Prioritization WG - Procedure

This document details the procedure the WG-prioritization follows to fill the agenda for the weekly meeting of T-compiler. The working group focuses mainly on triaging T-compiler regressions, identifying possibly critical (and thus potential release blocker) issues and building the agenda for the weekly T-compiler meeting summarizing the main points to be discussed.

General issues review process

  • Check the status of the issue
  • Try moving it forward if possible (ex. stimulate further comments from the issue author / reviewer)
  • Ask for more info if it’s needed
  • Is there an MCVE for the issue already?
  • Check if it’s a regression and label it accordingly (regression-* labels)
  • Figure out the area the issue belongs and label it accordingly (A-* labels)
  • Ping notify groups or relevant teams
  • Assign if possible
  • Nominate the issue if it’s unclear and needs to be discussed

Generating the T-compiler meeting’s agenda

The T-compiler agenda is generated from a template (available on HackMD or Github). We suggest working the following steps in this order:

Prepare agenda content

1. Add T-compiler labels where appropriate

2. Assign a priority label to issues where needed

Regressions labeled with I-prioritize are signaling that a priority assessment is waiting. When this label is added to an issue, the triagebot creates automatically a notification for @WG-prioritization members on the Zulip stream.

To assign a priority, we replace the I-prioritize label with one of P-critical, P-high, P-medium or P-low and adding a succinct comment to link the Zulip discussion where the issue prioritization occurred, example of a template for the comment:

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-XXX

Ideally, we want all T-compiler issues with a I-prioritize label to have a priority assigned, or strive to reach this goal: sometimes different factors are blocking issues from being assigned a priority label, either because the report or the context is unclear or because cannot be reproduced and an MCVE would help. Don’t hesitate to ask for clarifications to the issue reporter or ping the ICEbreaker team when an ICE (“Internal Compiler Errors”) needs a reduction (add a comment on the issue with @rustbot ping icebreakers-cleanup-crew)

Keep an eye also on regressions (stable, beta and nightly), ideally they should an assignee.

3. Accept MCPs

An MCP is a Major Change Proposal, in other words a change to the rust compiler that needs a bit more thought and discussion within the compiler team than a pull request. The life cycle of an MCP is described in the documentation. The relevant part for the WG-Prioritization is keeping an eye on them and accept all MCPs that have been on final-comment-period for 10 or more days.

To accept an MCP, remove final-comment-period label, add major-change-accepted label and close the issue. A notification to the relevant Zulip topic (in this stream) will be automatically sent by the triagebot.

Generate the meeting’s agenda

Run triagebot’s CLI to generate the agenda. You need to clone https://github.com/rust-lang/triagebot (there is no official prepackaged release for this tool) and export two environment variables: GITHUB_API_TOKEN and optionally a GOOGLE_API_KEY to access a public Google calendar (if this env var is not found, meetings should be manually copy&pasted from here).

To generate the meeting’s agenda, run:

$ cargo run --bin prioritization-agenda

Copy the content of the generated agenda on HackMD. This will be our starting point.

Add performance logs

Paste the markdown file of this week performance triage logs to the agenda and clean it up a little bit removing emojis (to make the text readable when pasted on Zulip).

Announce the meeting on Zulip

About two hours before the scheduled meeting, create a new topic on the Zulip stream #t-compiler/meetings titled “[weekly] YYYY-MM-DD” using the the following message template:

Hi @*T-compiler/meeting*; the triage meeting will happen tomorrow in about 2 hours.
*WG-prioritization* has done pre-triage in #**t-compiler/wg-prioritization/alerts**
@*WG-prioritization* has prepared the [meeting agenda](link_to_hackmd_agenda)

Working group checkins for today:
- @**WG-foo** by @**person1**
- @**WG-bar** by @**person2**

Working Group checkins rotation are generated by a script at this page (TODO: script is outdated and could probably be merged into the triagebot CLI code).

Checkins about the progress of working groups are not mandatory but we rotate them all to be sure we don’t miss on important progresses.

