Devstack Gate

Devstack-gate is a collection of scripts used by the OpenStack CI team to test every change to core OpenStack projects by deploying OpenStack via devstack on a cloud server.

What It Is

All changes to core OpenStack projects are "gated" on a set of tests so that it will not be merged into the main repository unless it passes all of the configured tests. Most projects require unit tests in python2.6 and python2.7, and pep8. Those tests are all run only on the project in question. The devstack gate test, however, is an integration test and ensures that a proposed change still enables several of the projects to work together. Currently, any proposed change to the following projects must pass the devstack gate test:

nova
glance
keystone
heat
horizon
neutron
ceilometer
python-novaclient
python-heatclient
python-keystoneclient
python-neutronclient
devstack
devstack-gate

Obviously we test nova, glance, keystone, horizon, neutron and their clients because they all work closely together to form an OpenStack system. Changes to devstack itself are also required to pass this test so that we can be assured that devstack is always able to produce a system capable of testing the next change to nova. The devstack gate scripts themselves are included for the same reason.

How It Works

The devstack test starts with an essentially bare virtual machine, installs devstack on it, and runs some simple tests of the resulting OpenStack installation. In order to ensure that each test run is independent, the virtual machine is discarded at the end of the run, and a new machine is used for the next run. In order to keep the actual test run as short and reliable as possible, the virtual machines are prepared ahead of time and kept in a pool ready for immediate use. The process of preparing the machines ahead of time reduces network traffic and external dependencies during the run.

The mandate of the devstack-gate project is to prepare those virtual machines, ensure that enough of them are always ready to run, bootstrap the test process itself, and clean up when it's done. The devstack gate scripts should be able to be configured to provision machines based on several images (eg, natty, oneiric, precise), and each of those from several providers. Using multiple providers makes the entire system somewhat highly-available since only one provider needs to function in order for us to run tests. Supporting multiple images will help with the transition of testing from oneiric to precise, and will allow us to continue running tests for stable branches on older operating systems.

To accomplish all of that, the devstack-gate repository holds several scripts that are run by Jenkins.

Once per day, for every image type (and provider) configured, the devstack-vm-update-image.sh script checks out the latest copy of devstack, and then runs the devstack-vm-update-image.py script. It boots a new VM from the provider's base image, installs some basic packages (build-essential, python-dev, etc) including java so that the machine can run the Jenkins slave agent, runs puppet to set up the basic system configuration for Jenkins slaves in the openstack-infra project, and then caches all of the debian and pip packages and test images specified in the devstack repository, and clones the OpenStack project repositories. It then takes a snapshot image of that machine to use when booting the actual test machines. When they boot, they will already be configured and have all, or nearly all, of the network accessible data they need. Then the template machine is deleted. The Jenkins job that does this is devstack-update-vm-image. It is a matrix job that runs for all configured providers, and if any of them fail, it's not a problem since the previously generated image will still be available.

Even though launching a machine from a saved image is usually fast, depending on the provider's load it can sometimes take a while, and it's possible that the resulting machine may end up in an error state, or have some malfunction (such as a misconfigured network). Due to these uncertainties, we provision the test machines ahead of time and keep them in a pool. Every ten minutes, a job runs to spin up new VMs for testing and add them to the pool, using the devstack-vm-launch.py script. Each image type has a parameter specifying how many machine of that type should be kept ready, and each provider has a parameter specifying the maximum number of machines allowed to be running on that provider. Within those bounds, the job attempts to keep the requested number of machines up and ready to go at all times. When a machine is spun up and found to be accessible, it as added to Jenkins as a slave machine with one executor and a tag like "devstack-foo" (eg, "devstack-oneiric" for oneiric image types). The Jenkins job that does this is devstack-launch-vms. It is also a matrix job that runs for all configured providers.

