Detailed Test Configuration

Test configuration

An integration test run takes three items of configuration:

  • targets: what hosts to run on; this is a dictionary mapping hosts to ssh host keys, like: “username@hostname.example.com: ssh-rsa long_hostkey_here”

  • roles: how to use the hosts; this is a list of lists, where each entry lists all the roles to be run on a single host. For example, a single entry might say [mon.1, osd.1].

  • tasks: how to set up the cluster and what tests to run on it; see below for examples

The format for this configuration is YAML, a structured data format that is still human-readable and editable.

For example, a full config for a test run that sets up a three-machine cluster, mounts Ceph via ceph-fuse, and leaves you at an interactive Python prompt for manual exploration (and enabling you to SSH in to the nodes & use the live cluster ad hoc), might look like this:

roles:
- [mon.0, mds.0, osd.0]
- [mon.1, osd.1]
- [mon.2, client.0]
targets:
    ubuntu@host07.example.com: ssh-rsa host07_ssh_key
    ubuntu@host08.example.com: ssh-rsa host08_ssh_key
    ubuntu@host09.example.com: ssh-rsa host09_ssh_key
tasks:
- install:
- ceph:
- ceph-fuse: [client.0]
- interactive:
repo: git://git.ceph.com/ceph.git

The number of entries under roles and targets must match.

Note the colon after every task name in the tasks section. Also note the dashes before each task. This is the YAML syntax for an ordered list and specifies the order in which tasks are executed.

The install task needs to precede all other tasks.

The listed targets need resolvable hostnames. If you do not have a DNS server running, you can add entries to /etc/hosts. You also need to be able to SSH in to the listed targets without passphrases, and the remote user needs to have passwordless sudo access. Note that the ssh keys at the end of the targets entries are the public ssh keys for the hosts. These are located in /etc/ssh/ssh_host_rsa_key.pub

If you saved the above file as example.yaml, you could run teuthology on it like this:

./virtualenv/bin/teuthology example.yaml

It is possible to configure installation so that specifying targets and host keys can be omitted. Teuthology is run with the --lock option which locks the targets based on roles in YAML. Teuthology grabs machines from a pool of available test machines; but since most times machines are busy, you might have to wait until they are free or else command fails due to lack of available machines. To avoid this you can specify --block with --lock which will make teuthology retry until it finds and locks required machines.

You could also pass the -v option for more verbose execution. See teuthology --help for more options.

Multiple config files

You can pass multiple files as arguments to teuthology. Each one will be read as a config file, and their contents will be merged. This allows you to share definitions of what a “simple 3 node cluster” is. The source tree comes with roles/3-simple.yaml, so we could skip the roles section in the above example.yaml and then run:

./virtualenv/bin/teuthology roles/3-simple.yaml example.yaml

Reserving target machines

Teuthology automatically locks nodes for you if you specify the --lock option. Without this option, you must specify machines to run on in a targets.yaml file, and lock them using teuthology-lock.

Note that the default owner of a machine is of the form: USER@HOST where USER is the user who issued the lock command and host is the machine on which the lock command was run.

You can override this with the --owner option when running teuthology or teuthology-lock.

With teuthology-lock you can also add a description, so you can remember which tests you were running. This can be done when locking or unlocking machines, or as a separate action with the --update option. To lock 3 machines and set a description, run:

./virtualenv/bin/teuthology-lock --lock-many 3 --desc 'test foo'

If machines become unusable for some reason, you can mark them down:

./virtualenv/bin/teuthology-lock --update --status down machine1 machine2

To see the status of all machines, use the --list option. This can be restricted to particular machines as well:

./virtualenv/bin/teuthology-lock --list machine1 machine2

Choosing machines for a job

It is possible to run jobs against machines of one or more machine_type values. It is also possible to tell teuthology to only select those machines which match the following criteria specified in the job’s YAML:

  • os_type (e.g. ‘rhel’, ‘ubuntu’)

  • os_version (e.g. ‘7.0’, ‘14.04’)

  • arch (e.g. ‘x86_64’)

Tasks

A task is a Python module in the teuthology.task package, with a callable named task. It gets the following arguments:

  • ctx: a context that is available through the lifetime of the test run, and has useful attributes such as cluster, letting the task access the remote hosts. Tasks can also store their internal state here. (TODO beware of namespace collisions.)

  • config: the data structure after the colon in the config file, e.g. for the above ceph-fuse example, it would be a list like ["client.0"].

Tasks can be simple functions, called once in the order they are listed in tasks. But sometimes it makes sense for a task to be able to clean up after itself: for example, unmounting the filesystem after a test run. A task callable that returns a Python context manager will have the manager added to a stack, and the stack will be unwound at the end of the run. This means the cleanup actions are run in reverse order, both on success and failure. A nice way of writing context managers is the contextlib.contextmanager decorator; look for that string in the existing tasks to see examples, and note where they use yield.

