Zing Me Real Time Web Chat Architect

Zing Me Web Chat Architect By Chau Nguyen Nhat Thanh ZingMe Technical Manager Web Technical - VNG

Agenda● About Zing Me● Zing Me platform strategy● Zing Me web chat architect ● Problem with real time message in HTTP ● Connection server ● Message server ● Online server● Some statistic information 2

About Zing Me

SNS Platform

Updated stats● 45M registered accounts● 2.2M daily active users● 7M monthly active users● > 500 servers (2 K cores) ● 70 DB servers, >60 Memcached servers ● ~ 150 Web servers ● 40 servers for Hadoop farm ● Others (storage, ...)

Zing Me Technology● Load balancing: HA proxy, LVS● Web server: Nginx, Lighttpd● Web caching: Squid, Varnish● Caching: Redis, Memcached, Membase● CDN: in progress● Programming language: PHP, C++,Java, Python, Bash script, Erlang● Searching: Solr, Lucene● DB: MySQL , Cassandra, HBase● Log system: Scriber + Hadoop

Zing Me platform strategy● Open platform ● Open Social API ● Open Auth ● Zing Connect ● http://open.me.zing.vn/● Open service ● Cloud Memcache ● Cloud Key Value Storage ● Virtualization for Hosting Service

Zing Me platform strategy● Focus on communication tools: ● Email: Zing mail ● Private message ● IM : ZingMe Web Chat ● Notification: Zing Notification System

Zing Me Web Chat Architect

Frontend UI

Problem with realtime message● Realtime message in HTTP ● Browser actively connect to web server ● How can web server push the new message to the browser ? ● COMET is the answer● COMET overview ● Comet is a web application model in which a long-held HTTP request allows a web server to push data to a browser, without the browser explicitly requesting it (wikipedia) ● Implementation: hiden iframe, ajax long-polling, script tag long polling

Frontend JS● 2 developers in 4 months● Building from the scratch based on zmCore.js, a Zing Me homemade js framework● Using long-polling for pushing new messge● Get online friend list● Get last message● Verify session

Backend● Must scalable● Handle large number of connetions● Connection server handles the long-polling connection● Friend Online server keeps track online friends● Message Server stores the messages● Message Delivery Worker transfers messages from the Message Server to Connection Server● Channel Server maps the users with their connections

Web Chat Architect Overview

Connection Server● Must handle large number of concurrent connections ( > 100K connections)● Implement in C++● Using native EPOLL system call● NONBLOCKING mode for async IO● Dev in 8 months

Connection Server Implementation● Long polling

Connection Server Implementation● Keep connections until message come or timeout● Server must keep a large number of connections (C100K)● Use the same solution like memcached, haproxy

Connection Server Implementation● Why EPOLL? ● General way to implement tcp servers is “one thread/process per connection”. But on high loads this approach can be not so efficient and we need to use another patterns of connection handling.(kovyri.net) ● Need an asynchronous way ● EPOLL is the solution

Connection Server Implementation● Coding with EPOLL ● Create specific file descriptor for epoll calls: epfd = epoll_create(EPOLL_QUEUE_LEN); ● After first step you can add your descriptors to epoll with following call: static struct epoll_event ev; int client_sock; ... ev.events = EPOLLIN | EPOLLPRI | EPOLLERR | EPOLLHUP; ev.data.fd = client_sock; int res = epoll_ctl(epfd, EPOLL_CTL_ADD, client_sock, &ev);

Connection Server Implementation● When all your descriptors will be added to epoll, your process can idle and wait to something to do with epoll’ed sockets: while (1) { // wait for something to do... int nfds = epoll_wait(epfd, events, MAX_EPOLL_EVENTS_PER_RUN, EPOLL_RUN_TIMEOUT); if (nfds < 0) die("Error in epoll_wait!"); // for each ready socket for(int i = 0; i < nfds; i++) { int fd = events[i].data.fd; handle_io_on_socket(fd); } }

Friend Online Server● Hard to scale● Implement in C++● Using some cheats to define user online● Caching is hard● Dev in 1 month

Message Server● Store the messages● Implement in Java● Problem with memory usage ● C++ version in progress● Notify new message by queue● Worker will deliver message to user by connection server

Web Chat statistic

Total message

Hourly stats

Q&AContact info: Chau Nguyen Nhat Thanh thanhcnn@vng.com.vn me.zing.vn/thanhcnn2000

http://open.zing.vn	2749
http://link.apps.zing.vn	108
http://bkit.co	87
http://me.zing.vn	26
http://twitter.com	4
http://yourails.com	3
https://twitter.com	1
http://bkitco.ipage.com	1

Zing Me Real Time Web Chat Architect

by Chau Thanh on Jul 25, 2011

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