How tornado future works?

Question

1. I am writing a web server in tornado and I wanted to know how does tornado.concurrent.Future works? I have seen the example of AsyncHTTPClient() but if I want to make my own function which has some some IO operations to perform like get the values from memcache how do I make it to work asynchronously?

2. When I use websocket.WebSocketHandler is the function call write_message() blocking the server? My code is like this below:

 `class SocketHandler(websocket.WebSocketHandler):  
     @gen.coroutine     
     def getMemcVal(self):      
         self.write_message("some test value")`

3. How does the Future differ from the callbacks?

Answer 1

An example about how async & await works:

# python
async def example():
    response = await request.get(“http://www.google.com”)
    result = await response.read()
    print(result)

equals to callback in nodejs:

function example() {
    request.get(“http://www.google.com”, function (response){
        response.read(function (result) {
            console.log(result)
        })
    })  
}

update

So what is Future? It is an abstract concept. You think an asynchronous function as an object, and then you think event loop is scheduling multiple objects like scheduling multiple threads by recognizing await.

But what is real inside it? Just the same as callback. It's just a syntactic sugar.