OK, there is no "they" and "they" wouldn't care if you knew anyway. After all, this isn't a blog about really important stuff like investing, acne cures, or cheap natural cleansing products. But the secrets are real. Super cloud scaling consultant Kent Langley has put together a comprehensive checklist to consider when developing for the cloud:
At eBay, one of the primary architectural forces we contend with every day is scalability. It colors and drives every architectural and design decision we make. With hundreds of millions of users worldwide, over two billion page views a day, and petabytes of data in our systems, this is not a choice - it is a necessity.
In a scalable architecture, resource usage should increase linearly (or better) with load, where load may be measured in user traffic, data volume, etc. Where performance is about the resource usage associated with a single unit of work, scalability is about how resource usage changes as units of work grow in number or size. Said another way, scalability is the shape of the price-performance curve, as opposed to its value at one point in that curve.
There are many facets to scalability - transactional, operational, development effort. In this article, I will outline several of the key best practices we have learned over time to scale the transactional throughput of a web-based system. Most of these best practices will be familiar to you. Some may not. All come from the collective experience of the people who develop and operate the eBay site.
Read the rest of the article on InfoQ.
The transport-level server load balancing architectures described in the first half of this article are more than adequate for many Web sites, but more complex and dynamic sites can't depend on them. Applications that rely on cache or session data must be able to handle a sequence of requests from the same client accurately and efficiently, without failing. In this follow up to his introduction to server load balancing, Gregor Roth discusses various application-level load balancing architectures, helping you decide which one will best meet the business requirements of your Web site.
The first half of this article describes transport-level server load balancing solutions, such as TCP/IP-based load balancers, and analyzes their benefits and disadvantages. Load balancing on the TCP/IP level spreads incoming TCP connections over the real servers in a server farm. It is sufficient in most cases, especially for static Web sites. However, support for dynamic Web sites often requires higher-level load balancing techniques. For instance, if the server-side application must deal with caching or application session data, effective support for client affinity becomes an important consideration.
Here in Part 2, I'll discuss techniques for implementing server load balancing at the application level to address the needs of many dynamic Web sites.
Read the rest of the article on JavaWorld.
Server farms achieve high scalability and high availability through server load balancing, a technique that makes the server farm appear to clients as a single server. In this two-part article, Gregor Roth explores server load balancing architectures, with a focus on open source solutions. Part 1 covers server load balancing basics and discusses the pros and cons of transport-level server load balancing.
The barrier to entry for many Internet companies is low. Anyone with a good idea can develop a small application, purchase a domain name, and set up a few PC-based servers to handle incoming traffic. The initial investment is small, so the start-up risk is minimal. But a successful low-cost infrastructure can become a serious problem quickly. A single server that handles all the incoming requests may not have the capacity to handle high traffic volumes once the business becomes popular. In such a situations companies often start to scale up: they upgrade the existing infrastructure by buying a larger box with more processors or add more memory to run the applications.
Read the rest of the article on JavaWorld.
EVE Online is "The World's Largest Game Universe", a massively multiplayer online game (MMO) made by CCP. EVE Online's Architecture is unusual for a MMOG because it doesn't divide the player load among different servers or shards. Instead, the same cluster handles the entire EVE universe. It is an interesting to compare this with the Architecture of the Second Life Grid. How do they manage to scale?
- EVE Insider Dev Blog
- EVE Online FAQ
- Massively - Eve Evolved: Eve Online's Server Model and its discussion on Slashdot
- EVE Online Forums
- Massively Multiplayer Game Development 2
- Stackless Python used for both server and client game logic. It allows programmers to reap the benefits of thread-based programming without the performance and complexity problems associated with conventional threads.
- SQL Server
- Blade servers with SSDs for high IOPS
- Plans to use Infiniband interconnects for low latency networking
- Founded in 1997
- ~300K active users
- Up to 40K concurrent users
- Battles involving hundreds of ships
- 250M transactions per day
- Proxy Blades - These are the public facing segment of the EVE Cluster - they are responsible for taking player connections and establishing player communication within the rest of the cluster.
- SOL Blades - These are the workhorses of Tranquility. The cluster is divided across 90 - 100 SOL blades which run 2 nodes each. A node is the primarily CPU intensive EVE server process running on one core. There are some SOL blades dedicated to one busy solar systems such as Jita, Motsu and Saila.
- Database Cluster - This is the persistence layer of EVE Online. The running nodes interact heavily with the Database, and of course pretty much everything to do with the game lives here. Thanks to Solid-state drives, the database is able to keep up with the enormous I/O load that Tranquility generates.
- With innovative ideas MMO games can scale up to the hundreds of players in the same battle.
- SSDs will in fact bridge the gap huge performance gap between the memory and disks to some extent.
