Contributing to Ceph: A Guide for Developers ¶

Author: Loic Dachary
Author: Nathan Cutler
License: Creative Commons Attribution Share Alike 3.0 (CC-BY-SA-3.0)

Note

You may also be interested in the Ceph Internals documentation.

Contents

Contributing to Ceph: A Guide for Developers

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. Another way to learn about what’s happening in Ceph is to check out our youtube channel , where we post Tech Talks, Code walk-throughs and Ceph Developer Monthly recordings.

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.

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:

Scope	Lead	GitHub nick
Ceph	Sage Weil	liewegas
RADOS	Neha Ojha	neha-ojha
RGW	Yehuda Sadeh	yehudasa
RGW	Matt Benjamin	mattbenjamin
RBD	Jason Dillaman	dillaman
CephFS	Patrick Donnelly	batrick
Dashboard	Lenz Grimmer	LenzGr
MON	Joao Luis	jecluis
Build/Ops	Ken Dreyer	ktdreyer

The Ceph-specific acronyms in the table are explained in Architecture.

History ¶

See the History chapter of the Wikipedia article.

Licensing ¶

Ceph is free software.

Unless stated otherwise, the Ceph source code is distributed under the terms of the LGPL2.1 or LGPL3.0. For full details, see the file COPYING in the top-level directory of the source-code tree.

Source code repositories ¶

The source code of Ceph lives on GitHub in a number of repositories below the Ceph “organization”.

To make a meaningful contribution to the project as a developer, a working knowledge of git is essential.

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.

The tracker has a Ceph project with a number of subprojects loosely corresponding to the various architectural components (see Architecture).

Mere registration in the tracker automatically grants permissions sufficient to open new issues and comment on existing ones.

To report a bug or propose a new feature, jump to the Ceph project and click on New issue.

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.

IRC ¶

In addition to mailing lists, the Ceph community also communicates in real time using Internet Relay Chat.

See https://ceph.com/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 file CONTRIBUTING.rst in the top-level directory of the source-code tree. There may be some overlap between this guide and that file.

All newcomers are encouraged to read that file carefully.

Building from source ¶

See instructions at Build Ceph.

Using ccache to speed up local builds ¶

Rebuilds of the ceph source tree can benefit significantly from use of ccache. Many a times while switching branches and such, one might see build failures for certain older branches mostly due to older build artifacts. These rebuilds can significantly benefit the use of ccache. For a full clean source tree, one could do

$ make clean

# note the following will nuke everything in the source tree that
# isn't tracked by git, so make sure to backup any log files /conf options

$ git clean -fdx; git submodule foreach git clean -fdx

ccache is available as a package in most distros. To build ceph with ccache one can:

$ cmake -DWITH_CCACHE=ON ..

ccache can also be used for speeding up all builds in the system. for more details refer to the run modes of the ccache manual. The default settings of ccache can be displayed with ccache -s.

Note

It is recommended to override the max_size, which is the size of cache, defaulting to 10G, to a larger size like 25G or so. Refer to the configuration section of ccache manual.

To further increase the cache hit rate and reduce compile times in a development environment, it is possible to set version information and build timestamps to fixed values, which avoids frequent rebuilds of binaries that contain this information.

This can be achieved by adding the following settings to the ccache configuration file ccache.conf:

sloppiness = time_macros
run_second_cpp = true

Now, set the environment variable SOURCE_DATE_EPOCH to a fixed value (a UNIX timestamp) and set ENABLE_GIT_VERSION to OFF when running cmake:

$ export SOURCE_DATE_EPOCH=946684800
$ cmake -DWITH_CCACHE=ON -DENABLE_GIT_VERSION=OFF ..

Note

Binaries produced with these build options are not suitable for production or debugging purposes, as they do not contain the correct build time and git version information.

Development-mode cluster ¶

See Developer Guide (Quick).

Kubernetes/Rook development cluster ¶

See Hacking on Ceph in Kubernetes with Rook

Backporting ¶

All bugfixes should be merged to the master branch before being backported. To flag a bugfix for backporting, make sure it has a tracker issue associated with it and set the Backport field to a comma-separated list of previous releases (e.g. “hammer,jewel”) that you think need the backport. The rest (including the actual backporting) will be taken care of by the Stable Releases and Backports team.

Guidance for use of cluster log ¶

If your patches emit messages to the Ceph cluster log, please consult this guidance: Use of the cluster log.

What is merged where and when ?¶

Commits are merged into branches according to criteria that change during the lifecycle of a Ceph release. This chapter is the inventory of what can be merged in which branch at a given point in time.

