Fix polling judge task blocking the global redis connection for randering cache

libs/judger.js

@@ -27,9 +27,10 @@ let judgeQueue;
 async function connect() {
   const JudgeState = syzoj.model('judge_state');
 
+  const  blockableRedisClient = syzoj.redis.duplicate();
   judgeQueue = {
     redisZADD: util.promisify(syzoj.redis.zadd).bind(syzoj.redis),
-    redisBZPOPMAX: util.promisify(syzoj.redis.bzpopmax).bind(syzoj.redis),
+    redisBZPOPMAX: util.promisify(blockableRedisClient.bzpopmax).bind(blockableRedisClient),
     async push(data, priority) {
       return await this.redisZADD('judge', priority, JSON.stringify(data));
     },