QAProcessContinuousRollouts

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Continuous Rollouts Process: the QA side

The proposed merge workflow is in https://dev.launchpad.net/MergeWorkflowDraft. This workflow relies on QA, enough to assume a branch able (or not) to be rolled out to production based on its QA state.

We need to do the bookkeeping to provide the QA information to the merger. Details on how we intent to do this are described in this wiki page.

Definition of QA

A bug is the smallest unit of QA. So, deciding if something needs QA is based on the existence of the bug. But, it's NOT required to have a bug for each branch. Informing that a branch is unQAable when landing it will QA-cover it.

A fix is considered QAed when falling into one of the following categories:

States of QA

qa-untestable, qa-rollback and qa-needstesting should be set by the Tagger. qa-bad and qa-ok should be manually set. The diagram shows the QA states of the bug and what causes them.

Connecting branches and QA

As a rule, if a branch needs QA, it should be represented by at least one bug. Rarely, QA is not necessary for some branches, or can't be done. Also rarely, some branches cannot be QA'd until more branches land -- they are incremental branches towards a larger bug. Equally rarely are expected branches that only revert others that are bad fixes or rollout blockers: they rollback other branches.

How to make branches QA-aware when landing them

To represent and sign those situations, there are three new commit message tags: [no-qa], [incr] and [rollback]. Note that the idea is to gather as much information as possible in the merge proposal, so the developer only has to use parameters on ec2 land and bzr lp-land instead of handcrafting the commit message for it to be recognized as in a QA-consistent state.

Each category below describes what the developer needs to do to make the assertion. It also tells the developer what automation it will trigger. In order to get the branch landed, the developer must assert that the branch falls in one of the following categories:

We can QA the branch, and it fixes one or more bugs (most common)

We can QA the branch, and it is an incremental step towards the fix of one or more bugs

We cannot QA the branch, and it is an incremental step towards the fix of one or more bugs

NOTE: Developer shouldn't use the --incremental option when landing the last branch in an incremental chain. Branch must be submitted like the most common case.

We cannot QA the branch, but it fixes one or more bugs

We cannot QA it, and it does not have an associated bug

We cannot QA it, and it's just a rollback of a previous qa-bad or blocker qa-needstesting branch

NOTE: Regular branches that fix qa-bad bugs should be submitted like the most common case.

Alternative way to linking bugs to branches using Launchpad UI

Using --fixes when doing local commits add the metadata to the branch. When the branch is pushed to Launchpad, it scans the revisions and automatically links the mentioned bugs to the branch.

PQM will enforce these rules with the usual regex dances. ec2 land and bzr lp-land help the developer conform to the PQM regex with quicker and more helpful error messages. Alternatively, the developer can add "[incr]", "[no-qa]" or "[rollback]" in the PQM submission message, if using pqm-submit directly, but it's not recommended considering it's not needed and other tools with faster response automatically check and enforce the tags.

Marking revisions as blessed: the blesser

The very important part of having the bugs tagged correctly is that this will determine the QA state of the branch that fixes it, and as a consequence say if the revision is blessed to be rolled out to production of if it's blocked, and therefore should not be rolled out.

There will be a small application called "the blesser". It will check each revision landed on the development branch, check the existence of bugs and commit messages, and mark them as follows:

  1. No bug: Blesser assumes the revision is qa-untestable, therefore revision is blessed.
  2. Bug AND it's qa-untestable, qa-ok or qa-rollback: Blesser assumes that's ok, therefore revision is blessed.
  3. Bug AND it's qa-needstesting or qa-bad: Blesser blocks the rollouts by marking the revision as blocked.

Here is a diagram that shows how developers and the tagger script will interact with bugs, leaving them ready for the blesser:

bug_machine_state.png