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============================================
Contributing to Ceph: A Guide for Developers
============================================
:Author: Loic Dachary
:Author: Nathan Cutler
:License: Creative Commons Attribution-ShareAlike (CC BY-SA)
.. note:: The old (pre-2016) developer documentation has been moved to :doc:`/dev/index-old`.
.. contents::
:depth: 3
Introduction
============
This guide has two aims. First, it should lower the barrier to entry for
software developers who wish to get involved in the Ceph project. Second,
it should serve as a reference for Ceph developers.
We assume that readers are already familiar with Ceph (the distributed
object store and file system designed to provide excellent performance,
reliability and scalability). If not, please refer to the `project website`_
and especially the `publications list`_.
.. _`project website`: http://ceph.com
.. _`publications list`: https://ceph.com/resources/publications/
Since this document is to be consumed by developers, who are assumed to
have Internet access, topics covered elsewhere, either within the Ceph
documentation or elsewhere on the web, are treated by linking. If you
notice that a link is broken or if you know of a better link, please
`report it as a bug`_.
.. _`report it as a bug`: http://tracker.ceph.com/projects/ceph/issues/new
Essentials (tl;dr)
==================
This chapter presents essential information that every Ceph developer needs
to know.
Leads
-----
The Ceph project is led by Sage Weil. In addition, each major project
component has its own lead. The following table shows all the leads and
their nicks on `GitHub`_:
.. _github: https://github.com/
========= =============== =============
Scope Lead GitHub nick
========= =============== =============
Ceph Sage Weil liewegas
RADOS Samuel Just athanatos
RGW Yehuda Sadeh yehudasa
RBD Josh Durgin jdurgin
CephFS Gregory Farnum gregsfortytwo
Build/Ops Ken Dreyer ktdreyer
========= =============== =============
The Ceph-specific acronyms in the table are explained under
`Architecture`_, below.
History
-------
See the `History chapter of the Wikipedia article`_.
.. _`History chapter of the Wikipedia article`: https://en.wikipedia.org/wiki/Ceph_%28software%29#History
Licensing
---------
Ceph is free software.
Unless stated otherwise, the Ceph source code is distributed under the terms of
the LGPL2.1. For full details, see `the file COPYING in the top-level
directory of the source-code tree`_.
.. _`the file COPYING in the top-level directory of the source-code tree`:
https://github.com/ceph/ceph/blob/master/COPYING
Source code repositories
------------------------
The source code of Ceph lives on `GitHub`_ in a number of repositories below
the `Ceph "organization"`_.
.. _`Ceph "organization"`: https://github.com/ceph
To make a meaningful contribution to the project as a developer, a working
knowledge of git_ is essential.
.. _git: https://git-scm.com/documentation
Although the `Ceph "organization"`_ includes several software repositories,
this document covers only one: https://github.com/ceph/ceph.
Redmine issue tracker
---------------------
Although `GitHub`_ is used for code, Ceph-related issues (Bugs, Features,
Backports, Documentation, etc.) are tracked at http://tracker.ceph.com,
which is powered by `Redmine`_.
.. _Redmine: http://www.redmine.org
The tracker has a Ceph project with a number of subprojects loosely
corresponding to the project components listed in `Architecture`_.
Mere `registration`_ in the tracker automatically grants permissions
sufficient to open new issues and comment on existing ones.
.. _registration: http://tracker.ceph.com/account/register
To report a bug or propose a new feature, `jump to the Ceph project`_ and
click on `New issue`_.
.. _`jump to the Ceph project`: http://tracker.ceph.com/projects/ceph
.. _`New issue`: http://tracker.ceph.com/projects/ceph/issues/new
Mailing list
------------
Ceph development email discussions take place on the mailing list
``ceph-devel@vger.kernel.org``. The list is open to all. Subscribe by
sending a message to ``majordomo@vger.kernel.org`` with the line: ::
subscribe ceph-devel
in the body of the message.
There are also `other Ceph-related mailing lists`_.
.. _`other Ceph-related mailing lists`: https://ceph.com/resources/mailing-list-irc/
IRC
---
In addition to mailing lists, the Ceph community also communicates in real
time using `Internet Relay Chat`_.
.. _`Internet Relay Chat`: http://www.irchelp.org/
See https://ceph.com/resources/mailing-list-irc/ for how to set up your IRC
client and a list of channels.
Submitting patches
------------------
The canonical instructions for submitting patches are contained in the
`the file CONTRIBUTING.rst in the top-level directory of the source-code
tree`_. There may be some overlap between this guide and that file.