Development releases (i.e. x.0.z)¶

What ?¶

features
bug fixes

Where ?¶

Features are merged to the master branch. Bug fixes should be merged to the corresponding named branch (e.g. “jewel” for 10.0.z, “kraken” for 11.0.z, etc.). However, this is not mandatory - bug fixes can be merged to the master branch as well, since the master branch is periodically merged to the named branch during the development releases phase. In either case, if the bugfix is important it can also be flagged for backport to one or more previous stable releases.

When ?¶

After the stable release candidates of the previous release enters phase 2 (see below). For example: the “jewel” named branch was created when the infernalis release candidates entered phase 2. From this point on, master was no longer associated with infernalis. As soon as the named branch of the next stable release is created, master starts getting periodically merged into it.

Branch merges¶

The branch of the stable release is merged periodically into master.
The master branch is merged periodically into the branch of the stable release.
The master is merged into the branch of the stable release immediately after each development x.0.z release.

Stable release candidates (i.e. x.1.z) phase 1 ¶

What ?¶

bug fixes only

Where ?¶

The branch of the stable release (e.g. “jewel” for 10.0.z, “kraken” for 11.0.z, etc.) or master. Bug fixes should be merged to the named branch corresponding to the stable release candidate (e.g. “jewel” for 10.1.z) or to master. During this phase, all commits to master will be merged to the named branch, and vice versa. In other words, it makes no difference whether a commit is merged to the named branch or to master - it will make it into the next release candidate either way.

When ?¶

After the first stable release candidate is published, i.e. after the x.1.0 tag is set in the release branch.

Branch merges¶

The branch of the stable release is merged periodically into master.
The master branch is merged periodically into the branch of the stable release.
The master is merged into the branch of the stable release immediately after each x.1.z release candidate.

Stable release candidates (i.e. x.1.z) phase 2 ¶

What ?¶

bug fixes only

Where ?¶

The branch of the stable release (e.g. “jewel” for 10.0.z, “kraken” for 11.0.z, etc.). During this phase, all commits to the named branch will be merged into master. Cherry-picking to the named branch during release candidate phase 2 is done manually since the official backporting process only begins when the release is pronounced “stable”.

When ?¶

After Sage Weil decides it is time for phase 2 to happen.

Branch merges¶

The branch of the stable release is merged periodically into master.

Stable releases (i.e. x.2.z)¶

What ?¶

bug fixes
features are sometime accepted
commits should be cherry-picked from master when possible
commits that are not cherry-picked from master must be about a bug unique to the stable release
see also the backport HOWTO

Where ?¶

The branch of the stable release (hammer for 0.94.x, infernalis for 9.2.x, etc.)

When ?¶

After the stable release is published, i.e. after the “vx.2.0” tag is set in the release branch.

Branch merges¶

Never

Issue tracker ¶

See Redmine issue tracker for a brief introduction to the Ceph Issue Tracker.

Ceph developers use the issue tracker to

1. keep track of issues - bugs, fix requests, feature requests, backport requests, etc.

2. communicate with other developers and keep them informed as work on the issues progresses.

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 Assignee field (to yourself) and changing the 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.

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:

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. Watch the Getting Started with Ceph Development video for a practical summary of the same.

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 and keep them informed as you make progress toward resolution. To this end, then, 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 with a short message like “I am working on this issue”.

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

forking the upstream repo on GitHub, and
cloning your fork to make a local working copy

See the the GitHub documentation 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:

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

While it is possible to clone the upstream repo directly, in this case 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.

Local environment ¶

In the local environment created in the previous step, you 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, you will need to sync your fork periodically. To do this, first add the upstream repo as a “remote” and fetch it:

$ 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 certain git commands.

For example, your local master branch can be reset to the upstream Ceph master branch by doing:

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

Finally, the master branch of your fork can then be synced to upstream master by:

$ git push -u origin master

Bugfix branch ¶

Next, create a branch for the bugfix:

$ 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.

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.

Possibly, your fix is very simple and requires only minimal testing. More likely, it 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.

A detailed discussion of the tools available for validating your bugfixes, see the Testing chapters.

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 using the --signoff option:

$ git commit -as

and push the changes to your fork:

$ 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. They will review it and may do additional testing on it.

In short, this is the point where you “go public” with your modifications. Psychologically, you should be prepared to receive suggestions and constructive criticism. Don’t worry! In our experience, the Ceph project is a friendly place!

If you are uncertain how to use pull requests, you may read this GitHub pull request tutorial.

For some ideas on what constitutes a “good” pull request, see the Git Commit Good Practice article at the OpenStack Project Wiki.

Once your pull request (PR) is opened, update the Issue tracker by adding a comment to the bug pointing the other developers to your PR. The update can be as simple as:

*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) 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 Testing chapters for details.

Notes on PR make check test¶

The GitHub make check test is driven by a Jenkins instance.

Jenkins merges the PR branch into the latest version of the base branch before starting the build, so you don’t have to rebase the PR to pick up any fixes.

