Jupyter and Python 3.7 compatibility

[gusutabopb]

Currently, the blocking mode won't work on Python 3.7 running on Jupyter. The code below:

import aioinflux
c = aioinflux.InfluxDBClient(db='mydb', mode='blocking')
c.show_measurements()

Raises RuntimeError: This event loop is already running

This is caused by the fact that the latest versions of Tornado (which is used by Jupyter/ipykernel) runs an asyncio loop on the main thread by default:

# Python 3.7
import asyncio
asyncio.get_event_loop()
# <_UnixSelectorEventLoop running=True closed=False debug=False>

# Python 3.6 (w/ tornado < 5)
import asyncio
asyncio.get_event_loop()
# <_UnixSelectorEventLoop running=False closed=False debug=False>

This is being discussed on jupyter/notebook#3397

From an aioinflux perspective, a possible work around would be to start a new event loop on a background thread and use asyncio.run_coroutine_threadsafe to run the coroutine and return a concurrent.futures.Future object that wraps the result.

[gusutabopb]

Another workaround that does not require any code changes is force-downgrading tornado, as mentioned in this comment: jupyter/notebook#3397 (comment)

[gusutabopb]

This issue has been fixed as of IPython 7.0. For more details, see this blog post.