Windows Azure Storage Blobs to zip file with Express - express

Question

I am trying to use this pluggin (express-zip). At the Azure Storage size we have getBlobToStream which give us the file into a specific Stream. What i do now is getting image from blob and saving it inside the server, and then res.zip it. Is somehow possible to create writeStream which will write inside readStream?

Answer 1

Edit: The question has been edited to ask about doing this in express from Node.js. I'm leaving the original answer below in case anyone was interested in a C# solution.
For Node, You could use a strategy similar to what express-zip uses, but instead of passing a file read stream in this line, pass in a blob read stream obtained using createReadStream.
Solution using C#:
If you don't mind caching everything locally while you build the zip, the way you are doing it is fine. You can use a tool such as AzCopy to rapidly download an entire container from storage.
To avoid caching locally, you could use the ZipArchive class, such as the following C# code:
internal static void ArchiveBlobs(CloudBlockBlob destinationBlob, IEnumerable<CloudBlob> sourceBlobs)
{
using (Stream blobWriteStream = destinationBlob.OpenWrite())
{
using (ZipArchive archive = new ZipArchive(blobWriteStream, ZipArchiveMode.Create))
{
foreach (CloudBlob sourceBlob in sourceBlobs)
{
ZipArchiveEntry archiveEntry = archive.CreateEntry(sourceBlob.Name);
using (Stream archiveWriteStream = archiveEntry.Open())
{
sourceBlob.DownloadToStream(archiveWriteStream);
}
}
}
}
}
This creates a zip archive in Azure storage that contains multiple blobs without writing anything to disk locally.

Answer 2

I'm the author of express-zip. What you are trying to do should be possible. If you look under the covers, you'll see I am in fact adding streams into the zip:
https://github.com/thrackle/express-zip/blob/master/lib/express-zip.js#L55
So something like this should work for you (prior to me adding support for this in the interface of the package itself):
var zip = zipstream(exports.options);
zip.pipe(express.response || http.ServerResponse.prototype); // res is a writable stream
var addFile = function(file, cb) {
zip.entry(getBlobToStream(), { name: file.name }, cb);
};
async.forEachSeries(files, addFile, function(err) {
if (err) return cb(err);
zip.finalize(function(bytesZipped) {
cb(null, bytesZipped);
});
});
Apologize if I've made horrible errors above; I haven't been on this for a bit.