Rule over hierarchical data!
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README.md

monarch

Rule over hierarchical data!

example

$ monarch set --changes petstore.yaml --source global.yaml --put 'petstore::version: "2"'
$ monarch apply --changes petstore.yaml --target env=dev
$ cat hieradata/env/dev.yaml 
petstore::version: '2'
$ cat hieradata/global.yaml 
petstore::version: '1'
$ monarch apply --changes petstore.yaml --target global.yaml
$ cat hieradata/env/dev.yaml 
$ cat hieradata/global.yaml 
petstore::version: '2'

screencast

install from tarball

  1. Download tar or zip @ https://github.com/alechenninger/monarch/releases/latest
  2. Extract somewhere you like to put things
  3. Have JRE8 installed
  4. Have java in your PATH or JAVA_HOME environment variable defined (for ex: "/etc/alternatives/java_sdk")
  5. Add a symlink 'monarch' to your PATH which points to ${where_you_extracted_zip}/bin/monarch-bin

install from source

  1. Fork or git clone git@github.com:alechenninger/monarch.git
  2. cd monarch
  3. Have gradle installed. I recommend using sdkman.
  4. Have JRE8 installed
  5. Have java in your PATH or JAVA_HOME defined (for ex: "/etc/alternatives/java_sdk")
  6. Run gradle installDist
  7. Add symlink 'monarch' to your path which points to ${where_you_put_git_things}/monarch/bin/build/install/monarch-bin/bin/monarch-bin
  8. Hack or git pull and gradle installDist whenever you want to update your executable

install from docker

  1. docker pull alechenninger/monarch
  2. docker tag alechenninger/monarch monarch
  3. docker run [-v ...:... -w ...] monarch

Few things to note when running with docker:

  • You will need to mount your data and output directories at a minimum.
  • You may also want to mount the locations of config files, and set your working directory appropriately, or use --config option.
  • The containers user is "root" so on your system monarch may look for default config files (in user's home directory) in a different location then in the container.

usage

See bin for command line usage.

See the tests for example library usage and edge cases.

motivation

The idea is something that can take a desired end state, a hierarchy of data sources, a "target" data source to change among them, the current state of all data sources in the hierarchy, and split out a new state of all data sources in the hierarchy with the given changes applied to the target data source and its children. In other words, it automates promoting values throughout the hierarchy, only affecting the data sources in the hierarchy you want, but allowing you to specify changes only as changes to root nodes that you eventually want applied but can't jump to right away.

A practical usage example is Hiera, used by Puppet. You organize configuration in a hierarchy of data sources. During releases, you might promote values from one environment's configuration to another. It can be tedious to copy these values among horizontal promotions, which do not inherit each other (say, a QA environment to a staging environment), as well as, finally, vertical promotions (say from QA and stage environments to a base configuration file which all environments inherit defaults from). This tool allows you to start with your end state, but be able to generate intermediate stages as you promote your release from one environment to another. Finally, when you are ready to generate your final state, redundant keys are removed.