.. _`the file CONTRIBUTING.rst in the top-level directory of the source-code tree`:
https://github.com/ceph/ceph/blob/master/CONTRIBUTING.rst
All newcomers are encouraged to read that file carefully.
Building from source
--------------------
See instructions at :doc:`/install/build-ceph`.
Development-mode cluster
------------------------
You can start a development-mode Ceph cluster, after compiling the source,
with:
.. code::
cd src
install -d -m0755 out dev/osd0
./vstart.sh -n -x -l
# check that it's there
./ceph health
Issue tracker
=============
See `Redmine issue tracker`_ for a brief introduction to the Ceph Issue Tracker.
Issue tracker conventions
-------------------------
When you start working on an existing issue, it's nice to let the other
developers know this - to avoid duplication of labor. Typically, this is
done by changing the :code:`Assignee` field (to yourself) and changing the
:code:`Status` to *In progress*. Newcomers to the Ceph community typically do not
have sufficient privileges to update these fields, however: they can
simply update the issue with a brief note.
.. table:: Meanings of some commonly used statuses
================ ===========================================
Status Meaning
================ ===========================================
New Initial status
In Progress Somebody is working on it
Need Review Pull request is open with a fix
Pending Backport Fix has been merged, backport(s) pending
Resolved Fix and backports (if any) have been merged
================ ===========================================
Basic workflow
==============
The following chart illustrates basic 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 \-------------/
\--------------/
Below we present an explanation of this chart. The explanation is written
with the assumption that you, the reader, are a beginning developer who
has an idea for a bugfix, but do not know exactly how to proceed.
Update the tracker
------------------
Before you start, you should know the `Issue tracker`_ number of the bug
you intend to fix. If there is no tracker issue, now is the time to create
one.
The tracker is there to explain the issue (bug) to your fellow Ceph
developers, so take care to provide a descriptive title as well as
sufficient information and details in the description.
If you have sufficient tracker permissions, assign the bug to yourself by
changing the ``Assignee`` field. If your tracker permissions have not yet
been elevated, simply add a comment to the issue to let the other
developers know you are working on the bug.
Upstream code
-------------
This section, and the ones that follow, correspond to the nodes in the
above chart.
The upstream code lives in https://github.com/ceph/ceph.git, which is
sometimes referred to as the "upstream repo", or simply "upstream". As the
chart illustrates, we will make a local copy of this code, modify it, test
our modifications, and submit the modifications back to the upstream repo
for review.
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 `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 show up at
https://github.com/mygithubaccount/ceph. Once you have created your fork,
you clone it by doing:
.. code::
$ git clone https://github.com/mygithubaccount/ceph
While it is possible to clone the upstream repo directly, in this case we
must fork it first, because that (forking) makes it possible 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, we now have a
copy of the ``master`` branch in ``remotes/origin/master``. Since the 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 developers, we will need
to add the upstream repo as a "remote" so we can fetch from it:
.. code::
$ git remote add ceph https://github.com/ceph/ceph.git
$ git fetch ceph
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 certain git commands.
For example, your local ``master`` branch can be reset to the upstream Ceph
``master`` branch by doing:
.. code::
$ git fetch ceph
$ git checkout master
$ git reset --hard ceph/master
The ``master`` branch of your fork can then be synced to upstream master by
doing:
.. code::
$ git push -u origin master
Bugfix branch
-------------
Next, create a branch for the bugfix:
.. code::
$ git checkout master
$ git branch -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.
Fix bug locally
---------------
At this point, change the status of the tracker issue to "In progress" to
communicate to the other Ceph developers that you have begun working on a
fix. If you don't have permission to change that field, your comment that
you are working on the issue is sufficient.
In the best case, your fix is very simple and requires only minimal testing.
In the typical worst case, fixing the bug is an iterative process involving
trial and error, not to mention skill. Fixing bugs is beyond the scope
of the current discussion.
For a more detailed discussion of the tools available for validating your
bugfixes, see the `Testing`_ chapter.
For now, let us just assume that you have finished work on the bugfix and
that you have tested it and believe it works. Commit the changes to your local
branch and push the changes to your fork like so:
.. code::
$ git push origin fix_1
GitHub pull request
-------------------
The next step is to open a GitHub pull request. The purpose of this step is
to make your bugfix available to the community of Ceph developers.
Additional testing will be done on it, and it will undergo code review.
