4. Development

This page covers the relevant aspects for developers.

4.1. Repository

The Git repository for the exporter project is GitHub: https://github.com/zhmcclient/zhmc-prometheus-exporter

4.2. Code of Conduct

Contribution must follow the Code of Conduct as defined by the Contributor Covenant.

4.3. Contributing

Third party contributions to this project are welcome!

In order to contribute, create a Git pull request, considering this:

Test is required.
Each commit should only contain one “logical” change.
A “logical” change should be put into one commit, and not split over multiple commits.
Large new features should be split into stages.
The commit message should not only summarize what you have done, but explain why the change is useful.
The commit message must follow the format explained below.

What comprises a “logical” change is subject to sound judgement. Sometimes, it makes sense to produce a set of commits for a feature (even if not large). For example, a first commit may introduce a (presumably) compatible API change without exploitation of that feature. With only this commit applied, it should be demonstrable that everything is still working as before. The next commit may be the exploitation of the feature in other components.

For further discussion of good and bad practices regarding commits, see:

4.4. Format of commit messages

A commit message must start with a short summary line, followed by a blank line.

Optionally, the summary line may start with an identifier that helps identifying the type of change or the component that is affected, followed by a colon.

It can include a more detailed description after the summary line. This is where you explain why the change was done, and summarize what was done.

It must end with the DCO (Developer Certificate of Origin) sign-off line in the format shown in the example below, using your name and a valid email address of yours. The DCO sign-off line certifies that you followed the rules stated in DCO 1.1. In short, you certify that you wrote the patch or otherwise have the right to pass it on as an open-source patch.

We use GitCop during creation of a pull request to check whether the commit messages in the pull request comply to this format. If the commit messages do not comply, GitCop will add a comment to the pull request with a description of what was wrong.

Example commit message:

cookies: Add support for delivering cookies

Cookies are important for many people. This change adds a pluggable API for
delivering cookies to the user, and provides a default implementation.

Signed-off-by: Random J Developer <random@developer.org>

Use git commit --amend to edit the commit message, if you need to.

Use the --signoff (-s) option of git commit to append a sign-off line to the commit message with your name and email as known by Git.

If you like filling out the commit message in an editor instead of using the -m option of git commit, you can automate the presence of the sign-off line by using a commit template file:

Create a file outside of the repo (say, ~/.git-signoff.template) that contains, for example:

<one-line subject>

<detailed description>

Signed-off-by: Random J Developer <random@developer.org>

Configure Git to use that file as a commit template for your repo:
```
git config commit.template ~/.git-signoff.template
```

4.5. Releasing a version

This section shows the steps for releasing a version to PyPI.

It covers all variants of versions that can be released:

Releasing a new major version (Mnew.0.0) based on the master branch
Releasing a new minor version (M.Nnew.0) based on the master branch
Releasing a new update version (M.N.Unew) based on the stable branch of its minor version

This description assumes that you are authorized to push to the remote repo at https://github.com/zhmcclient/zhmc-prometheus-exporter and that the remote repo has the remote name origin in your local clone.

Any commands in the following steps are executed in the main directory of your local clone of the zhmc-prometheus-exporter Git repo.

On GitHub, verify open items in milestone M.N.U.

Verify that milestone M.N.U has no open issues or PRs anymore. If there are open PRs or open issues, make a decision for each of those whether or not it should go into version M.N.U you are about to release.

If there are open issues or PRs that should go into this version, abandon the release process.

