On Mon, Jan 31, 2011 at 2:28 PM, Ertugrul Soeylemez wrote:

Michael Snoyman wrote:

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On Mon, Jan 31, 2011 at 1:09 PM, Ertugrul Soeylemez wrote:

...

Hello everybody,

how well do WAI, Yesod and the 'persistent' package play with concurrency?  For example, I'd like to write a program, which concurrently provides two related sites as well as a few background workers, which do something with the database.  My idea would look something like this:

 main :: IO ()  main =    withMyAppPool $ \pool -> do      forkIO $ worker1 ...   -- background worker      forkIO $ worker2 ...   -- background worker      forkIO $ worker3 ...   -- background worker      forkIO $ toWaiApp ...  -- site 1      forkIO $ toWaiApp ...  -- site 2

Will I run into problems with this?

There should not be any issues, just make sure you compile with -threaded. The persistent database connection pool should work just fine for this. If you find any issues, please let me know, but I have not had trouble in the past.

Thank you for your quick reply.  How are my chances to get patches to Yesod incorporated into the mainstream code?

If it's a clean patch and does not break backwards compatibility: very high. If it's a clean patch that *does* break backwards compatibility: still good, but you'll have to wait till a major release. For not-so-clean patches, I suppose it depends on how dirty we're talking ;). Michael

On Thu, Feb 3, 2011 at 3:14 PM, Ertugrul Soeylemez wrote:

Michael Snoyman wrote:

...

On Mon, Jan 31, 2011 at 1:09 PM, Ertugrul Soeylemez wrote:

...

how well do WAI, Yesod and the 'persistent' package play with concurrency?  For example, I'd like to write a program, which concurrently provides two related sites as well as a few background workers, which do something with the database.  My idea would look something like this:

 main :: IO ()  main =    withMyAppPool $ \pool -> do      forkIO $ worker1 ...   -- background worker      forkIO $ worker2 ...   -- background worker      forkIO $ worker3 ...   -- background worker      forkIO $ toWaiApp ...  -- site 1      forkIO $ toWaiApp ...  -- site 2

Will I run into problems with this?

There should not be any issues, just make sure you compile with -threaded. The persistent database connection pool should work just fine for this. If you find any issues, please let me know, but I have not had trouble in the past.

I've run into the first problem with this.  Without having to use subsites, what's an easy method to use wai-handler-devel with such a setup?

I believe the new architecture in use for wai-handler-devel 0.2 (which will work with Yesod 0.7) should work properly with multi-threaded apps. But yes, there's no easy way to do this with the current wai-handler-devel. Michael