Everything this server does assumes alerts arrive. If Prometheus stops
evaluating, or Alertmanager cannot reach us, nothing arrives — and
silence is indistinguishable from everything being fine. The cluster has
shipped the alert for exactly this case all along: Watchdog is
expr: vector(1), so it fires permanently and is re-sent forever, and it
is worth nothing unless something downstream notices it stop. Nothing
did. It arrived, opened no incident because a repeat_interval re-send is
not a new occurrence, and when the monitoring stack died the sweeper
quietly expired it and paged nobody.
So the handling is inverted for a configurable set of alerts: receiving
one opens no incident, and the absence of one does. TERDUT_DEADMAN_MATCHERS
selects them as label matchers, defaulting to alertname=Watchdog.
The unit of monitoring is the fingerprint rather than the alert name. Two
clusters sending the same Watchdog are two independent switches, so a
healthy one can never mask a dead one. Every matcher must name an
alertname, which keeps the sweeper's candidate query on alerts_name_idx
instead of JSON-extracting labels from every row, and leaves matching
with a single implementation.
A switch is dormant until its first heartbeat: a matcher nothing has ever
sent opens nothing, so a fresh deploy or a restored database does not
page. Resolving the incident by hand sticks, exactly as it does for an
alert-backed one, so a decommissioned source is a one-time page rather
than a nag; the switch re-arms only when the heartbeat comes back, and
dying again is a new incident.
The incident has no member alerts on purpose. Linking the heartbeat would
have the settled-incident cascade close it on the very sweep that opened
it, and there is no alert describing the problem anyway — the problem is
that no alert arrived. What happened is on the timeline instead, and
recovery is the only automatic way out.
One narrow exemption in the ingest guard makes recovery possible at all.
A heartbeat we declared dead is marked resolved, and the one that proves
us wrong carries the unchanged startsAt of an alert that never stopped
firing — so "resolution is terminal within an instance" would discard it
forever and a switch could die exactly once. The exemption is scoped to
resolution_source = 'deadman', which is the only resolution this server
infers from silence on a timeout of its own, so nothing another writer
set can be undone by a stale retry. Matched alerts are also held back
from the generic staleness expiry, which would otherwise resolve a
heartbeat as 'expiry' long before its own tighter deadline.
The timeout points the opposite way to TERDUT_STALE_AFTER: staleness is a
generous grace period around a repeat_interval you do not control, while
this is a deadline you set deliberately and configure the heartbeat's
route to beat. Inheriting a 4h or 12h repeat_interval gives a dead man's
switch with a twelve hour fuse, so the README spells out the route the
heartbeat needs.
The handler never deletes the token: it stays valid until expires_at and
is purged by the sweeper, so a second tap is an idempotent no-op rather
than a rejection. Caught by pressing Acknowledge twice against the live
server. What bounds the token is scope -- one incident, one action, one
day -- not a use count.
An incident opened, got assigned to whoever held today's schedule entry,
and then sat there silently until somebody thought to look. The schedule
and the incident model were both built; nothing reached the person
holding the pager.
Notifications go out through ntfy, over plain HTTP with no new
dependencies. Delivery is an outbox rather than an inline call: the pool
is limited to a single connection, so a POST made while holding the
webhook's transaction would stall every other request behind it. The
webhook inserts a row and a notifier goroutine sends it within a tick,
retrying with exponential backoff.
Only opening an incident has to resolve a topic from scratch. Reminders
and all-clears reuse whatever that first notification chose, which keeps
configuration out of resolveIfSettled and gives the right rule for free:
you only hear that something resolved if you were told it started.
Each push carries an Acknowledge button, because the useful thing to do
at 3am is stop the pager without unlocking anything. It POSTs to an
unauthenticated /api/notify/ack/{token} — a notification body lives on
the ntfy server and in the device cache, so a real API key must never
appear in one. The token is minted per delivery, scoped to one incident
and one action, and expires in a day.
Reminders repeat until the incident stops being untouched. The stop
conditions are the states that already mean somebody has it: acknowledged,
snoozed, resolved, archived. Snooze is the mute button, so there is no
separate reminder cap.
Notifications sent to the fallback topic carry no Acknowledge button. The
topic is shared, and a button on it would let any subscriber acknowledge
as somebody else.
The alerts row was both Alertmanager's record and the human work queue, and
the two have different owners. The webhook upsert rewrites that row on every
notification; acknowledgement, comments and archiving were columns on it that
the upsert happened not to touch. So an alert that resolved and re-fired days
later still read as acknowledged by whoever acked the first occurrence — the
ack outlived the thing it referred to. Nothing recorded transitions either:
rows are mutated in place, so there was no timeline and no way to compute how
long anything took.
Alerts are now read-only signal records with two states, and incidents are
the work item: triggered, acknowledged or resolved, with an assignee, a
snooze, notes and an append-only timeline. Many alerts map to one incident,
and a new occurrence opens a new incident, which is what makes a stale ack
impossible rather than merely unlikely.