If none of the open issues or PRs should go into this version, change their milestones to a future version, and proceed with the release process. You may need to create the milestone for the future version.
Set shell variables for the version that is being released and the branch it is based on:
- MNU - Full version M.N.U that is being released (or pre-release M.N.Ub/c/rcP)
- MN - Major and minor version M.N of that full version
- BRANCH - Name of the branch the version that is being released is based on
When releasing a new major version (e.g. 1.0.0) based on the master branch:
```
MNU=1.0.0
MN=1.0
BRANCH=master
```
When releasing a new minor version (e.g. 0.9.0) based on the master branch:
```
MNU=0.9.0
MN=0.9
BRANCH=master
```
When releasing a new update version (e.g. 0.8.1) based on the stable branch of its minor version:
```
MNU=0.8.1
MN=0.8
BRANCH=stable_${MN}
```
When releasing a alpha, beta or release candidate pre-version (e.g. 1.0.0b1) based on the master branch:
```
MNU=1.0.0b1
MN=1.0
BRANCH=master
```

Create a topic branch for the version that is being released:

git checkout ${BRANCH}
git pull
git checkout -b release_${MNU}

Edit the version file:
```
vi zhmc_prometheus_exporter/_version.py
```
and set the __version__ variable to the version that is being released:
```
__version__ = 'M.N.U'
```
Edit the change log:
```
vi docs/changes.rst
```
and make the following changes in the section of the version that is being released:
- Finalize the version.
- Change the release date to today’s date.
- Make sure that all changes are described.
- Make sure the items shown in the change log are relevant for and understandable by users.
- In the “Known issues” list item, remove the link to the issue tracker and add text for any known issues you want users to know about.
- Remove all empty list items.
Update the authors:
```
make authors
```

Commit your changes and push the topic branch to the remote repo:

git commit -asm "Release ${MNU}"
git push --set-upstream origin release_${MNU}

On GitHub, create a Pull Request for branch release_M.N.U.

Important: When creating Pull Requests, GitHub by default targets the master branch. When releasing based on a stable branch, you need to change the target branch of the Pull Request to stable_M.N.

Set the milestone of that PR to version M.N.U.

This PR should normally be set to be reviewed by at least one of the maintainers.

The PR creation will cause the “test” workflow to run. That workflow runs tests for all defined environments, since it discovers by the branch name that this is a PR for a release.
On GitHub, once the checks for that Pull Request have succeeded, merge the Pull Request (no review is needed). This automatically deletes the branch on GitHub.

If the PR did not succeed, fix the issues.
On GitHub, close milestone M.N.U.

Verify that the milestone has no open items anymore. If it does have open items, investigate why and fix. If the milestone does not have open items anymore, close the milestone.
Publish the package
```
git checkout ${BRANCH}
git pull
git branch -D release_${MNU}
git branch -D -r origin/release_${MNU}
git tag -f ${MNU}
git push -f --tags
```
Pushing the new tag will cause the “publish” workflow to run. That workflow builds the package, publishes it on PyPI, creates a release for it on Github, and finally creates a new stable branch on Github if the master branch was released.
Verify the publishing

Wait for the “publish” workflow for the new release to have completed: https://github.com/zhmcclient/zhmc-prometheus-exporter/actions/workflows/publish.yml

Then, perform the following verifications:
- Verify that the new version is available on PyPI at https://pypi.python.org/pypi/zhmc-prometheus-exporter/
- Verify that the new version has a release on Github at https://github.com/zhmcclient/zhmc-prometheus-exporter/releases
- Verify that the new version has documentation on ReadTheDocs at https://zhmc-prometheus-exporter.readthedocs.io/en/latest/changes.html
  
  The new version M.N.U should be automatically active on ReadTheDocs, causing the documentation for the new version to be automatically built and published.
  
  If you cannot see the new version after some minutes, log in to https://readthedocs.org/projects/zhmc-prometheus-exporter/versions/ and activate the new version.

4.6. Starting a new version

This section shows the steps for starting development of a new version.

This section covers all variants of new versions:

Starting a new major version (Mnew.0.0) based on the master branch
Starting a new minor version (M.Nnew.0) based on the master branch
Starting a new update version (M.N.Unew) based on the stable branch of its minor version

This description assumes that you are authorized to push to the remote repo at https://github.com/zhmcclient/zhmc-prometheus-exporter and that the remote repo has the remote name origin in your local clone.

