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fix: compressor didn't chunkify big payload #3

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merged 8 commits into from
Apr 26, 2022
Merged

fix: compressor didn't chunkify big payload #3

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0757db6
Update the compressor to chunk the bytes as per the standard
g11tech Apr 14, 2022
6e22a09
bump package version
g11tech Apr 14, 2022
ab41c6d
test for multi chunk compress
g11tech Apr 14, 2022
ce0a908
remove the dupilicated test
g11tech Apr 14, 2022
5c0a678
revering version bump as releases are auto created
g11tech Apr 15, 2022
d6c2786
benchmarks
g11tech Apr 25, 2022
0e7e5ef
log unhandled exception
g11tech Apr 25, 2022
21c7b4c
remove self
g11tech Apr 26, 2022
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39 changes: 27 additions & 12 deletions lib/compress-stream.js
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Original file line number Diff line number Diff line change
@@ -1,3 +1,11 @@
/**
* As per the snappy framing format for streams, the size of any uncompressed chunk can be
* no longer than 65536 bytes.
*
* From: https://github.com/google/snappy/blob/main/framing_format.txt#L90:L92
*/
const UNCOMPRESSED_CHUNK_SIZE = 65536;

var Transform = require('stream').Transform
, util = require('util')

Expand Down Expand Up @@ -52,18 +60,25 @@ CompressStream.prototype._uncompressed = function (chunk) {

CompressStream.prototype._transform = function (chunk, enc, callback) {
var self = this
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I guess we don't need self anymore now

async function compressChunks() {
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Why async function?

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@g11tech g11tech Apr 15, 2022 •
edited
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the API of transform is to call callback on the completion of transformation of the chunk, so don't want to holdup transform

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But there is no await in this body, and compressChunks() is called without any handling. Errors will become unhandled rejections. Can you just make it

  function compressChunks() {

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I guess the callback can error and cause unhandled rejection.

Maybe the implementation can look like:

new Promise(() => {
  ...
  callback(...);
  ...
}).catch((e) => logUnexpectedError(e);

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done, just console logged as nothing fancy available in lib

try {
for (let startFrom = 0; startFrom < chunk.length; startFrom += UNCOMPRESSED_CHUNK_SIZE) {
const endAt = startFrom + Math.min(chunk.length - startFrom, UNCOMPRESSED_CHUNK_SIZE);
const bytesChunk = chunk.slice(startFrom, endAt);
const compressed = snappy.compressSync(bytesChunk)
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Why switch to the sync version? If we want to do that we should do it in another PR as study in depth the implications

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@g11tech g11tech Apr 15, 2022 •
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@dapplion the async version where I chunk bytes from outside (like call compressStream.write(chunk)) which uses the original flow, compared to this where chunking happen in the transform using this way is 2X better slower

(i.e. compressSync based solution is coming out ahead):
image
(orig-snappy is the original with data chunked at compressStream.write level)

If I use async version inside with await Promise((resolve)=>... wrap to make sure the async returned data is written in a proper serial order, its 10-5% slower because of the overhead, if I don't care about the serial order in which chunks are written (which leads to incorrect stream), then async chunking version inside transform is 5% better.

I think for now this is our best bet 🙂

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Okay sounds good to me. Can you commit a benchmark tho? To inform us of the cost of compressing an uncompressing objects of 10Kb, 100Kb, 1000Kb

if (compressed.length < bytesChunk.length)
self._compressed(bytesChunk, compressed)
else
self._uncompressed(bytesChunk)

}
callback();
} catch (err) {
return callback(err);
}
}

snappy.compress(chunk, function (err, compressed) {
if (err)
return callback(err)

if (compressed.length < chunk.length)
self._compressed(chunk, compressed)
else
self._uncompressed(chunk)

callback()
})
compressChunks();
}

module.exports = CompressStream
module.exports = CompressStream
2 changes: 1 addition & 1 deletion package.json
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
{
"name": "@chainsafe/snappy-stream",
"version": "5.0.0",
"version": "5.1.0",
"description": "Compress data over a Stream using the snappy framing format",
"main": "index.js",
"scripts": {
Expand Down
31 changes: 30 additions & 1 deletion test/compress-test.js
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Original file line number Diff line number Diff line change
@@ -1,10 +1,16 @@
var spawn = require('child_process').spawn

, createCompressStream = require('../').createCompressStream
, test = require('tap').test
, largerInput = require('fs').readFileSync(__filename)
, largerInputString = largerInput.toString()

const UNCOMPRESSED_CHUNK_SIZE = 65536
let superLargeInput = largerInput;
for (let i = largerInput.length; i <= UNCOMPRESSED_CHUNK_SIZE; i += largerInput.length) {
superLargeInput = Buffer.concat([superLargeInput, largerInput]);
}
const superLargeInputString = superLargeInput.toString();

test('compress small string', function (t) {
var child = spawn('python', [ '-m', 'snappy', '-d' ])
, compressStream = createCompressStream()
Expand Down Expand Up @@ -48,3 +54,26 @@ test('compress large string', function (t) {
compressStream.write(largerInputString)
compressStream.end()
})


test('compress very very large string', function (t) {
var child = spawn('python', [ '-m', 'snappy', '-d' ])
, compressStream = createCompressStream()
, data = ''

child.stdout.on('data', function (chunk) {
data = data + chunk.toString()
})

child.stdout.on('end', function () {
t.equal(data, superLargeInputString)
t.end()
})

child.stderr.pipe(process.stderr)

compressStream.pipe(child.stdin)

compressStream.write(superLargeInputString)
compressStream.end()
})