In short, this is the point where you "go public" with your modifications.
If you are uncertain how to use pull requests, you may read
`this GitHub pull request tutorial`_.
.. _`this GitHub pull request tutorial`:
https://help.github.com/articles/using-pull-requests/
For some 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
Once your pull request is opened, update the `Issue tracker`_ by adding a
comment to the bug. The update can be as simple as:
.. code::
*PR*: https://github.com/ceph/ceph/pull/$NUMBER_OF_YOUR_PULL_REQUEST
Automated PR validation
-----------------------
When your PR hits GitHub, the Ceph project's `Continuous Integration (CI)
<https://en.wikipedia.org/wiki/Continuous_integration>`_
infrastructure will test it automatically. At the time of this writing
(March 2016), the automated CI testing included a test to check that the
commits in the PR are properly signed (see `Submitting patches`_) and a
``make check`` test.
The latter, ``make check``, builds the PR and runs it through a battery of
tests. These tests run on machines 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 can (and should) also test your modifications before you open a PR.
Refer to the the `Testing`_ chapter for details.
Integration tests AKA ceph-qa-suite
-----------------------------------
Since Ceph is a complex beast, it may also be necessary to test your fix to
see how it behaves on real clusters running either on real or virtual
hardware. Tests designed for this purpose live in the `ceph-qa-suite
repository`_ and are run via the `teuthology framework`_.
.. _`ceph-qa-suite repository`: https://github.com/ceph/ceph-qa-suite/
.. _`teuthology framework`: https://github.com/ceph/teuthology
If you have access to an OpenStack tenant, you are encouraged to run the
integration tests yourself using teuthology's OpenStack backend, called
`teuthology-openstack
<https://github.com/dachary/teuthology/tree/openstack#openstack-backend>`_,
and post the test results to the PR.
The Ceph community also uses the `Sepia lab
<http://ceph.github.io/sepia/>`_ where the integration tests can be run on
real 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.
Integration tests are discussed in more detail in the `Testing`_ 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 correspondence in the PR itself, but can be supplemented
by discussions on `IRC`_ and the `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 the changes are committed locally (to the ``fix_1`` branch in our
example), they need to be pushed to GitHub so they appear in the PR. If the
changes involved modification of the git history (because of a ``git
rebase`` or ``git commit --amend``), you will need to force push your branch
with:
.. code::
$ git push --force origin fix_1
Merge
-----
The bugfixing process culminates when one of the project leads decides to
merge your PR.
Testing
=======
Ceph has two types of tests: "make check" tests and integration tests.
The former are run via ``GNU Make <https://www.gnu.org/software/make/>``,
and the latter are run via the `teuthology framework`_.
Make check intro
----------------
After compiling Ceph, the ``make check`` command can be used to run the
code through a battery of tests covering various aspects of Ceph. For
inclusion in "make check", a test must:
* bind ports that do not conflict with other tests
* not require root access
* not require more than one machine to run
* complete within a few minutes
While it is possible to run ``make check`` directly, it can be tricky to
correctly set up your environment. Fortunately, a script is provided to
make it easier run "make check" on your code. It can be run from the
top-level directory of the Ceph source tree by doing:
.. code::
$ ./run-make-check.sh
You will need a minimum of 8GB of RAM and 32GB of free disk space for this
command to complete successfully. Depending on your hardware, it can take
from 20 minutes to three hours to complete, but it's worth the wait.
When you fix a bug, it's a good idea to add a test. See the `Writing make
check tests`_ chapter.
Integration tests intro
-----------------------
When a test requires multiple machines, root access or lasts for a
longer time (for example, to simulate a realistic Ceph deployment), it
is deemed to be an integration test. Integration tests are defined
in the `ceph-qa-suite repository`_ and run with the `teuthology
framework`_.
A number of integration tests are run on a regular basis against the
official Ceph repositories (on the master development branch and the
stable branches). Traditionally, these tests are called "the nightlies"
because most of the Ceph developers used to live and work in California and
from their perspective the tests were run overnight.
The results of the nightlies are visible at either http://pulpito.ceph.com/
and http://pulpito.ovh.sepia.ceph.com:8081/ (depending on how the tests
were run) and are also reported on the `ceph-qa mailing list
<http://ceph.com/resources/mailing-list-irc/>`_ for analysis.
Some Ceph developers have access to the hardware running these tests
(either bare metal or OpenStack provisioned) and are allowed to
schedule integration tests there (the developer nick shows in the test
results URL).
