Is process.env.NODE_ENV still slow in Node 8

Question

I'd heard on the grapevine a while ago that reading from process.env is a hit to performance in Node. I wondered if someone can clarify whether this is still the case, and calls to process.env should be avoided or whether it makes no difference to performance?

Thanks!

Answer 1

You can set up your own test for this using process.hrtime(), let's try reading it a bunch of times and see what we get:

const time = process.hrtime();
const NS_PER_SEC = 1e9;
const loopCount = 10000000;

let hrTime1 = process.hrtime(time);

for (var i = 0; i < loopCount; i++) 
{
    let result = process.env.TEST_VARIABLE
}

let hrTime2 = process.hrtime(time);

let ns1 = hrTime1[0] * NS_PER_SEC + hrTime1[1]; 
let ns2 = hrTime2[0] * NS_PER_SEC + hrTime2[1];

console.log(`Read took ${(ns2 - ns1)/loopCount} nanoseconds`);

The result on my machine (oldish Windows Tower, Node v8.11.2 ):

Read took 222.5536641 nanoseconds

So around ~0.2 microseconds.

This is pretty fast.. when we talk about performance issues everything is relative. If you really need to read this very frequently, it would be best to cache it.

To make this clear, let's test both scenarios:

// Cache
const test = process.env.TEST_VARIABLE;
let loopCount = 10000000; console.time("process.env cached"); for (var i = 0; i < loopCount; i++) { let result = test } console.timeEnd("process.env cached");


// No cache
loopCount = 10000000; console.time("process.env uncached"); for (var i = 0; i < loopCount; i++) { let result = process.env.TEST_VARIABLE } console.timeEnd("process.env uncached");

This takes ~10ms when caching, and ~2s when no variable is used to cache the value.