Snaplet-Tasks

Snap Framework ( http://snapframework.com ) support for command line tasks akin to Rake tasks from Ruby On Rails

Depends on Snap 0.7.* and

Installation

cabal install snaplet-tasks

Integration

in coolapp.cabal

Build-depends:
  snaplet-tasks

in Application.hs

import           Snap.Snaplet.Tasks



data App = App
    { _heist :: Snaplet (Heist App)
    
    , _tasks :: Snaplet TasksSnaplet
    }

in Site.hs

app = do
  h  <- nestSnaplet "heist" heist $ do
            heistInit "resources/templates"
  t <- nestSnaplet  "tasks" tasks $
            tasksInit
  return $ App h  t

Because we need full app state at disposal in our tasks the easiest way was to create them from normal handlers.

Thus, in order to run task - app has to be started. It is comparable with Ruby On Rails Rake tasks where whole app environment can be loaded for task as well. The only difference is that here in Snap - app also listens on TCP for connections - and that we utilize.

There are two constriants to running tasks:

1. You can't run them remotely ( meaning that you can't fire app task handler remotely )
2. Task route is being hashified and the only way to specify task is by using command line app arg switch T ( ex. T mysupertask or T namespace:second:supertask ) The supplied name of task is being hashified again and thus matched with route that responds to exaclty that hash.

Example command line usage:

yourapp T db:migrate

Or if you want to run app for tasks on different port:

yourapp T db:migrate -p 1234

This implies that you have to have some tool/function to create tasks so that they respond to hashified names. And indeed you have:

task :: String -> (Handler b v ()) -> (B.ByteString, Handler b v ())

This function takes name of the task ( ex. "db:migrate" ) and a handler and returns a tuple that you can use defining your app routes.