Any commands in the following steps are executed in the main directory of your local clone of the zhmc-prometheus-exporter Git repo.

Set shell variables for the version that is being started and the branch it is based on:
- MNU - Full version M.N.U that is being started
- MN - Major and minor version M.N of that full version
- BRANCH - Name of the branch the version that is being started is based on
When starting a new major version (e.g. 1.0.0) based on the master branch:
```
MNU=1.0.0
MN=1.0
BRANCH=master
```
When starting a new minor version (e.g. 0.9.0) based on the master branch:
```
MNU=0.9.0
MN=0.9
BRANCH=master
```
When starting a new minor version (e.g. 0.8.1) based on the stable branch of its minor version:
```
MNU=0.8.1
MN=0.8
BRANCH=stable_${MN}
```

Create a topic branch for the version that is being started:

git fetch origin
git checkout ${BRANCH}
git pull
git checkout -b start_${MNU}

Edit the version file:
```
vi zhmc_prometheus_exporter/_version.py
```
and update the version to a draft version of the version that is being started:
```
__version__ = 'M.N.U.dev1'
```

Edit the change log:

vi docs/changes.rst

and insert the following section before the top-most section:

Version M.N.U.dev1
^^^^^^^^^^^^^^^^^^

This version contains all fixes up to version M.N-1.x.

Released: not yet

**Incompatible changes:**

**Deprecations:**

**Bug fixes:**

**Enhancements:**

**Cleanup:**

**Known issues:**

* See `list of open issues`_.

.. _`list of open issues`: https://github.com/zhmcclient/zhmc-prometheus-exporter/issues

Commit your changes and push them to the remote repo:

git commit -asm "Start ${MNU}"
git push --set-upstream origin start_${MNU}

On GitHub, create a milestone for the new version M.N.U.

You can create a milestone in GitHub via Issues -> Milestones -> New Milestone.
On GitHub, create a Pull Request for branch start_M.N.U.

Important: When creating Pull Requests, GitHub by default targets the master branch. When starting a version based on a stable branch, you need to change the target branch of the Pull Request to stable_M.N.

No review is needed for this PR.

Set the milestone of that PR to the new version M.N.U.
On GitHub, go through all open issues and pull requests that still have milestones for previous releases set, and either set them to the new milestone, or to have no milestone.

Note that when the release process has been performed as described, there should not be any such issues or pull requests anymore. So this step here is just an additional safeguard.
On GitHub, once the checks for the Pull Request for branch start_M.N.U have succeeded, merge the Pull Request (no review is needed). This automatically deletes the branch on GitHub.

Update and clean up the local repo:

git checkout ${BRANCH}
git pull
git branch -D start_${MNU}
git branch -D -r origin/start_${MNU}

4.7. Building the distribution archives

You can build a binary (wheel) distribution archive and a source distribution archive (a more minimal version of the repository) with:

$ make build

You will find the files zhmc_prometheus_exporter-VERSION_NUMBER-py2.py3-none-any.whl and zhmc_prometheus_exporter-VERSION_NUMBER.tar.gz in the dist folder, the former being the binary and the latter being the source distribution archive.

The binary distribution archive could be installed with:

$ pip install zhmc_prometheus_exporter-VERSION_NUMBER-py2.py3-none-any.whl

The source distribution archive could be installed with:

$ tar -xfz zhmc_prometheus_exporter-VERSION_NUMBER.tar.gz
$ pip install zhmc_prometheus_exporter-VERSION_NUMBER

4.8. Building the documentation

You can build the HTML documentation with:

$ make builddoc

The root file for the built documentation will be build_docs/index.html.

4.9. Testing

You can perform unit tests with:

$ make test

The environment variables TESTCASES and TESTOPTS can be specified for unit tests. Invoke make help for details.

You can perform a flake8 check with:

$ make check

You can perform a pylint check with:

$ make pylint