You can trigger the 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, it’s good to write the request as “Jenkins, test this please”.

The make check log is the place to go if there is a failure and you’re not sure what caused it. To reach it, first click on “details” (next to the make check test in the PR) to get into the Jenkins web GUI, and then click on “Console Output” (on the left).

Jenkins is set up to grep the log for strings known to have been associated with make check failures in the past. However, there is no guarantee that the strings are associated with any given make check failure. You have to dig into the log to be sure.

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 sub-directory and are run via the teuthology framework.

The Ceph community has access to the Sepia lab where 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.

To request access to the Sepia lab, start here.

Integration testing is discussed in more detail in the integration 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.

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 for a good introduction to rebasing. When you are done with your modifications, you will need to force push your branch with:

$ git push --force origin fix_1

Merge ¶

The bugfixing process culminates when one of the project leads decides to merge your PR.

When this happens, it is a signal for you (or the lead who merged the PR) to change the 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 Backporting chapter for details).

Testing - unit tests ¶

Ceph has two types of tests: unit tests (also called make check tests) and integration tests. Strictly speaking, the make check tests are not “unit tests”, but rather tests that can be run easily on a single build machine after compiling Ceph from source, whereas integration tests require packages and multi-machine clusters to run.

What does “make check” mean?¶

After compiling Ceph, the code can be run through a battery of tests covering various aspects of Ceph. For historical reasons, this battery of tests is often referred to as make check even though the actual command used to run the tests is now ctest. For inclusion in this battery of tests, 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

For simplicity, we will refer to this class of tests as “make check tests” or “unit tests”, to distinguish them from the more complex “integration tests” that are run via the teuthology framework.

While it is possible to run ctest directly, it can be tricky to correctly set up your environment. Fortunately, a script is provided to make it easier run the unit tests on your code. It can be run from the top-level directory of the Ceph source tree by doing:

$ ./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 on x86_64 (other architectures may have different constraints). Depending on your hardware, it can take from 20 minutes to three hours to complete, but it’s worth the wait.

How unit tests are declared ¶

Unit tests are declared in the CMakeLists.txt files (multiple files under ./src) using the add_ceph_test or add_ceph_unittest CMake functions, which are themselves defined in ./cmake/modules/AddCephTest.cmake. Some unit tests are scripts, while others are binaries that are compiled during the build process. The add_ceph_test function is used to declare unit test scripts, while add_ceph_unittest is used for unit test binaries.

Unit testing of CLI tools ¶

Some of the CLI tools are tested using special files ending with the extension .t and stored under ./src/test/cli. These tests are run using a tool called cram via a shell script ./src/test/run-cli-tests. cram tests that are not suitable for make check may also be run by teuthology using the cram task.

Tox based testing of python modules¶

Most python modules can be found under ./src/pybind/.

Many modules use tox to run their unit tests. tox itself is a generic virtualenv management and test command line tool.

To find out quickly if tox can be run you can either just try to run tox or find out if a tox.ini exists.

Currently the following modules use tox:

Ansible (./src/pybind/mgr/ansible)
Insights (./src/pybind/mgr/insights)
Orchestrator cli (./src/pybind/mgr/orchestrator_cli)
Manager core (./src/pybind/mgr)
Dashboard (./src/pybind/mgr/dashboard)
Python common (./src/python-common/tox.ini)

Most tox configuration support multiple environments and tasks. You can see which environments and tasks are supported by looking into the tox.ini file to see what envlist is assigned. To run tox, just execute tox in the directory where tox.ini lies. Without any specified environments -e $env1,$env2, all environments will be run. Jenkins will run tox by executing run_tox.sh which lies under ./src/script.

Here some examples from ceph dashboard on how to specify different environments and run options:

## Run Python 2+3 tests+lint commands:
$ tox -e py27,py3,lint,check

## Run Python 3 tests+lint commands:
$ tox -e py3,lint,check

## To run it like Jenkins would do
$ ../../../script/run_tox.sh --tox-env py27,py3,lint,check
$ ../../../script/run_tox.sh --tox-env py3,lint,check

Manager core unit tests¶

Currently only doctests inside mgr_util.py are run.

To add more files that should be tested inside the core of the manager add them at the end of the line that includes mgr_util.py inside tox.ini.

Unit test caveats ¶

Unlike the various Ceph daemons and ceph-fuse, the unit tests are linked against the default memory allocator (glibc) unless explicitly linked against something else. This enables tools like valgrind to be used in the tests.

Testing - integration tests ¶

Ceph has two types of tests: make check tests and integration tests. 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 organized into “suites”, which are defined in the ceph/qa sub-directory and run with the teuthology-suite command.

The teuthology-suite command is part of the teuthology framework. In the sections that follow we attempt to provide a detailed introduction to that framework from the perspective of a beginning Ceph developer.

