Cloud-Ready Web Messaging with CometD
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A tour of the CometD Project features, including the clustering features that make CometD ready out-of-the-box to be deployed in cloud environments to achieve great scalability.
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Cloud-Ready Web Messaging with CometD
- 1. Simone Bordet sbordet@intalio.com Cloud-Ready Web Messagging with CometD CloudConf – Torino April 3rd, 2014
- 2. Simone Bordet sbordet@intalio.com Who Am I Simone Bordet sbordet@intalio.com @simonebordet Open Source Contributor Jetty, CometD, MX4J, Foxtrot, LiveTribe, JBoss, Larex Lead Architect at Intalio/Webtide Jetty's SPDY, FastCGI and HTTP client maintainer CometD project leader Web messaging framework
- 3. Simone Bordet sbordet@intalio.com Agenda What is CometD ? CometD Use Cases CometD Features Questions & Answers
- 4. Simone Bordet sbordet@intalio.com What is CometD ?
- 5. Simone Bordet sbordet@intalio.com What is CometD CometD is a web messaging framework Implements a publish/subscribe pattern on the web Web applications use a request/response paradigm Because historically web applications run over HTTP CometD uses a messaging paradigm For example: 1 “request” message, 3 “response” messages Server push – no “request”, 1-N “response” messages Cloud-ready Either stateless or easily clusterable
- 7. Simone Bordet sbordet@intalio.com CometD Use Cases Social Networking Chat and Notifications
- 8. Simone Bordet sbordet@intalio.com CometD Use Cases Online Gaming Not First Person Shooters – yet :)
- 9. Simone Bordet sbordet@intalio.com CometD Use Cases Auctions & Trading Updating bids, prices and availability
- 10. Simone Bordet sbordet@intalio.com CometD Use Cases Systems Monitoring Alerts and System Status
- 11. Simone Bordet sbordet@intalio.com CometD Use Cases Online Collaboration/Productivity Tools
- 12. Simone Bordet sbordet@intalio.com Comet Web Applications A new kind of web applications Server-side event driven Highly dynamic using AJAX / WebSocket on the client Asynchronous and concurrent by definition Big impacts on servers Servers must support async I/O Thread-per-request model does not scale Servers must support WebSocket With an easy fall-back to HTTP
- 14. Simone Bordet sbordet@intalio.com CometD Features CometD provides libraries Build your own solutions with the CometD libraries No out of the box products CometD JavaScript Libraries CometD Java Libraries
- 15. Simone Bordet sbordet@intalio.com CometD Performance CometD Load Test (using a real chat application) HTTP 20k clients 50k messages/s 200 ms median latency WebSocket 100k clients 50k messages/s 4 ms median latency
- 16. Simone Bordet sbordet@intalio.com CometD Performance CometD 3 Roughly 25% to 100% better than CometD 2 Depending on the load CometD 3 based on Servlet 3.1 Ships new HTTP transport based on Servlet 3.1 Async I/O Jetty 9.1 implements Servlet 3.1 Implementation already very stable
- 18. Simone Bordet sbordet@intalio.com CometD Features – JavaScript require(['dojox/cometd', 'dojo/domReady!'], function(cometd) { cometd.init('http://myserver/cometd'); cometd.subscribe('/my/channel', function(message) { var data = message.data; // Do something with the data }); cometd.publish('/my/channel', { chatText: 'hello!' }); cometd.disconnect(); });
- 19. Simone Bordet sbordet@intalio.com CometD Features – JavaScript Easy to make Comet “Hello Worlds” Very difficult to make it fail nicely in real scenarios – CometD does it Network disconnection detection Applications notified via function callback Message batching Sending multiple messages to server efficiently Page reload extension Reload a page in the browser without losing connectivity
- 20. Simone Bordet sbordet@intalio.com CometD Features – Server Spring Framework integration Confidentiality HTTPS and WSS supported out of the box Authentication Controlled via SecurityPolicy OAuth integration Authorization Coarse grained via SecurityPolicy Fine grained via channel Authorizers
- 21. Simone Bordet sbordet@intalio.com CometD Features – Server Transport independence (both client and server) Applications do not hardcode to a specific transport Lazy messages Deliver non important messages on first occasion Save I/O and CPU when it matters Acknowledge Extension Provides server-to-client ordering and acknowledgement of messages Activity Extension Disconnect idle clients after a period of inactivity
- 22. Simone Bordet sbordet@intalio.com CometD Cloud Features
- 23. Simone Bordet sbordet@intalio.com CometD Cloud Features The Cloud: Dynamic horizontal scaling under load Various degrees of support for fail-over Almost always requires application support Applications have to be aware of multiple nodes Data sharing / replication
- 24. Simone Bordet sbordet@intalio.com CometD Features – Clustering Oort CometD's scalability clustering solution Shards clients among nodes Not a high availability solution On node failure clients reconnect automatically But may have lost information Oort cluster members autodiscovery Multicast based Static based on “well known” nodes Existing nodes forward topology to new nodes
- 25. Simone Bordet sbordet@intalio.com CometD Features – Clustering
- 26. Simone Bordet sbordet@intalio.com CometD Features – Oort Oort cluster messages auto re-broadcasting For example, chat applications work out of the box No code needed ! B A C Client A Client B Client C
- 27. Simone Bordet sbordet@intalio.com CometD Features – Seti Seti Clustered peer-to-peer communication Oort performs broadcasting communication Seti maps a user ID token to a session ID Presence information is broadcasted on the cluster Each Seti knows the location of all user IDs Efficient peer-to-peer communication Multiple session IDs for the same user ID For example, connecting from desktop and mobile
- 28. Simone Bordet sbordet@intalio.com CometD Features – Seti B A C Client A Client B Client C
- 29. Simone Bordet sbordet@intalio.com CometD Features – OortObjects Distributed OortObjects Distribution of object state across nodes OortObject<T> A composite, uniquely named, object made of “parts” Only one “part” is owned by the node, others are read-only Trades more memory for smaller data access latency Typical Examples The number of users on each node The list of chat rooms a friend has joined The friends of a friend in a social application
- 30. Simone Bordet sbordet@intalio.com CometD Features – OortObjects A1, A2 B1 NodeA C1A C2A users A1, A2 B1 NodeB C1B users
- 31. Simone Bordet sbordet@intalio.com CometD Features – OortServices Distributed OortServices Forwarding of service actions across nodes OortService<R, C> One uniquely named service in each node Forwards actions to owner node (possibly itself) Trades less memory for higher data access latencies Typical Examples Precise counters (even unique-across-cluster) Update actions (e.g. chess moves)
- 32. Simone Bordet sbordet@intalio.com CometD Features – OortServices NodeA P1 game_service forward(...) NodeB P2 game_service onForward(...) onForwardSucceeded(...)
- 33. Simone Bordet sbordet@intalio.com CometD Features – Clustering OortObject and OortService allow sharding Geographical-based, load-based, business-based Typical examples US users vs EU users Play games locally for better performance
- 35. Simone Bordet sbordet@intalio.com References CometD http://cometd.org http://docs.cometd.org Jetty http://eclipse.org/jetty Intalio/Webtide https://webtide.com