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Sunday
Dec022007

nginx: high performance smpt/pop/imap proxy

nginx is a high performance smtp/pop/imap proxy that lets you do custom authorization and lookups and is very scalable. (just add nodes) Nginx by default is a reverse proxy and this is what it is doing here for pop/imap connections. It is also an excellelent reverse proxy for web servers. Advantage: You dont have to have a speacial database or ldap schema. Just an url to do auth and lookup with. A url that may be accessed by a unix or a tcp socket. Write your own auth handler - according to your own policy. For example: A user called atif tries to login with the pass testxyz. You pass this infomation to a URL such as socket:/var/tmp/xyz.sock or http://auth.corp.mailserver.net:someport/someurl The auth server replies with either a FAILURE such as Auth-Status: Invalid Login or password or with a success such as Auth-Status: OK Auth-Server: OneOfThe100Servers Auth-Port: optionalyAPort We have implemented it at our ISP and it has saves us a lot of headaches. This would work for both imap and pop. I have not yet tried for SMTP.

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Saturday
Dec012007

many website, one setup, many databases

Hi, I will need to host abound 500-1000 websites, all of them use drupal, What I thought was, to make all of these websites point to a single setup of drupal and make them run from there. I thought of using different databases for each website.. Do you think it'll work? Is there a better way to go about it?

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Friday
Nov302007

Strategy: Efficiently Geo-referencing IPs

A lot of apps need to map IP addresses to locations. Jeremy Cole in On efficiently geo-referencing IPs with MaxMind GeoIP and MySQL GIS succinctly explains the many uses for such a feature: Geo-referencing IPs is, in a nutshell, converting an IP address, perhaps from an incoming web visitor, a log file, a data file, or some other place, into the name of some entity owning that IP address. There are a lot of reasons you may want to geo-reference IP addresses to country, city, etc., such as in simple ad targeting systems, geographic load balancing, web analytics, and many more applications. This is difficult to do efficiently, at least it gives me a bit of brain freeze. In the same post Jeremy nicely explains where to get the geo-rereferncing data, how to load data, and the performance of different approaches for IP address searching. It's a great practical introduction to the subject.

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Tuesday
Nov272007

Starting a website from scratch - what technologies should I use?

Hi, if you were to design your own highly scalable website from scratch, what technologies would you use? Based on Web 2.0 popularity, LAMP seems to be high in the running. But would you tack on CakePHP? Drupal? or build your framework/CMS from scratch? What version of Linux runs best for a scalable website? Would you consider Windows and .NET? Java? Or do you want to throw a brick at me for even suggesting such heresies? Would you prefer Postgres, Tomcat, Perl, Python, or any of that other *NIX fancy stuff...why or why not? Please forget for the moment, "use what you know" argument. I am pretty versatile, and can look for an expert in whatever platform I choose. So all skills being equal, I'm looking for the best community support, the fastest development time and most importantly, the best scaling approach. Let's say, for fun, that I'm planning for the website to have as many messages going back & forth as an eBay. Definitely building this on a budget.. Jason

