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doc: crypto.randomBytes does not block when async #14993

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doc: crypto.randomBytes does not block when async 
It may not return random bytes right away, but when called
asynchronously it will not block.

PR-URL: #14993
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
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sam-github committed Aug 25, 2017
commit 68321b5cb0078e2964150772486be338011e5711
3 changes: 2 additions & 1 deletion doc/api/crypto.md
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Expand Up @@ -1717,7 +1717,8 @@ console.log(
`${buf.length} bytes of random data: ${buf.toString('hex')}`);
```

The `crypto.randomBytes()` method will block until there is sufficient entropy.
The `crypto.randomBytes()` method will not complete until there is
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@mscdex mscdex Aug 23, 2017 •
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Isn't this only the case for the async version of this function (e.g. when a callback is passed)? How does it not block when the sync version is invoked and there is not sufficient entropy at that time? I think we should be explicit here about this difference.

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@sam-github sam-github Aug 23, 2017

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Its the case for both versions. If its sync, it won't complete. If it's async, it won't complete. Can you suggest some other wording? I think the current wording applies equally to both, and the previous wording applied only to the sync version.

sufficient entropy available.
This should normally never take longer than a few milliseconds. The only time
when generating the random bytes may conceivably block for a longer period of
time is right after boot, when the whole system is still low on entropy.
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