High Scalability Building bigger, faster, more reliable websites.

OK,

I know this site is for scalable web site design. But as there aren't any sites I can find for graceful failure under "slashdotted" like pressure I'll ask here.

Does anyone have a sensible way, once you have a "web application" that either won't scale, or can't scale, that you can give some users a good consistent experience and bounce other users to a busy site page. I have seen sites do this to varying degrees, some of which work better than others, but no explanations beyond simply bouncing requests to a "we're busy page server" when you have more than a given number of connections. This is obviously useless as a web page likely requires multiple connection (ignoring keep-alive, pipelining etc) multiple connection to completely render properly.

The normal problem is users getting a page and not the "furniture" for that page like images or css. Other problems are having to wait ages to get the busy page or the site being slow even if you do "get in". And some site let a user "in" and then as they browse around they get bounced out suddenly to the busy page.

Obviously not being the developer for sites I deal with (I am an infrastructure bod) I can't solve the problem where it should have been pre-emptively solved. That is to say I can't write the code to be scalable or re-write the code to do some simple session filtering or the like (and not being a developer I get dirty looks when I point developers at information like your site ... I can hear them thinking "how dare you suggest I don't know how to code a web site you lowly infrastructure cretin").

Before developer on-line lynch me I should point out that sometimes the cause of not being able to scale a site is that I can't get in new hardware quick enough, but then who knows when you will get slashdotted right ?. So my question applies even when a developer of genius level brilliance has built a unsurpasibly scalable web site for me to run the infrastructure for.

My best guess so far is using something like HAProxy to load balance sessions, and then use it's more advanced total session count, and cookie issuing abilities to track users and bounce some at a given "heavy load" point. This isn't ideal as the heavy load point would have to be based on connection counts not server load or server response times, but it's the best I can come up with so far.

Also, having mentioned brilliant developers writing great sites not always making my question redundant, could I ask, do people normally think about coping with overload when designing scalable solution - surely they should but I don't see much talk about it. Couldn't a simple Java filter or the equivalent for other things be built into applications ? It'd be nice to have a site that not only scales, but "is nice" when waiting for the infrastructure it runs on to be scaled, which could be several days when you have to purchase new hardware.

Hey, this scaling stuff might just be important. Jim Scheinman, former Bebo and Friendster exec, puts the blame squarely on Friendster's inability to scale as why they lost the social networking race:

VB: Can you tell me a bit about what you learned in your time at Friendster?
JS: For me, it basically came down to failed execution on the technology side — we had millions of Friendster members begging us to get the site working faster so they could log in and spend hours social networking with their friends. I remember coming in to the office for months reading thousands of customer service emails telling us that if we didn’t get our site working better soon, they’d be ‘forced to join’ a new social networking site that had just launched called MySpace…the rest is history. To be fair to Friendster’s technology team at the time, they were on the forefront of many new scaling and database issues that web sites simply hadn’t had to deal with prior to Friendster. As is often the case, the early pioneer made critical mistakes that enabled later entrants to the market, MySpace, Facebook & Bebo to learn and excel. As a postscript to the story, it’s interesting to note that Kent Lindstrom (CEO of Friendster) and the rest of the team have done an outstanding job righting that ship.

Hopefully with all the quality information out now on the intertubes visionaries can concentrate on making good stuff instead of always fighting the plumbing. When you think about, is there any industry or group that gives so much value away for free as the software community? I don't think so. We are an amazingly giving group and the world has benefited greatly from that impulse. A thought for Thanksgiving.