Heroku buildpack: Hello

Usage

Example usage:

$ ls
hello.txt

$ heroku create --buildpack http://github.com/heroku/heroku-buildpack-hello.git

$ git push heroku master
...
-----> Heroku receiving push
-----> Fetching custom buildpack
-----> HelloFramework app detected
-----> Found a hello.txt

The buildpack will detect that your app has a hello.txt in the root. If this file has contents, it will be copied to goodbye.txt with instances of the world hello changed to goodbye.

Hacking

To use this buildpack, fork it on Github. Push up changes to your fork, then create a test app with --buildpack <your-github-url> and push to it.

For example, you can change the displayed name of the buildpack to GoodbyeFramework. Open bin/detect in your editor, and change HelloFramework to GoodbyeFramework.

Commit and push the changes to your buildpack to your Github fork, then push your sample app to Heroku to test. You should see:

-----> GoodbyeFramework app detected

Hardcoding app runtime directory in buildpacks severely impacts their flexibility

Firstly, an apology; I know this repository is not the perfect place to file this issue, but I was unable to find any other public open-source forum that is more appropriate. If there is a more appropriate place, please let me know and I'll re-post.

Secondly, a reference for the source of the issue: crohr/pkgr#93

The short version is that it is not guaranteed that the app ends up installed to /app; users of buildpacks other than Heroku require applications to be stored at other paths, such as pkgr which uses /opt/${APP_NAME}. Furthermore, the application may not be mounted at runtime at the same path as the build directory, since not every buildpack executor uses a layered filesystem, and so must resort to using a sandbox build directory.

It is necessary for some buildpacks to reference the runtime application mount directory (for example the PHP buildpack).

I propose a modification to the buildpack API to add a further argument to the compile phase called RUN_DIR whose default is /app but which may be overridden by the likes of pkgr to another value, and Buildpacks may then depend on this where they currently have /app hard-coded for runtime usage. Compile time usage would continue to use the BUILD_DIR option.

heroku / heroku-buildpack-hello Goto Github PK