Deploy Haskell code that uses the Snap Framework

问题:

What's your experience with deploying Haskell code for production in Snap in a stable fashion?

If the compilation fails on the server then I would like to abort the deployment and if it succeeds then I would like it to turn of the snap-server and start the new version instead.

I know there are plenty of ways. Everything from rsync to git-hooks (git pull was a nightmare). But I would like to hear your experiences.

回答1:

Where I work, we use Happstack and deploy on Ubuntu linux. We actually debianize the web app and all the dependencies, and then build them in the autobuilder.

To actually install on the server, we just run apt-get update && apt-get install webapp-production

The advantage of this system is that it makes it easy for all developers to develop against the same version of the dependencies. And you know that all the source code is checked in properly and can be rebuilt anywhere .. not just on one particular machine. Additionally, it provides a mechanism to make patches to libraries from hackage when needed.

The downside is that apt-get and cabal-install do not get along well. You either have to build everything via apt-get or do everything via cabal-install.

回答2:

Here's what we do. First off, our servers are all the same version of ubuntu, as well as our development machines. We write code, test, etc. in whatever os we care to use and when we're ready to push we build on the devel machine(s). As long as that compiled cleanly, we stop (number of frontend servers)/2, rsync the resources directory and a new copy of the binary, and then use scripts start it back up. Then repeat for the other half.

In my opinion, I think you should question the logic of maintaining a full toolchain on your frontend server(s) when you can easily transfer just the binary and static assets - provided that the external libraries (database, image, etc) versions match the build environment. Heck, you could just use a virtualbox instance to do the final compile, again, so long as the release of the os and libraries match.