The introduction of merge trains in GitLab represents a promising feature that can potentially streamline our workflow and replace the existing functionality provided by Marge-bot. We (Arvid and me) invested some time in testing this feature before considering a switch.

Detailed project description: https://codimd.nomadic-labs.com/ebRcnqq0T2C8cB-dNQ264w?view#

Work Breakdown

Study phase

• Initial study ( @arvid, @abate )
• Write detailed project description ( @abate) https://codimd.nomadic-labs.com/ebRcnqq0T2C8cB-dNQ264w?view#
• Simulation to establish benefits of the merge trains wrt margebot (https://gitlab.com/abate/train-marge-sim) - @abate
• Tests using the merge trains on a side project ( https://gitlab.com/abate/train-marge-sim/-/tree/master/tests?ref_type=heads ) , experiments - @abate

Trial Phase

• Write documentation for the new workflow ( #6647 (closed) ) @abate
• Present the new workflow to the merge team ( scheduled 12/12/2023 ) @abate slides
• Modify the .gitlab-ci.yml file on tezos/tezos to accommodate for merge trains (!13553 (merged))
• Adapt existing dashboard to accommodate merge trains
  • Make sure that MRs merged by trains appear
  • Distinguish merge train pipelines
  • Make sure that MB2 rejections comments are detected
  • Improve queue / process time for the old marge-bot
  • Add queue / process time for merge trains
  • Display failed (and successful?) merge train pipelines / create a panel for this.
  • Measure and graph number of active merge trains
  • Adapt the "Assigned to MB" to handle MRs not targeting master (perhaps make a tree).
  • Make it easier to run the dashboard (e.g. provide a docker compose file for this, fix hard-coded URLs)
  • Display failed (and successful?) merge train / create a panel for this.
• Prototype of a new margebot to mitigate the lack of support in merge trains of MR dependencies (https://gitlab.com/nomadic-labs/marge-bot2)
• Enable merge trains on tezos/tezos for a trial period of 4 days (Tentative: 2024-07-01 -> 2024-07-04)
• Collect feedback and study possible way to smooth the new workflow

Production Phase

• Install the new bot - if deemed necessary - on tezos/tezos to replace the current Margebot
• Re-enable merge train on tezos/tezos
• Collect more feedback
• Iterate``