Arm deadline warnings per phase and delete the per-minute sweep

[johnpooch]

What this PR does

Closes #1073 and supersedes the stale #1097. This is a fresh reimplementation on current main.

It deletes the phase.send_deadline_warnings cron job, which ran every minute and scanned every active game with a heavily prefetched queryset. In its place, each phase gets its own phase.send_deadline_warning(phase_id) job, scheduled at scheduled_resolution - deadline_warning_offset(...). This works the same way phase resolution is already scheduled.

Scheduling the job

• Add Phase.warning_job_id and PhaseManager.arm_warning. arm_warning has the same structure as arm_resolution: it reads the current job, computes the schedule, and if the schedule changed it cancels the old job and defers a new one. It is called from:
  • a second post_save receiver, next to the resolution one;
  • _apply_nmr_extensions, because that path moves the deadline with .update(), which does not fire post_save;
  • Game.pause / Game.unpause. unpause saves the phase while the game is still paused, so without this the warning would be cancelled and never re-armed.
• Keep a live job instead of re-arming it. An existing job is kept when its scheduled_at still matches and its status is todo, doing or succeeded. So a warning that has already gone out is not armed again when the phase is saved with the same deadline. A failed or cancelled job is replaced.

Sending the warning

send_deadline_warning runs in one transaction with the phase row locked. It only sends when all of these hold:

• the phase is armable (filter_armable());
• the deadline is still in the future;
• the warning time for the current deadline has arrived. This catches a job that was already running when the deadline moved and so could not be cancelled.

It keeps the old per-player checks (has_possible_orders, forced orders, actionable units, not confirmed, has a user). It also skips any player already warned for this exact deadline, using deadline_warning_sent_for. Because of that check and the transaction, a retry, a duplicate run or two jobs racing cannot warn anyone twice, and a failed send leaves no notifications or markers behind.

It emits deadline_warning exactly as before; the notification copy is unchanged.

Other changes

• Threshold table: moved into the pure helper phase.utils.deadline_warning_offset.
• Deleted: the periodic task and the send_deadline_warnings manager method.

deadline_warning_sent_for is kept (differs from #1097)

#1364 merged after #1097 and gave this field a second job: when a player was warned at an earlier deadline on the same phase, their next warning starts with "The deadline has been extended - still …". So the field stays. It now does two things:

• chooses between the normal and "extended" wording;
• stops a second warning for the same deadline.

Backfill in the migration (beyond #1097)

Migration 0023 adds the field and then arms a warning job for every live phase, following 0021_arm_resolution_jobs. Phases already inside their warning window are armed too, so their job runs immediately. The per-deadline marker skips players the old sweep already warned, and there is no gap between the last sweep and the migration.

Tests

• test_background_resolution.py::TestDeadlineWarningArming covers:
  • arming on create at deadline - offset;
  • no job for a pending phase, or one with no deadline;
  • cancel and re-arm when the deadline changes by save, extend_deadline or NMR extension;
  • no re-arm after the warning has fired for an unchanged deadline;
  • a failed job is re-armed on the next save;
  • pause cancels the job, and unpause re-arms it at the extended deadline;
  • cancel on completion;
  • a job running before its warning time sends nothing;
  • running the armed job warns only the unconfirmed player.
• test_deadline_reminders.py covers the fire-time checks:
  • completed, processing, past-deadline, paused and missing phases are skipped;
  • a player already warned for this deadline is not warned again;
  • a failed send leaves no notification or marker behind.
• phase/tests.py: the body-copy tests now call send_deadline_warning(phase.id), including both Stop deadline warnings piling up and repeating themselves #1364 "extended" tests.
• test_utils.py: a parametrised test for deadline_warning_offset.
• Query counts: assertions in phase and game went up by 1–5 queries per phase save, all from arming the warning. I checked this against the logged queries.
• Mutation check: I reverted each fix in the second commit one at a time and confirmed the matching new test fails.

Full backend suite: 2556 passed, 8 skipped, 1 failed. The failure is harness/tests.py::TestQualityMetricAggregation::test_accuracy_covers_ranked_samples_and_skips_the_rest, which also fails on main without this change.

Checklist

• This PR does one thing — no unrelated fixes, refactors, or drive-by cleanups bundled in
• For PRs of any significant complexity: I ran /review-pr against this PR in Claude Code and addressed (or responded to) its findings
• Tests cover the change
• Screenshots embedded in the PR description for any visual changes (see CLAUDE.md) — N/A, backend-only

Note: this makes 8 open PRs, over the soft limit of 5.

🤖 Generated with Claude Code

https://claude.ai/code/session_01TRFZ6aT4agJnpbA6WXJJVc

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