60 lines
2.2 KiB
Python
60 lines
2.2 KiB
Python
"""DTN custody header and simple custody policy helpers.
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This module provides a minimal CustodyHeader dataclass used by DTN custody
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holders to make decisions about storing/transferring PlanDelta payloads.
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It also exposes a small helper that decides whether to accept custody based
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on priority, remaining lifetime, and a node reputation score.
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The implementation is intentionally small and deterministic for unit testing.
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"""
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from dataclasses import dataclass, field
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from typing import List
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import time
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@dataclass
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class CustodyHeader:
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delta_id: str
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created_at: float = field(default_factory=time.time)
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lifetime_secs: int = 3600 # how long the custody is expected to be valid
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custody_chain: List[str] = field(default_factory=list)
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priority_key: int = 0 # combined urgency/impact key (0..127)
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def is_expired(self, now: float = None) -> bool:
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if now is None:
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now = time.time()
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return now > (self.created_at + self.lifetime_secs)
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def add_holder(self, node_id: str):
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# append to custody chain (no dedupe to keep deterministic append-only)
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self.custody_chain.append(node_id)
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def should_accept_custody(header: CustodyHeader, node_reputation: float, min_reputation: float = 0.2) -> bool:
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"""Decide whether a node should accept custody for a delta.
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Decision factors (simple heuristic):
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- If the header is already expired, refuse custody.
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- Prefer accepting higher priority_key values.
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- Gate acceptance by a minimum reputation threshold.
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Returns True if the node should accept custody.
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"""
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if header.is_expired():
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return False
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# Enforce a minimum reputation gate: nodes below min_reputation refuse custody
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if node_reputation < min_reputation:
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return False
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# decode urgency and impact from priority_key (urgency<<4)|impact
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urgency = (header.priority_key >> 4) & 0x07
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impact = header.priority_key & 0x0F
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# compute a simple desirability score
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score = urgency * 2 + impact + (node_reputation * 4)
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# threshold depends on min_reputation; higher min_reputation raises bar
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threshold = 5.0 + (1.0 - min_reputation) * 3.0
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return score >= threshold
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