Ceph developers who have access to an OpenStack tenant (could be the Sepia
OVH one or any other) can use the `ceph-workbench ceph-qa-suite`_ command
to run integration tests and publish the results at
http://teuthology-logs.public.ceph.com. This allows reviewers to verify
that changes to the code base do not cause regressions, or to analyze test
failures when they do occur.
.. _`ceph-workbench ceph-qa-suite`: http://ceph-workbench.readthedocs.org/
Understanding make check tests
==============================
Principles of make check tests, where to find the results, how to interpret
them, how to find the corresponding source code, how to write a make check
test.
Understanding integration tests
===============================
This is an introduction to integration tests. A detailed
description of each option is available from ``teuthology-suite --help``.
Reading a standalone integration test
-------------------------------------
A test is defined by yaml files found in the ``suites`` subdirectory
of the `ceph-qa-suite repository`_ and implemented by python code
found in the ``tasks`` subdirectory. Here is a commented example using
`rados/singleton/all/admin-socket.yaml <https://github.com/ceph/ceph-qa-suite/blob/master/suites/rados/singleton/all/admin-socket.yaml>`_ ::
roles:
- - mon.a
- osd.0
- osd.1
tasks:
- install:
- ceph:
- admin_socket:
osd.0:
version:
git_version:
help:
config show:
config set filestore_dump_file /tmp/foo:
perf dump:
perf schema:
The ``roles`` array determines the composition of the cluster (how
many MONs, OSDs, etc.) on which this test is designed to run, as well
as how these roles will be distributed over the machines in the
testing cluster. In this case, there is only one element in the
top-level array: therefore, only one machine is allocated to the
test. The nested array declares that this machine shall run a MON with
id ``a`` (that is the ``mon.a`` in the list of roles) and two OSDs
(``osd.0`` and ``osd.1``).
The body of the test is in the ``tasks`` array: each element is
evaluated in order and runs the corresponding python file found in the
``tasks`` subdirectory of the `teuthology repository`_ or
`ceph-qa-suite repository`_. The `install
<https://github.com/ceph/teuthology/blob/master/teuthology/task/install.py>`_
task comes first and installs the Ceph packages on each machine (as
defined by the ``roles`` array). A full description of the ``install``
task is `found in the python file
<https://github.com/ceph/teuthology/blob/master/teuthology/task/install.py>`_
(search for "def task").
The `ceph task
<https://github.com/ceph/ceph-qa-suite/blob/master/tasks/ceph.py#L1232>`_
starts OSDs and MONs as required by the ``roles`` array. In this example,
it will start one MON (``mon.a``) and two OSDs (``osd.0`` and ``osd.1``),
all on the same machine.
Once the Ceph cluster is healthy, the `admin_socket task
<https://github.com/ceph/ceph-qa-suite/blob/master/tasks/admin_socket.py#L18>`_
starts. The parameter of the ``admin_socket`` task (and any other
task) is a structure which is interpreted as documented in the
task. In this example the parameters are a set of commands to be sent
to the admin socket of ``osd.0``. The task verifies that each of them returns
on success (i.e. exit code zero).
This test can be run with::
teuthology-suite --suite rados/singleton/all/admin-socket.yaml
How are tests built from directories?
-------------------------------------
Most tests are not a single file but the concatenation of files
collected from a tree. For instance, the `ceph-disk suite
<https://github.com/ceph/ceph-qa-suite/tree/master/suites/ceph-disk/>`_
is as follows::
directory: ceph-disk/basic
file: %
directory: distros
file: centos_7.0.yaml
file: ubuntu_14.04.yaml
directory: tasks
file: ceph-disk.yaml
This is interpreted as two tests:
* the concatenation of centos_7.0.yaml and ceph-disk.yaml
* the concatenation of ubuntu_14.04.yaml and ceph-disk.yaml
Meaning the task found in ``ceph-disk.yaml`` is intended to run on
both CentOS 7.0 and Ubuntu 14.04.
