libuv is a cross-platform asynchronous I/O library designed for C programs, providing an event loop, timers, TCP/UDP sockets, and more. It uses a single-threaded event loop for I/O operations, with a thread pool primarily for file I/O. The library is widely used in various projects and has a rich set of features and utilities to support asynchronous programming.

1. libuv
Cross platform asynchronous i/o
Saúl Ibarra Corretgé — @saghul

2. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV
▸ Cross-platform async I/O and more
▸ Small (relatively) C library: ~30K LOC (without tests)
▸ Extensive test suite and CI coverage
▸ Designed for C programs that miss the joy of JavaScript
callback hell
▸ Used by many projects:
https://github.com/libuv/libuv/wiki/Projects-that-use-libuv

3. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV: FEATURES
▸ Event loop
▸ Timers
▸ TCP / UDP sockets
▸ Named pipes
▸ Filesystem operations
▸ Signal handling
▸ Child processes
▸ ANSI escaped TTY
▸ Threading utilities
▸ Coolest logo ever

4. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV: ARCHITECTURE
▸ The event loop: uv_loop_t
▸ Handles: uv_handle_t
▸ Requests: uv_req_t
▸ Other utilities

5. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV: ARCHITECTURE
OPERATING SYSTEM
NETWORK I/O FILE I/O OTHER STUFF
OS INDEPENDENT
STUFF

6. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV ARCHITECTURE: NETWORK I/O
OPERATING SYSTEM
UV_TCP_T UV_PIPE_T UV_TTY_T
UV_UDP_T UV_POLL_TUV_STREAM_T
UV__IO_T (UNIX ONLY)

7. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV ARCHITECTURE: FILE I/O
UV_FS_T UV_GETADDRINFO_T UV_GETNAMEINFO_T
UV__WORK_T
THREAD POOL
UV_WORK_T

8. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV: A WORD ON THREADS
▸ We only use threads for file i/o and getaddrinfo
▸ http://blog.libtorrent.org/2012/10/asynchronous-disk-io/
▸ Default thread pool size is 4
(runtime env var: UV_THREADPOOL_SIZE)
▸ NOT FOR NETWORK I/O
▸ NOT FOR NETWORK I/O
▸ NOT FOR NETWORK I/O

9. THE LIBUV EVENT LOOP IS
SINGLE THREADED. THE THREAD
POOL IS ONLY USED FOR FILE I/O.
The libuv police
CROSS PLATFORM ASYNCHRONOUS I/O

10. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV ARCHITECTURE: OTHER
▸ OS independent
▸ uv_timer_t
▸ uv_idle_t, uv_prepare_t, uv_check_t
aka “loop watchers”
▸ The thread pool
▸ OS dependent
▸ uv_signal_t
▸ uv_process_t
▸ Threading and miscellaneous utilities

11. CROSS PLATFORM ASYNCHRONOUS I/O
LIBUV: THE EVENT LOOP

12. libuv in Node

13. CROSS PLATFORM ASYNCHRONOUS I/O
NODE EVENT LOOP
Coalesced, 1 Node
timer != 1 libuv timer
Run on a
check + idle handleNext tick callbacks run from
node::MakeCallback

14. CROSS PLATFORM ASYNCHRONOUS I/O
ONION ARCHITECTURE (TM)
net.Socket
TCPWrap
uv_tcp_t
Socket._handle
TCPWrap.handle_
fd / HANDLE

15. A CHAT APP,
OF COURSE

16. CROSS PLATFORM ASYNCHRONOUS I/O
SAMPLE: A LIBUV CHAT APPLICATION
▸ Simple TCP server application
▸ A twist on libuv-chat by Ben Noordhuis in 2011
▸ Multiple users, single “chat room”
▸ Pokemon, because why not?
▸ https://github.com/saghul/libuv-chat

17. WHEN THERE IS
SOMETHING STRANGE
IN YOUR
EVENT LOOP

18. CROSS PLATFORM ASYNCHRONOUS I/O
WHO YOU GONNA CALL? @LIBUV/COLLABORATORS
▸ @piscisaureus
▸ @bnoordhuis
▸ @indutny
▸ @saghul
▸ @cjihrig
▸ @iWuzHere
▸ @santigimeno

19. RESOURCES
libuv.org
docs.libuv.org
#libuv on IRC
libuv Google Group
#libuv on StackOverflow