counterweight
3a9e1d5851
Three changes: detection windows tightened, a Signal transport deployed, and
alerts attached to all 84 non-transport endpoints.
── Failing faster ──────────────────────────────────────────────────────────
The heartbeat is a TICKER, not a deadline: Gatus wakes every interval and asks
"did anything arrive in the last interval", so real detection is 1-2x the
window. And a window can only ever be as tight as the push frequency - which is
why two checks moved rather than just having their numbers changed.
liveness, cpu, ups, service-health, probes 16m -> 11m
disk, zfs daily/30h -> 6-hourly/7h
backup store + pull job daily/30h -> 6-hourly/7h
DNS records 24h -> 6h
backup dump 30h -> 26h
backup-dump stays slow because the dump genuinely is daily. The store-side check
catches the same fault within 6h by reading the source's dump timestamp out of
the artefact filename, so 26h is a backstop rather than the primary signal.
── Thresholds differ by check type, deliberately ───────────────────────────
`failure-threshold` counts consecutive failures, but "consecutive" is a
different amount of wall-clock time per check: a push endpoint produces one
failure per heartbeat window, a pulled one per interval. The default of 3 would
mean 33 minutes on an 11m heartbeat and over a day on a 7h one.
More importantly the heartbeat window ALREADY encodes the tolerance - an 11m
window on a 5-minute push is exactly "one missed push forgiven" - so stacking a
threshold of 3 triples a tolerance that was already chosen. Hence:
push/heartbeat endpoints failure-threshold 1
pulled, 5m (public) failure-threshold 3 (= 15 minutes)
pulled, 6h/24h (dns, domain) failure-threshold 1
── The Signal transport ────────────────────────────────────────────────────
roles/signal_api runs signal-cli-rest-api on the observability host, pinned by
digest, MODE=native.
It publishes NO PORTS. The API has no authentication of any kind - anything that
reaches it can send messages as you and read your Signal. Gatus talks to it over
a shared docker network by service name, which is also WHY the network exists:
Gatus runs in a container, so the host's loopback is unreachable from it and a
port published on 127.0.0.1 would not have worked.
MODE=native and not json-rpc because this VPS has 464MB of RAM and already runs
Gatus and Caddy. The json-rpc modes hold a resident JVM; native runs a binary
per request, and alerts are rare enough that startup cost per alert is the right
trade.
Monitored - Gatus polls /v1/health over the same network path the alerts take,
so it proves the delivery route rather than mere container liveness. Deliberately
NOT backed up: the data directory holds Signal private keys and the recovery
path is to link the device again from the phone.
Neither the signal-api endpoint nor Gatus's self-check carries a Signal alert.
If either is down, Signal is precisely what cannot deliver the alert.
── Four traps hit while linking, all now in the role README ────────────────
* /v1/qrcodelink is BROKEN in native mode - returns "no data to encode" while
the binary itself emits a perfectly good URI. Not worked around by switching
MODE, which would put a JVM in the path of every alert permanently.
* The data dir must be owned by uid 1000, not root. A root-owned 0700 dir
cannot be traversed by the container user, so linking silently never
completes and /v1/accounts returns "Failed to read local accounts list".
* `docker exec` runs as ROOT while the service runs as uid 1000, so without
--config the account is written to /root/... on the container's ephemeral
layer. It reports success and is destroyed on the next recreate.
* The phone reporting "network error" was IPv6: chat.signal.org resolves to
dualstack AAAA records first, the container has no IPv6 address, and this
host's IPv6 path is broken - the same edge that 404'd the Go tarball. Fixed
with a mounted gai.conf that prefers IPv4.
Verified: provider loads (configuredProviders=[signal]), a test message was
delivered and confirmed received, 84 endpoints carry alerts, 86 UP / 0 DOWN.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
44 lines
2 KiB
YAML
44 lines
2 KiB
YAML
---
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# The Signal transport for Gatus alerts.
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#
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# Deliberately NOT published and NOT fronted by Caddy: the API has no
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# authentication of any kind, so it is reachable only from the shared docker
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# network that Gatus is on. See roles/signal_api/README.md, including the
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# one-time manual step to link the device.
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- name: Deploy the Signal API on the observability host
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hosts: observability
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become: yes
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roles:
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- signal_api
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# post_tasks, not a second play: the registration below needs the role's
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# defaults (service name, port) in scope, and a separate play would not have
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# them.
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post_tasks:
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# Monitored, because a dead alert transport is the worst kind of dead: every
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# check could be failing and nothing would tell you. Gatus polls it over the
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# shared network - the same path the alerts take - so this proves the actual
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# delivery route rather than merely that a container is running.
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#
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# Deliberately NOT backed up: the data directory holds Signal private keys,
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# and the recovery path is to link the device again from the phone. Backing
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# it up would copy a credential off the host to buy nothing.
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- name: Register the signal-api health endpoint with Gatus
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ansible.builtin.include_role:
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name: gatus_endpoint
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vars:
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gatus_endpoint_name: signal-api
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gatus_endpoint_pulled:
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- name: signal-api
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group: infrastructure
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url: "http://{{ signal_api_service_name }}:{{ signal_api_port }}/v1/health"
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interval: 5m
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# Deliberately NOT alerted via Signal: if this endpoint is down,
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# Signal is exactly what cannot deliver the alert. It is visible on
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# the dashboard, and its failure shows up indirectly as every other
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# alert going missing.
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conditions:
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# /v1/health answers 204 No Content, not 200 - checked live. Any
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# 2xx is asserted rather than the exact code, so an upstream
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# change from 204 to 200 does not read as an outage.
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- "[STATUS] < 300"
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