ncoghlan / modularity / fedmod

Forked from modularity/fedmod 3 years ago
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ncoghlan / modularity / fedmod

Forked from modularity/fedmod 3 years ago
Utility CLI and library to help with modulemd generation & management
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Nick Coghlan committed 3 years ago

fedmod modularity tools

fedmod provides tools for working with Fedora's modulemd metadata format that aren't related to actually building them (for build commands, see fedpkg and mbs-build).

Currently, this consists of:

  • fedmod rpm2module: generates a draft modulemd file based on the given RPM name (multiple RPM names can be given, but the resulting draft module will lack any descriptive metadata in that case)
  • fedmod fetch-metadata: download the F27 package and module metadata needed to generate draft module definitions (the metadata sets to use are not yet configurable)

Project status

fedmod is not yet released as an RPM, but can already generate basic draft modules from a local development checkout:

$ pipenv run fedmod fetch-metadata
$ pipenv run fedmod rpm2module graphite-web

This will generate a draft modulemd file called graphite-web.yaml in the current directory.

See the local development instructions below for info on setting up the execution environment with pipenv.

Note: while an initial release is available from PyPI, the dependency on the system level dnf and solv libraries means it can't be usefully installed with pipsi (as attempting to import those dependencies will fail at runtime).

Interim alternative

fedmod aims to generate draft module definitions based on the same repository level metadata that dnf module uses to actually install and manage modules.

While this is the most appropriate approach for generating further modules once we actually have an initial Fedora Modular Server release available with multiple modules defined (since it will ensure that the module metadata used is accurate and up to date), it has some limitations while that initial release is still being assembled.

In the meantime, https://github.com/fedora-modularity/dependency-report-scripts allows for new module definitions to be generated based on the expected contents of the initial module set. While modulemd files created that way are still reasonable for now, they're expected to lose accuracy over time as module maintainers focus on dist-git and the actual module build service, and stop updating the now redundant metadata files in https://github.com/modularity-modules.

For now, a decent approach is to run both modulemd generators, and then pick whichever one you think looks better as your starting point.

Modulemd creation

fedmod rpm2module [RPM NAMES] creates a modulemd file from the given package names and emits it on stdout. The YAML metadata can be written directly to a file instead by passing the `--output (or -o) option:

$ fedmod rpm2module -o graphite-web.yaml graphite-web

The following metadata is currently used as input to the draft module generation process:

  • Package dependency definitions are pulled from the regular Fedora 27 release and updates repositories, with the metadata being downloaded for local use via the fedmod fetch-metadata command

  • Installable module definitions are pulled from the modular Fedora Bikeshed repository, with the metadata being downloaded for local use via the fedmod fetch-metadata command

  • The definition of Fedora's build-only bootstrap module is retrieved directly from the relevant dist-git repository

  • Descriptive metadata is taken from the system running fedmod. Due to this, fedmod currently only supports Fedora 26+. (This will be fixed to use the same repository metadata as is used for package dependency resolution)

Module dependencies currently err on the side of making the generated modules smaller by permitting generated modules to depend on packages that aren't listed as part of the public API of other modules. This reflects the fact that those transitive dependencies are typically the reason for the lower level modules appearing in the dependency set in the first place, as well as the fact that true dependency isolation will start being enforced once modules begin including opaque container images, such that only the client libraries are installed into shared environments.

Other limitations in generated modulemd files:

  • components are only given a name and rationale, relying on the default settings for everything else
  • the stream for module level dependencies is currently hardcoded to f27. This isn't right, but we can't set anything better until the mechanism for depending on multiple streams without naming them specifically is defined.

Local development

Runtime dependencies

The preferred dependency management tool for development is pipenv:

$ pipenv --three --site-packages
$ PIP_IGNORE_INSTALLED=1 pipenv install --dev

The PIP_IGNORE_INSTALLED=1 setting means that everything available to pip will be installed into the virtual environment based on Pipfile.lock, and only components that aren't installable with pip will be used from the system Python installation.

Some dependencies aren't currently available from PyPI, and hence need to be installed system-wide:

$ sudo dnf install python3-dnf python3-solv

Additional development dependencies

pipenv itself isn't packaged for Fedora yet, so the recommended bootstrapping approach is to use the "pip script installer", pipsi:

$ sudo dnf install pipsi
$ pipsi install pew
$ pipsi install pipenv

This will create a pair of isolated virtual environments in your home directory specifically for pipenv and the tool it uses for virtual environment management, pew. These can later be updated to newer versions using pipsi:

$ pipsi upgrade pew
$ pipsi upgrade pipenv

(Note: the pipsi list command will list all packages installed via pipsi, and the commands they provide)

Running the tests

After going through the environment setup steps above, start a shell that's correctly configured to run the tests with fedmod and all of its dependencies available:

$ pipenv shell

The metadata needed by the module generator tests can then be installed with fedmod itself:

$ fedmod fetch-metadata

The tests can then be run in the launched subshell with:

$ pytest tests

Reviewing project dependencies

To see the Python level dependencies graph:

$ pew toggleglobalsitepackages
$ pipenv graph
$ pew toggleglobalsitepackages

(If you don't turn off global site-packages access first, you'll get the dependency graph of all the installed system Python components as well)