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""" |
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Graph memory service with optional Neo4j, in-memory fallback. |
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Endpoints: |
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- GET /health |
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- POST /upsert_nodes {nodes:[{id, labels, props}]} |
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- POST /upsert_edges {edges:[{src, dst, type, props}]} |
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- POST /neighbors {id, depth} |
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""" |
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import os |
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from typing import Dict, Any, List, Set |
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from fastapi import FastAPI, Request |
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from fastapi.middleware.cors import CORSMiddleware |
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from fastapi.responses import JSONResponse |
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from prometheus_client import Counter, Histogram, make_asgi_app |
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import uvicorn |
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PORT = int(os.getenv("PORT", "7011")) |
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NODES: Dict[str, Dict[str, Any]] = {} |
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EDGES: List[Dict[str, Any]] = [] |
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ADJ: Dict[str, Set[str]] = {} |
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app = FastAPI(title="Nova Graph Memory", version="0.1.0") |
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app.add_middleware( |
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CORSMiddleware, |
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allow_origins=["*"], |
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allow_credentials=True, |
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allow_methods=["*"], |
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allow_headers=["*"], |
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) |
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REQUESTS = Counter("graph_requests_total", "Graph service requests", ["route"]) |
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LATENCY = Histogram("graph_request_latency_seconds", "Latency", ["route"]) |
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@app.get("/health") |
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def health(): |
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REQUESTS.labels(route="health").inc() |
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return {"status": "ok", "port": PORT} |
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@app.post("/upsert_nodes") |
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async def upsert_nodes(req: Request) -> JSONResponse: |
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with LATENCY.labels(route="upsert_nodes").time(): |
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REQUESTS.labels(route="upsert_nodes").inc() |
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body = await req.json() |
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nodes = body.get("nodes", []) |
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neo_ok = False |
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try: |
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import os as _os |
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from neo4j import GraphDatabase |
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uri = _os.getenv("NEO4J_URI") |
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if uri: |
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driver = GraphDatabase.driver(uri, auth=(_os.getenv("NEO4J_USER", "neo4j"), _os.getenv("NEO4J_PASSWORD", "neo4j"))) |
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neo_ok = True |
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except Exception: |
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driver = None |
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for n in nodes: |
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nid = str(n.get("id")) |
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NODES[nid] = { |
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"id": nid, |
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"labels": n.get("labels", []), |
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"props": n.get("props", {}), |
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} |
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ADJ.setdefault(nid, set()) |
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if neo_ok: |
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try: |
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labels = ":" + ":".join(NODES[nid]["labels"]) if NODES[nid]["labels"] else "" |
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props = NODES[nid]["props"] |
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cypher = f"MERGE (n{labels} {{id:$id}}) SET n += $props" |
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with driver.session() as s: |
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s.run(cypher, id=nid, props=props) |
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except Exception: |
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pass |
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return JSONResponse(status_code=200, content={"upserted": len(nodes)}) |
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@app.post("/upsert_edges") |
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async def upsert_edges(req: Request) -> JSONResponse: |
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with LATENCY.labels(route="upsert_edges").time(): |
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REQUESTS.labels(route="upsert_edges").inc() |
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body = await req.json() |
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edges = body.get("edges", []) |
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for e in edges: |
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src = str(e.get("src")) |
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dst = str(e.get("dst")) |
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etype = e.get("type", "REL") |
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EDGES.append({"src": src, "dst": dst, "type": etype, "props": e.get("props", {})}) |
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ADJ.setdefault(src, set()).add(dst) |
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ADJ.setdefault(dst, set()) |
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try: |
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if neo_ok: |
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cypher = "MERGE (a {id:$src}) MERGE (b {id:$dst}) MERGE (a)-[r:%s]->(b) SET r += $props" % etype |
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with driver.session() as s: |
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s.run(cypher, src=src, dst=dst, props=e.get("props", {})) |
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except Exception: |
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pass |
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return JSONResponse(status_code=200, content={"upserted": len(edges)}) |
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@app.post("/neighbors") |
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async def neighbors(req: Request) -> JSONResponse: |
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with LATENCY.labels(route="neighbors").time(): |
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REQUESTS.labels(route="neighbors").inc() |
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body = await req.json() |
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start = str(body.get("id")) |
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depth = int(body.get("depth", 1)) |
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visited = set([start]) |
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frontier = [start] |
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hops = 0 |
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order = [] |
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while frontier and hops < depth: |
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next_frontier = [] |
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for nid in frontier: |
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for nb in ADJ.get(nid, set()): |
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if nb not in visited: |
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visited.add(nb) |
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next_frontier.append(nb) |
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order.append(NODES.get(nb, {"id": nb})) |
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frontier = next_frontier |
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hops += 1 |
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return JSONResponse(status_code=200, content={"neighbors": order}) |
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metrics_app = make_asgi_app() |
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app.mount("/metrics", metrics_app) |
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if __name__ == "__main__": |
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uvicorn.run(app, host="0.0.0.0", port=PORT) |
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