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Design
oto — System Design ProposalDomain Research: Prometheus Alertmanager + Slackoto — Red-Team Memooto — SCOPE BOUNDARY (the doctrine)oto — BINDING SPECIFICATION v1
ADRs
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
Setup
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`
Runbooks
oto runbooksAlert search — optional partial/substring matching on alert namesoto_clock_skew_secondsoto_delivery_claim_lost_totaloto_ingest_accepted_totaloto_ingest_alerts_totaloto_ingest_duplicate_totaloto_ingest_duration_secondsoto_ingest_fingerprint_mismatch_totaloto_ingest_process_duration_secondsoto_ingest_rejected_totaloto_ingest_shed_totaloto_job_duration_secondsoto_job_queue_depthoto_jobs_dead_totaloto_jobs_enqueued_totaloto_jobs_failed_totaloto_jobs_panics_totaloto_jobs_snoozed_totaloto_jobs_started_totaloto_jobs_succeeded_totaloto_jobs_unknown_version_totaloto_render_invalid_totaloto_slack_unknown_action_totaloto_stream_connectionsoto_stream_events_coalesced_totaloto_stream_events_dropped_totaloto_stream_events_fetched_totaloto_stream_events_published_totaloto_stream_fetch_errors_totaloto_stream_listener_reconnects_totaloto_stream_notify_malformed_totaloto_stream_notify_received_totaloto_stream_poll_recovered_totaloto_stream_resync_totaloto_thread_gap_recovered_totaloto_thread_head_wait_secondsoto_thread_order_decisions_total

oto_stream_events_coalesced_total
Type counter
Labels none
Registered in internal/streaming/service/metrics.go
Alertable no — informational, and non-zero is the feature working.

What it counts

Section titled “What it counts”

Frames superseded within the 250 ms coalescing window: latest wins. When an alert group changes three times in a quarter of a second, the browser is sent the final state once instead of three intermediate states it would immediately overwrite.

Why there is no response

Section titled “Why there is no response”

Nothing is lost. A coalesced frame is a frame whose content was replaced by a newer version of the same thing before it was sent, and the client ends up with the newer version — which is what it would have rendered anyway.

Worth reading, never worth paging:

  • A high coalesce ratio during a storm is the window doing its job and is the reason a storm does not melt the browser.
  • A coalesce rate that is high outside a storm suggests something is rewriting group state in a tight loop. That is worth a look in the ingest path, not in streaming.

Do not confuse this with oto_stream_events_dropped_total. Coalescing replaces; dropping discards and forces a resync.