- Low latency Infiniband network interconnect will enable larger clusters.
ArchitectureThe EVE Cluster is broken into 3 distinct layers
Lessons LearnedThere are many interesting facts about the architecture of the EVE Online MMOG such as the use of Stacless Python and SSDs.
One particularly interesting EC2 third party provider is GigaSpaces with their XAP platform that provides in memory transactions backed up to a database. The in memory transactions appear to scale linearly across machines thus providing a distributed in-memory datastore that gets backed up to persistent storage.
Abstract—This paper presents the architecture and characteristics of a memory database intended to be used as a cache engine for web applications. Primary goals of this database are speed and efficiency while running on SMP systems with several CPU cores (four and more). A secondary goal is the support for simple metadata structures associated with cached data that can aid in efficient use of the cache. Due to these goals, some data structures and algorithms normally associated with this field of computing needed to be adapted to the new environment.
Update: As expected I'm undergoing a massive spam attack for speaking truth to dark powers. This is the time to be strong. Together we can make a change. What change you may ask? I can't say, just change and lots more change. Let's link arms together and bravely stand against the forces of chaos for a better yesterday and a better tomorrow. CAPTCHA doesn't work. Even Google can't make CAPTCHA work (Spammers Choose GMail). And even if CAPTCHA worked it wouldn't really work because CAPTCHA solving markets (Inside India’s CAPTCHA solving economy) have evolved where for a mere $2 you can buy 1000 human broken CAPTCHA's. And we know once the free market tackles a problem that's it. Game over :-) Making ever more clever CAPTCHA programs won't outwit and outlast the CAPTCHA solving markets. Until Skynet evolves the only way to defeat humans is with humans.
Using Games to Get Humans to Do Work (like CAPTCHA) for FreeHow do we harness the power of humans to do battle with the CAPTCHA solving networks, without, of course, paying them anything? We make it a game! In particular we make a Game With a Purpose (GWAP). Read all about GWAPs in Designing games with a purpose. A GWAP is a game in which people, as a side effect of playing, perform tasks computers are unable to perform.
Google's Image LabelerA good example GWAP is Google's Image Labeler, a game in which people provide meaningful, accurate labels for images on the Web as a side effect of playing the game; for example, an image of a man and a dog is labeled "dog," "man," and "pet.". Now this sounds like work. And it is. But because it's made into a game people will do it for free! An example Labeler session looks like: In the game two people are matched at random to label the same set of images. Points are awarded when you and your partner match labels. Top scores are kept so you can earn your label street cred. But can't people cheat? GWAP games include cheating detection mechanisms, but we won't go into detail here, see Designing games with a purpose for cheater foiling strategies.
ESP Game, Tag a Tune, and SquiglMore games can be found at the GWAP Home Page. They have the ESP Game which is like Labeler. Tag a Tune is a game where players hear tunes, describe them, and through the description guess if they are listening to the same tune. In Squigl partners see an image and a word. Using the mouse each player traces the object described by the word in the image. Winning is when both players trace the same image. Here's what a Squigl session looks like: So you see the pattern. Players are picked from a pool. They are asked to do some task that's hard for computers to do. The task must be structured so that winning enables the system to learn something valid while providing a feeling of game play for the humans. Points are awarded and scores are kept to keep the poor human slaves playing.
Creating a Spam Catcher GameWith the basic ideas in place let's create a game for identifying and filtering out comment spam. According to Designing games with a purpose this appears to a be an output-agreement type game, which has the following structure:
The Final MoveSpam crushes many sites. Many site owners don't even allow comments anymore because of the time it takes to deal with spam, which is a shame, because without interactivity the internet might as well be a newspaper. We can't let those spammers win! A system like the Spam Catcher Game might be able provide the human oversight, quick latency, and high throughput needed to out compete the CAPTCHA solving networks. The game is finally afoot!
During the Coherence Special Interest Group meeting in London, Brian Oliver from Oracle yesterday announced the start of the Coherence Incubator project. Coherence Incubator is a new online repository of projects that provides reference implementation examples for commonly used design patterns and integration solutions based on Oracle Coherence.
A group of top Silicon Valley engineers (ex-Yahoo, Facebook, Google) have come together to launch a new startup called Cloudera.
Not yet launched, it intends to help other companies adopt a promising software platform called Hadoop.
Hadoop is an open-source software project (written in Java) designed to let developers write and run applications that process huge amounts of data. While it could potentially improve a wide range of other software, the ecosystem supporting its implementation is still developing. Which is where Cloudera hopes to make a place for itself.
More on Hadoop: It uses the Google-introduced MapReduce systems framework that divides applications into small blocks of work, creating multiple replicas of data blocks that it places on various computer nodes.
It is already in use at large companies like Yahoo.
Read more about Cloudera here.