Process invoked once a proposed change is approved by the core reviewers is as follows:

• Jenkins triggers the devstack gate test itself.
• This job runs on one of the previously configured "devstack-foo" nodes and invokes the devstack-vm-gate-wrap.sh script which checks out code from all of the involved repositories, and merges the proposed change.
• If the pre_test_hook function is defined it is executed.
• The wrap script defines a gate_hook function if one is not provided. By default it uses the devstack-vm-gate.sh script which installs a devstack configuration file, and invokes devstack.
• If the post_test_hook function is defined it is executed.
• Once devstack is finished, it runs exercise.sh which performs some basic integration testing.
• After everything is done, the script copies all of the log files back to the Jenkins workspace and archives them along with the console output of the run. The Jenkins job that does this is the somewhat awkwardly named gate-integration-tests-devstack-vm.

To prevent a node from being used for a second run, there is a job named devstack-update-inprogress which is triggered as a parameterized build step from gate-interation-tests-devstack-vm. It is passed the name of the node on which the gate job is running, and it disabled that node in Jenkins by invoking devstack-vm-inprogress.py. The currently running job will continue, but no new jobs will be scheduled for that node.

Similarly, when the node is finished, a parameterized job named devstack-update-complete (which runs devstack-vm-delete.py) is triggered as a post-build action. It removes the node from Jenkins and marks the VM for later deletion.

In the future, we hope to be able to install developer SSH keys on VMs from failed test runs, but for the moment the policies of the providers who are donating test resources do not permit that. However, most problems can be diagnosed from the log data that are copied back to Jenkins. There is a script that cleans up old images and VMs that runs frequently. It's devstack-vm-reap.py and is invoked by the Jenkins job devstack-reap-vms.

How to Debug a Devstack Gate Failure

When Jenkins runs gate tests for a change, it leaves comments on the change in Gerrit with links to the test run. If a change fails the devstack gate test, you can follow it to the test run in Jenkins to find out what went wrong. The first thing you should do is look at the console output (click on the link labeled "[raw]" to the right of "Console Output" on the left side of the screen). You'll want to look at the raw output because Jenkins will truncate the large amount of output that devstack produces. Skip to the end to find out why the test failed (keep in mind that the last few commands it runs deal with copying log files and deleting the test VM -- errors that show up there won't affect the test results). You'll see a summary of the devstack exercise.sh tests near the bottom. Scroll up to look for errors related to failed tests.

You might need some information about the specific run of the test. At the top of the console output, you can see all the git commands used to set up the repositories, and they will output the (short) sha1 and commit subjects of the head of each repository.

It's possible that a failure could be a false negative related to a specific provider, especially if there is a pattern of failures from tests that run on nodes from that provider. In order to find out which provider supplied the node the test ran on, look at the name of the jenkins slave near the top of tho console output, the name of the provider is included.

Below that, you'll find the output from devstack as it installs all of the debian and pip packages required for the test, and then configures and runs the services. Most of what it needs should already be cached on the test host, but if the change to be tested includes a dependency change, or there has been such a change since the snapshot image was created, the updated dependency will be downloaded from the Internet, which could cause a false negative if that fails.

Assuming that there are no visible failures in the console log, you may need to examine the log output from the OpenStack services. Back on the Jenkins page for the build, you should see a list of "Build Artifacts" in the center of the screen. All of the OpenStack services are configured to syslog, so you may find helpful log messages by clicking on "syslog.txt". Some error messages are so basic they don't make it to syslog, such as if a service fails to start. Devstack starts all of the services in screen, and you can see the output captured by screen in files named "screen-*.txt". You may find a traceback there that isn't in syslog.

After examining the output from the test, if you believe the result was a false negative, you can retrigger the test by re-approving the change in Gerrit. If a test failure is a result of a race condition in the OpenStack code, please take the opportunity to try to identify it, and file a bug report or fix the problem. If it seems to be related to a specific devstack gate node provider, we'd love it if you could help identify what the variable might be (whether in the devstack-gate scripts, devstack itself, OpenStack, or even the provider's service).

Simulating Devstack Gate Tests

Developers often have a need to recreate gating integration tests manually, and this provides a walkthrough of making a DG-slave-like throwaway server without the overhead of building other CI infrastructure to manage a pool of them. This can be useful to reproduce and troubleshoot failures or tease out nondeterministic bugs.

