counterweight
a3d3f063f8
The systemd unit checks alerted on failure-threshold 1, on the reasoning that the heartbeat window is the tolerance. That covers a MISSING push, but a unit caught mid-restart - a deploy, an upgrade, a backup stopping it - pushes an explicit false, and each of those paged and resolved ten minutes later. 2 means down on two consecutive 5-minute runs. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
124 lines
6.8 KiB
YAML
124 lines
6.8 KiB
YAML
---
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# Is each systemd-deployed service actually running?
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#
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# Every 5 minutes, with an 11-minute Gatus heartbeat - one missed run before
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# it alarms, so a reboot or a slow check does not page anyone, but a host that
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# stops reporting does.
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#
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# This closes the gap that let a real bug run unnoticed: a backup script left
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# forgejo, lnbits, headscale and memos stopped, and NOTHING caught it. The dumps
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# exited 0, the artefacts were correct, the deploy said failed=0, and liveness
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# only proves the HOST is up - not that anything on it is serving.
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#
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# One endpoint PER UNIT, not per host. A host running four services needs four
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# endpoints, or a single red light says "something on vipy is down" without
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# saying which - and that is the question you actually have at 3am. But only ONE
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# timer per host: the check iterates that host's units and pushes a result for
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# each, the same way check-backups.sh reports per source. Four units on vipy
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# would otherwise mean four scripts, four services and four timers.
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#
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# Which units each host runs is in host_vars/<host>/main.yml as
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# monitored_services, because "what runs here" is a property of the machine.
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#
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# Keys are host-qualified because unit names collide - caddy runs on four
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# machines. Gatus computes sanitize(group)_sanitize(name), so group "services"
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# and name "vipy/caddy" give services_vipy-caddy.
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# ─────────────────────────────────────────────────────────────────────────────
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# Register one endpoint per unit. Runs first: Gatus reloads within 30s, and the
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# host play above takes minutes, so every endpoint exists before its first push.
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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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# EXCEPT here, where the threshold is 2. The heartbeat only forgives a MISSING
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# push. These checks also push an explicit `false` whenever a unit is caught
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# mid-restart - a deploy, an unattended upgrade, a backup stopping the service
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# for its dump - and at 1 every one of those pages, then resolves ten minutes
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# later. 2 means "down on two consecutive 5-minute runs", i.e. 5-10 minutes.
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# A host that stops reporting altogether still alarms on the heartbeat alone.
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# ─────────────────────────────────────────────────────────────────────────────
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- name: Register the service checks with Gatus
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hosts: observability
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become: yes
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tasks:
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# Two plain steps rather than one clever expression: first collect which
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# units each host declares, then flatten that into endpoints.
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- name: Collect the units each host declares
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ansible.builtin.set_fact:
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host_units: "{{ host_units | default([]) + [{'host': item, 'units': hostvars[item].monitored_services}] }}"
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loop: "{{ groups['managed'] | sort }}"
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when: hostvars[item].monitored_services | default([]) | length > 0
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- name: Build one endpoint per unit
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ansible.builtin.set_fact:
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service_endpoints: "{{ service_endpoints | default([]) + [{
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'name': (item.0.host | lower | regex_replace('[/_.,# +&]', '-')) ~ '/' ~ item.1,
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'group': 'services',
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'token': gatus_push_tokens[item.0.host],
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'heartbeat': hostvars[item.0.host].service_health_heartbeat | default('11m')}] }}"
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loop: "{{ host_units | subelements('units') }}"
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- name: Register the service 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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# 2: tolerate one explicit `false` from a unit caught mid-restart.
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# See the note above.
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failure-threshold: 2
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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: services
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gatus_endpoint_external: "{{ service_endpoints }}"
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- name: Monitor systemd services on every host that has them
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hosts: managed
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become: yes
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vars:
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gatus_api: "https://{{ subdomains.gatus }}.{{ root_domain }}/api/v1/endpoints"
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host_key: "{{ inventory_hostname | lower | regex_replace('[/_.,# +&]', '-') }}"
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tasks:
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- name: Is every deployed service running?
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ansible.builtin.include_role:
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name: healthcheck
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vars:
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healthcheck_name: service-health
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healthcheck_description: "systemd services on {{ inventory_hostname }}"
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healthcheck_check: systemd-units
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healthcheck_units: "{{ monitored_services }}"
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healthcheck_units_key_prefix: "services_{{ host_key }}"
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# Cadence and heartbeat window are ONE decision, and both are a property
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# of the host: a host can set service_health_on_calendar and a matching
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# service_health_heartbeat in its host_vars. None does today; everything
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# runs 5min/11m. (monerod-box was daily during its initial sync.)
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#
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# An empty healthcheck_on_calendar means "use healthcheck_interval" -
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# see the timer template in roles/healthcheck.
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healthcheck_interval: "5min"
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healthcheck_on_calendar: "{{ service_health_on_calendar | default('') }}"
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healthcheck_randomized_delay: "{{ service_health_randomized_delay | default('30') }}"
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healthcheck_boot_delay: "2min"
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# The per-unit results go to keys under this collection; the role's own
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# single-result push is unused here, so only the base is set.
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healthcheck_push_base: "{{ gatus_api }}"
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healthcheck_push_token: "{{ gatus_push_tokens[inventory_hostname] }}"
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when: monitored_services | default([]) | length > 0
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