ceph/doc/dev/developer_guide/basic-workflow.rst

Basic Workflow
==============

The following chart illustrates the basic Ceph development workflow:

.. ditaa::

            Upstream Code                       Your Local Environment

           /----------\        git clone           /-------------\
           |   Ceph   | -------------------------> | ceph/master |
           \----------/                            \-------------/
                ^                                    |
                |                                    | git branch fix_1
                | git merge                          |
                |                                    v
           /----------------\  git commit --amend   /-------------\
           |  make check    |---------------------> | ceph/fix_1  |
           | ceph--qa--suite|                       \-------------/
           \----------------/                        |
                ^                                    | fix changes
                |                                    | test changes
                | review                             | git commit
                |                                    |
                |                                    v
           /--------------\                        /-------------\
           |   github     |<---------------------- | ceph/fix_1  |
           | pull request |         git push       \-------------/
           \--------------/

The below explanation is written with the assumption that you, the reader, are
a new contributor who has an idea for a bugfix or enhancement, but do not know
exactly how to proceed. Watch the `Getting Started with Ceph Development
<https://www.youtube.com/watch?v=t5UIehZ1oLs>`_ video for a practical summary
of this workflow.

Update the tracker
------------------

Before you start, you should know the :ref:`issue-tracker` (Redmine) number
of the bug you intend to fix. If there is no tracker issue, now is the time to
create one for code changes.  Straightforward documentation cleanup does
not necessarily require a corresponding tracker issue. However, an issue
(ticket) should be created if one is adding new documentation chapters or
files, or for other substantial changes.

The tracker ticket serves to explain the issue (bug) to your fellow Ceph
developers and keep them informed as you make progress toward resolution.  To
this end, please provide a descriptive title and write appropriate information
and details into the description.  When composing the ticket's title, consider "If I
want to search for this ticket two years from now, what keywords will I search
for?"

If you have sufficient tracker permissions, assign the bug to yourself by
setting the ``Assignee`` field.  If your tracker permissions have not been
elevated, simply add a comment with a short message like "I am working on this
issue".

Upstream code
-------------

This section, and the ones that follow, correspond to nodes in the above chart.

The upstream code is found at https://github.com/ceph/ceph.git, which is known
as the "upstream repo", or simply "upstream". As the chart shows, we will make
a local copy of this repository, modify it, test our modifications, then submit
the modifications for review and merging.

A local copy of the upstream code is made by

1. Forking the upstream repo on GitHub, and
2. Cloning your fork to make a local working copy

See the `GitHub documentation
<https://help.github.com/articles/fork-a-repo/#platform-linux>`_ for
detailed instructions on forking. In short, if your GitHub username is
"mygithubaccount", your fork of the upstream repo will appear at
https://github.com/mygithubaccount/ceph. Once you have created your fork,
clone it by running:

.. prompt:: bash $

   git clone https://github.com/mygithubaccount/ceph

While it is possible to clone the upstream repo directly, for the Ceph workflow
you must fork it first. Forking is what enables us to open a `GitHub pull
request`_.

For more information on using GitHub, refer to `GitHub Help
<https://help.github.com/>`_.

Local environment
-----------------

In the local environment created in the previous step, you now have a copy of
the ``master`` branch in ``remotes/origin/master``. This fork
(https://github.com/mygithubaccount/ceph.git) is frozen in time and the
upstream repo (https://github.com/ceph/ceph.git, typically abbreviated to
``ceph/ceph.git``) is updated frequently by other contributors, you must sync
your fork periodically. Failure to do so may result in your commits and pull
requests failing to merge because they refer to file contents that have since
changed.

First, ensure that you have properly configured your local git environment with
your name and email address.  Skip this step if you have already configured this
information.

.. prompt:: bash $

   git config user.name "FIRST_NAME LAST_NAME"
   git config user.email "MY_NAME@example.com"

Now add the upstream repo as a "remote" and fetch it:

.. prompt:: bash $

   git remote add ceph https://github.com/ceph/ceph.git
   git fetch ceph

Fetching downloads all objects (commits, branches) that were added since
the last sync. After running these commands, all the branches from
``ceph/ceph.git`` are downloaded to the local git repo as
``remotes/ceph/$BRANCH_NAME`` and can be referenced as
``ceph/$BRANCH_NAME`` in local git commands.

