February 4, 2015

...Learn TDD with Codemanship

Why Distribution & Concurrency Can Be A Lethal Cocktail For The Unwitting Dev Team

Picture the scene: it's Dec 31st 1990, a small town in upper state New York. I'm at a New Year's Eve party, young, stupid and eager to impress. The host mixes me my first ever Long Island Iced Tea. It tastes nice. I drink three large ones, sitting at their kitchen table, waxing eloquent about life, the universe and everything in my adorable English accent, and feeling absolutely fine. Better than fine.

And then, after about an hour, I get up to go to the bathroom. I'm not fine. Not fine at all. I appear to have lost the use of my legs, and developed an inner-ear problem that's affecting my normally balletically graceful poise and balance.

I proceed to be not-fine-at-all into the bathroom sink and several other receptacles, arguably none of which were designed for the purpose I'm now putting them to.

Long Island Iced Tea is a pretty lethal cocktail. Mixed properly, it tastes like a mildy alcoholic punch with a taste not dissimilar to real iced tea (hence the name), but one look at the ingredients puts pay to that misunderstanding: rum, gin, vodka, tequila, triple sec - ingredients that have no business being in the same glass together. It is a very alcoholic drink. Variants on the name, like "Three Mile Island" and "Adios Motherf***er", provide further clues that this is not something you serve at a child's birthday party.

I end the evening comatose on a water bed in a very hot room. This completes the effect, and Jan 1st 1991 is a day I have no memory of.

Vowing never to be suckered into a false sense of security by something that tastes nice and makes me feel better-than-fine for a small while, I should have known better than to get drawn like a lamb to the slaughter into the distributed components craze that swept software development in the late 1990's.

It went something like this:

Back in the late 1990's, aside from the let's-make-everything-a-web-site gold rush that was reaching a peak, there was also the let's-carve-up-applications-that-we-can't-even-get-working-properly-when-everything's-in-one-memory-address-space-and-there's-no-concurrency-and-distribute-the-bits-willy-nilly-adding-network-deficiencies-distributed-transactions-and-message-queues fad.

This was enabled by friendly technology that allowed us to componentise our software without the need to understand how all the undrelying plumbing worked. Nice in theory. You carve it, apply the right interfaces, deploy to your application server and everything's taken care of.

Except that it wasn't. It's very easy to get and up and running with these technologies, but we found ourselves continually having to dig down into the underlying detail to figure out why stuff wasn't working the way it was supposed to. "It just works" was a myth easily dispelled by looking at how many books on how this invisible glue worked were lying open on people's desktops.

To me, with the benefit of hindsight, object request brokers, remote procedure calls, message queues, application servers, distributed transactions, web services... these are the hard liquor of software development. The exponential increase in complexity - the software equivalent of alcohol units - can easily put unwitting development teams under the table.

I've watched so many teams merrily downing pints of lethal-but-nice-tasting cocktails of distribution and concurrency, feeling absolutely fine - better than fine - and then when it's time for the software to get up and walk any kind of distance... oh dear.

It turns out, this stuff is hard to get right, and the tools don't help much in that respect. They make it easy to mix these cocktails and easy to drink as much as you think you want, but they don't hold your hand when you need to go to the bathroom.

These tools are not your friends. They are the host mixing super-strength Long Island Iced Teas and ruining your New Year with a hangover that will never go away.

Know what's in your drink, and drink in moderation.






Posted 2 years, 10 months ago on February 4, 2015