Event API

[lo5]

Add mechanism to handle secondary events emitted from UI components. Blocks #19

[navdeep-G]

I was trying to render a table by testing by app on wave.h2o.ai and saw this in the logs:

2020/11/02 20:04:09 # {"addr":"10.1.78.50:54288","t":"disconnect"}
ERROR:websockets.server:Error in connection handler
Traceback (most recent call last):
  File "/resources/venv/lib/python3.7/site-packages/websockets/protocol.py", line 827, in transfer_data
    message = await self.read_message()
  File "/resources/venv/lib/python3.7/site-packages/websockets/protocol.py", line 895, in read_message
    frame = await self.read_data_frame(max_size=self.max_size)
  File "/resources/venv/lib/python3.7/site-packages/websockets/protocol.py", line 971, in read_data_frame
    frame = await self.read_frame(max_size)
  File "/resources/venv/lib/python3.7/site-packages/websockets/protocol.py", line 1051, in read_frame
    extensions=self.extensions,
  File "/resources/venv/lib/python3.7/site-packages/websockets/framing.py", line 105, in read
    data = await reader(2)
  File "/usr/local/lib/python3.7/asyncio/streams.py", line 679, in readexactly
    await self._wait_for_data('readexactly')
  File "/usr/local/lib/python3.7/asyncio/streams.py", line 473, in _wait_for_data
    await self._waiter
concurrent.futures._base.CancelledError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/resources/venv/lib/python3.7/site-packages/websockets/server.py", line 191, in handler
    await self.ws_handler(self, path)
  File "/resources/venv/lib/python3.7/site-packages/h2o_wave/server.py", line 127, in _serve
    async for req in ws:
  File "/resources/venv/lib/python3.7/site-packages/websockets/protocol.py", line 439, in __aiter__
    yield await self.recv()
  File "/resources/venv/lib/python3.7/site-packages/websockets/protocol.py", line 509, in recv
    await self.ensure_open()
  File "/resources/venv/lib/python3.7/site-packages/websockets/protocol.py", line 812, in ensure_open
    raise self.connection_closed_exc()
websockets.exceptions.ConnectionClosedError: code = 1006 (connection closed abnormally [internal]), no reason
2020/11/02 20:04:32 # {"addr":"10.2.77.6:50240","t":"connect","url":"ab82d740-b7ca-4243-883d-58bfe3f68762"}
2020/11/02 20:05:08 # {"error":"failed reading from service: write tcp 127.0.0.1:46440-\u003e127.0.0.1:55556: write: broken pipe","host":"ws://127.0.0.1:55556","route":"/","t":"relay"}

Not sure if it will help, but pasting here just in case. The table is about 580k rows by 31k columns