add redis to accelerate access of minio (#482)

### What problem does this PR solve?

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/utils/redis_conn.py

@@ -0,0 +1,55 @@
+import json
+
+import redis
+import logging
+from rag import settings
+from rag.utils import singleton
+
+@singleton
+class RedisDB:
+    def __init__(self):
+        self.REDIS = None
+        self.config = settings.REDIS
+        self.__open__()
+
+    def __open__(self):
+        try:
+            self.REDIS = redis.Redis(host=self.config.get("host", "redis").split(":")[0],
+                                     port=int(self.config.get("host", ":6379").split(":")[1]),
+                                     db=int(self.config.get("db", 1)),
+                                     password=self.config.get("password"))
+        except Exception as e:
+            logging.warning("Redis can't be connected.")
+        return self.REDIS
+
+    def is_alive(self):
+        return self.REDIS is not None
+
+    def get(self, k):
+        if not self.REDIS: return
+        try:
+            return self.REDIS.get(k)
+        except Exception as e:
+            logging.warning("[EXCEPTION]get" + str(k) + "||" + str(e))
+            self.__open__()
+
+    def set_obj(self, k, obj, exp=3600):
+        try:
+            self.REDIS.set(k, json.dumps(obj, ensure_ascii=False), exp)
+            return True
+        except Exception as e:
+            logging.warning("[EXCEPTION]set_obj" + str(k) + "||" + str(e))
+            self.__open__()
+        return False
+
+    def set(self, k, v, exp=3600):
+        try:
+            self.REDIS.set(k, v, exp)
+            return True
+        except Exception as e:
+            logging.warning("[EXCEPTION]set" + str(k) + "||" + str(e))
+            self.__open__()
+        return False
+
+
+REDIS_CONN = RedisDB()