Add details to the Agenda

1. Summarize stable/beta nominations

These are pull requests that the compiler team might want to backport to a release channel. Example a stable-to-beta-regression fix might want to be backported to the beta release channel. A stable-to-stable-regression fix particularly annoying might warrant a point release (i.e. release a 1.67.1 after a 1.67.0).

Follow the General issues review process.

2. Summarize PRs waiting on team

These are pull requests waiting on a discussion / decision from T-compiler (sometimes more than one team).

Try to follow the General issues review process. Explicitly nominate any issue that can be quickly resolved in a triage meeting.

3. Fill up the “Oldest PRs waiting for review”

This is probably the less automatable part of the agenda (and likely the least fun). The triagebot will emit a list of 50 pull requests ordering them by least recent update. The idea is to issue mentions to assigned reviewers during the meeting ensuring that they stay on top of them. We usually try to keep the number of these mentions to around 5 for each meeting.

There are two human factors here to keep in consideration:

  • Pull requests reviewers are volunteers, we respect and appreciate their work. We don’t want to remind them too often that there is a pile of pull requests waiting on them. Therefore we usually wait 2 or 3 weeks before reminding them about that pull requests. It seems like a long time to wait but let’s not forget what contributors accomplish in the meanwhile! Anyway, we are trying to find ways to improve on these metrics.
  • Contributors taking their time to submit a pull request deserve equally our appreciation so we try to not have them wait too long for a review or they will lose context about their work (or motivation to drive the contribution to completion).

Striking a balance between these two diverging forces requires some empathy and “tribal knowledge” that comes with practice. Other factors can be blocking a pull request progress:

  • The review is shared with another team (i.e. Team 1 says “OK”, now waiting on Team 2)
  • The alternating labels S-waiting-on-review and S-waiting-on author handling the life cycle of a pull request are not promptly applied. A pull request that is ready to be reviewed but it’s not labeled S-waiting-on-review is idling for no purpose.

4. Add some context to P-critical and P-high regressions without an assignee

Try to follow the General issues review process.

5. Summarize I-compiler-nominated issues

Issues labeled with I-compiler-nominated generally are nominated to specifically have the compiler team dedicate them a special slice of the meeting (generally towards the end). After the discussion, add a comment on Github linking the Zulip message where the discussion started (so everyone can read). T-compiler sometimes writes a summary of the discussion on the issue itself.

Try to follow the General issues review process:

  • Check if an issue needs a discussion and add the label I-compiler-nominated
  • When added to the agenda, add some context:
    • Who the assignee is
    • Is this an issue or a pull request: if it’s an issue, does it have a pull request that fixes it?
    • Why was it nominated
    • Other important details

6. Final review before the meeting

Re-run the triagebot CLI script and update the agenda on HackMD with new data (if any). This is useful when there are last second changes affecting the agenda content.

Follow-ups after meeting

The meeting is over! Time to cleanup a little bit.

  • Lock the agenda file on HackMD assigning write permissions to Owners. Download the markdown file and commit it to this repository.

  • Remove the to-announce label from MCPs, unless this label was added exactly during the meeting (and therefore will be seen during the following meeting).

  • Remove to-announce FCPs from rust repo, compiler-team repo and forge repo, same disclaimer as before.

  • Accept or decline beta nominated and stable nominated backports that have been accepted during the meeting. For more info check T-release backporting docs

    • To accept a backport, add a {beta,stable}-accepted label and keep the {beta,stable}-nominated label. Other automated procedures will process these pull requests, it’s important to leave both labels. Add a comment on Github linking the Zulip discussion.
    • To decline a backport, simply remove {beta,stable}-nominated label. Add a comment on Github explaining why the backport was declined and link the Zulip discussion.

  • Remove I-compiler-nominated label from issues that were discussed. Sometimes not all nominated issues are discussed (because of time constraints). In this case the I-compiler-nominated will stick until next meeting.

  • Create a new agenda stub for the following week using our template and post the link on Zulip, so it’s available for people if they want to add content during the week.