John Adams on Fixing Twitter: Improving the Performance and Scalability of the World's Most Popular Micro-blogging Site

by Jesse Robbins | @jesserobbins | comments: 2

Twitter is suffering outages today as they fend off a Denial of Service attack, and so I thought it would be helpful to post John Adams’ exceptional Velocity session about Operations at Twitter.

Good luck today John & team… I know it’s going to be a long day!

Update: Apparently Facebook & Livejournal have had similar attacks today. Rich Miller from Data Center Knowledge reminds us that this is just the latest in a series of major attacks.

Four short links: 1 July 2009

Web Awards, Speed Thrills, Magazines in the Cloud, Augmented Reality

by Nat Torkington | @gnat | comments: 0

1. The Onyas -- New Zealand web design awards launch, from the people behind Webstock and Full Code Press. The name comes from "good on ya", the highest praise that traditionally taciturn New Zealanders are allowed by law to give.
2. The Year of Business Metrics: Don't make your users run away! -- wrapup of the Velocity conference. AOL: Users who had a slower experience view far fewer pages. Some interesting notes on performance from a Google-Bing study: Notice that as the delays get longer the Time To Click increases at a more extreme rate (1000ms increases by 1900ms). The theory is that the user gets distracted and unengaged in the page. In other words, they've lost the user's full attention and have to get it back. [...] As much as five weeks later, some users, especially those who saw delays greater than 400MS, were still searching less than before. (via timoreilly on Twitter)
3. Printcasting -- very simple content management system for print magazines that lets anyone start a magazine, add content, sign up contributors, sell ads, and go. Clever!
4. Pachube Augmented Reality Hack -- sexy hack that pushes all my buttons: computer vision, Arduino, sensor network, ubiquitous computing, pervasive alternate reality cyborg villians with chalk designs hellbent on world domination and the enslavement of the human race to use as meatsack AA batteries for their sex toys. Okay, four out of five ain't bad. (via bruces on Twitter)

Pachube Augmented Reality Demo

Velocity and the Bottom Line

by Steve Souders | comments: 3

Velocity 2009 took place last week in San Jose, with Jesse Robbins and I serving as co-chairs. Back in November 2008, while we were planning Velocity, I said I wanted to highlight "best practices in performance and operations that improve the user experience as well as the company's bottom line." Much of my work focuses on the how of improving performance - tips developers use to create even faster web sites. What's been missing is the why. Why is it important for companies to focus on performance?

That question was answered at Velocity last week by speakers from AOL, Google, Microsoft, and Shopzilla.

• Eric Schurman (Bing) and Jake Brutlag (Google Search) co-presented results from latency experiments conducted independently on each site. Bing found that a 2 second slowdown changed queries/user by -1.8% and revenue/user by -4.3%. Google Search found that a 400 millisecond delay resulted in a -0.59% change in searches/user. What's more, even after the delay was removed, these users still had -0.21% fewer searches, indicating that a slower user experience affects long term behavior. (video, slides)
  
• Dave Artz from AOL presented several performance suggestions. He concluded with statistics that show page views drop off as page load times increase. Users in the top decile of page load times view ~7.5 pages/visit. This drops to ~6 pages/visit in the 3rd decile, and bottoms out at ~5 pages/visit for users with the slowest page load times. (slides)
• Marissa Mayer shared several performance case studies from Google. One experiment increased the number of search results per page from 10 to 30, with a corresponding increase in page load times from 400 milliseconds to 900 milliseconds. This resulted in a 25% dropoff in first result page searches. Adding the checkout icon (a shopping cart) to search results made the page 2% slower with a corresponding 2% drop in searches/user. (Watch the video to see the clever workaround they found.) Image optimizations in Google Maps made the page 2-3x faster, with significant increase in user interaction with the site. (video, slides)
• Phil Dixon, from Shopzilla, had the most takeaway statistics about the impact of performance on the bottom line. A year-long performance redesign resulted in a 5 second speed up (from ~7 seconds to ~2 seconds). This resulted in a 25% increase in page views, a 7-12% increase in revenue, and a 50% reduction in hardware. This last point shows the win-win of performance improvements, increasing revenue while driving down operating costs. (video, slides)
  

These case studies provide real world numbers that show the benefits of making your site faster. Other Velocity sessions share techniques for implementing performance improvements, including sessions from me, Doug Crockford, and the Facebook and Google frontend teams. But what about the user experience? In his session, Matt Mullenweg (of WordPress fame) makes sure we remember the importance of how the user feels while interacting with our site:

That's why [performance] is important and why we should be obsessed and not be discouraged when it doesn't change the funnel. My theory here is when an interface is faster, you feel good. And ultimately what that comes down to is you feel in control. The web app isn't controlling me, I'm controlling it. Ultimately that feeling of control translates to happiness in everyone. In order to increase the happiness in the world, we all have to keep working on this.

