JavaScript NodeJS

Fun with the Event Loop

19 Dec 2018

At the $NewGig we run a lot of services with NodeJS. Unless you live in a tech-less cave you know Node is “all the rage” these days. I won’t offer my $0.02 on everyone’s take — that would be a waste of both our time.

Everyone will tell you that “you get to do two things at once!” — which is not entirely true, its complicated. But at least you get to think about it that way. And while many languages are still catching up with asynchronous operations its easily Node’s biggest advantage. But its not what has me most excited.

Coming from more classical languages and environments there is a ton of flexibility I love about NodeJS. The event loop affords you some nice design choices. In other environments, everything has to happen within the lifecycle of the request. In order to get even the smallest thing outside of that request lifecycle, you need to spin up a background message queue, a fully separate architecture.

Not so in NodeJS because of the event loop. You can send the response back at any point in time, and defer any Promise’d code onto the stack that will keep running. Don’t get me wrong, this doesn’t mean background message queues are dead now. Far from it. And this technique can be easily abused and trash your performance. But you get to do some very nice, small, operations without running up a whole separate infrastructure, and re-querying to get all the data you already have in memory.

So far I’ve been able to do a few things with it.

I’ve increased observability and done so by taking some computationally taxing comparisons out of the request loop. Sending all that data back out to a message queue would be a terrible waste of bandwidth, creating needless complexity and other bottlenecks.

I’ve kept an API endpoint snappy by returning 200 as soon as I get a POST. In this case I am lucky, because returning an error is useless for the calling system. I also get to ignore any timeout settings from the caller, and just happily crunch away on this data, which can actually take some time based on what we’re doing.

NodeJS is very, very, flexible. It is bare bones. And it is fast. Layers of abstraction are powerful, and our entire world of computing is built upon them. Hundreds of layers by now — its kind of too much, but there is no turning back now. Many other environments add many more layers of abstraction, just to serve some HTML or JSON text. NodeJS doesn’t. I don’t need more abstractions, especially leaky ones. Give me power and let me wield it. NodeJS does just that.

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