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bvandeusenandClaude Opus 5 5b6f2ba526 fix: a Postgres connection was held across every celery round trip (4295)
Operator, 2026-09-23: *"something about changing the cap number is blocking to
the website... it shouldn't be"*.

Nothing here was slow in itself. A database connection was held across work
that is slow, and that is why it surfaced as the whole site stalling rather
than as one slow page.

`lane_view` took the session and kept it open through a celery inspect whose
budget is 11s. The System tab polls that endpoint every 15s — and with a lane
not answering, every inspect runs to nearly its full budget, so each poll
pinned a connection for most of the interval. SQLAlchemy's default pool is 5
plus 10 overflow. Two browser tabs, `/api/system/health` doing the same thing,
and a cap change adding two more inspects exhausts it, and every OTHER request
then waits for a connection.

Split so the database work finishes before the broker work starts:

- `lane_settings(session)` reads the caps and the oldest running task, then
  the session closes. `lane_view(settings)` does the inspect with none held.
- `store_lane_cap(session, …)` validates and commits, then the session closes.
  `push_lane_cap(lane, …)` does the live push with none held.

And a second finding while measuring it: **raising a cap now costs no broker
round trip at all.** The first cut only knew on/off, so it inspected on every
raise to find out whether the pool needed lowering — the control meant to be
instant still waited out an inspect. `store_lane_cap` returns the PREVIOUS cap
so the push knows the direction; only a lowering needs to say anything.

The guard is structural, not timed: `lane_view` and `push_lane_cap` must not
ACCEPT a session. A timing test would be flaky, and a call-order test would
pass against a version that took the session and merely used it early.

`/api/system/health` has the same shape and is NOT fixed here — it is
rate-limited by `refresh_if_stale` so it does not inspect on every request.
Worth doing, separately.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR
2026-09-23 14:52:36 -04:00
bvandeusenandClaude Opus 5 61641fbba7 fix: a test still described the control the cap replaced (4295)
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Run 7367, integration lane:

    FAILED test_a_cap_is_stored_even_when_it_cannot_be_pushed
    assert True is False

The code was right. Raising a cap is PERMISSION, not a request — it
deliberately does not grow the pool, because that would put workers on a lane
with nothing to do, and the sizing pass spends the permission on its next tick
if there is work. So nothing is pushed and `applied` is vacuously true.

The test was carried over from when the number meant "run this many", where
every write pushed. It asserted the old control's behaviour against the new
one — lesson #4338's shape again: an assertion encoding the thing that
changed, failing on the change rather than on a defect.

Split into the two cases that actually exist now:

- raising a cap stores it and pushes nothing, reporting applied;
- turning a lane OFF does push, because consumers follow the cap immediately
  in both directions — off must take effect when it is asked for — so with
  nothing answering it reports `applied: false` with a reason, and the value
  is still stored for the sizing pass to carry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR
2026-09-23 12:57:33 -04:00
bvandeusenandClaude Opus 5 445164c852 feat: one number per lane — the cap — and the autoscaler is the mechanism (4295)
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Operator, 2026-09-23: *"auto should be always on, not a setting, so that idle
instances quiet down when not running. the number that is visible and
something the user can tweak and manage should be the cap itself the number of
running workers is handled by the autoscaling function which is always on."*

They are right, and the reason it was not built this way is worth stating: the
manual dial came first (steps 2-4) and the autoscaler came last (step 7), as
an opt-in BESIDE a control that already existed. Nothing ever asked whether
the dial should still exist once something could move it automatically. Each
step was defensible; the result was three operator settings over one number.

## `slots`, `enabled` and `autoscale` are gone

`slots` was a MEASUREMENT wearing a preference's clothes. How many workers a
lane runs is read live and moved every minute; storing it meant the operator
had to keep two numbers in agreement and the autoscaler had to be told it was
allowed to touch one of them.

`autoscale` gated the mechanism behind a choice, so a lane nobody opted in
never gave its workers back — which is why an idle instance never quieted
down.