For example, your local ``master`` branch can be reset to the upstream Ceph
``master`` branch by running

.. prompt:: bash $

   git fetch ceph
   git checkout master
   git reset --hard ceph/master

Finally, the ``master`` branch of your fork is synced to the upstream
master by

.. prompt:: bash $

   git push -u origin master

Bugfix branch
-------------

Next, create a branch for your bugfix:

.. prompt:: bash $

   git checkout master
   git checkout -b fix_1
   git push -u origin fix_1

This creates a ``fix_1`` branch locally and in our GitHub fork. At this point,
the ``fix_1`` branch is identical to the ``master`` branch, but not for long!
You are now ready to modify the code.  Be careful to always run `git checkout
master` first, otherwise you may find commits from an unrelated branch mixed
with your new work.

Fix bug locally
---------------

Now change the status of the tracker issue to "In progress" to communicate to
other Ceph contributors that you have begun working on a fix.  This helps avoid
duplication of effort.  If you don't have permission to change that field, your
previous comment that you are working on the issue is sufficient.

Your fix may be very simple and require only minimal testing.  More likely,
this will be an iterative process involving trial and error, not to mention
skill. An explanation of how to fix bugs is beyond the scope of this
document. Instead, we focus on the mechanics of the process in the context of
the Ceph project.

For a detailed discussion of the tools available for validating bugfixes,
see the chapters on testing.

For now, let us just assume that you have finished work on the bugfix, that
you have tested, and that you believe it works. Commit the changes to your local
branch using the ``--signoff`` option

.. prompt:: bash $

   git commit -as

and push the changes to your fork

.. prompt:: bash $

   git push origin fix_1

GitHub pull request
-------------------

The next step is to open a GitHub pull request (PR). This makes your bugfix
visible to the community of Ceph contributors.  They will review it and may
perform additional testing and / or request changes.

This is the point where you "go public" with your modifications.  Be prepared
to receive suggestions and constructive criticism in the form of comments
within the PR. Don't worry!  The Ceph project is a friendly place!

If you are uncertain how to create and manage pull requests, you may read
`this GitHub pull request tutorial`_.

.. _`this GitHub pull request tutorial`:
   https://help.github.com/articles/using-pull-requests/

For ideas on what constitutes a "good" pull request, see
the `Git Commit Good Practice`_ article at the `OpenStack Project Wiki`_.

.. _`Git Commit Good Practice`: https://wiki.openstack.org/wiki/GitCommitMessages
.. _`OpenStack Project Wiki`: https://wiki.openstack.org/wiki/Main_Page

and our own `Submitting Patches <https://github.com/ceph/ceph/blob/master/SubmittingPatches.rst>`_ document.

Once your pull request (PR) is opened, update the :ref:`issue-tracker` by
adding a comment directing other contributors to your PR. The comment can be
as simple as::

    *PR*: https://github.com/ceph/ceph/pull/$NUMBER_OF_YOUR_PULL_REQUEST

Automated PR validation
-----------------------

When you create or update your PR, the Ceph project's `Continuous Integration
(CI) <https://en.wikipedia.org/wiki/Continuous_integration>`_ infrastructure
automatically tests it. At the time of this writing (September 2020), the
automated CI testing included five tests:

#. a test to check that the commits are properly signed (see :ref:`submitting-patches`):
#. a test to check that the documentation builds
#. a test to check that the submodules are unmodified
#. a test to check that the API is in order
#. a :ref:`make check<make-check>` test

Additional tests may be performed depending on which files your PR modifies.

The :ref:`make check<make-check>` test builds the PR and runs it through a battery of
tests. These tests run on servers operated by the Ceph Continuous
Integration (CI) team. When the tests complete, the result will be shown
on GitHub in the pull request itself.

You should test your modifications before you open a PR.
Refer to the chapters on testing for details.

Notes on PR make check test
^^^^^^^^^^^^^^^^^^^^^^^^^^^

The GitHub :ref:`make check<make-check>` test is driven by a Jenkins instance.

Jenkins merges your PR branch into the latest version of the base branch before
starting tests. This means that you don't have to rebase the PR to pick up any fixes.

You can trigger PR tests at any time by adding a comment to the PR - the
comment should contain the string "test this please". Since a human subscribed
to the PR might interpret that as a request for him or her to test the PR, we
recommend that you address Jenkins directly. For example, write "jenkins retest
this please".  For efficiency a single re-test can also be requested with
e.g. "jenkins test signed".  For reference, a list of these requests is
automatically added to the end of each new PR's description.

If there is a build failure and you aren't sure what caused it, check the
:ref:`make check<make-check>` log. To access it, click on the "details" (next
to the :ref:`make check<make-check>` test in the PR) link to enter the Jenkins web
GUI. Then click on "Console Output" (on the left).