The special file percent (``%``) is interpreted as a requirement to
generate tests combining all files found in the current directory and
in its direct subdirectories. Without the file percent, the
``ceph-disk`` tree would create three independant tests:
* ceph-disk/basic/distros/centos_7.0.yaml
* ceph-disk/basic/distros/ubuntu_14.04.yaml
* ceph-disk/basic/distros/ceph-disk.yaml
To share parts of the test description between suites, the special
file plus (``+``) can be used to concatenate them. For instance::
directory: rbd/thrash
file: %
directory: clusters
file: +
file: fixed-2.yaml
file: openstack.yaml
directory: workloads
file: rbd_api_tests_copy_on_read.yaml
file: rbd_api_tests.yaml
creates two tests:
* rbd/thrash/{clusters/fixed-2.yaml, clusters/openstack.yaml,
workloads/rbd_api_tests_copy_on_read.yaml}
* rbd/thrash/{clusters/fixed-2.yaml, clusters/openstack.yaml,
workloads/rbd_api_tests.yaml}
Because of the special file plus (``+``), ``fixed-2.yaml`` and
``openstack.yaml`` are concatenated together and treated as a single
file. Without the special file plus, they would have been combined
with the files from the workloads directory to create four tests:
* rbd/thrash/{clusters/openstack.yaml, workloads/rbd_api_tests_copy_on_read.yaml}
* rbd/thrash/{clusters/openstack.yaml, workloads/rbd_api_tests.yaml}
* rbd/thrash/{clusters/fixed-2.yaml, workloads/rbd_api_tests_copy_on_read.yaml}
* rbd/thrash/{clusters/fixed-2.yaml, workloads/rbd_api_tests.yaml}
The ``clusters/fixed-2.yaml`` file is shared among many suites to
define the following ``roles``::
roles:
- [mon.a, mon.c, osd.0, osd.1, osd.2, client.0]
- [mon.b, osd.3, osd.4, osd.5, client.1]
The tests generated from the ``ceph-disk`` directory can be run with::
teuthology-suite --suite ceph-disk
.. _`teuthology repository`: https://github.com/ceph/teuthology/
Test descriptions are unique identifiers
----------------------------------------
Each test is uniquely identified by its description which is made of
the names of all files concatenated together. For instance the test::
ceph-disk/basic/{distros/centos_7.0.yaml tasks/ceph-disk.yaml}
is the concatenation of the files:
* ceph-disk/basic/distros/centos_7.0.yaml
* ceph-disk/basic/tasks/ceph-disk.yaml
Filtering tests by their description
------------------------------------
When a few jobs fail and need to be run again, the ``--filter`` option
will select the tests with a matching description. For instance if the
``rados`` suite fails the `all/peer.yaml <https://github.com/ceph/ceph-qa-suite/blob/master/suites/rados/singleton/all/peer.yaml>`_ test, the following will only run the tests that contain this file::
teuthology-suite --suite rados --filter all/peer.yaml
The ``--filter-out`` option does the opposite (it matches test that do
not contain a given string), and can be combined with the ``--filter``
option.
Both ``--filter`` and ``--filter-out`` take a comma-separated list of strings (which
means comma are implicitly forbidden in filenames found in the
`ceph-qa-suite repository`_). For instance::
teuthology-suite --suite rados --filter all/peer.yaml,all/rest-api.yaml
will run tests that contain either
`all/peer.yaml <https://github.com/ceph/ceph-qa-suite/blob/master/suites/rados/singleton/all/peer.yaml>`_
or
`all/rest-api.yaml <https://github.com/ceph/ceph-qa-suite/blob/master/suites/rados/singleton/all/rest-api.yaml>`_
Each string is looked up anywhere in the test description and has to
be an exact match: they are not regular expressions.
Reducing the number of tests
----------------------------
The rados suite generates thousands of tests out of a few hundred
files. For instance all tests in the `rados/thrash suite <https://github.com/ceph/ceph-qa-suite/tree/master/suites/rados/thrash>`_ run for ``ext4``, ``xfs`` and ``btrfs`` because they are combined (the ``%`` file system)
with the `fs directory <https://github.com/ceph/ceph-qa-suite/tree/master/suites/rados/thrash/fs>`_
All these tests are required before a Ceph release is published but it
is too much when verifying a contribution can be merged without
risking a trivial regression. The ``--subset`` option can be used to
reduce the number of tests that are triggered. For instance::
teuthology-suite --suite rados --subset 0/4000
will run as few tests as possible. The tradeoff is that some tests
will only run on ``ext4`` and not on ``btrfs``, but all files in the
suite will be in at least one test.
The ``--limit`` option only runs the first ``N`` tests in the suite:
this is however rarely useful because there is no way to control which test
will be first.
Inventory
---------
The ``suites`` directory of the `ceph-qa-suite repository`_ contains
all the integration tests, for all the Ceph components.
