[GitHub] [arrow] lidavidm commented on pull request #10318: ARROW-12050: [C++][Python][FlightRPC] Make Flight operations interruptible in Python

[GitBox <gi...@apache.org>]

lidavidm commented on pull request #10318:
URL: https://github.com/apache/arrow/pull/10318#issuecomment-844030751


   It solves a problem for Python users: if you Ctrl-C in something like read_all(), nothing will happen because control is in C++/Flight code, and then you're stuck waiting for the call to complete. 
   
   If you apply this diff to python/examples/flight/server.py:
   ```diff
   diff --git a/python/examples/flight/server.py b/python/examples/flight/server.py
   index 7a6b6697e..bc1df21d1 100644
   --- a/python/examples/flight/server.py
   +++ b/python/examples/flight/server.py
   @@ -73,6 +73,7 @@ class FlightServer(pyarrow.flight.FlightServerBase):
                yield self._make_flight_info(key, descriptor, table)
    
        def get_flight_info(self, context, descriptor):
   +        return self._make_flight_info("", descriptor, pyarrow.schema([]).empty_table())
            key = FlightServer.descriptor_to_key(descriptor)
            if key in self.flights:
                table = self.flights[key]
   @@ -86,10 +87,10 @@ class FlightServer(pyarrow.flight.FlightServerBase):
            print(self.flights[key])
    
        def do_get(self, context, ticket):
   -        key = ast.literal_eval(ticket.ticket.decode())
   -        if key not in self.flights:
   -            return None
   -        return pyarrow.flight.RecordBatchStream(self.flights[key])
   +        import itertools
   +        schema = pyarrow.schema([])
   +        rb = pyarrow.RecordBatch.from_arrays([], schema=schema)
   +        return pyarrow.flight.GeneratorStream(schema, itertools.repeat(rb))
    
        def list_actions(self, context):
            return [
   ```
   
   Then you can start the server:
   
   ```sh
   arrow/python$ env PYTHONPATH=$(pwd) python examples/flight/server.py --port 2000 &
   arrow/python$ env PYTHONPATH=(pwd) python examples/flight/client.py get localhost:2000 -c foo
   ```
   
   Without this patch, if you Ctrl-C, your client will still be stuck forever. With this patch you'll interrupt the call as expected.


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