Multihost synchronization

[adiosnb]

The issue gathers all discussions regarding synchronization problems in multi-host tests.

[adiosnb]

Adding several points and proposals from the last discussion.

All sync is an enumerator with these values:

• start - synchronize at the beginning of the step, the first test execution
• name - synchronize with the same test names
• index - synchronize all tests, synchronization barrier before each test
• none - do not synchronize

Multihost

• L1 metadata (test metadata) key multihost: true
  • Could be used for filtering relevant multihost tests
  • Could be worked around by “filter: tag:multihost”
  • Could also be useful for syncing multihost tests only
• Mixing singlehost & multihost tests has a real use case
  • For example single host setup tasks
  • There could be a different number of setup tasks on server/client
  • Or sandwich testing: setup / test / inter-setup / test-again
• wow differentiates setup tasks and init tasks
  • BeakerJobWatch uses this information

Keyword correct location

Defining sync in the execution step is too late and hard to process. The current proposal is to make sync a step attribute with the values defined above.

Examples

prepare:
  - name: packages
    how: ansible
    playbook: plans/packages.yml
 - name: services
    how: shell
    script: systemctl start service
    sync: index

execute:
  how: tmt
  sync: start

discover:
  - name: setup-tasks
    how: fmf
    url: https://github.com/teemtee/tmt
    sync: none
  - name: multihost-tests
    how: fmf
    url: https://src.fedoraproject.org/rpms/tmt/
    where: client
    sync: name

[adiosnb]

It would be great to gather more advanced user stories or test cases requiring complex synchronization patterns and barriers.

@sopos @kkaarreell : Would you please provide your feedback and use-cases?

[kkaarreell]

@adiosnb See https://github.com/teemtee/tmt/discussions/1702#discussioncomment-4226375

[adiosnb]

Generic multi-host test discussion can be found here: https://github.com/teemtee/tmt/discussions/1702

[happz]

@adiosnb hi, is this issue still valid? There is a degree of synchronization implemented in tmt, as described in https://tmt.readthedocs.io/en/stable/guide.html#multihost-testing, and the test-level synchronization is not implemented on purpose, and 3rd party libraries can be used for that, as documented in https://tmt.readthedocs.io/en/stable/guide.html#synchronization-libraries.

[psss]

Basic synchronization implemented, for more advanced use cases users are adviced to check synchronization libraries.