Use domains
var copy = function (from, to, cb) {
return fs.createReadStream(from)
.pipe(fs.createWriteStream(to))
.on("end", cb)
}
domain.run(function () {
copy("a", "b", next)
})
On Sun, Oct 7, 2012 at 5:54 PM, Alexey Petrushin <[email protected]
> wrote:
> Tried to copy files using streams and pipe and got funny results. Let's
> consider following code (highlighted version
> https://gist.github.com/3850106 ):
>
> var copy = function(from, to, cb){
> var fromStream = fs.createReadStream(from)
> fromStream.on('error', cb)
> var toStream = fs.createWriteStream(to)
> toStream.on('error', cb)
> fromStream.on('end', cb)
> }
>
> copy('non existing file a', 'non existing dir/file b', function(err){
> console.log(err)
> })
>
> There are errors in both streams (non existing source file and no parent
> directory for destination file) - so, both of them will emit
> 'error' event, and the callback will be called twice with both errors.
>
> // Error will be reported twice:
> //
> // { [Error: ENOENT, open 'non existing file a'] errno: 34,
> // code: 'ENOENT', path: 'non existing file a' }
> // { [Error: ENOENT, open 'non existing dir/file b'] errno: 34,
> // code: 'ENOENT', path: 'non existing dir/file b' }
>
> I found the solution by looking at the source of `util.pump` - it does it
> by wrapping callback into function that calls callback only once - for the
> fist error and ignoring others.
>
> But maybe it would be nice to have a callback for `createXxxStream` or
> something like 'ready' or 'success' events to know that it created
> successfully?
>
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