`enabled` is derived: a cap of zero means no consumers. "Off" and "may use no
workers" were two spellings of one fact, stored separately, free to disagree.

## Two sweeps become one

`reconcile_lanes_sync` drove the pool to the stored `slots`; `autoscale_lanes_
sync` moved it away from that same number; and most of step 7's hardest
reasoning — a stored value that is a FLOOR, a target of `max(stored, current)`
— existed only to stop them fighting. Delete the stored number and the problem
is not solved, it is absent.

`size_lanes_sync` runs every minute and owns both consumers and pool size. It
also subsumes what the reconcile was for: a worker restarted at its ENV
concurrency is corrected on the next tick rather than after five.

Growth is immediate, shrink is one worker per tick. Deliberately asymmetric —
"always on" is only pleasant if the ramp keeps up, and +1/minute would take
four minutes to answer a burst. Being one worker too large for a minute costs
a sleeping process; being too small costs work not happening. For ML the
asymmetry matters most: every new slot reloads a multi-GB model, so the slow
shrink is what stops a quiet patch from paying that cost again a minute later.

## The caps ship at one, and zero for ML

Per the operator. Conservative on purpose — and a conservative default nobody
knows how to raise is just a slow product, which is the other half of what
they asked for:

    "there needs to be something that tells the user to bump those numbers to
     improve processing rate or they'd never know the controls exist."

So a lane running everything its cap allows while work piles up says so, in
its own row, with the headroom named: *"4,060 waiting and all 1 worker busy.
Raise the cap to run more at once — this machine allows up to 7."*

It fires only when raising the cap would actually help. Not when the lane is
keeping up, not when the sizing pass has room it has not taken, and not at the
machine ceiling — where "raise the cap" is advice nobody can take.

## Migration 0105 rewrites the caps rather than carrying them

The old defaults (4/2/2/1) bounded a manual control and were loose because
moving within them was the ordinary act. The number now means "the most
workers this lane may use", which is a different promise; carrying the old
figure over would quadruple the worker lane on every existing install at the
moment this deploys.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR
2026-09-23 12:48:22 -04:00
bvandeusenandClaude Opus 5 abe16aa382 feat: the System tab is one bounded table, and the dial is the switch (4295)
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Operator, 2026-09-23, on the screenshot: *"I feel that we can probably combine
the two sections into a single table and to format it in such a way that it
appears more bounded and less free-form or open. also there's nothing to
describe what 'auto' means or why their needs to be or should be on/off
toggles. almost all of it always needs to run there's only one optional piece
and it is killed by moving the 'cap' to zero."*

Three separate things, all correct.

## The four lanes were listed twice

The roster (milestone 365) said "ML tagging is running", and four hundred
pixels below it the lanes pane said "ML tagging · 1/1 busy". Two answers to
one question from two endpoints, free to disagree on screen. I moved the
second pane onto this tab yesterday and did not notice it duplicated the
first.

Now one row per part, with controls on the rows that have a lane and none on
the rows that do not. The join is on the QUEUE SET, because that is what
`service_roster` keys a celery part on — as a set, not as a string, so neither
side has to agree about order.

It lives in `utils/systemParts.js` rather than inline, and has a spec, because
its failure is SILENT and is the exact thing it exists to prevent: a lane that
stops matching its part does not throw, it grows a second row for the same
worker. The duplication, returning through the code that removed it.

## Bounded, not free-form

A real table — header, column rules, one bordered card — instead of dotted
rows floating on the page background with nothing saying where the list began
or what a column meant.

## The dial is the switch

There was an `On` switch per lane beside the slots dial. Of four lanes, three
must run for the application to work at all, so that switch offered a choice
that was never real — and for the one lane that IS optional, "off" and "zero
slots" were two ways of saying the same thing that could disagree with each
other.

So `enabled` is now DERIVED from the number: `set_lane` sets it from
`slots > 0` when the caller did not say. It stays on the API and in the model
— it is still the mechanism, and a drain-before-restart may still want a lane
holding its process with consumers cancelled without destroying the operator's
slot count to say so.

