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Gojko Adzic » QCon London 2009: Upgrading Twitter without service disruptions

Tags: twitter, architecture, Performance on 2009-07-03 and saved by 5 people -All Annotations (6) -About

more fromgojko.net

A very interesting observation during the talk was that Twitter started up with a CMS model and that they gradually moved towards a messaging model. I’ve seen this in a few applications so far, including a casino system, where the messaging model seems to fit best an application intended to power massive community of online users, it seems regardless of what the application actually does business wise. Applications start out completely different, but then more and more functionality gets bolted on top of user messaging capabilities that the whole architecture on the end gets refactored to utilise the messaging channels as the core information transport. With Twitter, I’d expect this to be more obvious from the start as it was intended to help people notify each other.
The interesting thing, however, was that all the upgrades were done live, without shutting down the system. The changes were always introduced to one node, then regression issues were sorted out, and then the software would be rolled out to the whole cluster. They went as far as building a whole messaging system based on memcached APIs in order to be able to slot in such changes.
a write-through vector cache of primary tweet keys with 99% hit ratio, a write-through row cache for tweets and users with 95% hit rate and a read-through fragment cache with rendered versions of different tweets for different clients with 95% hit rate. All these caches are based on memcached.
this change allowed them to increase the web server performance from 3.32 requests per second without caching to 139.03 requests per second. Weaver said that API services work about four times faster than the web, which means that the API performance is roughly 550 requests/s [my calculation, not given during the talk].
- Web is only 10-20% of the traffic, the rest is through API services
- Web servers are still 50% of the cluster.
- Regular incoming traffic peaks are around 80 tweets per second. I expected this to be a lot more.
- before the upgrades their web servers shipped only 3.32 requests per second!
- For each tweet, message gets inserted for each user which follows a tweet. In average, a user has 120 followers so this comes to about 9600 messages/s at peak times
- Message servers run on three nodes. They decided to write their own messaging software in order to make the protocol memcached-like, and did not evaluate other available solutions.
- During Obama’s inauguration, they peaked at about 350 tweets per second for around five minutes.
- They had a ton of problems with garbage collection but strangelly haven’t looked into JRockit RT or something similar that has predictable GC. Twitter JVM middleware runs on the SUN JVM

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InfoQ: Twitter, an Evolving Architecture

Tags: twitter, architecture, Performance on 2009-07-03 and saved by 12 people -All Annotations (3) -About

more fromwww.infoq.com

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Scaling Twitter: Making Twitter 10000 Percent Faster | High Scalability

Tags: scalability, twitter on 2009-07-03 and saved by 37 people -All Annotations (3) -About

more fromhighscalability.com

TwitterNotes

Tags: twitter, notes on 2009-07-03 and saved by 63 people -All Annotations (0) -About

more fromtwitternotes.com

What Twitter Looks Like For Twitter Employees (SCREENSHOTS)

Tags: twitter, backend, sysadmin on 2009-05-02 -All Annotations (0) -About

more fromwww.businessinsider.com

369.pdf (application/pdf Object)

Tags: twitter on 2009-03-17 and saved by 18 people -All Annotations (0) -About

more fromebiquity.umbc.edu

Mischaud_final.pdf (application/pdf Object)

Tags: twitter on 2009-03-17 and saved by 9 people -All Annotations (0) -About

more fromwww.lse.ac.uk

Friends versus Followers: Twitter’s elegant design for grouping contacts | Futuristic Play by @Andrew_Chen

Tags: twitter, follow, friends on 2009-03-17 and saved by 9 people -All Annotations (1) -About

more fromandrewchenblog.com

The 5 P's of Twitter's runaway success ~ Authentic Boredom

Tags: twitter, Review on 2009-03-06 and saved by 2 people -All Annotations (0) -About

more fromcameronmoll.com

Tweeght

Tags: twitter, idea on 2009-02-03 and saved by 8 people -All Annotations (4) -About

more fromtweeght.com

140 Characters » How Twitter Was Born

Tags: twitter, web2.0, startup, experience on 2009-02-01 and saved by 50 people -All Annotations (5) -About

more fromwww.140characters.com

Tweetvisor A Contender For Best Alternate Twitter Interface

Tags: twitter on 2009-01-11 and saved by 4 people -All Annotations (0) -About

more fromwww.techcrunch.com

GroupTweet

Tags: twitter, group on 2008-12-24 and saved by 145 people -All Annotations (3) -About

more fromgrouptweet.com

Twitter relaunches name search, still no tweet search on site » VentureBeat

Tags: twitter, people, search on 2008-12-24 and saved by 2 people -All Annotations (0) -About

more fromventurebeat.com

Logic+Emotion: The Human Feed: How Twitter & Networks Filter Signal From Noise

Tags: information, overload, twitter on 2008-12-24 and saved by 4 people -All Annotations (8) -About

in list: The next web

more fromdarmano.typepad.com

Tweet Link Monster

Tags: twitter, link on 2008-12-21 and saved by 2 people -All Annotations (0) -About

more fromtweetlinkmonster.com

Twitpic Blog » Blog Archive » Be yourself

Tags: twitter, picture, startups on 2008-12-21 -All Annotations (0) -About

more fromblog.twitpic.com

Twitpay

Tags: twitter, payment on 2008-12-21 and saved by 37 people -All Annotations (0) -About

more fromtwitpay.me

twistori

Tags: twitter, mashup, social on 2008-12-21 and saved by 275 people -All Annotations (0) -About

more fromtwistori.com

Twilert twitter alert

Tags: twitter, alert on 2008-12-15 and saved by 69 people -All Annotations (2) -About

more fromwww.twilert.com

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