Re: [Haskell-cafe] One of the new buzz phrases is Event-Sourcing; is Haskell suitable for this?
Hi, On Sun, Sep 30, 2012 at 4:22 AM, Alberto G. Corona agocor...@gmail.com wrote: It´´s a very iteresting concept. The Workflow Monad transformer [1], in Control.Workflow perform logging and recovery of application istate from the log created. It has no implementation of roll-back or limited recovery upto a point, but this is easy to implement. Is Control.Workflow similar with acid-state with respect to the way you recovery the current state? It also has many inspection and synchronization primitives. It has been used also for translating the log of a program and recovering the state in another machine. The log can be pretty-printed for debugging. Can you somehow recover impure (IO) computations? [1] http://hackage.haskell.org/package/Workflow Regards, Marcelo 2012/9/30 KC kc1...@gmail.com: http://martinfowler.com/eaaDev/EventSourcing.html http://martinfowler.com/articles/lmax.html -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Alberto. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One of the new buzz phrases is Event-Sourcing; is Haskell suitable for this?
Hi,Marcelo, No. .Acid state is explcitly managed by the process by means of state management primitives In Control.Workflow the state is managed in a implicit way. It is a monad transformer mainly is designed for wrapping IO computations. the lifting primitive, step, store the intermediate result and recover the application state. in acid state the process choose what to write in the state in workflow the state written is the complete state of the process. See the example in the documentation. the process , http://hackage.haskell.org/packages/archive/Workflow/0.7.0.7/doc/html/Control-Workflow.html import Control.Workflow import Control.Concurrent(threadDelay) import System.IO (hFlush,stdout) mcount n= do step http://hackage.haskell.org/packages/archive/Workflow/0.7.0.7/doc/html/Control-Workflow.html#v:step $ do putStr (show n ++ ) hFlush stdout threadDelay 100 mcount (n+1) return () -- to disambiguate the return type main= exec1 http://hackage.haskell.org/packages/archive/Workflow/0.7.0.7/doc/html/Control-Workflow.html#v:exec1 count $ mcount (0 :: Int) *runghc demos\sequence.hs*0 1 2 3 CTRL-C Pressed *runghc demos\sequence.hs*3 4 5 6 7 CTRL-C Pressed *runghc demos\sequence.hs*7 8 9 10 11 ... in subsequent executions the process start to execute IO computations from the last point logged: As the documentation says some side effect can be re-executed after recovery if the log is not complete. This may happen after an unexpected shutdown (in this case Contro-C has been pressed) or due to an asynchronous log writing policy. (see syncWritehttp://hackage.haskell.org/packages/archive/Workflow/0.7.0.7/doc/html/Control-Workflow.html#v:syncWrite ) (writing is cached). Althoug this is not event sourcing, The logging and recovery facilities can be used for even sourcing. Alberto 2012/9/30 Marcelo Sousa dipyt...@gmail.com Hi, On Sun, Sep 30, 2012 at 4:22 AM, Alberto G. Corona agocor...@gmail.com wrote: It´´s a very iteresting concept. The Workflow Monad transformer [1], in Control.Workflow perform logging and recovery of application istate from the log created. It has no implementation of roll-back or limited recovery upto a point, but this is easy to implement. Is Control.Workflow similar with acid-state with respect to the way you recovery the current state? It also has many inspection and synchronization primitives. It has been used also for translating the log of a program and recovering the state in another machine. The log can be pretty-printed for debugging. Can you somehow recover impure (IO) computations? [1] http://hackage.haskell.org/package/Workflow Regards, Marcelo 2012/9/30 KC kc1...@gmail.com: http://martinfowler.com/eaaDev/EventSourcing.html http://martinfowler.com/articles/lmax.html -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Alberto. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Alberto. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One of the new buzz phrases is Event-Sourcing; is Haskell suitable for this?
On 09/30/2012 02:46 AM, KC wrote: http://martinfowler.com/eaaDev/EventSourcing.html http://martinfowler.com/articles/lmax.html Sure, why not? See http://hackage.haskell.org/package/cqrs-0.8.0 and http://hackage.haskell.org/package/cqrs-example-0.8.0 for an example application. I should note that the cqrs package API is by no means finalized; there are some limitations(*) to the current implementation, but I've not had time to actually get rid of those limitations. (*) The major ones being the requirement for a global version number and lack of streaming event sourcing. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One of the new buzz phrases is Event-Sourcing; is Haskell suitable for this?
On Sat, Sep 29, 2012 at 8:46 PM, KC kc1...@gmail.com wrote: http://martinfowler.com/eaaDev/EventSourcing.html http://martinfowler.com/articles/lmax.html This notion of Capture all changes to an application state as a sequence of events sounds a lot like what John Carmack did in Quake 3 [1]: I settled on combining all forms of input into a single system event queue, similar to the windows message queue. My original intention was to just rigorously define where certain functions were called and cut down the number of required system entry points, but it turned out to have much stronger benefits. [1]: http://www.team5150.com/~andrew/carmack/johnc_plan_1998.html#d19981014 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] One of the new buzz phrases is Event-Sourcing; is Haskell suitable for this?
http://martinfowler.com/eaaDev/EventSourcing.html http://martinfowler.com/articles/lmax.html -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One of the new buzz phrases is Event-Sourcing; is Haskell suitable for this?
On Sat, Sep 29, 2012 at 8:46 PM, KC kc1...@gmail.com wrote: http://martinfowler.com/eaaDev/EventSourcing.html STM? And I believe there's work on the debugger in ghci to run programs backwards. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One of the new buzz phrases is Event-Sourcing; is Haskell suitable for this?
It´´s a very iteresting concept. The Workflow Monad transformer [1], in Control.Workflow perform logging and recovery of application istate from the log created. It has no implementation of roll-back or limited recovery upto a point, but this is easy to implement. It also has many inspection and synchronization primitives. It has been used also for translating the log of a program and recovering the state in another machine. The log can be pretty-printed for debugging. [1] http://hackage.haskell.org/package/Workflow 2012/9/30 KC kc1...@gmail.com: http://martinfowler.com/eaaDev/EventSourcing.html http://martinfowler.com/articles/lmax.html -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Alberto. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