Teuthology consumes packages ¶

It may take some time to understand the significance of this fact, but it is very significant. It means that automated tests can be conducted on multiple platforms using the same packages (RPM, DEB) that can be installed on any machine running those platforms.

Teuthology has a list of platforms that it supports (as of December 2017 the list consisted of “CentOS 7.2” and “Ubuntu 16.04”). It expects to be provided pre-built Ceph packages for these platforms. Teuthology deploys these platforms on machines (bare-metal or cloud-provisioned), installs the packages on them, and deploys Ceph clusters on them - all as called for by the test.

The nightlies ¶

A number of integration tests are run on a regular basis in the Sepia lab against the official Ceph repositories (on the master development branch and the stable branches). Traditionally, these tests are called “the nightlies” because the Ceph core developers used to live and work in the same time zone and from their perspective the tests were run overnight.

The results of the nightlies are published at http://pulpito.ceph.com/. The developer nick shows in the test results URL and in the first column of the Pulpito dashboard. The results are also reported on the ceph-qa mailing list for analysis.

Testing priority ¶

The teuthology-suite command includes an almost mandatory option -p <N> which specifies the priority of the jobs submitted to the queue. The lower the value of N, the higher the priority. The option is almost mandatory because the default is 1000 which matches the priority of the nightlies. Nightlies are often half-finished and cancelled due to the volume of testing done so your jobs may never finish. Therefore, it is common to select a priority less than 1000.

Any priority may be selected when submitting jobs. But, in order to be sensitive to the workings of other developers that also need to do testing, the following recommendations should be followed:

Priority < 10: Use this if the sky is falling and some group of tests must be run ASAP.
10 <= Priority < 50: Use this if your tests are urgent and blocking other important development.
50 <= Priority < 75: Use this if you are testing a particular feature/fix and running fewer than about 25 jobs.
75 <= Priority < 100: Tech Leads will regularly schedule integration tests with this priority to verify pull requests against master.
100 <= Priority < 150: This priority is to be used for release QA.
150 <= Priority < 200: Use this priority for 100 jobs or fewer of a particular feature/fix that you’d like results on in a day or so.
200 <= Priority < 1000: Use this priority for large test runs that can be done over the course of a week.

Suites inventory ¶

The suites directory of the ceph/qa sub-directory contains all the integration tests, for all the Ceph components.

ceph-deploy: install a Ceph cluster with ceph-deploy (ceph-deploy man page)
dummy: get a machine, do nothing and return success (commonly used to verify the integration testing infrastructure works as expected)
fs: test CephFS
kcephfs: test the CephFS kernel module
krbd: test the RBD kernel module
powercycle: verify the Ceph cluster behaves when machines are powered off and on again
rados: run Ceph clusters including OSDs and MONs, under various conditions of stress
rbd: run RBD tests using actual Ceph clusters, with and without qemu
rgw: run RGW tests using actual Ceph clusters
smoke: run tests that exercise the Ceph API with an actual Ceph cluster
teuthology: verify that teuthology can run integration tests, with and without OpenStack
upgrade: for various versions of Ceph, verify that upgrades can happen without disrupting an ongoing workload

teuthology-describe-tests ¶

In February 2016, a new feature called teuthology-describe-tests was added to the teuthology framework to facilitate documentation and better understanding of integration tests (feature announcement).

The upshot is that tests can be documented by embedding meta: annotations in the yaml files used to define the tests. The results can be seen in the ceph-qa-suite wiki.

Since this is a new feature, many yaml files have yet to be annotated. Developers are encouraged to improve the documentation, in terms of both coverage and quality.

How integration tests are run ¶

Given that - as a new Ceph developer - you will typically not have access to the Sepia lab, you may rightly ask how you can run the integration tests in your own environment.

One option is to set up a teuthology cluster on bare metal. Though this is a non-trivial task, it is possible. Here are some notes to get you started if you decide to go this route.

If you have access to an OpenStack tenant, you have another option: the teuthology framework has an OpenStack backend, which is documented here. This OpenStack backend can build packages from a given git commit or branch, provision VMs, install the packages and run integration tests on those VMs. This process is controlled using a tool called ceph-workbench ceph-qa-suite. This tool also automates publishing of test results at http://teuthology-logs.public.ceph.com.

Running integration tests on your code contributions and publishing the results allows reviewers to verify that changes to the code base do not cause regressions, or to analyze test failures when they do occur.

Every teuthology cluster, whether bare-metal or cloud-provisioned, has a so-called “teuthology machine” from which tests suites are triggered using the teuthology-suite command.

