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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_delivery_claim_lost_total
Type counter
Labels mode — post_root, update_root, thread_reply, broadcast_reply
Registered in internal/notification/service/metrics.go; incremented in internal/notification/service/dispatch.go
Alertable YES — page on it. The code says: this counter is an alert, not a statistic
Rule OtoDeliveryClaimLost in deploy/prometheus/oto-rules.yaml

What it counts

Section titled “What it counts”

Sends that reached the provider and could not be recorded, because the row was no longer this worker’s to write: the §G.5 claim lease expired mid-call and another worker reclaimed it, or a recovery resolved the slot.

Why every single increment matters

Section titled “Why every single increment matters”

There is now a message in somebody’s channel with no sent row behind it. Concretely:

  • oto has forgotten a delivery it made, so the timeline is missing a message that exists;
  • the slot may be retried or recovered, so oto may send it again — duplicates in the channel;
  • for post_root, the thread’s root handle was not written, so subsequent replies may start a second thread for the same group.

Nothing is retried automatically here, deliberately: returning an error would retry a send that has already happened. The counter, plus the log line, are the entire recovery mechanism.

What to check

Section titled “What to check”
  1. The log record — it carries everything needed to find the orphan: 
    msg="notification: a delivery landed but its claim was gone; nothing was recorded"
    delivery_id= thread_id= mode= provider_message_id= provider_conversation_id= attempts=
    provider_message_id is the message in Slack. Go and look at it.
  2. notification_deliveries for delivery_id: what status is it in now, and did another worker complete it?
  3. channel_threads for thread_id: is provider_thread_id set, and does it match the orphan?
  4. oto_job_duration_seconds for kind="deliver.dispatch" — compare the provider-call latency against the 120 s lease.

What to do

Section titled “What to do”
  • Sustained non-zero means the claim lease is shorter than the provider’s real latency. That is the diagnosis the code states outright. Confirm with the duration histogram; if p99 of a dispatch is anywhere near 120 s, the lease is the problem, not the provider.
  • Check for two workers on the same queue with clock disagreement. The lease is time-based, so a skewed pod reclaims rows that are not stale.
  • Look for pods being killed mid-send (OOM, aggressive rolling restarts): a worker that dies holding a claim releases it by expiry, and the retry lands on the same message.
  • After the fact, reconcile by hand: the timeline entry can be recovered from provider_message_id, and duplicates in the channel should be explained rather than deleted.