Before going further, you may want to inform yourself about the basic prerequisites, both knowledge and equipment, you need to make the best use of this tutorial
This tutorial is cabalized. You can install it, and chase down all the HAppS dependencies it needs, simply by doing
cabal install happs-tutorial
The cabal installation is kind of slow. I've had it take up to 15 minutes. But it should succeed in one shot. (This is a symptom of the HAppS slow linking bug.)
Unfortunately, the above statement is false on ghc 6.10.1 at the moment, because
the crypto package won't cabal install out of the box. You can build crypto first by doing
darcs get http://code.haskell.org/crypto
cd crypto
cabal install
Hopefully the crypto package will get a version bump on hackage soon so I can delete this ugly orange paragraph.
If you've never used cabal install or need more detailed info....
I cabalized happs-tutorial was for the dependency chasing you get with cabal install, not for actually running it.
Cabal installs an executable somewhere that you can run, but the tutorial pages won't display because the executable needs template files to display pages correctly. To actually run the tutorial locally, copy the happs-tutorial.tar.gz distribution file that cabal downloaded -- probably somewhere under ~/.cabal if you're on linux:
find ~/.cabal | grep -i happs-tutorial
should show you a tar file. Or you can just download the tar file from hackage. Once you have the tar file, untar this somewhere, cd into that, build and run here as described below. Or, you could darcs get happs-tutorial and run there.
To run the app, either do ./hackInGhci.sh and then execute runInGhci inside Main.hs, or recompile the executable using ./runServerWithCompileNLink.sh. Really you only need to be inside ghci if you are experiencing the slow link time issue. This isn't a problem at time of writing but seems to crop up from time to time.
Shutdown with ctrl-c.
You should now be able to browse this tutorial offline by running the executable, and opening http://localhost:5001 in your browser.
Every so often, when starting via runInGhci, you may get an error message like:
*Main> runInGhci happs tutorial running in ghci. exit :q ghci completely and reenter ghci, before restarting. *** Exception: _local/happs-tutorial_state/events-0000000006: openFile: resource busy (file is locked)
Don't worry about it. Every time I get this error I simply run runInGhci again, and the second time it always works.
As far as I know, this issue does not occur when you run the tutorial from a compiled executable, which is of course how you should be running for a production application.
You may also want to start HAppS on boot.
Next up is the HAppS server main function.