ØMQ and Perl

Introduction to ØMQ, how to use it in Perl, and some patterns you'll need when building an application.

Transcript

1. ØMQ and Perl Anthony Johnson <aj@ohess.org> @agjhnsn
2. What is ØMQ? And what isn’t it?
3. A better socket • Abstracts connection boilerplate • Gracefully handles connections • Messages don’t change during send
4. A better message queue • Queues packets being sent or received • One-way and two-way message patterns for concurrency • Decentralized
5. It’s not: • A BSD/POSIX socket • Low latency • A job queue
6. When to use ØMQ? • Replacing an RPC or RESTful API • Asynchronous tasks model with workers • Cross language support is needed • Just need to write a socket
7. ØMQ isn’t a replacement for • A client-facing HTTP API • Low latency sockets • Job queues
8. ØMQ Socket Foundations
9. Paired socket types • REQ/REP - send packet, expect response • PUSH/PULL - send/receive packet, no response • PUB/SUB - similar to pull, packet duplicated to all clients • ROUTER/DEALER - accumulate and distribute packets • REQ/ROUTER and DEALER/REP - load balancing
10. Rouer/dealer model
11. Multipart messages • Message can be grouped for throughput • Queues in memory • Won’t send automatically • Delivers all or none
12. Messages are strings • ØMQ knows nothing about your data • Data is a string and string length • Optionally use a serializer
13. Queue HWM (High Water Mark) • Each socket has a HWM • Sockets have send and/or receive buffers • When the HWM is reached, sockets may block or drop • ØMQ v2 HWM is infinite • ØMQ v3 HWM is 1000 messages
14. ØMQ and Perl
15. Installing • ZMQ • ZMQ::LibZMQ2 or ZMQ::LibZMQ3 • ZeroMQ is deprecated • Development library
16. Forcing ZMQ::LibZMQ2
17. What does it look like?
18. The server
19. The client
20. Common Patterns
21. Serialization Using JSON for serialization
23. Socket reliability • Protect against socket failure • Poll receiving socket instead of blocking • Resend request after timeout, abandon if still no replies
24. Polling sockets • Not blocking on receive • Can poll on multiple sockets • On socket receive, execute callback
26. Polling multiple sockets
27. “Classy programmers are like classy hit men Always clean-up when you finish the job.”
28. Cleaning up • Set the linger option on sockets as they are closed • Sockets that aren’t flushed cause the context to hang
30. Dynamic Discovery How do sockets know of each other?
31. Static discovery
32. Dynamic discovery through routing
33. Broker
34. Preemptively use a broker Don’t wait to scale out
35. Or, decentralize EVERYTHING.
36. More Advice • Mind your context scope when forking • Don’t be afraid to over engineer
37. Resources • ØMQ Guide http://zguide.zeromq.org/ • ØMQ zguide on Github https://github.com/imatix/zguide