advertise
Monday
Jul092007

LiveJournal Architecture

A fascinating and detailed story of how LiveJournal evolved their system to scale. LiveJournal was an early player in the free blog service race and faced issues from quickly adding a large number of users. Blog posts come fast and furious which causes a lot of writes and writes are particularly hard to scale. Understanding how LiveJournal faced their scaling problems will help any aspiring website builder. Site: http://www.livejournal.com/

Information Sources

  • LiveJournal - Behind The Scenes Scaling Storytime
  • Google Video
  • Tokyo Video
  • 2005 version

    Platform

  • Linux
  • MySql
  • Perl
  • Memcached
  • MogileFS
  • Apache

    What's Inside?

  • Scaling from 1, 2, and 4 hosts to cluster of servers.
  • Avoid single points of failure.
  • Using MySQL replication only takes you so far.
  • Becoming IO bound kills scaling.
  • Spread out writes and reads for more parallelism.
  • You can't keep adding read slaves and scale.
  • Shard storage approach, using DRBD, for maximal throughput. Allocate shards based on roles.
  • Caching to improve performance with memcached. Two-level hashing to distributed RAM.
  • Perlbal for web load balancing.
  • MogileFS, a distributed file system, for parallelism.
  • TheSchwartz and Gearman for distributed job queuing to do more work in parallel.
  • Solving persistent connection problems.

    Lessons Learned

  • Don't be afraid to write your own software to solve your own problems. LiveJournal as provided incredible value to the community through their efforts.
  • Sites can evolve from small 1, 2 machine setups to larger systems as they learn about their users and what their system really needs to do.
  • Parallelization is key to scaling. Remove choke points by caching, load balancing, sharding, clustering file systems, and making use of more disk spindles.
  • Replication has a cost. You can't just keep adding more and more read slaves and expect to scale.
  • Low level issues like which OS event notification mechanism to use, file system and disk interactions, threading and even models, and connection types, matter at scale.
  • Large sites eventually turn to a distributed queuing and scheduling mechanism to distribute large work loads across a grid.

    Click to read more ...

  • Sunday
    Jul082007

    Welcome to High Scalability

    We started High Scalability to help you build successful scalable websites. This site tries to bring together all the lore, art, science, practice, and experience of building scalable websites into one place so you can learn how to build your system with confidence. Hopefully this site will move you further and faster along the learning curve of success. Please Start Here.

    Click to read more ...

    Friday
    Jul062007

    Start Here

    This page is here to help you get started using High Scalability. Here are a few useful topics to get you going...

    1. Why does the High Scalability site exist?
    2. How does this site work?
    3. Good things to read.
    4. Participate by reading and posting in the forums.
    5. Participate by adding your own links to interesting sites and articles.
    6. Participate by signing up for the RSS feed.
    7. Consider the many benefits of registering as a user.
    8. How do I get notification of content and comment changes?
    9. Contacting High Scalability.
    10. About.

    Why does the High Scalability site exist?

    To help you build successful scalable websites. This site tries to bring together all the lore, art, science, practice, and experience of building scalable websites into one place so you can learn how to build your website with confidence. When it becomes clear you must grow your website or die, most people have no idea where to start. It's not a skill you learn in school or pick up from a magazine article on a plane flight home. No, building scalable systems is a body of knowledge slowly built up over time from hard won experience and many failed battles. Hopefully this site will move you further and faster along the learning curve of success. Makers of popular web sites eventually run into this all important question: How do I scale? Every builder of successful web sites must answer and that question and put their answers into practice. You might wonder:
    • How do I handle being digged or slashdotted?
    • What can I accomplish on my budget?
    • How do I add more and more users?
    • What software should I use? LAMP, WAMP, or .Net?
    • Should I use managed or unmanaged systems? Dedicated, co-located, VPS hosting or something else?
    • Which machine and OS should I use?
    • How do I recover from a disaster?
    • How do I measure and improve performance?
    • Where do I get people to help me?
    • Which data center should I use?
    • Which ISP should I use?
    • How can I structure my software to scale?
    • How do we setup caching?
    • What should my database schema look like?
    • Which database should I use?
    • Which language and framework should I use?
    • How do I ensure my data is always available and never lost?
    • How do I monitor all my software and machines?
    • How do I train my programmers to build this type of software?
    • How do I failover my web servers, databases, etc?
    • How do I expand to multiple geographical locations?
    • How should I handle session data?
    • How do I handle support and upgrades and feature rollouts?
    You probably have 1000s of questions like these. Where do you find the answers? The answers are out there. How to build a scalable website is not a secret, the information is just spread out. And it's still more art than science. Every problem is different. Your site may have specific requirements that make it just different enough that you could use some advice. And that's what this site is all about. Bringing like-minded people together to help each learn everything we can about creating the best websites we can.

    How does this site work?

    You might be a little bit overwhelmed at first when you hit the front page of this site for the first time. There's a lot a going on. But it's really pretty simple once you learn the secret of what's where and why. The front page is divided into 4 major sections: middle page content section, top main menu section, left hand navigation section, and the right hand interesting stuff section.