First, it helps if you have access to a virtual machine from one of the providers the OpenStack project is using for gating, since their performance characteristics and necessary build parameters are already known. The same thing can of course be done locally or on another provider, but you'll want to make sure you have a basic Ubuntu 12.04 LTS (Precise Pangolin) image with sufficient memory and processor count. These days Tempest testing is requiring in excess of 2GiB RAM (4 should be enough but we typically use 8) and completes within an hour on a 4-CPU virtual machine.

If you're using a nova provider, it's usually helpful to set up an environment variable list you can include into your shell so you don't have to feed a bunch of additional options on the nova client command line. A provider settings file for Rackspace would look something like:

export OS_USERNAME=<provider_username>
export OS_PASSWORD='<provider_password>'
export OS_TENANT_NAME=<provider_tenant>
export OS_AUTH_URL=https://identity.api.rackspacecloud.com/v2.0/
export OS_REGION_NAME=DFW
export NOVA_RAX_AUTH=1
export FLAVOR='8GB Standard Instance'
export IMAGE='Ubuntu 12.04 LTS (Precise Pangolin)'

By comparison, a provider settings file for HPCloud:

export OS_USERNAME=<provider_username>
export OS_PASSWORD='<provider_password>'
export OS_TENANT_NAME=<provider_tenant>
export OS_AUTH_URL=https://region-a.geo-1.identity.hpcloudsvc.com:35357/v2.0
export OS_REGION_NAME=az-3.region-a.geo-1
export FLAVOR='standard.large'
export IMAGE='Ubuntu Precise 12.04 LTS Server 64-bit 20121026 (b)'

Source the provider settings, boot a server named "testserver" (chosen arbitrarily for this example) with your SSH key allowed, and log into it:

. provider_settings.sh
nova boot --poll --flavor "$FLAVOR" --image "$IMAGE" \
  --file /root/.ssh/authorized_keys=$HOME/.ssh/id_rsa.pub testserver
nova ssh testserver

If you get a cryptic error like ERROR: 'public' then you may need to manually look up the IP address with nova list --name testserver and connect by running ssh root@<ip_address> instead.

Upgrade the server, install git and pip packages, add tox via pip (because the packaged version is too old), set up a "jenkins" account and reboot to make sure you're running a current kernel:

apt-get install -y git \
&& git clone https://review.openstack.org/p/openstack-infra/config \
&& config/install_puppet.sh && config/install_modules.sh \
&& puppet apply --modulepath=/root/config/modules:/etc/puppet/modules \
-e "class { openstack_project::slave_template: install_users => false,
ssh_key => \"$( cat .ssh/authorized_keys )\" }" \
&& echo HostKey /etc/ssh/ssh_host_ecdsa_key >> /etc/ssh/sshd_config \
&& reboot

Wait a few moments for the reboot to complete, then log back in with nova ssh --login jenkins testserver or ssh jenkins@<ip_address> and set up parts of the environment expected by devstack-gate testing (the "devstack-vm-gate-dev.sh" script mentioned below in the Developer Setup section implements a similar workflow for testing changes to devstack-gate itself, but could be modified to automate much of this for ease of repetition):

export REPO_URL=https://review.openstack.org/p
export ZUUL_URL=/home/jenkins/workspace-cache
export ZUUL_REF=HEAD
export WORKSPACE=/home/jenkins/workspace/testing
mkdir -p $WORKSPACE

Specify the project and branch you want to test for integration:

export ZUUL_PROJECT=openstack/nova
export ZUUL_BRANCH=master

Get a copy of the tested project. After these steps, apply relevant patches on the target branch (via cherry-pick, rebase, et cetera) and make sure HEAD is at the ref you want tested:

git clone $REPO_URL/$ZUUL_PROJECT $ZUUL_URL/$ZUUL_PROJECT \
&& cd $ZUUL_URL/$ZUUL_PROJECT \
&& git checkout remotes/origin/$ZUUL_BRANCH

