Hi All!

tl;dr: if you're a developer looking for guidance on how to deploy changes to Wikimedia's MediaWiki cluster read https://w.wiki/36nY ; if you have thoughts on our existing deployment documentation comment on https://w.wiki/36nZ

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Over time The Train™ has become the default way to deploy changes to Wikimedia's MediaWiki cluster -- for some patches that may not always be the right path. If a developer needs a change deployed *now*, or if there is a desire to deploy a change in isolation then backports might be a better path.

As with all things, some exceptions may apply. The Release Engineering team has created some guidelines[0] that will hopefully help explain when something MUST, SHOULD, or MAY[1] be deployed via the train or via backport.

This documentation is a bookmarkable quick reference for developers. It does not change our backport window guidelines[2] or special deployment window guidelines[3], those documents should not be in conflict with the advice in the new guidelines. The new guidelines target a different use-case.

Our deployment documentation is up-to-date but sprawling. The same information is in multiple places and multiple audiences and use-cases are often mixed into the same documents. Work to improve deployment documentation is tracked on Phabricator[4].

Please reach out in #wikimedia-releng on freenode in IRC or attend the Deployment Office Hours meeting (weekly on Mondays at 17:00UTC in #wikimedia-office on freenode in IRC) if you have questions.

Thank you!
-- Tyler

[0]: <https://wikitech.wikimedia.org/wiki/Deployments/Train_vs_backport>
[1]: <https://tools.ietf.org/html/rfc2119>
[2]: <https://wikitech.wikimedia.org/wiki/Backport_windows#Guidelines>
[3]: <https://wikitech.wikimedia.org/wiki/Deployments/Inclusion_criteria>
[4]: <https://phabricator.wikimedia.org/T273802>