pyuv 0.10.0 relased!

Today I’m happy to announce that pyuv 0.10.0 has been released! Following libuv’s versioning, this is a stable release, that is, no API changes will occur during the 0.10.x branch cycle.

It has been a while since the last stable release, there have been many changes, even though not all of them are directly visible in the public API. Here is a short list of the most relevant changes for version 0.10.0 since the 0.8 series:

  • Added a true signal watcher
  • Added ability to handle uncaught exceptions (Loop.excepthook)
  • Added TCP.open and UDP.open methods
  • Added support for compilation with Visual Studio in Windows
  • Added thread module with several thread synchronization primitives
  • Added mode parameter to Loop.run (default, once or nowait)
  • Added fileno and get_timeout methods to Loop
  • Added ability to cancel threadpool, getaddrinfo and fs requests
  • Added ability to stop the event loop (Loop.stop)
  • Moved getaddrinfo to util module
  • Removed builtin c-ares resolver
  • Removed get/set process title functions
  • Fixed numerous refcounting issues
  • Multiple fixes for Windows
  • Multiple memory related internal optimizations

There are many more changes, all listed in the changelog file.

I’m glad to say that pyuv is now in better shape than it ever has been. Not only because I have learned many things along the way, but also because I got really good pull requests and help which enhanced pyuv in many different ways. I’m not a Windows guy and got invaluable help from people which helped make pyuv work properly on Windows. Releases 0.9.5-6 contain more commits from others than from myself, and I love that!

Last, I’d like to thank the libuv core team, more specifically Ben and Bert. They do a great job both coding libuv itself and helping others get involved in the project. This is one of the projects I’m really happy I contribute to. Oh, I also scored 4th in the libuv contributions (in lines of code) for Node 0.10.0!

You can get the source code at the usual place, and check the updated documentation here.

Rose: a PEP-3156 compatible event loop based on pyuv

For those who don’t know, PEP 3156 is a proposal for asynchronous I/O in Python, starting with Python 3.3. Until now each framework (Twisted, Tornado, …) has defined it’s own interface for defining protocols and transports. This makes very difficult if not impossible to reuse a protocol implementation across frameworks. PEP 3156 tries to fix that, among other things.

The reference implementation is called Tulip and can be found here. It’s a fast moving target, but it already contains working event loops for Windows and Unix systems. It uses pollers available in the select module for the Unix side, and a C module wrapping Windows IOCP functionality for Windows.

I was really excited to see this come through, so I started playing with it by implementing a pyuv based event loop. I called that it rose. It was a lot easier to implement than expected and it currently passes the entire test suite 🙂

Code can be found on GitHub.

Here is a quick example, the usual echo server, using rose and tulip:

Come and join the discussion in the python-ideas mailing list!

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How do event loops work in Python?

I had the pleasure to give a presentation at the first ever Python Devroom at FOSDEM. I talked about how event loops work internally and how pyuv can help by abstracting a lot of the problems with a pretty simple to use API. I also introduced rose, a pyuv based PEP-3156 event loop implementation, but I’ll write a followup post on that 🙂

Thanks a lot to everyone who attended the talk, and for those who couldn’t here are the slides!


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TLS connections with pyuv and pyOpenSSL

Those of you who have been following the pyuv and/or libuv libraries may have run into this at some point: “how do I use TLS with this”? pyuv provides something similar to a socket with a completion style interface, but it only does TCP. There is also the Poll handle, which can be used to use a regular Python socket with pyuv.

Of course, this second approach is the quickest/easiest in order to get TLS working, because the Python sockets already have TLS support thanks to the ssl module. I wanted to experiment with adding some sort of TLS handle, in the same fashion as the TCP handle, that is, not with regular Python sockets.

There are 2 main libraries providing TLS support (in general): OpenSSL and GnuTLS. What I basically wanted to do was encrypt/decrypt the data in memory and read/write it to a pyuv TCP handle. OpenSSL has this functionality through the BIO API, but I didn’t see anything similar in GnuTLS at a first glance so I went with OpenSSL.

I created a quick TLS handle with the ideas expressed above, it can be found in this gist.

It contains the TLS handle, example echo server and client and some sample certificates. Here is the client implementation sample, for the rest check the full gist.

It’s pretty basic, but I hope it serves as a starting point for using pyuv with TLS. I plan to analyze the performance compared to regular Python sockets in another blog post.

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Fast(er) locks in Python?

While searching for some information on Python locks I recently ran across this great post by David Beazley. In it, he explains how the syncronization primitives in the Python standard library are implemented. Basically, Lock is implemented as a binary semaphore in C, and the rest are implemented in pure Python. Even if the post is from 2009 this is still the case. UPDATE: As Antoine Pitrou points out in the comments, starting with CPython 3.2, RLock is now implemented in C.