Jenkins is configured to search logs for strings known to have been associated
with :ref:`make check<make-check>` failures in the past. However, there is no
guarantee that these known strings are associated with any given
:ref:`make check<make-check>` failure. You'll have to read through the log to determine the
cause of your specific failure.

Integration tests AKA ceph-qa-suite
-----------------------------------

Since Ceph is complex, it may be necessary to test your fix to
see how it behaves on real clusters running on physical or virtual
hardware. Tests designed for this purpose live in the `ceph/qa
sub-directory`_ and are run via the `teuthology framework`_.

.. _`ceph/qa sub-directory`: https://github.com/ceph/ceph/tree/master/qa/
.. _`teuthology repository`: https://github.com/ceph/teuthology
.. _`teuthology framework`: https://github.com/ceph/teuthology

The Ceph community has access to the `Sepia lab
<https://wiki.sepia.ceph.com/doku.php>`_ where :ref:`integration
tests<testing-integration-tests>` can be run on physical hardware. Other
developers may add tags like "needs-qa" to your PR. This allows PRs that need
testing to be merged into a single branch and tested all at the same time.
Since teuthology suites can take hours (even days in some cases) to run, this
can save a lot of time.

To request access to the Sepia lab, start `here
<https://wiki.sepia.ceph.com/doku.php?id=vpnaccess>`_.

Integration testing is discussed in more detail in the :ref:`integration
tests<testing-integration-tests>` chapter.

Code review
-----------

Once your bugfix has been thoroughly tested, or even during this process,
it will be subjected to code review by other developers. This typically
takes the form of comments in the PR itself, but can be supplemented
by discussions on :ref:`irc` and the :ref:`mailing-list`.

Amending your PR
----------------

While your PR is going through testing and `Code Review`_, you can
modify it at any time by editing files in your local branch.

After updates are committed locally (to the ``fix_1`` branch in our
example), they need to be pushed to GitHub so they appear in the PR.

Modifying the PR is done by adding commits to the ``fix_1`` branch upon
which it is based, often followed by rebasing to modify the branch's git
history. See `this tutorial
<https://www.atlassian.com/git/tutorials/rewriting-history>`_ for a good
introduction to rebasing. When you are done with your modifications, you
will need to force push your branch with:

.. prompt:: bash $

   git push --force origin fix_1

Why do we take these extra steps instead of simply adding additional commits
the the PR?  It is best practice for a PR to consist of a single commit; this
makes for clean history, eases peer review of your changes, and facilitates
merges.  In rare circumstances it also makes it easier to cleanly revert
changes.

Merge
-----

The bugfix process completes when a project lead merges your PR.

When this happens, it is a signal for you (or the lead who merged the PR)
to change the :ref:`issue-tracker` status to "Resolved". Some issues may be
flagged for backporting, in which case the status should be changed to
"Pending Backport" (see the :ref:`backporting` chapter for details).

See also :ref:`merging` for more information on merging.

Proper Merge Commit Format
^^^^^^^^^^^^^^^^^^^^^^^^^^

This is the most basic form of a merge commit::

       doc/component: title of the commit 

       Reviewed-by: Reviewer Name <rname@example.com>

This consists of two parts:

#. The title of the commit / PR to be merged.
#. The name and email address of the reviewer. Enclose the reviewer's email 
   address in angle brackets.

Using .githubmap to Find a Reviewer's Email Address
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If you cannot find the email address of the reviewer on his or her GitHub
page, you can look it up in the **.githubmap** file, which can be found in
the repository at **/ceph/.githubmap**.

Using "git log" to find a Reviewer's Email Address
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If you cannot find a reviewer's email address by using the above methods, you
can search the git log for their email address. Reviewers are likely to have
committed something before.  If they have made previous contributions, the git
log will probably contain their email address.

Use the following command

.. prompt:: bash [branch-under-review]$

   git log

Using ptl-tool to Generate Merge Commits
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Another method of generating merge commits involves using Patrick Donnelly's
**ptl-tool** pull commits. This tool can be found at
**/ceph/src/script/ptl-tool.py**.  Merge commits that have been generated by
the **ptl-tool** have the following form::

     Merge PR #36257 into master
     * refs/pull/36257/head:
             client: move client_lock to _unmount()
             client: add timer_lock support
     Reviewed-by: Patrick Donnelly <pdonnell@redhat.com>

.. _Integration Testing: ../testing_integration_tests/tests-integration-testing-teuthology-intro
.. _Sepia lab: https://wiki.sepia.ceph.com/doku.php