# About Launchpad branches #### IMPORTANT This document has been migrated from our old wiki as is, and has not yet been revised. The content might be outdated, links and images could be broken. We are aware and will fix any issues as soon as possible. ## Where’s trunk? Launchpad has four master branches (this is unusual; most projects only have one). They are: 1. [master](https://code.launchpad.net/~launchpad/launchpad/+git/launchpad/+ref/master) Where most development takes place (except anything that involves changing the database schema; see below). 2. [db-devel](https://code.launchpad.net/~launchpad/launchpad/+git/launchpad/+ref/db-devel) Changes that modify the database schema get merged here first. 3. [stable](https://code.launchpad.net/~launchpad/launchpad/+git/launchpad/+ref/stable) This is fed by regular merges from the **master** branch, and is deployed to [qastaging.launchpad.net](https://qastaging.launchpad.net/) frequently. 4. [db-stable](https://code.launchpad.net/~launchpad/launchpad/+git/launchpad/+ref/db-stable) This is fed by regular merges from the **db-devel** branch. It is deployed to [staging.launchpad.net](https://staging.launchpad.net) frequently, and deployed to [launchpad.net](https://launchpad.net/) on each DB schema deployment. After deployment, **db-stable** is merged back into **master**, completing the cycle. In summary: **db-stable** is the post-test-run counterpart of **db-devel**, and **stable** is the post-test-run counterpart of **master**, where *“post-test-run”* means that once code hits foo-devel it is only cleared into foo-stable if the buildbot test runner succeeds. If you want to know how all of this works behind the scenes, read [The journey of a Launchpad change from a developer’s branch to production](https://ubuntu.com/docs/launchpad/developer/explanation/developing-for-launchpad/journey-of-a-change-to-production/index.html.md#journey-change-production) (after reading the rest of this page). ## Look at the pretty pictures Diagrams might be the best way to understand this. (If they don’t work, there’s text afterwards, don’t worry.)  Below, we break the process down a bit with a different diagramming approach. Here’s what happens when you submit to **master**:  Where are the expected potential problems in the process? Glad you asked!  It is also possible to submit directly to the **db-devel** branch.  ## Let’s Try That in Words Database changes can be destabilising to other work, so we isolate them out into a separate branch (**db-devel**). Then there are two arenas for stabilising changes for deployment: **stable** (which ends up on [qastaging](https://qastaging.launchpad.net) and is fed from the **master** branch), and **db-stable** (which ends up on [staging](https://staging.launchpad.net) and is fed from the **db-devel** branch). (Note that the actual images here date from the Bazaar world, and so talk about “devel” rather than “master”. You can regard these two names as interchangeable. Feel free to update the images if you have time.) In summary: - Developers submit to **master** and **db-devel**. - Buildbot tests the tip of **db-devel**, in addition to **master**. If a **db-devel** change passes, it is pushed automatically to **db-stable**. - When changes are approved by buildbot to go from **master** to **stable**, a script also generates a PQM request to merge **stable** with **db-devel**, sent as if it came from the Launchpad list. The Launchpad list will be informed of merge failures, and Launchpad developers will collectively be responsible for correcting them. (**\*TODO: is this some internal list?\***) - Staging runs **db-stable**; qastaging runs **stable**. We will deploy production DB schema changes from **db-stable**. (After a deployment, **db-stable** is manually pushed to **devel** and **stable**.) ### Problems that can occur - **The merge from stable to db-devel fails.** That’s a real risk : but we expect it to occur infrequently. When it does occur, the Launchpad list (**\*TODO: which one?\***) will be emailed, and it is the collective responsibility of everyone to fix the problem, by manually submitting a branch to **db-devel** that includes the branch that failed to merge plus any necessary adjustments. ### Where to send merge requests Merge requests that do any of the following should be targeted at the **db-devel** branch: - adds a cold database patch (see [Create a database patch](https://ubuntu.com/docs/launchpad/developer/how-to/common-development-tasks/create-a-db-patch/index.html.md#create-a-db-patch)) - depends on database schema change only in **db-devel** / **db-stable** All other developer merge requests for the launchpad tree should be targeted at the **master** branch. The current \`buildbot-poller.py\` script on the PQM box monitors buildbot to discover what revisions have passed the tests. When a new revision is “blessed” by buildbot, the script copies it over to **stable**. The poller script merges the blessed revision into the **db-devel** branch. It is also responsible for checking a new buildbot build testing **db-devel**. The poller will copy revisions of **db-devel** that buildbot blesses to **db-stable**. Staging releases should run code from **db-stable**. qastaging and production should continue to run code from **stable**. When a DB schema deployment is made, the **db-stable** code should be merged into **master**. This is the responsibility of the person who organised the deployment. Problems with the automated merge requests are sent to the Launchpad list (**\*TODO: which list?\***). When the merge of **stable** -> **db-devel** does not work automatically, it should be done manually and submitted. The tests do not need to be run (rationale: the bots don’t run the tests when they do it automatically, and the failure messages can clutter up the ML really fast.) ## How do I submit to db-devel? See also WorkingWithDbDevel. ```default cd ~/canonical/launchpad/launchpad git checkout -b mydbbranch db-devel make build make schema ``` …hack until ready to submit… ```default git push -u myusername mydbbranch ``` Now create and land a merge proposal. ## FAQ ### Can I land a test fix before buildbot has finished a test run that has failed or will fail? Yes you can, and please do if appropriate, because this will mean that other developers will not encounter a broken tree at all. ### What happens if the automatic merge from stable to db-devel fails? The (internal! change?) launchpad list gets an email. This is described on the /Trunk page. ### A build failed for some reason other than a test failure. What do I do? Force a build at [https://lpbuildbot.canonical.com/force](https://lpbuildbot.canonical.com/force).