The anatomy of uploading

Question

I am wondering what is the general consensus for uploading moderately large files. I have a web app, and every time a user uploads a file (typically larger than 5mb), the web server tends to hang until the file upload is finished.

The above seems normal, because a single upload can take up a single HTTP request handler. Do web devs take this into consideration and either:

a) Pay for more HTTP handlers

b) Use some other method to overcome this by using AJAX, or other approach

I've heard that it is quite normal for web apps to have a few HTTP request handlers to take care of this, which will cost quite a bit more. On the other, if cost is an issue, then some have suggested trying to upload directly to the web server or storage service (i.e. Amazon S3) directly via Flash + AJAX. The latter method takes a bit of scripting and is a bit messy.

My second concern:

By using ajax to upload files onto a server. Does this still take up a whole HTTP request handler? i.e. does the server hang until the upload is finished?

Even with flash, I would still need to specify a url to upload to. The url would be one of the actions on my controller. Which would mean that processing still takes place on the server side. Is this right so far?

I was thinking. If I were, in the other hand, to use one of the upload scripts (plupload, uploadify, swfupload, etc) to upload directly to Amazon S3, then the processing is handled on the S3 server instead of the local web server. Which wont hang the web app at all. Am I understanding this correctly?

Would like to hear your feedback.

Answer 1

For large uploads you should use non-blocking, evented servers like Node.js, Twisted on Pyhon, AnyEvent on Perl or EventMachine on Ruby. Using the thread-per-connection model is just too expensive for long running connections.

It is not uncommon for Node.js users to have so many simultaneous connections that they actually hit their operating systems limits while still not using all their resources - for example see this question asked by someone who was concerned by having only 30 thousand simultaneous connections and then managed to reach over 60 thousand connections on a single server with 4GB of RAM.

The point is that if your are concerned about your connections blocking your server from serving new requests, then you shouldn't use a blocking server in the first place.