scotty-timerstate

Extends the scotty global state example slightly to add a background timer thread that modifies the state at regular intervals.

Use make shell to create and start a docker container based on Nix with the build environment - around 3.8 Gigs! Once you have the [nix-shell:/working]# prompt you can build and run using nix commands or cabal (easier for dev).

nix-build release.nix
result/bin/scotty-timerstate

cabal run scotty-timerstate

Once running on http://localhost:3000 you can trigger manual state changes by going to http://localhost:3000/plusone and http://localhost:3000/plustwo. After a while you should see an increased tickCount value and various channel values in the JSON returned by the server e.g.

{"channels":["timer","timer","timer","plustwo","timer","plusone","timer","timer","initial"],"tickCount":21}

After updating dependencies in working.cabal use cabal2nix . > default.nix to update the nix configuration.

Useful links

• Threading explanation
• Haskell nix intro
• Nix and Haskell in production