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wiki: add Tailscale SSH reauth article; update Netdata Docker alarm tuning (50 articles)

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- New: Tailscale SSH unexpected re-authentication prompt — diagnosis and fix
- Updated: netdata-docker-health-alarm-tuning — add delay: up 3m to suppress
  Nextcloud AIO PHP-FPM ~90s startup false alerts; update settings table and notes
- Updated: 05-troubleshooting/index.md and SUMMARY.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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MajorLinux
2026-03-21 00:12:52 -04:00
parent 4d59856c1e
commit c4d3f8e974
4 changed files with 74 additions and 5 deletions
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11
02-selfhosting/monitoring/netdata-docker-health-alarm-tuning.md
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@@ -5,7 +5,7 @@ category: monitoring
tags: [netdata, docker, nextcloud, alarms, health, monitoring]
status: published
created: 2026-03-18
updated: 2026-03-18
updated: 2026-03-21
---
# Tuning Netdata Docker Health Alarms to Prevent Update Flapping
@@ -40,7 +40,7 @@ component: Docker
every: 30s
lookup: average -5m of unhealthy
warn: $this > 0
delay: down 5m multiplier 1.5 max 30m
delay: up 3m down 5m multiplier 1.5 max 30m
summary: Docker container ${label:container_name} health
info: ${label:container_name} docker container health status is unhealthy
to: sysadmin
@@ -49,10 +49,11 @@ component: Docker
| Setting | Default | Tuned | Effect |
|---|---|---|---|
| `every` | 10s | 30s | Check less frequently |
| `lookup` | average -10s | average -5m | Must be unhealthy for sustained 5 minutes |
| `delay` | none | down 5m (max 30m) | Grace period after recovery before clearing |
| `lookup` | average -10s | average -5m | Smooths transient unhealthy samples over 5 minutes |
| `delay: up 3m` | none | 3m | Won't fire until unhealthy condition persists for 3 continuous minutes |
| `delay: down 5m` | none | 5m (max 30m) | Grace period after recovery before clearing |
A typical Nextcloud AIO update cycle (30–90 seconds of container restarts) won't sustain 5 minutes of unhealthy status, so no alert fires. A genuinely broken container will still be caught.
The `up` delay is the critical addition. Nextcloud AIO's `nextcloud-aio-nextcloud` container checks both PostgreSQL (port 5432) and PHP-FPM (port 9000). PHP-FPM takes ~90 seconds to warm up after a restart, causing 2–3 failing health checks before the container becomes healthy. With `delay: up 3m`, Netdata waits for 3 continuous minutes of unhealthy status before firing — absorbing the ~90 second startup window with margin to spare. A genuinely broken container will still trigger the alert.
## Applying the Config