Thanks to the Velocity speakers & their organizations for overcoming the many challenges required to present this data for the first time. We're now equipped with the financial justification, the technical know-how, and the visceral motivation to go out and make the Web a faster place. We'll have more performance success stories next year. Your company could be one of them! Capture your performance improvements and bottom line impact. We'd love to hear from you at Velocity 2010.

Announcing: Spike Night at Velocity

by Scott Ruthfield | @scottru | comments: 5

Guest blogger Scott Ruthfield is a Program Committee member of the O'Reilly Velocity: Web Performance & Operations Conference. 

Velocity Preview - The Greatest Good for the Greatest Number at Microsoft

by James Turner | comments: 4

The psychology of engineering user experiences on the web can be difficult. How much rich content can you place up on a page before the load time drives away your visitors? Get the answer wrong, and you can end up with a ghost town; get it right and you're a star. Eric Schurman knows this well, since he is responsible for just those kind of trade-off decisions on some of Microsoft's highest traffic pages. He'll be speaking at O'Reilly's Velocity Conference in June, and he recently talked with us about how Microsoft tests different user experiences on small groups of visitors.

James Turner: Why don't you start by describing what your gig at Microsoft is now and what your career path has been there?

Eric Schurman: I'm a principal dev lead for Live Search, what used to be MSN Search. And I started at Microsoft back in the late 90s working in Microsoft's Press organization, where we actually were developing training software that would emulate new Microsoft products, but didn't require those products to be on a user's machine. So, for example, if you had an organization that was running Windows 95, we would have a training system for Windows 98 that would emulate a bunch of the functionality of Windows 98 so that you could deploy it to your people. They could train their people on how to use Windows 98 before they actually deployed it.

I then moved on to the Microsoft Press website, where I became the dev lead for it. I made a few other moves and ended up going to Microsoft.com, where I ran the download center, the Microsoft.com homepage, the product catalog, and a bunch of other places from a dev perspective.

I then moved to what was then MSN Search, back in about 2005, and was there through the MSN to Live transition. At the time, I wasn't working on performance; I was just working on the Live Search application. And it became very obvious that we had some major performance problems. Performance has always been one of my really strong interests, so I took on addressing a lot of those. And when we addressed them, we had very significant improvements in our business metrics. That really surfaced how important performance was to the organization, and I moved into a role where I was really focusing just on performance. I've been in that role now for about two years.

JT: You've worked on at least three very different parts of the Microsoft website. The homepage has lots of hits, fairly static. The download page is a lot of data for long periods of time. Live Search is high volume, but there's also a lot of backend on that. In what ways do you need to architect them differently? And where can you reuse the same lessons?

ES:: That's a great question. On the web, you've got different concerns on what you have for client apps. The main things that tend to impact end-user perceived performance on the web are often things about how you've designed your application from a network perspective. So how many different HTTP get requests are you making? How are those get requests structured? So, for example, are they serialized? Did you have a JavaScript file that then gets returned to the browser that requests another JavaScript file and another JavaScript file and then some content and then it finally gets rendered? So the number of assets that you request, that's going to be something that's important no matter what product your doing.

There are other things, like how much script do you have on the page, how much CSS you have on the page, how much actual content are your rendering to the page, etcetera. There are tricks that you can use like combining many different graphics into a single tiled image and sending that down to the browser. It's much faster to send one image to the browser than, say, 20 images. Even if you end up sending the same overall graphics, but combined into one, it's still must faster to send it as one request.

There are also different data volume concerns. They're also different from a business perspective. A lot of what we were sending out from the download center was extremely time critical. We would have an update go out, and we needed to make sure that update was going to be available anywhere in the world within a certain time frame, which required us to handle very high bandwidth, and a very high volume of requests coming into the site that were transferring lots of bits. So that required something totally different than something like the Microsoft.com homepage.

