Yet another scaling question

Rails
1

Hi,

I have written a rails application that runs very well (that’s so good
!!!).

This application serves up file downloads for about 150 users.

These downloads are protected by some authorization rules, precedence
rules,
and so on (not public downloads…).

Well, I have setup 10 fatcgi processes (I’m planning to setup 10
mongrels
cluster with mod_proxy).

When 10 concurrent users are downloading files, the other 140 must wait
for
a free rail process.

Now my question is: what is the best way to scale this application ? I
cannot have 150 processes or 150 mongrels of about 100Mb each (total =
15.000 Mb => 15 Gb ram…) to handle 150 concurrent users…

Does anyone know how to handle this ?

Thanks in advance…

2

Hello Gianluca,

I went through this same pain. I was using “sendfile” in a controller
action
served by a mongrel cluster proxied via nginx. Mongrel is going to
hang things
up until it’s sendfile is complete.

Here’s the switch to make…

Use your web services to send the file, not mongrel. Think of this
like using your
apache/nginx for sending static files and not loading down mongrel
with that task.
For example (my case a csv file), in the controller you use:

response.headers[‘Content-Type’] = ‘text/csv’
response.headers[‘Content-Disposition’] = “attachment;
filename=my_file.csv”
response.headers[‘X-Accel-Redirect’] = “/custom_download_path/
my_file.csv”
render :nothing => true

Now configure your web service to turn sendfile on and add a
definition of
the “custom_download_path” you named above:

location /custom_download_path {
  root /the/real/path/to/the/files;
  default_type  text/csv;
  expires 1h;
  add_header  Cache-Control  private;
  internal;
}

This is an nginx example, but there are plenty of apache examples on-
line.
Nginx uses X-Accel-Redirect in the header, while apache will use X-
Sendfile.

There is a Rails plug-in to avoid the setting of response headers
directly, as
I did above, but I haven’t converted over to using it yet.

John Guen discusses it here :
http://john.guen.in/past/2007/4/17/send_files_faster_with_xsendfile/

Good luck,

Jim

3

JimCifarelli ha scritto:

Use your web services to send the file, not mongrel. Think of this
render :nothing => true
internal;

Hi Jim

Thank you very much for your solution, I’ll try it ASAP !!!

Have a nice day !

4

You may want to have the web server deliver the files by setting a X-
Accel-Redirect (or your webserver’s equivalent) HTTP header.

Additionally, take a look at Merb: http://merbivore.com

Merb is Rails like Ruby framework targeted at high performance.

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