    First a Word About How Tags are Used on This Site

    Most content on the site can be
    tagged. You can invent your own tags or use existing tags from the glossary page. The tag edit field will provide suggestions based on the first letters you type in. A tag categorizes a chunk of content and determines which lists it shows up in. For example, if you want a weblink you submit to show up in the Real Life Architectures page then you would tag the link with the Example tag. Here's a list of tags and where a tag makes the content show up: * Example - in the Real Life Architectures page. This page presents case studies of how real websites like eBay and Flickr implement their websites so you can learn from them how to implement your own website. * Book - in the Useful Books page. The book page presents books that will be helpful in building your site. * Blog- in the Useful Blogs page. The blog page presents blogs with ongoing useful information you can continue to learn from everyday. * Paper- in the Useful Papers page. * Product- in the Useful Products page. The product page presents products you might find useful in building your own site. There are an amazing variety of website related products out in the world. We'll try to show you real products used by real people to get real results. * Strategy- in the Strategy page. These are useful techniques you can directly use to help scale your site. Use these tags when you add content and it will show in the right place for everyone to see.

    Middle Page Content Section

    In the middle of the front page you see content from a blog or a weblink post that has been promoted to the front page for everyone to see. Not all content is displayed on the front page, just what's worth everyone seeing. When you look at the middle page section you'll primarily see content submitted via the Submit a Link top menu link. This is like Digg or Reddit in that if you are registered user you can submit scalability related links for other people to read. The idea is for this to be community site generating high quality scalability related links. Content isn't just available on the front page, it's also available through the same links we talked about in the tagging section. You can see all weblinks by category in the All Weblinks top menu item. You see the most recent content on the front page, but the content is always available via the menu system as well. So don't worry when you see a lot of technical articles on the front page, these are just scalability related posts you can page attention to or not pay attention to.

    Top Main Menu Section

    The main menu links to some of the more important things a frequent user of the site can do on the site.

    Left Hand Navigation Section

    On the left hand side of the page you'll see other things you can do on the site. There's not enough room in the top menu so all your other options are place on the left.

    Right Hand Interesting Stuff Section

    The right hand side of the page shows you what's happening currently on the site. You'll see: recent comments people have made in the forum, new and active forum topics, the post popular tags users are using, new links that users have posted, and new articles from scalability related RSS feeds.

    Good things to read.

    If you are interested in this site then you probably want to build your own monster website. There's no better way to learn than learning from the best
    Real Life Architectures out there. Real Life Architectures is a continuing series of posts on how real successful websites like eBay, Flickr, MySpace, LiveJournal, and Amazon build their websites. Learn from those who have already done it and add your own personal twist to make it your own. But the learning doesn't stop there! For more helpful ideas on building the next big thing, please visit Useful Books, Useful Products, Useful Blogs, Useful Papers, and Useful Strategies. And if you want to ask questions or help other people with their questions, please take a look at the Forums. If you are looking for a web host then web hosting is a good hosting guide to help you determine what you need for hosting.

    Participate by reading and posting in the forums.

    Forums are where the main action is. You can get to the forums using the
    Forums link from the navigation panel on the left or the menu in the upper right hand section of the page. We'll keep the forum structure very simple until it's clear creating new groups will do more good than harm. Nothing is worse than a 100 different groups with no posts! We'll just have a General Discussion group and an Interesting Resource group to discuss individual scalability related links found on the web.

    Participate by adding your own links to interesting sites and articles.

    One of the incredible free to the user rewards for
    registering as a user of High Scalability is that you can post weblink articles to the front page. A weblink article is short link to existing page on the web. If you happen to come across anything interesting in your intertube travels you can share it with the community by posting a quick weblink. Think of it as digg without all the silly high school popularity theatrics. The amount of materials on High Scalability topics is vast and ever evolving, so if people share what they find that will help everyone keep up on what's new. To post your own weblinks all you have to do is: * Register as a user. * Click the Submit a Link menu item in the upper right hand corner of the page. * Fill out the weblink form and click on submit. And you're done! * Remember to use the proper tags for each link you create. * Insert the <!--break--> comment just after the teaser section you want to show up on the front page, otherwise the whole article will show up on the front page. The break comment tag is Drupal's rather odd way of breaking a page up into its teaser and content sections.

    Participate by signing up for the RSS feed.

    If you would like to participate in this web site by reading RSS postings then just paste the following URL into your favorite RSS reader: http://highscalability.com/rss.xml.

    Consider the many benefits of registering as a user.

    OK, to be honest, there aren't that many benefits of
    registering as a user. We hate sites that make you register before you can do anything useful. We've made it so you can do most everything interesting without registering. But if you do register you can:
    1. Post weblinks to the front page.
    2. Upload a nice avatar of someone who looks nothing like your real self.
    3. Not have to answer those taxing math captcha questions.
    4. Helps us brag about how many registered users we have.
    That's about it. Hopefully we'll have some nice door prizes later.

    How do I get notification of content and comment changes?

    1. Register as a user.
    2. Click on My account in the left hand navigation menu.
    3. Click on My notification settings in the page menu.
    4. Select what you want to get notified about and how you want to get notified.
    5. Click on the Save setting button on the bottom of the page.
    6. Notification are sent out on a regular basis so you should get changes soon.

    Contacting High Scalability.

    If you would like to contact a real live person you can email us through this contact
    form.

    About

    Some people have asked who I am. Good question. I am still working on that :-) My name, however, is Todd Hoff and my personal website is at http://possibility.com/Tmh/. I have a lot of experience in large scale distributed systems and a long standing interest in the subject. I finally decided since I'm reading this stuff all the time I might as well start a site about it! I hope you find this site useful in your day-to-day work in the trenches.

    Click to read more ...

    Page 1 ... 208 209 210 211 212