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oto — System Design ProposalDomain Research: Prometheus Alertmanager + Slackoto — Red-Team Memooto — SCOPE BOUNDARY (the doctrine)oto — BINDING SPECIFICATION v1
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0001 — PostgreSQL is the sole datastore; River is the job queue0002 — `internal/<domain>/{api,service,repository,domain}` with three model sets0003 — Alert, AlertOccurrence and AlertEvent are three distinct entities0004 — oto owns alert identity; Alertmanager's fingerprint is recomputed, not trusted0005 — A durable group key, and the AlertGroup generation owns the Slack thread0006 — The Alertmanager API v2 reconciler is mandatory, not optional0007 — Webhook response contract: 202 or 503. Never 4xx, never 429.0008 — Slack: `chat.update` in place is primary; threads are secondary; one colour attachment0009 — Rule definitions are snapshotted and versioned at fire time0010 — Server-Sent Events with durable resume, not WebSocket0011 — Validation is seven layers with two opposite trust models0012 — Pastel product chrome, saturated colour reserved exclusively for state0013 — oto is alert-first: the Flight Recorder Test defines the scope boundary0014 — Postgres is the only store; no TSDB or column store in v10015 — No stream processor; River in Postgres is the pipeline0016 — Cluster context arrives via MCP, on demand; never the Kubernetes event firehose0017 — Alertmanager-style matchers, not CEL; and a filter AST that keeps the door open0018 — Slack distribution: a customer-built internal app, credentials in config0019 — MIT licence0020 — Broadcast the transitions that must be seen0021 — Correctness and testing strategy0022 — Length-prefixed identity pre-images0023 — Terminal thread states are decided first, and the send is three phases0024 — Retention defaults, what each boundary destroys, and cold storage0025 — The alert list resolves rule snapshots in a batch, not per row0026 — `refire_grace` and the flap thresholds, derived from a real rule corpus0027 — Delivery drills: a synthetic alert through the real pipeline, and the mark that keeps it out of the numbers0028 — Non-urgency motion: one-shot events, honest activity loops, and nothing else0029 — Type and radius scales, read off the product rather than drawn for it0030 — Tier A repainted as Washi & Ink / Konshi Sutra; accent moves to beni0031 — Sharp corners and higher-contrast grid lines within Washi & Ink; colours unchanged0032 — Dark-theme accent moves from beni to plum-blossom blue-and-white; light untouched0033 — The alert filters are a toolbar above the table, not a panel in the rail0034 — Notifications is a destination, and the record it keeps is readable0035 — Decorative ink as a masked wash: one primitive, four motifs, and the placements it is refused0036 — AlertOccurrence becomes AlertCase, and `case` is argued against FR-1 by name0037 — A Wording is Liquid, and the structure around it stays oto's0038 — The group key is derived from the alert's own labels0039 — Group close stays activity-driven0040 — A Case is `open` or `closed`, and it is never reopened0041 — The Alert/Case allocation, and the one rule that decides it0042 — Storm damping is removed, because the defence was built before its object0043 — The Slack action row renders five elements, and the fifth is the snooze pair0044 — A count condition is a silence the operator asked for, and `below_threshold` is how oto says so0045 — A Case is a conversation, and one Slack thread per alert is the accepted cost0046 — Corners round again: ADR 0031's radius override is reversed0047 — A channel answers to a connection, and Slack gets two scopes back0048 — A Wording is spelled by its channel, and the marks in between are oto's0049 — A Wording is selected by its own clause, not by a route0050 — A NotificationTemplate is one whole message, and its policy says which one0051 — A `raw` template owns the whole message, and a template may carry its replies0052 — An Incident is drawn over Cases, and its response is handed off0053 — An Investigator reads, proposes, and never decides delivery0054 — A Remedy earns the write path0055 — An incident-tool integration is data or a bridge, never code inside oto0056 — A Case the upstream stopped speaking about expires, and says why
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Configuration referenceReaching an incident tool: the envelope, a mapping, or a bridgeInvestigatorsRemediesConnecting oto to SlackThe live Slack verification runTuning otoConnecting oto to VictoriaMetrics (vmalert)The generic webhook and `oto.notification.v1`
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0010 — Server-Sent Events with durable resume, not WebSocket

Status: Accepted · 2026-08-07

Context

Section titled “Context”

The alert wall must be live. The traffic is entirely server→client: every client→server action already has a REST endpoint, and Slack interactivity arrives over webhooks or Socket Mode. The real requirement is not “push” — it is correctness after a gap. An engineer’s laptop sleeps through an incident and must wake into a correct UI, not a stale one.

Decision

Section titled “Decision”

One endpoint: GET /api/v1/stream, text/event-stream, with Last-Event-ID resume backed by a durable ui_events table.

  • ui_events.seq is a monotonic BIGSERIAL and is the SSE event id. On reconnect the browser sends Last-Event-ID: N automatically; the server replays seq > N from the last 24 hours, then attaches live.
  • If the gap exceeds 10 000 rows or falls outside the retention window, the server sends a single resync frame and the client refetches.
  • Fan-out: each API pod holds one pgx connection issuing LISTEN oto_events. Writers NOTIFY oto_events, '<org_id>:<seq>' in the same transaction that wrote ui_events. The payload is deliberately tiny — the 8 kB NOTIFY limit is a trap; the hub re-reads the rows.
  • Coalescing: at most one frame per connection per 250 ms per (kind, resource_id).
  • Backpressure: a bounded ring buffer per connection; on overflow, drop and send resync. Never block a writer for a reader.
  • Fallback: every stream-fed list endpoint also accepts ?since_seq= for pure polling, used when a corporate proxy kills SSE.

Consequences

Section titled “Consequences”
  • SSE is plain HTTP: it inherits the existing auth middleware, proxies, tracing and metrics, and EventSource is five lines in the browser. There is no second serialisation path and no custom reconnect logic.
  • Resume is free and correct. WebSocket gives none of this without building a replay log anyway — at which point the socket buys nothing.
  • ui_events is an hourly-partitioned table with 24-hour retention, and one more writer obligation inside domain transactions.
  • Solid’s fine-grained reactivity means an SSE-driven store update re-renders exactly one table row. That is Solid’s superpower and the reason it is in the stack.
  • Client→server subscription changes require a reconnect with different query parameters. Acceptable.

Alternatives rejected

Section titled “Alternatives rejected”
  • WebSocket: bidirectional capability we do not need, plus connection state, heartbeats, custom reconnect and a second serialisation path. It becomes necessary only for collaborative editing or high-frequency client-initiated subscriptions — at which point it is an additive endpoint, not a rewrite.
  • Long polling: more requests, worse latency, same amount of code.
  • Polling only: simpler, and visibly worse for a live alert wall. Retained as the fallback, not the default.