144 lines
5.6 KiB
ReStructuredText
144 lines
5.6 KiB
ReStructuredText
===========================
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Telemetry review guidelines
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===========================
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General guidelines for reviewing changes
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========================================
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These are the general principles we follow when reviewing changes.
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- *Be constructive.* Both reviewers and patch authors should be allies that aim to get the change landed together.
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- *Consider the impact.* We deliver critical data that is processed and used by many systems and people. Any disruption should be planned and intentional.
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- *Be diligent.* All changes should be tested under typical conditions.
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- *Know your limits.* Defer to other peers or experts where sensible.
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Main considerations for any change
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========================================
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For any change, these are the fundamental questions that we always need satisfactory answers for.
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- Does this have a plan?
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- Is there a specific need to do this?
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- Does this change need `a proposal <https://github.com/mozilla/Fx-Data-Planning/blob/master/process/ProposalProcess.md>`_ first?
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- Do we need to announce this before we do this? (e.g. for `deprecations <https://github.com/mozilla/Fx-Data-Planning/blob/master/process/Deprecation.md>`_)
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- Does this involve the right people?
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- Does this change need input from... A data engineer? A data scientist?
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- Does this change need data review?
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- Is this change complete?
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- Does this change have sufficient test coverage?
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- Does this change have sufficient documentation?
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- Do we need follow-ups?
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- Do we need to file validation bugs? Or other follow-up bugs?
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- Do we need to communicate this to our users? Or other groups?
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Additional considerations
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=========================
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Besides the basic considerations above, these are additional detailed considerations that help with reviewing changes.
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Considerations for all changes
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------------------------------
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- Follow our standards and best practices.
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- Firefox Desktop:
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- :ref:`The Mozilla coding style <Coding style>`
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- `The toolkit code review guidelines <https://wiki.mozilla.org/Toolkit/Code_Review>`_
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- Mobile:
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- `Android/Kotlin code style <https://kotlinlang.org/docs/reference/coding-conventions.html>`_
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- `iOS/Swift code style <https://github.com/mozilla-mobile/firefox-ios/wiki/Swift-Style-Guides>`_
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- Does this impact performance significantly?:
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- Don't delay application initialisation (unless absolutely necessary).
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- Don't ever block on network requests.
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- Make longer tasks async whenever feasible.
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- Does this affect products more broadly than expected?
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- Consider all our platforms: Windows, Mac, Linux, Android.
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- Consider all our products: Firefox, Fenix, Glean.
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- Does this fall afoul of common architectural failures?
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- Prefer APIs that take non-String types unless writing a parser.
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- Sanity checking:
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- How does this behave in a release build? Have you tested this?
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- Does this change contain test coverage? We require test coverage for every new code, changes and bug fixes.
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- Does this need documentation updates?
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- To the :ref:`in-tree docs <Telemetry>`?
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- To the `firefox-data-docs <https://docs.telemetry.mozilla.org/>`_ (`repository <https://github.com/mozilla/firefox-data-docs>`_)?
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- To the `glean documentation <https://mozilla.github.io/glean/dev/>`_?
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- Following up:
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- Do we have a validation bug filed yet?
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- Do all TODOs have follow-up bugs filed?
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- Do we need to communicate this to our users?
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- `fx-data-dev <https://mail.mozilla.org/listinfo/fx-data-dev>`_ (Main Firefox data list)
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- `firefox-dev <https://mail.mozilla.org/listinfo/firefox-dev>`_ (Firefox application developers)
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- `dev-platform <https://lists.mozilla.org/listinfo/dev-platform>`_ (Gecko / platform developers)
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- `mobile-firefox-dev <https://mail.mozilla.org/listinfo/mobile-firefox-dev>`_ (Mobile developers)
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- fx-team (Firefox staff)
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- Do we need to communicate this to other groups?
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- Data engineering, data science, data stewards, ...?
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Consider the impact on others
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-----------------------------
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- Could this change break upstream pipeline jobs?
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- Does this change the format of outgoing data in an unhandled way?
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- E.g. by adding, removing, or changing the type of a non-metric payload field.
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- Does this require ping schema updates?
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- Does this break jobs that parse the registry files for metrics? (Scalars.yaml, metrics.yaml, etc.)
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- Do we need to involve others?
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- Changes to data formats, ping contents, ping semantics etc. require involving a data engineer.
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- Changes to any outgoing data that is in active use require involving the stakeholders (e.g. data scientists).
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Considerations for Firefox Desktop
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----------------------------------
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- For profiles:
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- How does using different profiles affect this?
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- How does switching between profiles affect this?
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- What happens when users switch between different channels?
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- Footguns:
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- Does this have side-effects on Fennec? (Unified Telemetry is off there, so behavior is pretty different.)
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- Is your code gated on prefs, build info, channels? Tests should cover that.
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- If test is gated on isUnified, code should be too (and vice-versa)
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- Test for the other case
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- Any code using `new Date()` should get additional scrutiny
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- Code using `new Date()` should be using Policy so it can be mocked
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- Tests using `new Date()` should use specific dates, not the current one
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- How does this impact Build Faster support/Artifact builds/Dynamic builtin scalars or events? Will this be testable by others on artifact builds?
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- We work in the open: Does the change include words that might scare end users?
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- How does this handle client id resets?
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- How does this handle users opting out of data collection?
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