Correlation uses Alertmanager's own groupKey. It already grouped the alerts
according to the group_by routing tree the operator configured and sends the
result on every webhook, where it was being discarded; adopting it means
changing group_by in alertmanager.yml changes correlation here, with no
second grouping scheme to configure and keep in sync.
An incident opens only when an alert transitions into firing — an unseen
fingerprint, a newer startsAt, or a resolved alert starting again. The
unchanged notifications Alertmanager re-sends every repeat_interval are none
of those. That rule is what lets manual resolution be terminal: without it,
closing an incident by hand would be undone by the next re-send of an alert
that never stopped firing, and the button would be a lie. Snooze covers the
"not now" case instead. Incidents otherwise resolve by cascade, once every
alert under them has stopped firing, whether by webhook or by expiry.
New incidents are assigned to whoever holds today's schedule entry. The
schedule table has existed since the first release with nothing reading it.
Also here, following from the split:
- Incident severity is a high-water mark over its alerts, never lowered.
An incident that hit critical was a critical incident, and downgrading a
live one would demote it in the queue while the work is still open.
- /api/stats/incidents reports MTTA and MTTR, null rather than zero until
there is something to average. Neither was computable before.
- Alert archiving becomes sweeper-only housekeeping; the archive people
interact with is the incident's.
Breaking: the alert acknowledge, archive and comment endpoints are gone, and
the alert object drops the acknowledgement fields and gains incident_id. The
README maps each removed endpoint to its replacement. Migration 008 backfills
an incident per existing alert, archived ones included so no comment is
orphaned, carrying acknowledgements across and turning comments into timeline
notes.
Both documented alert contracts are untouched: received_at still advances on
every accepted payload, re-sends included, and resolution_source still says
how much to trust ends_at. The upsert is byte-for-byte what it was, now
running inside the ingest transaction.
Alerts can be manually archived (POST /api/alerts/{id}/archive) or
unarchived (DELETE /api/alerts/{id}/archive). A background goroutine
auto-archives resolved alerts older than TERDUT_ARCHIVE_AFTER (default 7d).
GET /api/alerts hides archived alerts by default; ?archived=true shows them.
- GET /api/stats/alerts — total/firing/resolved counts
- GET /api/stats/alerts/top — most frequent alert names (?limit, default 10)
- GET /api/stats/alerts/by-hour — counts for all 24 hours (zeros filled in)
- GET /api/stats/alerts/by-day — counts for all 7 days with names (zeros filled in)
- All endpoints accept optional ?from/?to (YYYY-MM-DD) to filter by received_at
- Migration 005: schedule_entries table (date TEXT UNIQUE, one person per day)
- POST /api/schedule — assign user to one or more dates in a single
transaction; any date conflict rejects the whole request (409)
- GET /api/schedule — list all entries ordered by date, optional ?from/?to
- GET /api/schedule/current — today's on-call user (UTC date), 404 if none
- DELETE /api/schedule/{id} — remove an entry (204)
- Migration 004: acknowledged_by/acknowledged_at columns on alerts,
alert_comments table (FK cascade on delete)
- POST /api/alerts/{id}/acknowledge — stamps authed user + timestamp,
returns updated alert with acknowledged_by username
- DELETE /api/alerts/{id}/acknowledge — clears ack (204)
- GET /api/alerts/{id}/comments — list in chronological order
- POST /api/alerts/{id}/comments — add comment (returns 201)
- DELETE /api/alerts/{id}/comments/{commentID} — own comments only (204)
- All alert queries now LEFT JOIN users for ack username
- Migration 003: alerts table with fingerprint UNIQUE, JSON label/annotation
columns, nullable ends_at, and indexed status/name/received_at
- POST /api/alertmanager/webhook — upserts each alert by fingerprint;
zero endsAt ("0001-01-01") stored as NULL (still firing)
- GET /api/alerts — filtered list (?status, ?name, ?from, ?to, ?limit)
- GET /api/alerts/{id} — single alert lookup
- Migration 002: users and api_keys tables (Unix timestamps, FK cascade)
- POST /api/bootstrap — creates first user + key when DB is empty
- POST/GET/DELETE /api/users — user CRUD
- POST/DELETE /api/users/{id}/api-keys — key issuance and revocation
- AuthMiddleware: SHA-256 bearer token lookup, last_used_at tracking
- Raw key returned once on creation; only SHA-256 hash stored
- go mod init with chi, modernc.org/sqlite, golang.org/x/crypto
- Custom embedded migration runner (no CGO dependency)
- Config from TERDUT_ADDR / TERDUT_DB_PATH env vars
- chi router with /healthz endpoint
- Graceful shutdown on SIGINT/SIGTERM
Niklas Ye