Rails Concurrent Requests

rubyonrails-talk
1

Hi, i'm building a big Rails application, i really like the way that rails manage our normal problems building a web app. Yesterdays I found myself into a deadlock, why?, because in my rails app, there is a functionality to call another app to create some things, and that app, has a listener that calls my app saying "this" was created. Those are 2 separated functionalities. So in one request I was calling the other app, and waiting for the response, and the other app, was calling me.. And o found that my Rails app, can not handle 2 request at the same time, so i started to look for the answer of that problem, first i thought it was the development mode, but i fast realized that was not the problem. I've been googling for the answer, but i found some estrange answers, that i can't believe. That's why i'm writing here.

It is true that a single Rails App instance can't handle more than 1 request at the same time?

I've been looking to the passenger solution for this, and the mongrel one, and others, but the solutions, are App pools, ans things like that, but nobody explain this in a right way. I need a direct answer to this question.

I know some workarounds, like clustering or pools, that's not what i want right now.

Thanks!

2

It is true that a single Rails App instance can't handle more than 1 request at the same time?

It used to be true, but as of 2.2.2 you can turn on thread safe mode. How much you benefit depends on what ruby interpreter you use what your app does etc.

Fred

3

First of all, Thanks frederick fr the fast response!

I'll been tryint this, i found a BIG incrementation of the performance. On the other hand, i can't beleibe how this is a feature that I have to enable, and is not a default. What is the use of a web application, that can't handle 2 request at the same time? IMO that is useless. There are any concern about this?.. this feature is ready for production?.. or it is experimental.

I've read in some places that you must be sure that your code is thread safe, and that is obvious. Is there any other "problem" with that feature?

Thanks

4

First of all, Thanks frederick fr the fast response!

I'll been tryint this, i found a BIG incrementation of the performance. On the other hand, i can't beleibe how this is a feature that I have to enable, and is not a default. What is the use of a web application, that can't handle 2 request at the same time? IMO that is useless.

An awful lot of rails applications seem to get along just fine (especially as MRI's threading means that you don't take advantage of multiple cores, one thread can block the entire VM etc.)

Fred

5

I would use JRuby because implements threads with Java threads, so it is thread safe but can use multiple core as any J2EE web app. You can see this video about JRuby featues: JRuby: The power of Java and Ruby - YouTube (included threads and GC)

Riccardo.

6

The problem is that my app, uses a lot of external partners.. connecting with web services, so a single request can take between 2 and 8 seconds.. imagine 100 people using my app :S... Can you elaborate a bit about this "not multicore" issue? How one thread can block the entire interpreter if i have the config.threadsafe! on?

7

The problem is that my app, uses a lot of external partners.. connecting with web services, so a single request can take between 2 and 8 seconds.. imagine 100 people using my app :S... Can you elaborate a bit about this "not multicore" issue? How one thread can block the entire interpreter if i have the config.threadsafe! on?

Because MRI's threading isn't great - ruby threads don't map to native threads. Pure ruby code shouldn't block the entire interpreter but C stuff can (eg a mysql query). jruby is much better in this respect.

Fred

8

The problem is that my app, uses a lot of external partners…

connecting with web services, so a single request can take between 2

and 8 seconds… imagine 100 people using my app :S…

Can you elaborate a bit about this “not multicore” issue? How one

thread can block the entire interpreter if i have the

config.threadsafe! on?

In short, each thread must obtain Global Interpreter Lock (GIL) before it can

be executed. Thus, enabling config.threadsafe! will allow one to handle more

than one request but they are not processed in parallel but rather in FIFO (i.e. a

basic queue) order by the interpreter.

-Conrad

9

Is there a solution, for this issue?... i'm using postgres db. As far as i understand what you say, every access to a native library, will be locked and only one thread at a time will access.

10

German wrote:

Is there a solution, for this issue?... i'm using postgres db. As far as i understand what you say, every access to a native library, will be locked and only one thread at a time will access.

Yes: use one of the pooled solutions like Passenger. I know you may think it silly, but at the moment, it's the best way if you're not using JRuby.

On Oct 18, 8:06�pm, Frederick Cheung <frederick.che...@gmail.com>

Best,

11

Thanks, I have a passenger environment, with a pool of app's.. but this schema is eating my server.. what if i have 10.000 rq per second.. the solution is JRuby?

12

On the other hand, Clustering or pooling are solutions for Reliability not for performance. Clustering does not give better performance, in fact, most of the times gives you less performance one of the reasons is the load balancer. It's true that every application has a limit of request to handle, all the servers have that limit, and there is where you need to do a pool or a cluster to "solve" the problem, but if my limit is "one request", i should think i have another problem..

13

Ok Robert, you are right.

So, if I have calls to native C libraries, my threads will be locked there. So the only way to have concurrency there is with more than one application?