RuntimeError: Task attached to a different loop

问题

Hi I'm using AsyncIOMotorClient for asynchronous db calls to mongoDb. Below is my code.

xyz.py
async def insertMany(self,collection_name,documents_to_insert):
    try:
        collection=self.database[collection_name]
        document_inserted = await collection.insert_many(documents_to_insert)
        return document_inserted
    except Exception:
        raise

def insertManyFn(self,collection_name,documents_to_insert):
    try:
        loop=asyncio.new_event_loop()
        asyncio.set_event_loop(loop)
        loop1=asyncio.get_event_loop()
        inserted_documents_count = loop1.run_until_complete(self.insertMany(collection_name, documents_to_insert))
        if inserted_documents_count==len(documents_to_insert):
            document_to_insert={Config.DB_JOB_COLUMN:Job.job_id,Config.DB_JOB_RESULT_COLUMN:Config.DB_JOB_RESULT_SUCCESS}
            loop1.run_until_complete(self.insertOne(Config.DB_JOB_COLLECTION, document_to_insert))
    except Exception:
        raise

xyz1.py
t=Timer(10,xyz.insertManyFn,\
                (collection_name,documents_to_insert))
t.start()   

While running this I'm getting an exception

RuntimeError: Task <Task pending coro=<xyz.insertMany() running at <my workspace location>/xyz.py:144> cb=[_run_until_complete_cb() at /usr/lib64/python3.5/asyncio/base_events.py:164]> got Future <Future pending cb=[_chain_future.<locals>._call_check_cancel() at /usr/lib64/python3.5/asyncio/futures.py:431]> attached to a different loop

In the above program insertManyFn will be called after 10sec and do the insert operation. But when it make the first call to insertMany I'm getting an exception.

回答1:

According to the documentation, AsyncIOMotorClient should be passed an ioloop if you don't use the default one. Try creating the client after you create your event loop:

loop=asyncio.new_event_loop()
asyncio.set_event_loop(loop)
client = AsyncIOMotorClient(io_loop=loop)

回答2:

I've modified the code and it's working.

def insertManyFn(self,loop,collection_name,documents_to_insert):
    try:
        inserted_documents_count = loop.run_until_complete(self.insertMany(event_loop,collection_name, documents_to_insert))
        if len(inserted_documents_count)==len(documents_to_insert):
            document_to_insert={Config.DB_JOB_COLUMN:Job.job_id,Config.DB_JOB_RESULT_COLUMN:Config.DB_JOB_RESULT_SUCCESS}
            loop1.run_until_complete(self.insertOne(Config.DB_JOB_COLLECTION, document_to_insert))
    except Exception:
        raise

loop=asyncio.get_event_loop()   
t=Timer(10,self.xyz.insertManyFn,(loop,collection_name,documents_to_insert))
t.start()

Explanation- I'm using python threading timer, which creates own thread to execute a function after a certain time. So, inside this thread I was getting event loop which should not be the correct approach, it should be first getting the event loop and create a timer thread in it. I guess this is the only reason.

来源：https://stackoverflow.com/questions/41584243/runtimeerror-task-attached-to-a-different-loop