feat(router): Phase 2 - Atomic session token tracking via Redis Lua script

router/router.py

@@ -2,6 +2,19 @@ import os, json, time, logging, traceback, threading, queue, statistics, math
 import requests, redis
 from flask import Flask, request, jsonify, Response, stream_with_context
 
+
+
+# Phase 2: Atomic session token update  Redis Lua script
+SESSION_LUA_SCRIPT = """
+local key = KEYS[1]
+local new_val = tonumber(ARGV[1])
+local current = tonumber(redis.call('GET', key) or 0)
+local max_val = math.max(current, new_val)
+redis.call('SET', key, max_val, 'EX', 86400)
+return max_val
+"""
+
+
 REDIS_URL = os.environ.get("REDIS_URL", "redis://redis:6379")
 GPU_MOE_URL = os.environ.get("GPU_MOE_URL", "http://192.168.68.15:8080/v1")
 GPU_DENSE_URL = os.environ.get("GPU_DENSE_URL", "http://192.168.68.8:8080/v1")
@@ -435,15 +448,14 @@ def chat():
         # Allow agent to override queue timeout via header
         q_timeout = int(request.headers.get("X-Queue-Timeout", str(QUEUE_TIMEOUT)))
         
-        # Cross-turn context tracking: accumulate tokens per session
+        # Cross-turn context tracking: accumulate tokens per session (Phase 2: atomic Lua)
         session_id = request.headers.get("X-Session-Id", "")
         session_tokens = 0
         if session_id and r:
             try:
-                prev = int(r.get("session:" + session_id) or 0)
                 current = estimate_tokens(rd.get("messages",[]))
-                session_tokens = max(prev, current)  # context only grows
-                r.set("session:" + session_id, session_tokens, ex=86400)  # TTL 24h
+                # Atomic GET/MAX/SET via Lua script  prevents race conditions
+                session_tokens = r.eval(SESSION_LUA_SCRIPT, 1, "session:" + session_id, current)
             except Exception: pass
         
         d = route(rd, tier, agent)