A detailed and up-to-date description of each teuthology-suite option is available by running the following command on the teuthology machine:

$ teuthology-suite --help

How integration tests are defined ¶

Integration tests are defined by yaml files found in the suites subdirectory of the ceph/qa sub-directory and implemented by python code found in the tasks subdirectory. Some tests (“standalone tests”) are defined in a single yaml file, while other tests are defined by a directory tree containing yaml files that are combined, at runtime, into a larger yaml file.

Reading a standalone test ¶

Let us first examine a standalone test, or “singleton”.

Here is a commented example using the integration test 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, causing the corresponding python file found in the tasks subdirectory of the teuthology repository or ceph/qa sub-directory to be run. “Running” in this case means calling the task() function defined in that file.

In this case, the install task comes first. It 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 (search for “def task”).

The ceph task, which is documented here (again, search for “def task”), starts OSDs and MONs (and possibly MDSs as well) 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. Control moves to the next task when the Ceph cluster reaches HEALTH_OK state.

The next task is admin_socket (source code). 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 parameter is 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 fs/ext4.yaml

Test descriptions ¶

Each test has a “test description”, which is similar to a directory path, but not the same. In the case of a standalone test, like the one in Reading a standalone test, the test description is identical to the relative path (starting from the suites/ directory of the ceph/qa sub-directory) of the yaml file defining the test.

Much more commonly, tests are defined not by a single yaml file, but by a directory tree of yaml files. At runtime, the tree is walked and all yaml files (facets) are combined into larger yaml “programs” that define the tests. A full listing of the yaml defining the test is included at the beginning of every test log.

In these cases, the description of each test consists of the subdirectory under suites/ containing the yaml facets, followed by an expression in curly braces ({}) consisting of a list of yaml facets in order of concatenation. For instance the test description:

ceph-deploy/basic/{distros/centos_7.0.yaml tasks/ceph-deploy.yaml}

signifies the concatenation of two files:

ceph-deploy/basic/distros/centos_7.0.yaml
ceph-deploy/basic/tasks/ceph-deploy.yaml

How tests are built from directories ¶

As noted in the previous section, most tests are not defined in a single yaml file, but rather as a combination of files collected from a directory tree within the suites/ subdirectory of the ceph/qa sub-directory.

The set of all tests defined by a given subdirectory of suites/ is called an “integration test suite”, or a “teuthology suite”.

Combination of yaml facets is controlled by special files (% and +) that are placed within the directory tree and can be thought of as operators. The % file is the “convolution” operator and + signifies concatenation.

Convolution operator¶

The convolution operator, implemented as an empty file called %, tells teuthology to construct a test matrix from yaml facets found in subdirectories below the directory containing the operator.

For example, the ceph-deploy suite is defined by the suites/ceph-deploy/ tree, which consists of the files and subdirectories in the following structure:

directory: ceph-deploy/basic
    file: %
    directory: distros
       file: centos_7.0.yaml
       file: ubuntu_16.04.yaml
    directory: tasks
       file: ceph-deploy.yaml

This is interpreted as a 2x1 matrix consisting of two tests:

ceph-deploy/basic/{distros/centos_7.0.yaml tasks/ceph-deploy.yaml}
ceph-deploy/basic/{distros/ubuntu_16.04.yaml tasks/ceph-deploy.yaml}

i.e. the concatenation of centos_7.0.yaml and ceph-deploy.yaml and the concatenation of ubuntu_16.04.yaml and ceph-deploy.yaml, respectively. In human terms, this means that the task found in ceph-deploy.yaml is intended to run on both CentOS 7.0 and Ubuntu 16.04.

Without the file percent, the ceph-deploy tree would be interpreted as three standalone tests:

ceph-deploy/basic/distros/centos_7.0.yaml
ceph-deploy/basic/distros/ubuntu_16.04.yaml
ceph-deploy/basic/tasks/ceph-deploy.yaml

(which would of course be wrong in this case).

Referring to the ceph/qa sub-directory, you will notice that the centos_7.0.yaml and ubuntu_16.04.yaml files in the suites/ceph-deploy/basic/distros/ directory are implemented as symlinks. By using symlinks instead of copying, a single file can appear in multiple suites. This eases the maintenance of the test framework as a whole.

All the tests generated from the suites/ceph-deploy/ directory tree (also known as the “ceph-deploy suite”) can be run with:

$ teuthology-suite --suite ceph-deploy

An individual test from the ceph-deploy suite can be run by adding the --filter option:

$ teuthology-suite \
    --suite ceph-deploy/basic \
    --filter 'ceph-deploy/basic/{distros/ubuntu_16.04.yaml tasks/ceph-deploy.yaml}'

Note

To run a standalone test like the one in Reading a standalone test, --suite alone is sufficient. If you want to run a single test from a suite that is defined as a directory tree, --suite must be combined with --filter. This is because the --suite option understands POSIX relative paths only.

