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>
47 lines
1.6 KiB
Django/Jinja
47 lines
1.6 KiB
Django/Jinja
# Managed by Ansible (roles/signal_api)
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services:
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{{ signal_api_service_name }}:
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image: {{ signal_api_image }}
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container_name: {{ signal_api_service_name }}
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restart: unless-stopped
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environment:
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MODE: "{{ signal_api_mode }}"
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volumes:
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# Prefer IPv4. See gai.conf.j2 - without this, signal-cli reaches for
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# chat.signal.org's IPv6 address, which is unreachable from here, and
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# linking fails with an opaque "network error" on the phone.
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- {{ signal_api_dir }}/gai.conf:/etc/gai.conf:ro
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# Holds the Signal identity: the linked-device keys and registration
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# state. Lose this and the device must be linked again by scanning a new
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# QR code from the phone. It is also the most sensitive thing on this
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# host - anyone with these keys can send and read Signal as you.
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- {{ signal_api_data_dir }}:/home/.local/share/signal-cli
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networks:
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- {{ signal_api_network }}
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# NO PORTS. Deliberately.
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#
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# This API has no authentication whatsoever - no key, no token, nothing.
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# Publishing it, even on 127.0.0.1, would expose "send a Signal message as
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# this identity" to anything that can reach the host. Gatus talks to it over
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# the shared docker network by service name instead, which is why no port is
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# published and why there is no Caddy vhost.
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healthcheck:
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test: ["CMD", "curl", "-fsS", "http://localhost:8080/v1/health"]
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interval: 60s
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timeout: 5s
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retries: 3
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logging:
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driver: json-file
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options:
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max-size: "10m"
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max-file: "3"
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networks:
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{{ signal_api_network }}:
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external: true
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