Super Fast Gevent Introduction
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This document discusses gevent, a library for asynchronous programming that uses greenlets and monkey patching. It provides a simple example of gevent, describes how gevent works by monkey patching functions like sockets and threading to be cooperative instead of preemptive. It also discusses how gevent provides a fast event loop and WSGI server using libevent under the hood, and notes that monkey patching makes gevent incompatible with some third party libraries.
Super Fast Gevent Introduction
- 1. Super Fast Gevent By Walter Liu
- 2. Agenda • Simple Example • About Gevent • About libevent • Monkey patch of gevent • Other notes • About monkey patch
- 3. C10K problem and Gevent Performance
- 7. About GEvent • Fast event loop based on libevent or libevent2 • Light weight execution unit based on greenlets • Use Monkey patch • See monkey patch to know what it works on. • Simple API • Fast WSGI server
- 8. libevent • /dev/poll • kqueue(2) • event ports • POSIX select(2) • Windows select() • poll(2) • epoll(4) • Diff in different platform
- 9. Gevent Monkey Patch • socket (dns=True) • ssl • os.fork() • time.sleep() • select • threading => become co-routine • _thread_local.local • subprocess • sys • stdin, stdout, stderr
- 10. Other Notes • Monkey patch • It’s patching sys.modules, so it’s global patching. • Apply monkey patch before other import. (especially on thread) • Apply monkey patch after fork/multi-process. • Be noted about 3rd party library compatibility • Be noted about blocking functions in your program. • Gevent with Python web framework • Played uWSGI with gevent. (very good performance) • Tried using it in Django to accelerate crawling. • How about gunicorn?
- 11. Monkey patch
- 13. Good for unit test
- 14. Tips • Life time of monkey patch is till the end of process. • You may chose not to monkey unpatch, but it may breaks the whole program. • Basically, it’s a dirty workaround. • Thus, only use it on unit test or something like gevent.