55 lines
2 KiB
Python
55 lines
2 KiB
Python
"""DataBus Key Affinity - Consistent Hashing for API Key Selection"""
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import hashlib
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import logging
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logger = logging.getLogger("databus.key_affinity")
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class KeyAffinitySelector:
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"""Select API keys with consistent affinity based on request params.
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Same entity (address, token) always uses the same key.
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This maximizes cache locality in downstream rate-limited APIs.
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When a key is exhausted, remaining traffic redistributes to healthy keys.
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"""
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def __init__(self):
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self._assignments: dict[str, str] = {} # entity_hash -> key_id
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def select_key(self, pool_name: str, available_keys: list, **kwargs) -> object | None:
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"""Select a key using consistent hashing of request params."""
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if not available_keys:
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return None
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if len(available_keys) == 1:
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return available_keys[0]
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# Hash the most relevant parameter
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entity = kwargs.get("address") or kwargs.get("mint") or kwargs.get("token") or kwargs.get("entity") or ""
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if entity:
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affinity_key = f"{pool_name}:{entity}"
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# Check cached assignment
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assigned = self._assignments.get(affinity_key)
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if assigned:
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# Verify the assigned key is still available
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for k in available_keys:
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if k.key_id == assigned and k.is_available():
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return k
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# New assignment via consistent hash
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h = int(hashlib.md5(affinity_key.encode()).hexdigest(), 16)
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idx = h % len(available_keys)
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selected = available_keys[idx]
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if selected.is_available():
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self._assignments[affinity_key] = selected.key_id
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return selected
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# Fallback: first available
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for k in available_keys:
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if k.is_available():
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return k
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return None
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def stats(self) -> dict:
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return {"affinity_assignments": len(self._assignments)}
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# Module-level singleton instance
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key_affinity = KeyAffinitySelector()
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