Attempt to record GRPC response time

test.py

from tornado.ioloop import IOLoop
from tornado.gen import Future

def _fwrap(f, gf, ioloop, start_time):
    try:
        gf_result = gf.result()
        response_time = ioloop.time() - start_time
        f.set_result(gf_result)
    except Exception as e:
        f.set_exception(e)

def fwrap(gf, ioloop=None):
    '''
        Wraps a GRPC result in a future that can be yielded by tornado
        
        Usage::
        
            @coroutine
            def my_fn(param):
                result = yield fwrap(stub.function_name.future(param, timeout))
        
    '''
    f = Future()

    if ioloop is None:
        ioloop = IOLoop.current()
    
    start_time = ioloop.time()
    gf.add_done_callback(lambda _: ioloop.add_callback(_fwrap, f, gf, ioloop, start_time))
    return f