`ceph-deploy <https://github.com/ceph/ceph-qa-suite/tree/master/suites/ceph-deploy>`_
install a Ceph cluster with ``ceph-deploy`` (`ceph-deploy man page`_)
`ceph-disk <https://github.com/ceph/ceph-qa-suite/tree/master/suites/ceph-disk>`_
verify init scripts (upstart etc.) and udev integration with
``ceph-disk`` (`ceph-disk man page`_), with and without `dmcrypt
<https://gitlab.com/cryptsetup/cryptsetup/wikis/DMCrypt>`_ support.
`dummy <https://github.com/ceph/ceph-qa-suite/tree/master/suites/dummy>`_
get a machine, do nothing and return success (commonly used to
verify the integration testing infrastructure works as expected)
expected
`fs <https://github.com/ceph/ceph-qa-suite/tree/master/suites/fs>`_
test CephFS
`kcephfs <https://github.com/ceph/ceph-qa-suite/tree/master/suites/kcephfs>`_
test the CephFS kernel module
`krbd <https://github.com/ceph/ceph-qa-suite/tree/master/suites/krbd>`_
test the RBD kernel module
`powercycle <https://github.com/ceph/ceph-qa-suite/tree/master/suites/powercycle>`_
verify the Ceph cluster behaves when machines are powered off
and on again
`rados <https://github.com/ceph/ceph-qa-suite/tree/master/suites/rados>`_
run Ceph clusters including OSDs and MONs, under various conditions of
stress
`rbd <https://github.com/ceph/ceph-qa-suite/tree/master/suites/rbd>`_
run RBD tests using actual Ceph clusters, with and without qemu
`rgw <https://github.com/ceph/ceph-qa-suite/tree/master/suites/rgw>`_
run RGW tests using actual Ceph clusters
`smoke <https://github.com/ceph/ceph-qa-suite/tree/master/suites/smoke>`_
run test that exercise the Ceph API with an actual Ceph cluster
`teuthology <https://github.com/ceph/ceph-qa-suite/tree/master/suites/teuthology>`_
verify that teuthology can run integration tests, with and without OpenStack
`upgrade <https://github.com/ceph/ceph-qa-suite/tree/master/suites/upgrade>`_
for various versions of Ceph, verify that upgrades can happen
without disrupting an ongoing workload
.. _`ceph-deploy man page`: ../../man/8/ceph-deploy
.. _`ceph-disk man page`: ../../man/8/ceph-disk
Architecture
============
Ceph is a collection of components built on top of RADOS and provide
services (RBD, RGW, CephFS) and APIs (S3, Swift, POSIX) for the user to
store and retrieve data.
See :doc:`/architecture` for an overview of Ceph architecture. The
following sections treat each of the major architectural components
in more detail, with links to code and tests.
.. FIXME The following are just stubs. These need to be developed into
detailed descriptions of the various high-level components (RADOS, RGW,
etc.) with breakdowns of their respective subcomponents.
.. FIXME Later, in the Testing chapter I would like to take another look
at these components/subcomponents with a focus on how they are tested.
RADOS
-----
RADOS stands for "Reliable, Autonomic Distributed Object Store". In a Ceph
cluster, all data are stored in objects, and RADOS is the component responsible
for that.
RADOS itself can be further broken down into Monitors, Object Storage Daemons
(OSDs), and client APIs (librados). Monitors and OSDs are introduced at
:doc:`/start/intro`. The client library is explained at
:doc:`/rados/api/index`.
RGW
---
RGW stands for RADOS Gateway. Using the embedded HTTP server civetweb_, RGW
provides a REST interface to RADOS objects.
.. _civetweb: https://github.com/civetweb/civetweb
A more thorough introduction to RGW can be found at :doc:`/radosgw/index`.
RBD
---
RBD stands for RADOS Block Device. It enables a Ceph cluster to store disk
images, and includes in-kernel code enabling RBD images to be mounted.
To delve further into RBD, see :doc:`/rbd/rbd`.
CephFS
------
CephFS is a distributed file system that enables a Ceph cluster to be used as a NAS.
File system metadata is managed by Meta Data Server (MDS) daemons. The Ceph
file system is explained in more detail at :doc:`/cephfs/index`.
.. WIP
.. ===
..
.. Building RPM packages
.. ---------------------
..
.. Ceph is regularly built and packaged for a number of major Linux
.. distributions. At the time of this writing, these included CentOS, Debian,
.. Fedora, openSUSE, and Ubuntu.
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