyStatus.DEGRADED}
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),
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TopologyStatus.TORN_DOWN: frozenset(),
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}
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class TopologyStatusError(ValueError):
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"""Raised when an illegal topology status transition is attempted."""
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class TopologyNotEditable(RuntimeError):
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"""Raised when a pending-only mutation hits a non-pending topology.
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Pre-deploy edits (update_lan, delete_lan, update/delete decky,
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delete_edge) are only legal while the topology is ``pending``.
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After deploy the mutator's reconciler + topology_mutations table
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take over.
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"""
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def __init__(self, *, status: str, reason: str = "") -> None:
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self.status = status
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self.reason = reason
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super().__init__(
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f"topology not editable (status={status!r})"
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+ (f": {reason}" if reason else "")
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)
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class VersionConflict(RuntimeError):
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"""Raised when a topology write is supplied a stale ``expected_version``.
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Optimistic concurrency guard: the caller passed the version it last
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observed, and the topology has since been mutated by someone else.
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The caller should re-read and retry.
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"""
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def __init__(self, *, current: int, expected: int) -> None:
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self.current = current
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self.expected = expected
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super().__init__(
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f"topology version conflict: expected {expected}, current is {current}"
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)
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def assert_transition(current: str, new: str) -> None:
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"""Validate ``current → new`` or raise :class:`TopologyStatusError`."""
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if current not in TopologyStatus.ALL:
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raise TopologyStatusError(f"unknown current status: {current!r}")
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if new not in TopologyStatus.ALL:
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raise TopologyStatusError(f"unknown new status: {new!r}")
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if new not in _LEGAL[current]:
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raise TopologyStatusError(
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f"illegal transition: {current!r} → {new!r}"
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)
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def legal_next(current: str) -> frozenset[str]:
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"""Return the set of legal successor statuses from ``current``."""
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if current not in _LEGAL:
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raise TopologyStatusError(f"unknown status: {current!r}")
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return _LEGAL[current]
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