Nktalk is an integrated instant messaging service for the Polish social networking platform nasza-klasa.pl, designed to handle massive concurrent users and messages. Built using Erlang and the XMPP protocol, it offers high availability and error isolation, crucial for its demanding web-based application. The integration of HTTP with BOSH allows for efficient communication between the web browser and the ejabberd server while adhering to the unique requirements of the service.

1. NKtalk Case Study Kraków Erlang User Group 26 January 2010 Bartłomiej Puzoń, Michał Ptaszek [email_address] Erlang Solutions Ltd

2. Agenda What is NKtalk? Challenges Technologies chosen Erlang XMPP Integration

3. What is NKtalk? nasza-klasa.pl - large Polish social networking service Over 13 mln users Service aims at being a communication platform NKtalk is an integrated instant messaging service Provides new means of communication

4. Challenges Massive number of messages per second concurrent users Integration with the portal HTTP Contact lists Short time to market

5. Technologies chosen: Erlang What's Erlang? Functional programming language Unlike C++, Java, C# Like LISP, Haskell Open Source (www.erlang.org) Platform independent, runs on UNIX/Linux Windows Mac Embedded Systems

6. Why Erlang? Created for a concurrent world NKtalk: tens of thousands of users communicating simultaneously Erlang provides concurrency based on share-nothing actors

7. Why Erlang? Created for a world that grows NKtalk users number grows Erlang has a built-in support for distributed applications It is easy to extend an Erlang cluster with new nodes depending on the needs

8. Why Erlang? Created for a networked world NKtalk is a web-based application Erlang has an extensive build-in support for TCP/IP and HTTP

9. Why Erlang? Created for a demanding world NKtalk requires high availability If there is an error in one of the 10.000 connections, the other 9.999 can not be affected Erlang encourages error isolation

10. Technologies chosen: XMPP What's XMPP? eXtended Messaging and Presence Protocol Based on XML Used for instant messaging (GoogleTalk)

11. Why XMPP? XMPP advantages open popular software and libraries available proven used since 1998 standarized (IETF) extensible many extensions already available

12. XMPP + Erlang = Ejabberd Ejabberd – E rlang jabber (XMPP) d aemon (server) Open source Modular Utilizes the aforementioned Erlang traits Successful deployments for million concurrent users

13. Integration: The Problem Ejabberd and other XMPP servers assume a stream-oriented connection TCP NKtalk works over the Web HTTP HTTP is a response-request protocol TCP is a stream oriented protocol

14. Integration: The Solution BOSH (Bidirectional-streams Over Synchronous HTTP) BOSH emulates a stream-oriented connection (TCP) over a response-request (HTTP) protocol XMPP messages that would be sent over TCP are encapsulated into HTTP request HTTP-specific mechanisms are used to emulate bidirectional connection

15. Overview user's web browser nktalk.pl Internet node1 Ejabberd Cluster (powered by Erlang ) node2 node3 node4 HTTP requests

16. Overview user's web browser Internet Hola! XMPP stanza Hola! HTTP request XMPP stanza Hola!

17. Overview nktalk.pl Internet node1 Ejabberd Cluster (powered by Erlang ) node2 HTTP request XMPP stanza Hola! BOSH module (extracts XMPP) Ejabberd Server (routes traffic) Long-term storage XMPP stanza