PooledMySQLDatabase MaxConnectionsExceeded
http://docs.peewee-orm.com/en/latest/peewee/playhouse.html#pool

You are not managing your connections.

Call connect at the beginning of a request/thread, and close() at the end. This ensures that your conns are returned to the pool.
I use PooledMySQLDatabase  for  a pool , when I with atomic for create , but  case MaxConnectionsExceeded
```
def logic_create_event_item(operate_dict):
    user_id = operate_dict["user_id"]
    content_type = "event"
    event_id = operate_dict["event_id"]
    operate_type = "create"
    user_operate_log = UserOperateLog.get_or_none(
        UserOperateLog.user_id == user_id, UserOperateLog.content_type == content_type,
        UserOperateLog.event_id == event_id, UserOperateLog.operate_type == operate_type)
    if user_operate_log:
        return
    with settings.DB.atomic() as txn:
        try:
            user_operate_log = UserOperateLog()
            user_operate_log.user_id = user_id
            user_operate_log.content_type = content_type
            user_operate_log.content_id = event_id
            user_operate_log.operate_type = operate_type
            user_operate_log.content = "创建埋点"
            user_operate_log.save(force_insert=True)
        except Exception as e:
            txn.rollback()
            raise e
```
![image](https://user-images.githubusercontent.com/32890883/150620761-475a7d32-ecc7-4fdd-8843-a3f1718617f7.png)