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Tuesday
Nov272007

Solving the Client Side API Scalability Problem with a Little Game Theory

Now that the internet has become defined as a mashup over a collection of service APIs, we have a little problem: for clients using APIs is a lot like drinking beer through a straw. You never get as much beer as you want and you get a headache after. But what if I've been a good boy and deserve a bigger straw? Maybe we can use game theory to model trust relationships over a life time of interactions over many different services and then give more capabilities/beer to those who have earned them? Let's say Twitter limits me to downloading only 20 tweets at a time through their API. But I want more. I may even want to do something so radical as download all my tweets. Of course Twitter can't let everyone do that. They would be swamped serving all this traffic and service would be denied. So Twitter does that rational thing and limits API access as a means of self protection. As does Google, Yahoo, Skynet, and everyone else. But when I hit the API limit I think, but hey it's Todd here, we've been friends a long time now and I've never hurt you. Not once. Can't you just trust me a little? I promise not to abuse you. I never have and won't in the future. At least on purpose, accidents do happen. Sometimes there's a signal problem and we'll misunderstand each other, but we can work that out. After all, if soldiers during WW1 can learn how to stop the killing through forgiveness, so can we. The problem is Twitter doesn't know me so we haven't built up trust. We could replace trust with money, as in a paid service where I pay for each batch of downloads, but we're better friends than that. Money shouldn't come between us. And if Twitter knew what a good guy I am I feel sure they would let me download more data. But Twitter doesn't know me and that's the problem. How could they know me? We could set up authority based systems like the ones that let certain people march ahead through airport security lines, but that won't scale and I have feeling we all know how that strategy will work out in the end. Another approach to trust is a game theoretic perspective for assessing a user's trust level. Take the iterated prisoner's dilemma problem where variations on the tit for tat strategy are surprisingly simple ways cooperation could evolve in API world. We start out cooperating and if you screw me I'll screw you right back. In a situation where communication is spotty (like through an API) there can be bad signals sent so if people have trusted before then they'll wait for another iteration to see if the other side defects again, in which case they retaliate. Perhaps if services modeled API limits like a game and assessed my capabilities by how we've played the game together, then capabilities could be set based on earned and demonstrated trust rather than simplistic rules. A service like Mashery could takes us even further by moving us out of the direct reciprocity model, where we judge each other on our one on one interactions, and into a more sophisticated indirect reciprocity model, where agents can make decisions to help those who have helped others. Mashery can take a look at how API users act in the wider playing of multiple services and multiple agents. If you are well behaved using many different services, shouldn't you earn more trust and thus more capabilities? In the real world if someone vouches for you to a friend then you will likely get more slack because you have some of the trust from your friend backing you. This doesn't work in one on one situation because there's no way to establish your reputation. Mashery on the other hand knows you and knows which APIs you are using and how you are using them. Mashery could vouch for you if they detected you were playing fair so you get more capabilities initially and transit the capability scale faster if you continued to behave. You can obviously go on and on imaging how such a system might work. Of course, there's a dark side. Situations are possible like on Ebay where people spend eons setting up a great reputation only to later cash in their reputations in some fabulous scam. That's what happens in a society though. We all get more capabilities at the price of some extra risk.

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Monday
Nov262007

Scale to China

Hello all, does anyone have experience in scaling a european website to china? The main problem in china is the internet connectivity to websites outside china, that means latency and packetloss (and perhaps filtering) make things difficult. The options I see are: 1. Host you application in china, but where? I haven't got a answer from any chinese ISP I contacted. On the other hand I don't really want to host in china. 2. Build your own CDN. Wikipedia shows how it goes. Get a bunch of machines (but where? see point 1) put squid on them, implement intelligent cache invalidation and you're set. But where can I get machines in china? Where do I need them in china? There are soe big isps with limited peering capability, so I'd need servers in every network. 3. Get professional CDN services. Akamai, ChinaCache, CDNetworks, etc etc.. They all provide services in china. The problem is: they are all very expensive. 4. Amazon EC2/S3 ? Is it worth thinking about this way? I am not sure, because they only have US and Ireland based datacenters. So we are stuck to the connectivity problem.. My favourite way: Rent a bunch of linux servers in 4-5 big cities in china in different networks and build my own CDN. What do you think? Regards Bjoern

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Thursday
Nov222007

Why not Cache from Intersystems?

I have some experience with a very large OLTP system that is 7+ TB in size and performs very well for 30K+ concurrent users. It is built using Intersystems Cache based on the very old but very scalable MUMPS platform. Why don't I see more discussions about archiectures such as these in this forum? I am curious why this platform scales so much better then the typical RDBMS.

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Wednesday
Nov212007

n-phase commit for FS writes, reads stay local

I am trying to find a Linux FS that will allow me to replicate all writes synchronously to n nodes in a web server cluster, while keeping all reads local. It should not require specialized hardware.

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Tuesday
Nov202007

what is j2ee stack

I see everyone talk about lamp stack is less than j2ee stack .i m newbie can anyone plz explain what is j2ee stack

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Tuesday
Nov202007

Product: SmartFrog a Distributed Configuration and Deployment Framework

From Wikipedia: SmartFrog is an open-source software framework, written in Java, that manages the configuration, deployment and coordination of a software system broken into components. These components may be distributed across several network hosts. The configuration of components is described using a domain-specific language, whose syntax resembles that of Java. It is a prototype-based object-oriented language, and may thus be compared to Self. The framework is used internally in a variety of HP products. Also, it is being used by HP Labs partners like CERN.

Related Articles

  • Distributed Testing with SmartFrog
  • Puppet the Automated Administration System

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