Concatenation operator¶

For even greater flexibility in sharing yaml files between suites, the special file plus (+) can be used to concatenate files within a directory. For instance, consider the suites/rbd/thrash tree:

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

This 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 the clusters/ subdirectory contains the special file plus (+), all the other files in that subdirectory (fixed-2.yaml and openstack.yaml in this case) are concatenated together and treated as a single file. Without the special file plus, they would have been convolved with the files from the workloads directory to create a 2x2 matrix:

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 rbd/thrash suite as defined above, consisting of two tests, can be run with:

$ teuthology-suite --suite rbd/thrash

A single test from the rbd/thrash suite can be run by adding the --filter option:

$ teuthology-suite \
    --suite rbd/thrash \
    --filter 'rbd/thrash/{clusters/fixed-2.yaml clusters/openstack.yaml workloads/rbd_api_tests_copy_on_read.yaml}'

Filtering tests by their description ¶

When a few jobs fail and need to be run again, the --filter option can be used to select tests with a matching description. For instance, if the rados suite fails the 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 tests 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 the comma character is implicitly forbidden in filenames found in the ceph/qa sub-directory). For instance:

teuthology-suite --suite rados --filter all/peer.yaml,all/rest-api.yaml

will run tests that contain either all/peer.yaml or 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 tens or even hundreds of thousands of tests out of a few hundred files. This happens because teuthology constructs test matrices from subdirectories wherever it encounters a file named %. For instance, all tests in the rados/basic suite run with different messenger types: simple, async and random, because they are combined (via the special file %) with the msgr directory

All integration tests are required to be run before a Ceph release is published. When merely verifying whether a contribution can be merged without risking a trivial regression, it is enough to run a subset. 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 in this case is that not all combinations of test variations will together, but no matter how small a ratio is provided in the --subset, teuthology will still ensure that all files in the suite are in at least one test. Understanding the actual logic that drives this requires reading the teuthology source code.

The --limit option only runs the first N tests in the suite: this is rarely useful, however, because there is no way to control which test will be first.

Testing in the cloud ¶

In this chapter, we will explain in detail how use an OpenStack tenant as an environment for Ceph integration testing.

Assumptions and caveat ¶

We assume that:

you are the only person using the tenant
you have the credentials
the tenant supports the nova and cinder APIs

Caveat: be aware that, as of this writing (July 2016), testing in OpenStack clouds is a new feature. Things may not work as advertised. If you run into trouble, ask for help on IRC or the Mailing list, or open a bug report at the ceph-workbench bug tracker.

Prepare tenant ¶

If you have not tried to use ceph-workbench with this tenant before, proceed to the next step.

To start with a clean slate, login to your tenant via the Horizon dashboard and:

terminate the teuthology and packages-repository instances, if any
delete the teuthology and teuthology-worker security groups, if any
delete the teuthology and teuthology-myself key pairs, if any

Also do the above if you ever get key-related errors (“invalid key”, etc.) when trying to schedule suites.

Getting ceph-workbench ¶

Since testing in the cloud is done using the ceph-workbench ceph-qa-suite tool, you will need to install that first. It is designed to be installed via Docker, so if you don’t have Docker running on your development machine, take care of that first. You can follow the official tutorial to install if you have not installed yet.

Once Docker is up and running, install ceph-workbench by following the Installation instructions in the ceph-workbench documentation.

Linking ceph-workbench with your OpenStack tenant ¶

Before you can trigger your first teuthology suite, you will need to link ceph-workbench with your OpenStack account.

First, download a openrc.sh file by clicking on the “Download OpenStack RC File” button, which can be found in the “API Access” tab of the “Access & Security” dialog of the OpenStack Horizon dashboard.

Second, create a ~/.ceph-workbench directory, set its permissions to 700, and move the openrc.sh file into it. Make sure that the filename is exactly ~/.ceph-workbench/openrc.sh.

Third, edit the file so it does not ask for your OpenStack password interactively. Comment out the relevant lines and replace them with something like:

export OS_PASSWORD="aiVeth0aejee3eep8rogho3eep7Pha6ek"

When ceph-workbench ceph-qa-suite connects to your OpenStack tenant for the first time, it will generate two keypairs: teuthology-myself and teuthology.

Run the dummy suite ¶

You are now ready to take your OpenStack teuthology setup for a test drive:

$ ceph-workbench ceph-qa-suite --suite dummy

Be forewarned that the first run of ceph-workbench ceph-qa-suite on a pristine tenant will take a long time to complete because it downloads a VM image and during this time the command may not produce any output.

The images are cached in OpenStack, so they are only downloaded once. Subsequent runs of the same command will complete faster.

Although dummy suite does not run any tests, in all other respects it behaves just like a teuthology suite and produces some of the same artifacts.

