This Python library was evolved at IronPort Systems and has been provided as open source by Cisco Systems under an MIT license.
Shrapnel is a library for high-performance concurrency. It uses coroutines to implement user threads on top of either kqueue (FreeBSD, OS X) or /dev/epoll (linux), and is written mostly in Pyrex/Cython, supporting both 32-bit and 64-bit platforms. It is the culmination of about 8 years of work at IronPort Systems, a provider of high-speed mail appliances. It was open-sourced by Cisco Systems in late 2011.
Apr 18, 2013: I've recently merged in a long chain of branches for several important features:
- Support for pure-cython servers (branch 'pxdfix')
- Full DNS resolver implementation (branch 'dns-cache')
- Updated postgres support (branch 'postgres')
- Included OpenSSL support
- Lightweight threads, event-driven scheduler.
- Underneath: non-blocking operations on descriptors, like sockets and pipes.
- On top, synchronous API for straight-line, simple code.
- Highly scalable - tens or hundreds of thousands of connections/threads.
- Thread synchronization primitives, like mutexes, semaphores, etc...
- with_timeout(): wrap any funcall with a timeout.
- Wait on kqueue events like file/directory changes, signals, processes, etc... [kqueue only]
- DNS resolver and cache
- HTTP server and client (plus WebSocket, RFC6455 & hixie-76)
- Support for TLS via tlslite and openssl (plus NPN for both)
- other protocols/codecs: ldap, asn1, ftp, mysql, postgres, AMQP.
- MIT License.
Compared to other concurrency packages available for Python, Shrapnel gives you:
- Speed and Efficiency: the entire scheduler, poller, socket layer, synchronization objects, etc... are written in Cython, with an emphasis on performance and low memory usage.
- Stock Python: Shrapnel works with out-of-the-box CPython [2.X]. No special variants of Python are needed, it will even work with your OS's OEM python installation. So you can use all the external libraries/modules you've come to rely on.
- No Callbacks: no need to cuisinart your application into a thousand callbacks. No need to decompose every action into a state machine. Write simple, performant code now without having to send your programmers to class.
- Drop to Cython for speed: all the capabilities of the system are available from Cython, so you can e.g. write a server entirely in Cython for speed. You can interface with external libraries, and do thread switches from Cython or C. It's even possible to have external C code call back into shrapnel. This makes it easy to prototype your application in Python, and then push only the hot spots into Cython.
- Timeouts: Shrapnel provides a general timeout mechanism that can be used to wrap any function call with a timeout.
- Profiler: Thread-aware profiler generates HTML reports.