Distributed app development with nodejs and zeromq
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This document discusses using Node.js and ZeroMQ for distributed application development. It defines distributed applications as apps distributed across multiple cloud locations that communicate via a standardized protocol. ZeroMQ is introduced as a socket library that can be used for inter-app communication, with common patterns being push-pull for sending data and req-rep for request-response. Scaling is discussed as adding more app instances for push-pull and adding more rep apps for req-rep. Sample ZeroMQ code in Node.js is also provided.
Distributed app development with nodejs and zeromq
- 1. Distributed app development node.js + zeroMQ = awwyeah
- 2. ZeroMQ from a noob’s viewpoint
- 3. RUBEN TAN • NodeJS enthusiast • Author of eazy (https://github.com/soggie/eazy) • Dota 2-er
- 4. DISCLAIMER • I AM NOT A ZEROMQ EXPERT • (not even remotely close) • Case study by consulting a successful implementer of ZMQ in an adserver
- 5. Objective • 1,000,000,000 ad impressions per month (on average) • 80ms maximum response time for each ad • Good luck, Apache
- 6. Webserver Choices • Netty - Java can actually be fast https://netty.io • Gevent - For Python lovers http://gevent.org/ • Node.js - The reason why you’re here http://nodejs.org/
- 7. So... which one? • All 3, but that’s not the point • Speed isn’t the most important factor • Reliability under load is more important than pure performance • 1 missed impression = 1 potential disaster (imagine BMW ads showing up in ThePirateBay) • (but secretly, I prefer node.js)
- 8. Welcome to the distributed app ecosystem
- 9. Definitions, definitions • Distributed: distributed across multiple geological “clouds” • Apps: each app handles a small scope of responsibility • Ecosystem: apps talk to apps via a standardized protocol
- 10. Distributed • Route 53 -> HAProxy -> Webserver -> Apps • Scale webservers by creating new instances behind HAProxy • Scale apps by creating new instances in their own clouds
- 11. Distributed Route 53 (DNS) HAProxy “LB layer” Webserver Webserver Webserver App cloud App cloud (EU) (NA)
- 12. Apps • Each app should perform ONE single domain of function • Write the app like you’re writing an API • The simpler the app, the better • App can be written in any language
- 13. User app • List of exposed API: • create new user • edit user • delete user • merge user accounts • authenticate user
- 14. Ecosystem • Apps communicate using JSON-RPC • Apps connect to each other using ZMQ • “Controller” scripts and monit handles lifecycle
- 15. Quick & dirty ZeroMQ • ZMQ = socket library • Types of socket: • inproc • IPC • TCP • pgm • epgm
- 16. Socket Types • Push-pull • Req-rep • Pub-sub (not covered) • Dealer-router (not covered) • Xreq-xrep (not covered)
- 17. Push-pull • Push socket pushes data to pull socket(s) • Pull socket pulls data from push socket(s) Push Pull Socket Socket
- 18. Push-pull • Use cases: • Sending email: apps pushes email data to email app • Logging: apps pushes messages to a logging app • Data crunching: apps pushes partials to processing app(s) to work on • Analytics: apps pushes tracking data to analytics app to process
- 19. Push-pull • Push socket can connect to multiple pull sockets (fan-out) • Pull sockets can listen on multiple push sockets (fan-in) • Best part: ZeroMQ handles the load balancing (usually via a LRU)
- 20. Advanced Push-Pull • Example: Log file processing • Log file needs to be parsed • Push app (ventilator) parses the log file • Push app continuously fires partials to pull apps (workers) • Workers push into another pull app (collector)
- 21. Advanced Push-pull Worker Worker push push Ventilator Collector pull pull Worker Worker
- 22. How do we scale?
- 23. ADD MORE WORKERS
- 24. Req-rep • Req socket sends data to rep socket • Rep socket receives data from req socket • Rep socket replies to req socket • NOTE: Req socket always expects replies (remember that girl that you waited 5 years for?)
- 25. Req-rep • Use cases: • Inter-app communications: apps that has dependencies between each other uses a REQ-REP pattern • Caching: apps req cached items from cache app, cache app rep with cached item • API: 3rd party developers issue req to your API app, which filters the request and replies with the results
- 26. Req-rep REQ REP Socket Socket req REQ REP Socket Socket rep REQ REP Socket Socket
- 27. How to scale?
- 28. ADD MORE REP APPS
- 30. Sample ZMQ code: 01 var zmq = require('zmq'), 02 push = zmq.socket('push'), 03 pullA = zmq.socket('pull'), 04 pullB = zmq.socket('pull'); 05 06 pullA.on('message', function (msg) { 07 console.log('pullA received ' + msg); 08 }); 09 10 pullB.on('message', function (msg) { 11 console.log('pullB received ' + msg); 12 }); 13 14 pullA.bindSync('inproc://nodehack-rocks'); 15 pullB.bindSync('inproc://oh-la-la'); 16 17 push.connect('inproc://nodehack-rocks'); 18 push.connect('inproc://oh-la-la'); 19 20 for (var i = 0; i < 10; i++) { 21 push.send('this is message ' + i); 22 }
- 31. Notes • Each app can define and use multiple ZMQ sockets • You can organize your app’s internals using inproc ZMQ sockets (better MVC) • Controller scripts are important • There are advanced patterns for reliability (read the ZMQ guide)
- 32. Libraries • NodeJS ZMQ binding (https://github.com/JustinTulloss/zeromq.node) • ZMQ Guide (http://zguide.zeromq.org/page:all) • Eazy (https://github.com/soggie/eazy)
- 33. - the end -