The last bit of output should look something like this:

pulpito web interface: http://149.202.168.201:8081/
ssh access           : ssh -i /home/smithfarm/.ceph-workbench/teuthology-myself.pem ubuntu@149.202.168.201 # logs in /usr/share/nginx/html

What this means is that ceph-workbench ceph-qa-suite triggered the test suite run. It does not mean that the suite run has completed. To monitor progress of the run, check the Pulpito web interface URL periodically, or if you are impatient, ssh to the teuthology machine using the ssh command shown and do:

$ tail -f /var/log/teuthology.*

The /usr/share/nginx/html directory contains the complete logs of the test suite. If we had provided the --upload option to the ceph-workbench ceph-qa-suite command, these logs would have been uploaded to http://teuthology-logs.public.ceph.com.

Run a standalone test ¶

The standalone test explained in Reading a standalone test can be run with the following command:

$ ceph-workbench ceph-qa-suite --suite rados/singleton/all/admin-socket.yaml

This will run the suite shown on the current master branch of ceph/ceph.git. You can specify a different branch with the --ceph option, and even a different git repo with the --ceph-git-url option. (Run ceph-workbench ceph-qa-suite --help for an up-to-date list of available options.)

The first run of a suite will also take a long time, because ceph packages have to be built, first. Again, the packages so built are cached and ceph-workbench ceph-qa-suite will not build identical packages a second time.

Interrupt a running suite ¶

Teuthology suites take time to run. From time to time one may wish to interrupt a running suite. One obvious way to do this is:

ceph-workbench ceph-qa-suite --teardown

This destroys all VMs created by ceph-workbench ceph-qa-suite and returns the OpenStack tenant to a “clean slate”.

Sometimes you may wish to interrupt the running suite, but keep the logs, the teuthology VM, the packages-repository VM, etc. To do this, you can ssh to the teuthology VM (using the ssh access command reported when you triggered the suite – see Run the dummy suite) and, once there:

sudo /etc/init.d/teuthology restart

This will keep the teuthology machine, the logs and the packages-repository instance but nuke everything else.

Upload logs to archive server ¶

Since the teuthology instance in OpenStack is only semi-permanent, with limited space for storing logs, teuthology-openstack provides an --upload option which, if included in the ceph-workbench ceph-qa-suite command, will cause logs from all failed jobs to be uploaded to the log archive server maintained by the Ceph project. The logs will appear at the URL:

http://teuthology-logs.public.ceph.com/$RUN

where $RUN is the name of the run. It will be a string like this:

ubuntu-2016-07-23_16:08:12-rados-hammer-backports---basic-openstack

Even if you don’t providing the --upload option, however, all the logs can still be found on the teuthology machine in the directory /usr/share/nginx/html.

Provision VMs ad hoc ¶

From the teuthology VM, it is possible to provision machines on an “ad hoc” basis, to use however you like. The magic incantation is:

teuthology-lock --lock-many $NUMBER_OF_MACHINES \
    --os-type $OPERATING_SYSTEM \
    --os-version $OS_VERSION \
    --machine-type openstack \
    --owner $EMAIL_ADDRESS

The command must be issued from the ~/teuthology directory. The possible values for OPERATING_SYSTEM AND OS_VERSION can be found by examining the contents of the directory teuthology/openstack/. For example:

teuthology-lock --lock-many 1 --os-type ubuntu --os-version 16.04 \
    --machine-type openstack --owner foo@example.com

When you are finished with the machine, find it in the list of machines:

openstack server list

to determine the name or ID, and then terminate it with:

openstack server delete $NAME_OR_ID

Deploy a cluster for manual testing ¶

The teuthology framework and ceph-workbench ceph-qa-suite are versatile tools that automatically provision Ceph clusters in the cloud and run various tests on them in an automated fashion. This enables a single engineer, in a matter of hours, to perform thousands of tests that would keep dozens of human testers occupied for days or weeks if conducted manually.

However, there are times when the automated tests do not cover a particular scenario and manual testing is desired. It turns out that it is simple to adapt a test to stop and wait after the Ceph installation phase, and the engineer can then ssh into the running cluster. Simply add the following snippet in the desired place within the test YAML and schedule a run with the test:

tasks:
- exec:
    client.0:
      - sleep 1000000000 # forever

(Make sure you have a client.0 defined in your roles stanza or adapt accordingly.)

The same effect can be achieved using the interactive task:

tasks:
- interactive

By following the test log, you can determine when the test cluster has entered the “sleep forever” condition. At that point, you can ssh to the teuthology machine and from there to one of the target VMs (OpenStack) or teuthology worker machines machine (Sepia) where the test cluster is running.

