Mongo错误记录：MongoClient opened before fork. Create MongoClient

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)

配合flask和gunicorn使用报错

使用pymongo配合flask和gunicorn使用的时候触发以下错误信息：

[CRITICAL] WORKER TIMEOUT 
/home/for4c/projects/excel.d/venv3.4/lib/python3.4/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 "
[2017-09-19 15:20:10 +0800] [25896] [INFO] Worker exiting (pid: 25896)

 原因解释

提示的意思是MongoClient在fork之前开启了，官方文档指出：

PyMongo is not fork-safe. Care must be taken when using instances of MongoClient with fork(). Specifically, instances of MongoClient must not be copied from a parent process to a child process.

fork是启动新进程的方法，并且由于PyMongo不是进程安全的，所以不应该将该实例从父进程中复制到子进程当中。在这个flask应用中，flask使用gunicorn作为网关接口，在启动的时候会启动一个主进程和多个子进程，也就是master/workers，这个时候就出现了MongoClient实例在进程之间的传递。

为了解决这个问题，在实例化MongoClient对象的时候也要加上connect=False参数。

app.mongo = MongoClient(host='0.0.0.0',port=27017,connect=False)

完结～～