It's also interesting looking at the volume of traffic and how that traffic reflects real users. So, for example, one of the problems that you end up with on both the Microsoft homepage and Live Search is that we have a huge number of bots that are trying to hit the system, lots of people trying to do SEO work are trying to hit search engines to gather information about their site, about competitor sites, about all sorts of things. On the Microsoft.com homepage, it's always under distributed denial of service attacks. It's not a question of how frequently does it happen; it's just what is the rate right now? Also, the Microsoft.com homepage has historically had such a high up-time rate that it's actually hit by a lot of hardware devices simply to check for connectivity to the internet. And so you'd want to treat a request from that kind of "user" very differently from a request that's coming from a real user.

So that's kind of a long, rambling answer to your question. Do you have any areas that you want me to drill in or maybe talk about something else?

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Velocity 2009 - Big Ideas (early registration deadline)

by Jesse Robbins | @jesserobbins | comments: 7

My favorite interview question to ask candidates is: "What happens when you type www.(amazon|google|yahoo).com in your browser and press return?"

While the actual process of serving and rendering a page takes seconds to complete, describing it in real detail can take an hour. A good answer spans every part of the Internet from the client browser & operating system, DNS, through the network, to load balancers, servers, services, storage, down to the operating system & hardware, and all the way back again to the browser. It requires an understanding of TCP/IP, HTTP, & SSL deep enough to describe how connections are managed, how load-balancers work, and how certificates are exchanged and validated... and that's just the first request!

Web Performance & Operations is an emerging discipline which requires incredible breadth, focusing less on specific technologies and more on how the entire system works together. While people often specialize on particular components, great engineers always think of that component in relation to the whole. The best engineers are able to fly to the 50,000 foot view and see the entire system in motion and then zoom in to microscopic levels and examine the tiny movements of an individual part.

John Allspaw recently described this interconnectedness on his blog:

With websites, the introduction of change (for example, a bad database query) can affect (in a bad way) the entire system, not just the component(s) that saw the change. Adding handfuls of milliseconds to a query that’s made often, and you’re now holding page requests up longer. The same thing applies to optimizations as well. Break that [bad] query into two small fast ones, and watch how usage can change all over the system pretty quickly. Databases respond a bit faster, pages get built quicker, which means users click on more links, etc. This second-order effect of optimization is probably pretty familiar to those of us running sites of decent scale.

Working with these systems requires an understanding not only of the way technology interacts, but the way that people do as well. The structure, operation, and development of a website mirrors the organization that creates it, which is why so many people in WebOps focus on understanding and improving management culture & process.

Organizing a conference like Velocity is a wonderful challenge because it requires the same sort of thinking. We focus on the big concepts that everyone needs to know and then go deep into the technologies that change our understanding of the system. We find ways to share the unique experience that can only be gained by operating at scale. We make it safe to share as much of the "Secret Sauce" as we can.

Please join us at Velocity this year, we have an amazing lineup of speakers & participants. Early registration ends on Monday, May 11th at 11:59 PM Pacific. (Radar readers can use "vel09cmb" for an additional 15% discount.)

Velocity Preview - Keeping Twitter Tweeting

by James Turner | comments: 3

If there's a site that exemplifies explosive growth, it has to be Twitter. It seems like everywhere you look, someone is Tweeting, or talking about Tweeting, or Tweeting about Tweeting. Keeping the site responsive under that type of increase is no easy job, but it's one that John Adams has to deal with every day, working in Twitter Operations. He'll be talking about that work at O'Reilly's Velocity Conference, in a session entitled Fixing Twitter: Improving the Performance and Scalability of the World's Most Popular Micro-blogging Site, and he spent some time with us to talk about what is involved in keeping the site alive.

James Turner: Can you start by describing the platforms and technologies that make Twitter run today?

John Adams: Twitter currently runs on Ruby on Rails. And we also use a combination of Java and Scala, and a number of homegrown scripts that run the site. We also use a lot of open-source tools like Apache, MySQL, memcached.

JT: What type of hardware are you running on?

JA: It's all Linux, so a lot of x86 hardware. I can't tell you the brands or how many.

