mongodb+pool多进程，在启动时会有如下提示：
/home/kk/python3.6_kk/lib/python3.6/site-packages/pymongo/topology.py:145: UserWarning: MongoClient opened before fork. Create MongoClient with connect=False, or create client after forking. See PyMongo's documentation for details: http://api.mongodb.org/python/current/faq.html#pymongo-fork-safe>
"MongoClient opened before fork. Create MongoClient "/home/kk/python3.6_kk/lib/python3.6/site-packages/pymongo/topology.py:145: UserWarning: MongoClient opened before fork. Create MongoClient with connect=False, or create client after forking. See PyMongo's documentation for details: http://api.mongodb.org/python/current/faq.html#pymongo-fork-safe> "MongoClient opened before fork. Create MongoClient "/home/kk/python3.6_kk/lib/python3.6/site-packages/pymongo/topology.py:145: UserWarning: MongoClient opened before fork. Create MongoClient with connect=False, or create client after forking. See PyMongo's documentation for details: http://api.mongodb.org/python/current/faq.html#pymongo-fork-safe> "MongoClient opened before fork. Create MongoClient "/home/kk/python3.6_kk/lib/python3.6/site-packages/pymongo/topology.py:145: UserWarning: MongoClient opened before fork. Create MongoClient with connect=False, or create client after forking. See PyMongo's documentation for details: http://api.mongodb.org/python/current/faq.html#pymongo-fork-safe> "MongoClient opened before fork. Create MongoClient "
"MongoClient opened before fork. Create MongoClient "
只需要在数据库连接时 加上，connect=False
client=pymongo.MongoClient('localhost',27017,connect=False) 就可以了。