Sergey Antropoff
50 lines
1.5 KiB
Python
50 lines
1.5 KiB
Python
"""Seeded deterministic fault-rule evaluation."""
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from __future__ import annotations
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import hashlib
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from dataclasses import dataclass
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@dataclass(frozen=True, slots=True)
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class FaultContext:
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method: str
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path: str
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principal: str | None = None
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node: str | None = None
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vmid: str | None = None
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call_number: int = 1
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@dataclass(frozen=True, slots=True)
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class FaultRule:
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kind: str
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probability: float = 1.0
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method: str | None = None
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path_prefix: str | None = None
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principal: str | None = None
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node: str | None = None
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vmid: str | None = None
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call_number: int | None = None
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def __post_init__(self) -> None:
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if not 0 <= self.probability <= 1:
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raise ValueError("fault probability must be between zero and one")
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def matches(rule: FaultRule, context: FaultContext, seed: int) -> bool:
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filters = (
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(rule.method, context.method),
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(rule.principal, context.principal),
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(rule.node, context.node),
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(rule.vmid, context.vmid),
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(rule.call_number, context.call_number),
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)
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if any(expected is not None and expected != actual for expected, actual in filters):
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return False
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if rule.path_prefix is not None and not context.path.startswith(rule.path_prefix):
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return False
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material = f"{seed}:{rule.kind}:{context.method}:{context.path}:{context.call_number}"
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sample = int.from_bytes(hashlib.sha256(material.encode()).digest()[:8], "big") / 2**64
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return sample < rule.probability
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