Further details on some of the more complex tasks such as install or workunit can be obtained via python help. For example:

>>> import teuthology.task.workunit
>>> help(teuthology.task.workunit)

displays a page of more documentation and more concrete examples.

Some of the more important / commonly used tasks include:

  • ansible: Run the ansible task.

  • install: by default, the install task goes to gitbuilder and installs the results of the latest build. You can, however, add additional parameters to the test configuration to cause it to install any branch, SHA, archive or URL. The following are valid parameters.

    • branch: specify a branch (firefly, giant…)

    • flavor: specify a flavor (next, unstable…). Flavors can be thought of as subsets of branches. Sometimes (unstable, for example) they may have a predefined meaning.

    • project: specify a project (ceph, samba…)

    • sha1: install the build with this sha1 value.

    • tag: specify a tag/identifying text for this build (v47.2, v48.1…)

  • ceph: Bring up Ceph

  • overrides: override behavior. Typically, this includes sub-tasks being overridden. Overrides technically is not a task (there is no ‘def task’ in an overrides.py file), but from a user’s standpoint can be described as behaving like one. Sub-tasks can nest further information. For example, overrides of install tasks are project specific, so the following section of a yaml file would cause all ceph installations to default to using the jewel branch:

    overrides:
  install:
    ceph:
      branch: jewel

  • workunit: workunits are a way of grouping tasks and behavior on targets.

  • sequential: group the sub-tasks into a unit where the sub-tasks run sequentially as listed.

  • parallel: group the sub-tasks into a unit where the sub-tasks all run in parallel.

Sequential and parallel tasks can be nested. Tasks run sequentially unless specified otherwise.

The above list is a very incomplete description of the tasks available on teuthology. The teuthology/task subdirectory contains the teuthology-specific python files that implement tasks.

Extra tasks used by teuthology can be found in ceph-qa-suite/tasks. These tasks are not needed for teuthology to run, but do test specific independent features. A user who wants to define a test for a new feature can implement new tasks in this directory.

Many of these tasks are used to run python scripts that are defined in the ceph/ceph-qa-suite.

If machines were locked as part of the run (with the –lock switch), teuthology normally leaves them locked when there is any task failure for investigation of the machine state. When developing new teuthology tasks, sometimes this behavior is not useful. The unlock_on_failure global option can be set to true to make the unlocking happen unconditionally.

Troubleshooting

Postmortem Debugging

After completion of a test, the archive subdirectory is archived under the corresponding remote subdirectory. We can disable this behavior using the top-level configuration, like:

archive-on-error: true

If archive-on-error is true, the archive subdirectory is archived only for failed tests.

If the size of the archived file exceeds 128MB, the file will be compressed using GZip. This threshold can be configured using the top-level option named log-compress-min-size, like:

log-compress-min-size: 256GB

Other size unit postfixes are also supported, see humanfriendly document for more details.

Situ Debugging

Sometimes when a bug triggers, instead of automatic cleanup, you want to explore the system as is. Adding a top-level:

interactive-on-error: true

as a config file for teuthology will make that possible. With that option, any task that fails will have the interactive task called after it. This means that before any cleanup happens, you get a chance to inspect the system – both through Teuthology and via extra SSH connections – and the cleanup completes only when you choose. Just exit the interactive Python session to continue the cleanup.

You can enable interactive-on-error with the teuthology command option --interactive-on-error

Interactive task facilities

The interactive task presents a prompt for you to interact with the teuthology configuration. The ctx variable is available to explore, and a pprint.PrettyPrinter().pprint object is added for convenience as pp, so you can do things like pp(dict-of-interest) to see a formatted view of the dict.

This is also useful to pause the execution of the test between two tasks, either to perform ad hoc operations, or to examine the state of the cluster. Hit control-D to continue when done.

You need to nest interactive underneath tasks in your config. You can have has many interactive tasks as needed in your task list.

An example:

tasks:
- ceph:
- interactive:

Test Sandbox Directory

Teuthology currently places most test files and mount points in a sandbox directory, defaulting to /home/$USER/cephtest. To change the location of the sandbox directory, the following option can be specified in $HOME/.teuthology.yaml:

test_path: <directory>

Shaman options

Shaman is a helper class which could be used to build the uri for specified packages based the ‘shaman_host’: ‘shaman.ceph.com’.

Options:

use_shaman: True # Enable to use Shaman, False as default
shaman:
  force_noarch: True # Force to use "noarch" to build the uri