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.
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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. Any proposed change to the configured set of projects must pass the devstack gate test:
Obviously we test nova, glance, keystone, horizon, quantum 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.
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.
When a proposed change is approved by the core reviewers, 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. That script then calls devstack-vm-gate.sh which installs a devstack configuration file, and invokes devstack. 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.
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).
If you’d like to work on the devstack-gate scripts and test process, see the README in the devstack-gate repo for specific instructions.