The web is a big place now. We need to support thousands of clients at a time, and here comes Tornado. Tornado is a Python web framework and asynchronous network library, originally developed at FriendFreed.
Tornado uses non-blocking network-io. Due to this, it can handle thousands of active server connections. It is a saviour for applications where long polling and a large number of active connections are maintained.
What is Tornado? Tornado is a python web framework and asynchronous networking library. It is scalable and non-blocking. It specializes in dealing with event-driven networking. As tornado supports concurrent connections, naturally, a server can take advantage of this behavior and handle a lot of web socket connections within a single node.
Tornado is a Python web framework and asynchronous networking library. By using non-blocking network I/O, Tornado can scale to tens of thousands of open connections, making it ideal for long polling, WebSockets, and other applications that require a long-lived connection to each user.
Tornado is not like most Python frameworks. It's not based on WSGI, while it supports some features of WSGI using module `tornado.wsgi`. It uses an event loop design that makes Tornado request execution faster.
Because Tornado doesn't require any external configuration, we can dive right into writing the Python code that'll run our application. Let's make our inner todo directory and fill it with the first few files we'll need. This is the first video of my concerning series about #tornado #webframework. Let's jump right into it.Github: https://github.com/r3ap3rpy/trnado/blob/master.
What is Synchronous Program?
A function blocks,performs its computation, and returns, once done . A function may block for many reasons: network I/O, disk I/O, mutexes, etc.
Application performance depends on how efficiently application uses CPU cycles, that's why blocking statements/calls must be taken seriously. Consider password hashing functions like bcrypt, which by design use hundreds of milliseconds of CPU time, far more than a typical network or disk access. As the CPU is not idle, there is no need to go for asynchronous functions.
A function can be blocking in one, and non-blocking in others. In the context of Tornado, we generally consider blocking due to network I/O and disk, although all kinds of blocking need to be minimized.
What is Asynchronous Program?
1) Single-threaded architecture:
Means, it can't do computation-centric tasks parallely.
2) I/O concurrency:
It can handover IO tasks to the operating system and continue to the next task to achieve parallelism.
3) epoll/ kqueue:
Underline system-related construct that allows an application to get events on a file descriptor or I/O specific tasks.
4) Event loop:
It uses epoll or kqueue to check if any event has happened, and executes callback that is waiting for those network events.
Asynchronous vs Synchronous Web Framework:
In case of synchronous model, each request or task is transferred to thread or routing, and as it finishes, the result is handed over to the caller. Here, managing things are easy, but creating new threads is too much overhead.
On the other hand, in Asynchronous framework, like Node.js, there is a single-threaded model, so very less overhead, but it has complexity.
Let's imagine thousands of requests coming through and a server uses event loop and callback. Now, until request gets processed, it has to efficiently store and manage the state of that request to map callback result to the actual client.
Node.js vs Tornado
Most of these comparison points are tied to actual programming language and not the framework:
Node.js has one big advantage that all of its libraries are Async. In Python, there are lots of available packages, but very few of them are asynchronous
As Node.js is JavaScript runtime, and we can use JS for both front and back-end, developers can keep only one codebase and share the same utility library
Google’s V8 engine makes Node.js faster than Tornado. But a lot of Python libraries are written in C and can be faster alternatives.
One can use a WebSocket client application to connect to the server, message can be any integer. After processing, the client receives the result if the integer is prime or not. Here is one more example of actual async features of Tornado. Many will find it similar to Golang’s Goroutine and channels.
Tornado Python Book
In this example, we can start worker(s) and they will listen to the 'tornado.queue'. Rectangle coloring pages pdf. This queue is asynchronous and very similar to the asyncio package.
1) Asynchronous frameworks are not much of use when most of the computations are CPU centric and not I/O.
2) Due to a single thread per core model and event loop, it can manage thousands of active client connections.
Simple train drawing. 3) Many say Django is too big, Flask is too small, and Tornado is just right:)
Tornado is a Python web framework and asynchronous networking library. You can write Tornado web apps on PythonAnywhere, but you won't be able to use all of Tornado's features.
Tornado Python Websocket
PythonAnywhere web applications are connected to clients (ie. users' web browsers) using a protocol called WSGI. WSGI is designed for traditional web apps, where the client makes a request to the server for a specific resource, and is given the resource. Each request for a new page (or image, or other file) is made in a different request, and there is no way for the server to push data to the client.
Tornado, however, is optimised for asynchronous communication with client web browsers -- that is, a client opens a connection, but then the connection is kept open and the server can push data back to the client. This doesn't work with WSGI, so it doesn't work on PythonAnywhere.
However, if you're using Tornado as a web framework and don't care about the asynchronous stuff, you can use it on PythonAnywhere. Here's a step-by-step guide:
Go to the 'Web' tab
Create a new web app, using the 'Manual configuration' option.
Edit the WSGI file (there should be a link when you get the 'All done' message on the web tab)
Replace the code in the WSGI file with this:
Visit your app, and you should get the results you expect.
Python Tornado Websocket
For more information about Tornado and WSGI, check out this page in the Tornado docs. One thing to keep an eye out for -- in their example, they create a WSGI server to serve up the Tornado app:
Don't do that on PythonAnywhere -- it will break your web app completely.