Hi, I admit I am relatively new to RoR, but, I have a question about
threading…
I have my ruby app and one of the things it can do is import a huge
quantity of data into the database via the web interface. When I kick
off this command no other requests to ruby respond. I have to wait
until the command finishes.
A similar app (we are enhancing and porting an existing app) running
under Tomcat/Java servlets does the same action but Tomcat still lets
me serve other requests while it is happening.
Is this a setting I need to set, or is Ruby only capable of switching
requests when idle? Or some other restriction?
As we get closer to live this is becoming more of an issue as we can’t
have our live site frozen when one of us is importing new data.
Is this a setting I need to set, or is Ruby only capable of switching
requests when idle? Or some other restriction?
Rails is single-threaded. To handle multiple requests in parallel you
need to add more Ruby processes.
I suggest you check out http://mongrel.rubyforge.org/docs/index.html
for a lot of info on RoR deployment.
If you expect a lot of concurrent long-lived requests (e.g. large file
uploads), you should consider handing those off to a
threading-friendly framework, e.g. Merb, as RoR-instances are somewhat
heavy.
Rails is single-threaded. To handle multiple requests in parallel you
need to add more Ruby processes.
On this topic, I have a small problem with lighttpd with this
configuration :
proxy.balance = “fair”
proxy.server = ( “” =>
( ( “host” => “127.0.0.1”, “port” => 8000 ),
( “host” => “127.0.0.1”, “port” => 8001 ),
( “host” => “127.0.0.1”, “port” => 8002 ) ) )
It seems that with this configuration the lighttpd (1.4.18) proxy module
can forward request to an already busy server even if there are only 2
simultaneous page accesses.
proxy.balance = “fair” should try to avoid this situation but I believe
that in my situation (Mongrel is used to serve static files too which is
probably the case for many others), the static files serving can force
lighttpd to use all Mongrels at once even if there are only 2
simultaneous page accesses (there can be 5-10 static files to serve when
counting images/css/js for one page load) -> the Mongrel handling the
long running request is reused for another dynamic request, which
blocks.
I believe reconfiguring lighttpd to short-circuit Mongrel for static
files could help there by lowering the load on the mongrel cluster which
would make sure one of the 3 Mongrels is available even if there are 2
simultaneous page accesses, but I wonder if there is another way which
would involve less lighttpd configuration? In fact I don’t see a quick
lighttpd configuration for the “directly serving static content” when
using mod_proxy yet.
Outside of making sure you have multiple Rails processes proxied
through an HTTP server, you should also use a tool like BackgrounDrb
for such specifically long-taking tasks as uploading and processing a
ton of data. Then, when the user uploads the data, the page comes back
as soon as the data is done uploading, while a separate process on the
server is doing the actual processing of said data.
That’s a solution of course, but in my case these long running processes
usually only run for 5-10 seconds and are the least used of the site.
There’s no usability problem for the person doing them: 5-10 seconds are
considered normal, but for simple site navigation this is annoying
(which as explained happen sometimes in my case). Developping a
BackgroundRB solution would solve the problem but might be heavy handed
for the time being (if there’s a simple lighttpd solution for serving
static files without the mongrel cluster used by mod_proxy).
I’m not knowledgeable with Lighty, but I do know that there are pretty
major
issues with the most recent proxy engine. I personally use Nginx +
Mongrel
Cluster which works surprisingly well. Nginx is also one of the fastest
as
serving up static data, wether it be images, javascript, stylesheets, or
cached Rails pages, it’s fast and completely bypasses proxying.
proxy.balance = “fair”
that in my situation (Mongrel is used to serve static files too which is
would involve less lighttpd configuration? In fact I don’t see a quick
lighttpd configuration for the “directly serving static content” when
using mod_proxy yet.
Lionel
Outside of making sure you have multiple Rails processes proxied through
an
HTTP server, you should also use a tool like BackgrounDrb for such
specifically long-taking tasks as uploading and processing a ton of
data.
Then, when the user uploads the data, the page comes back as soon as the
data is done uploading, while a separate process on the server is doing
the
actual processing of said data.
This concerns me a little. We have a website that needs to support 150
200 simultaneous active users. Are you telling me I need to have 150
200 mongrels running to do this? That’s crazy!
“Active users” isn’t a useful metric on it’s own, try to break it down
into requests per second instead. And keep in mind that production
mode is likely to speed your actions up a little.
This concerns me a little. We have a website that needs to support 150
200 simultaneous active users. Are you telling me I need to have 150
200 mongrels running to do this? That’s crazy!
Depending on your application and hardware specifics, an average Mongrel
can serve about 100 requests/second. So you’ll want to run a cluster of
at least two and probably more just to smooth everything out.
Yeah, the important stat to look at is requests / second, not “active
users”, which is pretty vague. I would recommend starting with 3
mongrels
and adding more if you need it.
Jason
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