Tornado vs gevent: What are the differences?

Introduction

In this article, we will discuss the key differences between Tornado and gevent, two popular frameworks used for building high-performance web applications in Python. These frameworks offer different approaches to handling concurrency and asynchronous programming, which can greatly impact the scalability and performance of web applications.

1. Concurrency Model: Tornado utilizes a single-threaded, non-blocking I/O approach, also known as an event-driven concurrency model. It achieves high performance by using non-blocking socket operations and an event loop that efficiently handles multiple requests concurrently. On the other hand, gevent is based on the greenlet library and utilizes a cooperative multitasking model. It uses a combination of greenlets and a monkey-patched standard library to achieve concurrency, allowing developers to write blocking-style code that performs well under heavy load.

2. Resource Usage: Tornado is known for its low memory footprint and efficient resource usage. Since it uses a single-threaded model, it can handle a large number of concurrent connections with a small number of threads. This makes it ideal for applications that require high scalability. In contrast, gevent creates a separate greenlet for each connection, which can lead to higher memory usage and potentially limit scalability in certain scenarios where a large number of connections are needed.

3. Compatibility with Existing Libraries: Tornado is designed to work well with external libraries that are also built for non-blocking I/O, making it easier to integrate with existing asynchronous code. It provides integrations with popular libraries like SQLAlchemy, Redis, and others. On the other hand, gevent's monkey patching approach may cause compatibility issues with some existing libraries, as it modifies the behavior of standard blocking I/O calls.

4. Community and Ecosystem: Tornado has a well-established and active community with extensive documentation, tutorials, and examples available. It has been widely adopted by companies and individuals for building scalable and high-performance web applications. Gevent, although not as popular as Tornado, also has an active community and ecosystem. It offers a range of libraries and tools specifically designed to work with the greenlet-based concurrency model.

5. Development Paradigm: Tornado follows a more traditional callback-based programming paradigm, where developers need to write callback functions to handle asynchronous operations. It can be challenging to reason about complex control flow and handle error scenarios in this style of programming. Gevent, on the other hand, provides a more familiar synchronous programming style, allowing developers to write code that appears to be blocking but executes asynchronously under the hood.

6. Third-party Integration: Tornado provides built-in support for HTTP server capabilities, including a high-performance web server, while gevent is primarily a concurrency library and does not come with an out-of-the-box HTTP server. However, gevent can be combined with other frameworks like Flask or Django to build complete web applications.

In summary, Tornado and gevent differ in their concurrency models, resource usage, compatibility with existing libraries, community and ecosystem support, development paradigms, and third-party integration capabilities. Both frameworks have their strengths and considerations, and the choice depends on the specific requirements and trade-offs of the project.