The VMs (or “instances” in OpenStack terminology) created by ceph-workbench ceph-qa-suite are named as follows:

teuthology - the teuthology machine

packages-repository - VM where packages are stored

ceph-* - VM where packages are built

target* - machines where tests are run

The VMs named target* are used by tests. If you are monitoring the teuthology log for a given test, the hostnames of these target machines can be found out by searching for the string Locked targets:

2016-03-20T11:39:06.166 INFO:teuthology.task.internal:Locked targets:
  target149202171058.teuthology: null
  target149202171059.teuthology: null

The IP addresses of the target machines can be found by running openstack server list on the teuthology machine, but the target VM hostnames (e.g. target149202171058.teuthology) are resolvable within the teuthology cluster.

Running tests from qa/ locally ¶

How to run s3-tests locally ¶

RGW code can be tested by building Ceph locally from source, starting a vstart cluster, and running the “s3-tests” suite against it.

The following instructions should work on jewel and above.

Step 1 - build Ceph¶

Refer to Build Ceph.

You can do step 2 separately while it is building.

Step 2 - vstart¶

When the build completes, and still in the top-level directory of the git clone where you built Ceph, do the following, for cmake builds:

cd build/
RGW=1 ../src/vstart.sh -n

This will produce a lot of output as the vstart cluster is started up. At the end you should see a message like:

started.  stop.sh to stop.  see out/* (e.g. 'tail -f out/????') for debug output.

This means the cluster is running.

Step 3 - run s3-tests¶

To run the s3tests suite do the following:

$ ../qa/workunits/rgw/run-s3tests.sh

Running test using vstart_runner.py ¶

CephFS and Ceph Manager code is be tested using vstart_runner.py.

Running your first test¶

The Python tests in Ceph repository can be executed on your local machine using vstart_runner.py. To do that, you’d need teuthology installed:

$ git clone https://github.com/ceph/teuthology
$ cd teuthology/
$ virtualenv -p python2.7 ./venv
$ source venv/bin/activate
$ pip install --upgrade pip
$ pip install -r requirements.txt
$ python setup.py develop
$ deactivate

Note

The pip command above is pip2, not pip3; run pip --version.

The above steps installs teuthology in a virtual environment. Before running a test locally, build Ceph successfully from the source (refer Build Ceph) and do:

$ cd build
$ ../src/vstart.sh -n -d -l
$ source ~/path/to/teuthology/venv/bin/activate

To run a specific test, say test_reconnect_timeout from TestClientRecovery in qa/tasks/cephfs/test_client_recovery, you can do:

$ python2 ../qa/tasks/vstart_runner.py tasks.cephfs.test_client_recovery.TestClientRecovery.test_reconnect_timeout

The above command runs vstart_runner.py and passes the test to be executed as an argument to vstart_runner.py. In a similar way, you can also run the group of tests in the following manner:

$ # run all tests in class TestClientRecovery
$ python2 ../qa/tasks/vstart_runner.py tasks.cephfs.test_client_recovery.TestClientRecovery
$ # run  all tests in test_client_recovery.py
$ python2 ../qa/tasks/vstart_runner.py tasks.cephfs.test_client_recovery

Based on the argument passed, vstart_runner.py collects tests and executes as it would execute a single test.

Note

vstart_runner.py as well as most tests in qa/ are only compatible with python2. Therefore, use python2 to run the tests locally.

vstart_runner.py can take the following options -

--clear-old-log: deletes old log file before running the test
--create: create Ceph cluster before running a test
--create-cluster-only: creates the cluster and quits; tests can be issued later
--interactive: drops a Python shell when a test fails
--log-ps-output: logs ps output; might be useful while debugging
--teardown: tears Ceph cluster down after test(s) has finished runnng
--kclient: use the kernel cephfs client instead of FUSE

Note

If using the FUSE client, ensure that the fuse package is installed and enabled on the system and that user_allow_other is added to /etc/fuse.conf.

Note

If using the kernel client, the user must have the ability to run commands with passwordless sudo access. A failure on the kernel client may crash the host, so it’s recommended to use this functionality within a virtual machine.

Internal working of vstart_runner.py -¶

vstart_runner.py primarily does three things -

collects and runs the tests
vstart_runner.py setups/teardowns the cluster and collects and runs the test. This is implemented using methods scan_tests(), load_tests() and exec_test(). This is where all the options that vstart_runner.py takes are implemented along with other features like logging and copying the traceback to the bottom of the log.
provides an interface for issuing and testing shell commands
The tests are written assuming that the cluster exists on remote machines. vstart_runner.py provides an interface to run the same tests with the cluster that exists within the local machine. This is done using the class LocalRemote. Class LocalRemoteProcess can manage the process that executes the commands from LocalRemote, class LocalDaemon provides an interface to handle Ceph daemons and class LocalFuseMount can create and handle FUSE mounts.
provides an interface to operate Ceph cluster
LocalCephManager provides methods to run Ceph cluster commands with and without admin socket and LocalCephCluster provides methods to set or clear ceph.conf.