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feat: slightly improved v1 perf #453

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merged 4 commits into from
May 25, 2020
Merged

feat: slightly improved v1 perf #453

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a361e29
feat: slightly improved v1 perf
awwit May 21, 2020
056d3e3
revert: throw original Error
awwit May 25, 2020
1b158ff
test: added comment for v1 in benchmark
awwit May 25, 2020
45b85d4
Merge branch 'master' into improve/v1-perf
ctavan May 25, 2020
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8 changes: 7 additions & 1 deletion examples/benchmark/benchmark.js
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,13 @@ suite
uuidv1();
})
.add('uuidv1() fill existing array', function () {
uuidv1(null, array, 0);
try {
uuidv1(null, array, 0);
} catch (err) {
if (err.code !== 'UUID_V1_LIMIT_PER_SEC') {
throw err;
}
}
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Revert?

Why is this needed? Are we hitting the rate limit with our benchmark? If so, that's kind of cool... but it also invalidates the benchmark so should probably be abort()ed with an appropriate message.

Note: Silently dropping errors in catch blocks is a very strong code smell. At a minimum, there should be a comment explaining the rationale for it.

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@broofa periodically the limit is exceeded on my machine and an exception is thrown.
This is strange, but the block try/catch does not affect the performance %)
If an exception is thrown, the following tests will fail.

In new versions of nodejs (v13.14.0), performance is even higher. Exceptions are thrown more often.

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@broofa broofa May 23, 2020 •
edited
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periodically the limit is exceeded on my machine

This is surprising. It's the first time I've seen this limit hit in the real world. (I added that rate check years ago to comply with the spec, never really expecting to hit it in practice.) What hardware are you running on if I may ask?

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@broofa I have my own computer on which I run tests (nodejs v12.16.3):

CPU: AMD Ryzen 7 1700
RAM: 32 Gb 2999 MHz

Typically, an exception occurs the first few times the benchmark is launched. And then the testing goes fine. Maybe it's a bug. (With try/catch I never get a performance close or higher to 10M)

The exception is much more likely to occur on new versions of nodejs (v13). Because the overall performance of the library is increasing.

On nodejs v13 I usually get performance: uuidv1() fill existing array x 8,777,105 ops/sec ±0.82% (96 runs sampled).

})
.add('uuidv4()', function () {
uuidv4();
Expand Down
42 changes: 19 additions & 23 deletions src/bytesToUuid.js
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Expand Up @@ -2,40 +2,36 @@
* Convert array of 16 byte values to UUID string format of the form:
* XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
*/
const byteToHex = [];
const bth = [];
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for (let i = 0; i < 256; ++i) {
byteToHex.push((i + 0x100).toString(16).substr(1));
bth.push((i + 0x100).toString(16).substr(1));
}

function bytesToUuid(buf, offset) {
const i = offset || 0;

const bth = byteToHex;

function bytesToUuid(buf, offset = 0) {
// Note: Be careful editing this code! It's been tuned for performance
// and works in ways you may not expect. See https://github.com/uuidjs/uuid/pull/434
return (
bth[buf[i + 0]] +
bth[buf[i + 1]] +
bth[buf[i + 2]] +
bth[buf[i + 3]] +
bth[buf[offset + 0]] +
bth[buf[offset + 1]] +
bth[buf[offset + 2]] +
bth[buf[offset + 3]] +
'-' +
bth[buf[i + 4]] +
bth[buf[i + 5]] +
bth[buf[offset + 4]] +
bth[buf[offset + 5]] +
'-' +
bth[buf[i + 6]] +
bth[buf[i + 7]] +
bth[buf[offset + 6]] +
bth[buf[offset + 7]] +
'-' +
bth[buf[i + 8]] +
bth[buf[i + 9]] +
bth[buf[offset + 8]] +
bth[buf[offset + 9]] +
'-' +
bth[buf[i + 10]] +
bth[buf[i + 11]] +
bth[buf[i + 12]] +
bth[buf[i + 13]] +
bth[buf[i + 14]] +
bth[buf[i + 15]]
bth[buf[offset + 10]] +
bth[buf[offset + 11]] +
bth[buf[offset + 12]] +
bth[buf[offset + 13]] +
bth[buf[offset + 14]] +
bth[buf[offset + 15]]
).toLowerCase();
}

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8 changes: 6 additions & 2 deletions src/v1.js
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Expand Up @@ -16,7 +16,7 @@ let _lastNSecs = 0;
// See https://github.com/uuidjs/uuid for API details
function v1(options, buf, offset) {
let i = (buf && offset) || 0;
const b = buf || [];
const b = buf || new Array(16);
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options = options || {};
let node = options.node || _nodeId;
Expand All @@ -27,6 +27,7 @@ function v1(options, buf, offset) {
// system entropy. See #189
if (node == null || clockseq == null) {
const seedBytes = options.random || (options.rng || rng)();

if (node == null) {
// Per 4.5, create and 48-bit node id, (47 random bits + multicast bit = 1)
node = _nodeId = [
Expand All @@ -38,6 +39,7 @@ function v1(options, buf, offset) {
seedBytes[5],
];
}

if (clockseq == null) {
// Per 4.2.2, randomize (14 bit) clockseq
clockseq = _clockseq = ((seedBytes[6] << 8) | seedBytes[7]) & 0x3fff;
Expand Down Expand Up @@ -70,7 +72,9 @@ function v1(options, buf, offset) {

// Per 4.2.1.2 Throw error if too many uuids are requested
if (nsecs >= 10000) {
throw new Error("uuid.v1(): Can't create more than 10M uuids/sec");
const error = new Error("uuid.v1(): Can't create more than 10M uuids/sec");
error.code = 'UUID_V1_LIMIT_PER_SEC';
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If we keep this, I suggest to align it with Node.js error code naming and call ist something like ERR_UUID_V1_RATE_EXCEEDED.

Since, as explained below, this is the only runtime error of this library, I would prefer to revert this for now (or extract this into a separate PR so we can merge the perf optimization first and think about error codes a bit more).

throw error;
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Revert.

code is a non-standard error property, and so better to avoid. Yes, other modules do this but typically it's for the purpose of forwarding codes in some underlying API.

If this is needed (which I'm on the fence about, and 'would like to get @ctavan's opinion here) I'd suggest something along these lines...

// Create minimal Error subclass (Define in UuidRateError.js file so it can be exported as part of src/index.js?)
export class UuidRateError extends Error {}

// ... Throw in this file when rate exceeded ...
throw new UuidRateError(`UUID creation rate limit exceeded`)

// ... use `instanceof` elsewhere to detect... 
import {v1 as uuidv1, UuidRateError} from 'uuid'
// ...
try {
  uuidv1()
} catch (err) {
  if (err instanceof UuidRateError) // etc...
}

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@broofa it will be harder for library users. They will need to guess that non-standard exceptions are thrown. When it is already accepted in nodejs to identify an error by code.

https://nodejs.org/api/errors.html#errors_error_code

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Huh... I wasn't aware code was used by node core. Interesting.

}

_lastMSecs = msecs;
Expand Down