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Rasmus "Pez" Wejlgaard
029c35fba6
Convert remaining ASCII art diagrams to mermaid syntax: - monitoring.md: stack overview diagram - networking.md: Tailscale mesh diagram + DNS request flow architecture.md already used mermaid, no changes needed. PESO-123
112 lines
3.5 KiB
Markdown
112 lines
3.5 KiB
Markdown
# Monitoring
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## Stack Overview
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```mermaid
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graph TD
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subgraph "london-a (FreeBSD)"
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Prometheus[":9090 Prometheus"] -->|query| Grafana[":3000 Grafana"]
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end
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Prometheus -->|scrape over Tailscale| NE["node_exporter<br/>(all hosts) :9100"]
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Prometheus -->|scrape over Tailscale| SE["smartctl_exporter<br/>(london-b) :9633"]
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Prometheus -->|scrape over Tailscale| PE["plex_exporter<br/>(london-b)"]
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```
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Both Prometheus and Grafana are accessible via:
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- **grafana.pez.sh** (behind Authelia)
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- **prometheus.pez.sh** (behind Authelia)
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## Prometheus
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Prometheus runs on london-a and scrapes metrics from exporters across the fleet. All scrape targets are reached over Tailscale — no ports need to be exposed on the public internet.
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### Scrape Targets
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| Target | Host | Port | What |
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|--------|------|------|------|
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| node_exporter | All hosts | 9100 | System metrics (CPU, memory, disk, network) |
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| smartctl_exporter | london-b | 9633 | Disk SMART health data |
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| prom-plex-exporter | london-b | (varies) | Plex streaming activity |
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node_exporter is deployed to every host via Ansible. It's one of the first things that gets installed on a new server.
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### Adding a scrape target
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1. Deploy the exporter to the host (via Ansible or Docker)
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2. Add the target to the Prometheus config in `services/prometheus/`
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3. Deploy the updated config (Ansible or manual restart)
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4. Verify it shows up in Prometheus targets page
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## Grafana
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Grafana reads from Prometheus and provides dashboards for everything worth watching.
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### Dashboards
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| Dashboard | What it shows |
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|-----------|--------------|
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| Server Health | CPU, memory, disk usage, network I/O across all hosts |
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| ZFS | Pool status, usage, scrub results for london-b |
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| SMART | Disk health metrics, temperature, error counts |
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| Plex | Active streams, transcoding status, library stats |
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### Adding a dashboard
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Dashboards are defined in `services/grafana/`. Export as JSON from Grafana and commit to the repo to keep them in version control.
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## Exporters
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### node_exporter
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Standard Prometheus node exporter. Deployed on every host. Provides system-level metrics:
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- CPU usage and load averages
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- Memory usage
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- Disk space and I/O
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- Network traffic
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- System uptime
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Installed via Ansible as part of the base server setup.
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### smartctl_exporter
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Runs on london-b (the ZFS storage server with 8 spinning disks). Exposes SMART data from all drives:
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- Temperature
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- Reallocated sectors
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- Read/write error rates
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- Power-on hours
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- Overall health assessment
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Critical for catching dying drives before they take out a RAIDZ1 vdev.
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### prom-plex-exporter
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Runs on london-b. Scrapes the Plex API and exposes metrics about:
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- Active streams
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- Transcode sessions
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- Library size
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- User activity
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Mostly for fun — it's satisfying to see the Plex dashboard light up when people are streaming.
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## Status Page
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**status.pez.sh** is a lightweight public status page that shows service availability.
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- Pulls availability data from Prometheus
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- Shows 90-day uptime history
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- Hosted on helsinki-a at `/srv/status`
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- Source: [RWejlgaard/pez-status](https://github.com/RWejlgaard/pez-status)
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- Not behind Authelia — it's public by design
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## Alerting
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Prometheus alerting rules can be configured in the Prometheus config. Alert conditions worth monitoring:
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- Host down (node_exporter unreachable)
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- Disk space critical (>90% usage)
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- ZFS scrub errors
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- SMART drive failures
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- High memory usage
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Grafana can also be configured with alert channels (email, webhooks, etc.) for dashboard-based alerts.
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