This got me thinking. As you know I’ve created pyuv, a Python wrapper for libuv, and libuv includes cross-platform implementations for mutexes, semaphores, conditions rwlocks and barriers, which I never bothered to add to pyuv. I just didn’t add them because I thought they didn’t add any value, but after reading David’s article I decided to do a quick test: implement wrappers for a mutex and a condition variable and use them in a Queue implementation in order to see if there was any difference in performance. Not that I ever ran into performance issues related to that, but I was curious anyway 🙂

Someone may think “oh, but given that Python has the GIL, how does using multiple threads and speeding up the locks matter?”. The GIL is released whenever a IO operation is performed, so if your Python application is multithreaded and it mainly deals with IO-bound tasks, they GIL is not that relevant. If your application is CPU bound, however, better have a look at the multiprocessing module.

So, lets get into the code! I implemented Barrier, Condition, Mutex, RWLock and Semaphore in this pyuv branch, which directly wrap their libuv counterpats. Then I copied the Queue implementation from the standard library and used the freshly wrapped synchronization primitives:

For the testing part, I used the timeit function from IPython with 5 runs. Not sure if it’s the best way, but results suggest it is a good way 🙂 Here is the test script:

Here are the results:

The tests were run with 2, 4 and 100 threads, and since I was testing performance, I added PyPy to the mix. Now, as you can see in the results, the custom Queue is about 33% faster than the one in the standard library, so I was pretty happy about that. Until I tested PyPy. It just beats the shit out of both, which is awesome 🙂

The performance increase on CPython is nice, there is a downside, however: libuv treats errors in this primitives a bit “abruptly”, it calls abort(). This means that if you use the locks incorrectly your program will core dump. I personally like it, because it helps you find and fix the problem right away, but not everyone may like it.

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uvent: a gevent core implemented using libuv

After working on it on-and-off for a few weeks today I’m open sourcing uvent. uvent is a gevent core implementation using libuv.

I’ve written about libuv earlier in this blog, but to put it shortly: libuv is the new black. Specially when we are talking about asynchronous IO.

uvent is still experimental, but results are encouraging, not all tests are failing! :–) I think libuv is the perfect match for a library such as gevent, we’ll see where this goes.

The code can be checked out here and for those who want to know the scary details I wrote a short document with some notes here

Hope you like it!

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pyuv 0.8.0 released!

Yesterday NodeJS 0.8.0 was released, and libuv got its dedicated branch for maintenance of the 0.8.X version cycle. Since pyuv now implements all the features offered by libuv I chose to follow the same path and branch out pyuv 0.8.0.

From now on pyuv’s v0.8 branch will only get bugfixes from the corresponding libuv branch. pyuv’s master branch will use libuv master and have version number 0.9.0-dev, there will not be a release of that branch soon, I guess.

So, what’s new on pyuv 0.8.0 then?

  • FSPoll handle, for polling for file changes using the stat syscall
  • Several fixes in the fs module for Windows
  • Bugfixes that came with libuv

For version 0.9, apart from following libuv’s development I have plans to make the following changes:

  • Move the getaddrinfo function to the util module
  • Overhaul the dns module, provide a raw wrapper on top of c-ares
    instead of exposing a complete DNS resolver (I’ll cover this in a
    future blog post, when I approach the implementation)

Last but not least, I’d like to thank again the NodeJS and libuv developers, they are really doing a great job!

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Integrating Twisted and Tornado with pyuv

With yesterday’s pyuv release the door was open for integrating pyuv with other event loops or applications. Thanks to the Poll handle we can now create a regular socket in Python and put it in pyuv’s event loop, so we can also use pyuv to replace other event loops ;–)

I created a couple of projects for toying around with this feature. The first project implements a Tornado IOLoop which runs on top of pyuv, and the second one implements a Twisted reactor on top of pyuv.

They are not feature complete yet, but basics are working and I’ll be adding more features as time allows.

Go check them out on GitHub!

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pyuv 0.7.0 released!

It’s been a while since I haven’t mentioned pyuv, let me show you what the new version has to offer.

But first, I’d like to thank Ben Noordhuis, Bert Belder and all contributors to the libuv project for such a great job, the library is pleasure to work with and it gets better every week!

Having that said, pyuv 0.7.0 is out and full of nice features, check them out here. To highlight some:

  • Ability to poll arbitrary file descriptors
  • Overhauled reference counting scheme
  • Python 3 support (was added in a previous release)
  • Windows support (was added in a previous release)
  • And more!

You can download pyuv from the GitHub repository or just install it with pip:

Documentation is available here as always.

As of right now pyuv implements all features available on libuv, which took a while to accomplish, but we are finally there :–)

I’ll be publishing a couple of projects built with pyuv shortly, so stay tuned!

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