35 lines
1.4 KiB
Python
35 lines
1.4 KiB
Python
"""Conversation fingerprinting for prompt-cache-aware routing."""
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import hashlib
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from typing import Optional
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def _conversation_fingerprint(model: str, messages: Optional[list],
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prompt: Optional[str]) -> Optional[str]:
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"""
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Stable hash over (model, first system + first user turn). That prefix
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determines whether the backend's prompt cache is reusable; later turns
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don't influence the routing decision because they extend the same prefix.
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Returns None when there is no usable prefix.
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"""
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parts: list[str] = [model or "_"]
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if messages:
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for m in messages:
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role = m.get("role") if isinstance(m, dict) else None
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if role not in ("system", "user"):
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continue
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content = m.get("content")
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if isinstance(content, list): # OpenAI multimodal parts
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content = "".join(
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p.get("text", "") for p in content
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if isinstance(p, dict) and p.get("type") == "text"
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)
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if not isinstance(content, str):
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continue
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parts.append(f"{role}:{content}")
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if role == "user":
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break
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elif prompt:
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parts.append(f"user:{prompt}")
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else:
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return None
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return hashlib.sha1("\x1f".join(parts).encode("utf-8", "replace")).hexdigest()
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