JT: Do you make any kind of attempt to stay homogeneous in that?

JA: Yes, we do. All of our hardware is very consistent. It makes deployment of new software very easy. And we also use a number of configuration management tools like Puppet to deliver software to those machines.

JT: As anyone can see, Twitter has had a pretty explosive growth, especially recently. Were you prepared for this kind of ramp up?

JA: I don't think so. I mean we're growing week over week in enormous numbers. And we spend a lot of time calculating the growth and scalability of the site to make sure that we can handle the upcoming load.

JT: I mean obviously there are events like Oprah decides she's going to Tweet that are going to be spikes. Do you try to get warning of that stuff?

JA: Yeah. And frequently we know of major events happening. Major events are very predictable like Macworld, even any massive amount of media interaction, we have some fair warning beforehand.

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AT&T Fiber cuts remind us: Location is a Basket too!

by Jesse Robbins | @jesserobbins | comments: 3

The fiber cuts affecting much of the San Francisco Bay Area this week are similar to the outages in the Middle East last year (radar post), although far more limited in scope and impact.   What I said last year still holds true and is repeated below: 

From an operations perspective these kinds of outages are nothing new, and underscore why having "many eggs in few baskets" is such a problem. I believe we will see similar incidents when we have the first multi-datacenter failures where multiple providers lose significant parts of their infrastructure in a single geographic area.

Remember: Don't put all your eggs in one basket... and Location is a basket too!

To really understand the issue, I recommend Neal Stephenson's incredible (and lengthy) Wired article from 1996 entitled "Mother Earth Mother Board":

[...] It sometimes seems as though every force of nature, every flaw in the human character, and every biological organism on the planet is engaged in a competition to see which can sever the most cables. The Museum of Submarine Telegraphy in Porthcurno, England, has a display of wrecked cables bracketed to a slab of wood. Each is labeled with its cause of failure, some of which sound dramatic, some cryptic, some both: trawler maul, spewed core, intermittent disconnection, strained core, teredo worms, crab's nest, perished core, fish bite, even "spliced by Italians." The teredo worm is like a science fiction creature, a bivalve with a rasp-edged shell that it uses like a buzz saw to cut through wood - or through submarine cables. Cable companies learned the hard way, early on, that it likes to eat gutta-percha, and subsequent cables received a helical wrapping of copper tape to stop it.

[...] There is also the obvious threat of sabotage by a hostile government, but, surprisingly, this almost never happens. When cypherpunk Doug Barnes was researching his Caribbean project, he spent some time looking into this, because it was exactly the kind of threat he was worried about in the case of a data haven. Somewhat to his own surprise and relief, he concluded that it simply wasn't going to happen. "Cutting a submarine cable," Barnes says, "is like starting a nuclear war. It's easy to do, the results are devastating, and as soon as one country does it, all of the others will retaliate."

As the capacity of optical fibers climbs, so does the economic damage caused when the cable is severed. FLAG makes its money by selling capacity to long-distance carriers, who turn around and resell it to end users at rates that are increasingly determined by what the market will bear. If FLAG gets chopped, no calls get through. The carriers' phone calls get routed to FLAG's competitors (other cables or satellites), and FLAG loses the revenue represented by those calls until the cable is repaired. The amount of revenue it loses is a function of how many calls the cable is physically capable of carrying, how close to capacity the cable is running, and what prices the market will bear for calls on the broken cable segment. In other words, a break between Dubai and Bombay might cost FLAG more in revenue loss than a break between Korea and Japan if calls between Dubai and Bombay cost more.

The rule of thumb for calculating revenue loss works like this: for every penny per minute that the long distance market will bear on a particular route, the loss of revenue, should FLAG be severed on that route, is about $3,000 a minute. So if calls on that route are a dime a minute, the damage is $30,000 a minute, and if calls are a dollar a minute, the damage is almost a third of a million dollars for every minute the cable is down. Upcoming advances in fiber bandwidth may push this figure, for some cables, past the million-dollar-a-minute mark. [Link]

It's also worth mentioning the outages to multiple service providers hosted in a single colocation facility when the FBI sized all the equipment in the facility, the big outage at 365 Main from two years ago, and many others (see: Radar posts & comprehensive coverage at Data Center Knowledge).

