alerting: Signal via signal-cli-rest-api, and faster failure detection
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>
This commit is contained in:
parent
85040d5f67
commit
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GPG key ID:
883EDBAA726BD96C
20 changed files with 752 additions and 181 deletions
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@ -34,6 +34,23 @@
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# slow apt run, a reboot - does not raise an alarm, but a check that has
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# genuinely stopped does.
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# ─────────────────────────────────────────────────────────────────────────────
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# ─────────────────────────────────────────────────────────────────────────────
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# Alerting thresholds, and why they differ by check type.
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#
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# `failure-threshold` counts CONSECUTIVE failures, but "consecutive" means a
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# different amount of wall-clock time per check:
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#
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# push/heartbeat endpoints a failure is produced once per heartbeat window
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# pulled endpoints a failure is produced once per interval
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#
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# So the default of 3 would mean 33 minutes on an 11m heartbeat and over a day
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# on a 7h one - and the heartbeat window ALREADY encodes the tolerance. An 11m
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# window on a 5-minute push is precisely "one missed push forgiven"; stacking a
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# threshold of 3 on top triples a tolerance that was already chosen.
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#
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# Hence: push endpoints alert on the FIRST heartbeat failure. Pulled endpoints
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# have no built-in tolerance, so the threshold is where it belongs for them.
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# ─────────────────────────────────────────────────────────────────────────────
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- name: Register the host checks with Gatus
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hosts: observability
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become: yes
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@ -47,7 +64,7 @@
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'name': item,
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'group': 'liveness',
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'token': gatus_push_tokens[item],
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'heartbeat': '16m'}] }}"
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'heartbeat': '11m'}] }}"
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loop: "{{ monitored }}"
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- name: Build the disk endpoint list
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@ -56,13 +73,20 @@
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'name': item,
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'group': 'disk',
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'token': gatus_push_tokens[item],
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'heartbeat': '30h'}] }}"
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'heartbeat': '7h'}] }}"
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loop: "{{ monitored }}"
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- name: Register liveness endpoints
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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_default_alerts:
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- type: signal
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# 1, not 3: the heartbeat window is the tolerance. See the note above.
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failure-threshold: 1
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success-threshold: 2
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send-on-resolved: true
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minimum-reminder-interval: 6h
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gatus_endpoint_name: liveness
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gatus_endpoint_external: "{{ liveness_endpoints }}"
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@ -70,6 +94,13 @@
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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_default_alerts:
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- type: signal
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# 1, not 3: the heartbeat window is the tolerance. See the note above.
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failure-threshold: 1
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success-threshold: 2
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send-on-resolved: true
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minimum-reminder-interval: 6h
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gatus_endpoint_name: disk
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gatus_endpoint_external: "{{ disk_endpoints }}"
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@ -77,20 +108,27 @@
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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_default_alerts:
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- type: signal
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# 1, not 3: the heartbeat window is the tolerance. See the note above.
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failure-threshold: 1
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success-threshold: 2
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send-on-resolved: true
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minimum-reminder-interval: 6h
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gatus_endpoint_name: hypervisor
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gatus_endpoint_external:
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- name: cpu
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group: hypervisor
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token: "{{ gatus_push_tokens['nodito'] }}"
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heartbeat: "16m"
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heartbeat: "11m"
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- name: zfs
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group: hypervisor
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token: "{{ gatus_push_tokens['nodito'] }}"
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heartbeat: "30h"
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heartbeat: "7h"
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- name: ups
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group: hypervisor
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token: "{{ gatus_push_tokens['nodito'] }}"
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heartbeat: "16m"
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heartbeat: "11m"
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- name: Deploy host liveness and disk checks
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hosts: managed
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@ -120,10 +158,13 @@
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healthcheck_name: disk-usage
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healthcheck_description: "Disk usage for {{ inventory_hostname }}"
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healthcheck_check: disk-usage
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# Daily. RandomizedDelaySec spreads twelve hosts across the hour rather
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# than having them all report in the same second.
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healthcheck_on_calendar: "*-*-* 07:00:00"
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healthcheck_randomized_delay: "3600"
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# Every 6h rather than daily. Disk usage itself moves slowly, but the
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# heartbeat can only be as tight as the push frequency - a daily push
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# forces a >24h window, and a stuck check then hides for a day and a
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# half. Six-hourly buys a 7h window. RandomizedDelaySec spreads the
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# hosts so twelve boxes do not all report in the same second.
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healthcheck_on_calendar: "*-*-* 00/6:00:00"
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healthcheck_randomized_delay: "900"
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healthcheck_boot_delay: "5min"
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healthcheck_push_url: "{{ gatus_api }}/disk_{{ host_key }}/external"
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healthcheck_push_token: "{{ host_token }}"
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@ -157,7 +198,7 @@
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healthcheck_check: zfs-health
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healthcheck_packages: [curl, jq]
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healthcheck_zfs_pool: "{{ zfs_pool_name }}"
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healthcheck_on_calendar: "*-*-* 07:20:00"
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healthcheck_on_calendar: "*-*-* 00/6:20:00"
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healthcheck_boot_delay: "10min"
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healthcheck_push_url: "{{ gatus_api }}/hypervisor_zfs/external"
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healthcheck_push_token: "{{ host_token }}"
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