Should be possible to use `crypto.randomBytes`'s async API

Running my program with --trace-sync-io, I see:

WARNING: Detected use of sync API
at _rng (/home/blong/trello-idea-powerup/node_modules/node-uuid/uuid.js:60:53)
at v4 (/home/blong/trello-idea-powerup/node_modules/node-uuid/uuid.js:224:55)
// etc.

The problem is that you’re using crypto.randomBytes synchronously, and don’t seem to provide a way to pass a callback and use the async API.

[janaz]

It’s possible to use the library in async mode by providing the random option item obtained in an async fashion:

const crypto = require('crypto');
const uuid = require('uuid/v4');

const uuidPromise = (u) => new Promise((resolve, reject) => {
  crypto.randomBytes(16, (err, random) => {
    if (err) {
      return reject(err);
    }
    resolve(u({random}));
  });
});

// Usage
uuidPromise(uuid)
 .then(u => console.log("UUID", u))
 .catch(e => console.error(e));

[jstewmon]

👋 Hi, stumbled across this issue today, read through the comments and wanted to mention that I think the case for using the async version of randomBytes is to avoid blocking the event loop because the operation may block waiting for entropy, which will almost never happen outside of a virtualized or containerized environment.

But, it is not a hypothetical problem for workloads running in virtualized or containerized environments. A quick search for random entropy block virtualized containerized will turn up plenty of material on the subject.

Personally, I’ve seen this problem manifest a few times in automated test suites that run in a containerized environment running on a virtualized environment - tests would time out waiting on randomBytes.

Anyway, I haven’t noticed this issue with this library specifically (great library by the way!), and as was mentioned, it is possible to BYO random bytes, which can be procured asynchronously, so there doesn’t seem to be change required. I just wanted to try to add some context regarding why using the async version would be preferential for some use cases. ✌️