The test case below can trigger a race condition and cause the copied file corrupted:
const eventEmitter = new EventEmitter();
let finishCount = 0;
const hash1 = crypto.createHash('sha1');
const hash2 = crypto.createHash('sha1');
const destination = path.join(os.tmpdir(), 'bigFile');
const bigFile1 = path.join(__dirname, 'bigFiles', 'bigFile1');
const bigFile2 = path.join(__dirname, 'bigFiles', 'bigFile2');
const file1Content = fs.readFileSync(bigFile1);
const original1Hash = hash1.update(file1Content).digest();
const file2Content = fs.readFileSync(bigFile2);
const original2Hash = hash2.update(file2Content).digest();
fs.rmSync(destination, {recursive: true, force: true});
// operation A
ncp(bigFile1, destination, function (err)
{
if (err)
{
return console.error(err);
}
eventEmitter.emit('done');
console.log('done!');
});
// operation B
ncp(bigFile2, destination, function (err)
{
if (err)
{
return console.error(err);
}
eventEmitter.emit('done');
console.log('done!');
});
eventEmitter.on('done', () =>
{
finishCount++;
if (finishCount === 2)
{
const hash3 = crypto.createHash('sha1');
const copiedBigFile = destination;
const copiedFileContext = fs.readFileSync(copiedBigFile);
const copiedHash = hash3.update(copiedFileContext).digest();
assert.ok(copiedHash.equals(original1Hash)
|| copiedHash.equals(original2Hash),
`Copied file is different from any original files
originalFile1Hash: ${original1Hash.toString('hex')}
originalFile2Hash: ${original2Hash.toString('hex')}
copiedFileHash: ${copiedHash.toString('hex')}
`);
}
});
The execution result is:
done!
node:assert:400
throw err;
^
AssertionError [ERR_ASSERTION]: Copied file is different from any original files
originalFile1Hash: b9b855fd78c3e68c7e127dcba3db8111be1eea6c
originalFile2Hash: 36c07a7f47f5478248695505f6993e2ecb83b3f5
copiedFileHash: 62736f6530b1903a91113ebe32a2943a2654942e
At the beginning, both A and B think that destination does not exist. So both operation A and B will directly create write streams to destination and write through the streams at the same time, which I think is problematic.
The test case below can trigger a race condition and cause the copied file corrupted:
The execution result is:
I think the bug is caused by the codes here:
https://github.com/AvianFlu/ncp/blob/6820b0fbe3f7400fdb283c741ef88b6d8e2d4994/lib/ncp.js#L113-L126
At the beginning, both A and B think that
destination
does not exist. So both operation A and B will directly create write streams todestination
and write through the streams at the same time, which I think is problematic.