Switch to the workspace and get a copy of devstack-gate:

cd $WORKSPACE \
&& git clone --depth 1 $REPO_URL/openstack-infra/devstack-gate

At this point you're ready to set the same environment variables and run the same commands/scripts as used in the desired job. The definitions for these are found in the openstack-infra/config project under the modules/openstack_project/files/jenkins_job_builder/config directory in a file named devstack-gate.yaml. It will probably look something like:

export PYTHONUNBUFFERED=true
export DEVSTACK_GATE_TEMPEST=1
export DEVSTACK_GATE_TEMPEST_FULL=1
cp devstack-gate/devstack-vm-gate-wrap.sh ./safe-devstack-vm-gate-wrap.sh
./safe-devstack-vm-gate-wrap.sh

If you're trying to figure out which devstack gate jobs run for a given project+branch combination, this is encoded in the openstack-infra/config project under the modules/openstack_project/files/zuul directory in a file named layout.yaml. You'll want to look in the "projects" section for a list of jobs run on a given project in the "gate" pipeline, and then consult the "jobs" section of the file to see if there are any overrides indicating which branches qualify for the job and whether or not its voting is disabled.

After the script completes, investigate any failures. Then log out and nova delete testserver or similar to get rid of it once no longer needed. It's possible to re-run certain jobs or specific tests on a used VM (sometimes with a bit of manual clean-up in between runs), but for proper testing you'll want to validate your fixes on a completely fresh one.

Refer to the Jenkins Job Builder and Zuul documentation for more information on their configuration file formats.

Contributions Welcome

All of the OpenStack developer infrastructure is freely available and managed in source code repositories just like the code of OpenStack itself. If you'd like to contribute, just clone and propose a patch to the relevant repository:

https://github.com/openstack-infra/devstack-gate
https://github.com/openstack/openstack-infra-puppet

You can file bugs on the openstack-ci project:

https://launchpad.net/openstack-ci

And you can chat with us on Freenode in #openstack-dev or #openstack-infra.

Developer Setup

If you'd like to work on the devstack-gate scripts and test process, this should help you bootstrap a test environment (assuming the user you're working as is called "jenkins"):

export WORKSPACE=/home/jenkins/workspace
export DEVSTACK_GATE_PREFIX=wip-
export SKIP_DEVSTACK_GATE_PROJECT=1
export SKIP_DEVSTACK_GATE_JENKINS=1
export ZUUL_BRANCH=master
export ZUUL_PROJECT=testing

cd /home/jenkins/workspace
git clone https://github.com/openstack-infra/devstack-gate
cd devstack-gate
python vmdatabase.py
sqlite3 /home/jenkins/vm.db

With the database open, you'll want to populate the provider and base_image tables with your provider details and specifications for images created.

By default, the update-image script will produce a VM that only members of the OpenStack CI team can log into. You can inject your SSH public key by setting the appropriate env variable, like so:

export JENKINS_SSH_KEY=$(head -1 ~/.ssh/authorized_keys)

Then run:

./devstack-vm-update-image.sh <YOUR PROVIDER NAME>
./devstack-vm-launch.py <YOUR PROVIDER NAME>
python vmdatabase.py

So that you don't need an entire Jenkins environment during development, The SKIP_DEVSTACK_GATE_JENKINS variable will cause the launch and reap scripts to omit making changes to Jenkins. You'll need to pick a machine to use yourself, so chose an IP from the output from 'python vmdatabase.py' and then run:

./devstack-vm-gate-dev.sh <IP>

To test your changes. That script copies the workspace over to the machine and invokes the gate script as Jenkins would. When you're done, you'll need to run:

./devstack-vm-reap.py <YOUR PROVIDER NAME> --all-servers

To clean up.

Production Setup

In addition to the jobs described under "How It Works", you will need to install a config file at ~/devstack-gate-secure.conf on the Jenkins node where you are running the update-image, launch, and reap jobs that looks like this:

[jenkins]
server=https://jenkins.example.com
user=jekins-user-with-admin-privs
apikey=1234567890abcdef1234567890abcdef