Skip to content
oto
Menu
Overview
IntroductionConceptsArchitectureContributingReleasing
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_ingest_shed_total
Type counter
Labels reason — pool_exhausted, in_flight, queue_depth
Registered in internal/ingestion/service/metrics.go, incremented in internal/ingestion/api/shed.go
Alertable yes, on a sustained rate
Rule OtoIngestShedding in deploy/prometheus/oto-rules.yaml

What it counts

Section titled “What it counts”

Requests answered 503 with a Retry-After as deliberate backpressure.

Shedding is a feature (C17, ADR 0007), not a failure. Alertmanager retries 5xx — and only 5xx — for about five minutes, so a 503 is a designed and sufficient backpressure channel. A 429 would be a 4xx, and Alertmanager deletes a notification permanently and silently on any 4xx, which is why oto has no rate limiter on this path.

So: a brief spike during a storm is the system working. A sustained rate is spending the upstream’s retry budget on queueing, and once it is spent the notification is gone.

The reasons, and what each one actually says

Section titled “The reasons, and what each one actually says”
reason What was full First thing to look at
queue_depth the ingest River queue is past MaxQueueDepth (default 25 000) the workers, not the database
pool_exhausted the ingest pgx pool has no free connection Postgres latency, and the ingest queue workers sharing that pool
in_flight the concurrency gate filled and the acquisition budget (ingest.acquire_timeout, 500 ms) elapsed the same two, one level up

The distinction is the point: “we are out of database” and “the workers are behind” have different fixes.

What to check

Section titled “What to check”
  1. oto_job_queue_depth for queue="ingest", state="available" — the 25 000 default is roughly two and a half minutes of backlog at 16 workers, chosen to sit inside Alertmanager’s retry budget.
  2. GET /readyz — the pools block reports saturation without scraping /metrics.
  3. oto_ingest_process_duration_seconds: are batches slow, or merely numerous?
  4. Postgres: log_min_duration_statement is 500 ms in the dev compose; look for the statement that got slow, and for lock waits.

What to do

Section titled “What to do”
  • queue_depth: add ingest workers or pods. Do not simply raise MaxQueueDepth — that converts “shed early enough to be retried” into “accept work the upstream will give up on”, which turns a 202 into a promise oto cannot keep.
  • pool_exhausted: raise OTO_DB_INGEST_SHARE_PERCENT or the total pool, and check OTO_DB_INGEST_STATEMENT_TIMEOUT is still being honoured. Remember the accept handler and the ingest queue workers share this pool.
  • in_flight: MaxInFlight should equal the ingest pool size. Setting it higher moves the queue into pgx where it is invisible and unmeasured.
  • Never respond by returning 429 or 4xx from this path.