It's Really Just a Series of Tubes

by Jesse Robbins | @jesserobbins | comments: 12

Molly Wright Steenson hit the Ignite jackpot at Etech this year with her explanation of the steam powered network of pneumatic tubes of the 1800s. If you're someone that, like me, has a somewhat obsessive relationship with Internet Infrastructure, you must watch this talk.

Understanding Web Operations Culture - the Graph & Data Obsession

by Jesse Robbins | @jesserobbins | comments: 8

We’re quite addicted to data pr0n here at Flickr. We’ve got graphs for pretty much everything, and add graphs all of the time.

-John Allspaw, Operations Engineering Manager at Flickr & author of The Art of Capacity Planning

One of the most interesting parts of running a large website is watching the effects of unrelated events affecting user traffic in aggregate. Web traffic is something that companies typically keep very secret, and often the only time engineers can talk about it is late at night, at a bar, and very much off the record.

There are many good reasons for keeping this kind of information confidential, particularly for publicly traded companies with complicated disclosure requirements. There are also downsides, the biggest being that is difficult for peers to learn from each other and compare notes.

John Allspaw recently created a WebOps Visualizations group on Flickr for sharing these kinds of graphs with the confidential information removed. Here’s an example of a traffic drop seen both by Flickr & by Last.FM that coincided with President Obama’s inauguration.

Similar traffic drop on Last.FM seen on the right

Google saw a similar drop as well

Was it because everybody went to Twitter?

Besides being an interesting story, sharing these kinds of graphs help people build better monitoring tools and processes. As just one example: How should the WebOps team respond to this dip in traffic? Is it an outage? The inaguration was a very well known event and so it’s easy to explain the drop in traffic… what happens when a similar drop in traffic occurs? Should the WebOps team be looking at CNN (or trends in twitter) along with everything else?

How do you tell when that unexpected 10% drop in traffic is really just people with something more important to do than browse your site?

(Note: Updated since original posting to add Google & Twitter graphs and annotations, and to switch the Last.FM graphic with an annotated one after I got permission.)

Data Center Power Efficiency

by Jesse Robbins | @jesserobbins | comments: 8

James Hamilton is one of the smartest and most accomplished engineers I know. He now leads Microsoft's Data Center Futures Team, and has been pushing the opportunities in data center efficiency and internet scale services both inside & outside Microsoft. His most recent post explores misconceptions about the Cost of Power in Large-Scale Data Centers:

I’m not sure how many times I’ve read or been told that power is the number one cost in a modern mega-data center, but it has been a frequent refrain. And, like many stories that get told and retold, there is an element of truth to the it. Power is absolutely the fastest growing operational costs of a high-scale service. Except for server hardware costs, power and costs functionally related to power usually do dominate.

However, it turns out that power alone itself isn’t anywhere close to the most significant a cost. Let’s look at this more deeply. If you amortize power distribution and cooling systems infrastructure over 15 years and amortize server costs over 3 years, you can get a fair comparative picture of how server costs compare to infrastructure (power distribution and cooling). But how to compare the capital costs of server, and power and cooling infrastructure with that monthly bill for power?

The approach I took is to convert everything into a monthly charge. [...]

Velocity 2009: Themes, ideas, and call for participation...

by Jesse Robbins | @jesserobbins | comments: 0

Last year's Velocity conference was an incredible success. We expected around 400 people and we ended up maxing out the facility with over 600. This year we're moving the conference to a bigger space and extending it to 3 days to accommodate workshops and longer sessions. Velocity 2009 will be on June 22-24th, 2009 at the Fairmont Hotel in San Jose, CA.

This year's conference will be especially important. I've said many times that Web Performance and Operations is critical to the success of every company that depends on the web. In the current economic situation, it's becoming a matter of survival. The competitive advantage comes from the ability to do two things:

1. Generate more revenue with fewer resources
2. Respond quickly to change

Our Velocity 2009 mantra is "Fast, Scalable, Efficient, Available", a slight change from last year. (We've replaced "Resilient" with "Efficient" to make focus clear.)

I'm excited to announce that joining Steve Souders & I on this year's program committee are John Allspaw, Artur Bergman, Scott Ruthfield, Eric Schurman, and Mandi Walls.  We've already started working on the program, and have just opened the Call for Participation.

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