Two things fell out that a test now pins:

- The consumer command is sent on the CHANGE, not on the field being present.
  Otherwise every slots write re-sends a command that changes nothing —
  lesson #4183's churn, arriving through the new derivation.
- The model fetch fires on the off→on TRANSITION. It used to test `enabled is
  True`, the field having been sent. The UI no longer sends it, so the
  download that makes the ML lane usable would simply never have fired and the
  lane would have come on to consume a queue it had no model for.

## And Auto now says what it is

A legend under the table, in the operator's terms: what a slot is, that zero
turns a lane off, that three of the four are not optional, what `of N` means,
and that Auto lets a lane add slots by itself when its queue is backed up AND
every slot is busy — with why it is off by default, since it is the only thing
on the page that acts without being asked.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR
2026-09-23 11:26:27 -04:00
bvandeusenandClaude Opus 5 a9c1b421a7 feat: change a lane's slots on a running system, over the broker (4292)
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Milestone 422 step 2. `GET /api/system/workers` reports every lane joined to
its live pool; `POST /api/system/workers/<name>` changes it.

NO DOCKER SOCKET. Milestone 365 deferred "acting on the state" because
restarting a dead worker needs a socket the web container deliberately does
not have. That holds for restarting a CONTAINER; it does not hold for
changing how much work a RUNNING worker does. celery's pool_grow /
pool_shrink / add_consumer / cancel_consumer send a message over the Redis
the app already uses, and the worker resizes itself. No new privilege, no new
surface, and the security question that deferred this is never raised.

PERSIST AND PUSH, in one call, in that order. pool_grow is not durable — a
restart drops every lane to its env concurrency — so a UI that only pushed
would lose the setting on the next deploy with nothing to show for it (lesson
#4202). Storing alone would describe nothing until something restarted. A
failed PUSH is not a failed setting: 200 with `applied: false` and a reason,
so the UI says "saved, not yet live" rather than "that didn't work". Step 3's
reconcile carries it when the lane answers again.

PER-REPLICA DELTAS. `pool_grow(n, destination=[...])` adds n to EACH
destination, so while `worker` runs `replicas: 2` a single delta from an
aggregate is wrong for both. `slots` therefore means what CELERY_CONCURRENCY
means — one process's pool — and each replica is driven to it from its OWN
current size, so replicas that drifted apart converge rather than moving in
lockstep. I wrote this wrong first: the docstring claimed per-replica while
the code computed one delta from the max across replicas. LaneLiveState now
carries `pools` per hostname and exposes `pool` as a property.

A replica already at the target is sent nothing at all — the reachable fixed
point step 3's periodic reconcile needs, or it re-issues a grow of zero every
tick forever (lesson #4183). A replica that answered inspect but not stats is
NAMED in the error rather than skipped silently, since otherwise it would run
at a size the UI claims it does not.

`present=False` is not "zero slots", it is "nothing answered" — kept distinct
throughout, because step 3 skips an absent lane rather than correcting it.

/workers now also reports pool size (from `insp.stats()`) and RESERVED count.
Celery prefetches, so tasks that have left the Redis list but not started are
invisible to LLEN: a lane can read depth 0 with thirty tasks held in worker
memory. `pending` is depth + reserved. The UI is misleading without this and
step 7's autoscaler would be simply wrong.

Also kills the THIRD copy of the queue list: system_activity's _QUEUE_NAMES,
whose own comment admitted the coupling ("must match celery_app.task_routes")
and which sat alongside task_routes and the ROLE_NAMES copy step 1 collapsed.
Now derived from LANES. The rendered order changes to lane grouping, which is
the better shape for a lane-oriented UI.

Separate blueprint rather than folding into system_activity, which states in
its first line that it is read-only and answers a different question — its
/workers is keyed on celery HOSTNAME and reports which nodes answered.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR
2026-09-22 08:01:23 -04:00