[Prometheus](https://prometheus.io/) endpoint to report the health check status of Docker containers.

# Usage
```
usage: dockstat.py [-h] [-H]

optional arguments:
  -h, --help         show this help message and exit
  -H, --healthcheck  Simply exit with 0 for healthy or 1 when unhealthy
```

# Example
## Output
```
curl -qsS localhost:8080/metrics
# HELP container_inspect_state_health_status Container's healthcheck value (binary)
# TYPE container_inspect_state_health_status gauge
container_inspect_state_health_status{id="21ac232f35edc4e630ed0c6b19b828a40df3dbc280c6bcf779b02a1488a741c3",name="alertify",value="healthy"} 1.0
container_inspect_state_health_status{id="73a3d19d996de90f15da6cea016d2b1733d0e63bca4d36b0a1bcb2d680d6f108",name="dockstat",value="healthy"} 1.0
container_inspect_state_health_status{id="db14abb41eec0ff06dc11b740b71839aec2b3855192b83a4ba31ee77bd21abfd",name="gotify",value="healthy"} 1.0
container_inspect_state_health_status{id="470e17a15751881cc0787f9aab6f1af000b7bbce7e590d82de987c583425b4ef",name="down-example",value="unhealthy"} 0.0
# HELP container_inspect_state_running Container's running state (binary)
# TYPE container_inspect_state_running gauge
container_inspect_state_running{id="21ac232f35edc4e630ed0c6b19b828a40df3dbc280c6bcf779b02a1488a741c3",name="alertify"} 1.0
container_inspect_state_running{id="73a3d19d996de90f15da6cea016d2b1733d0e63bca4d36b0a1bcb2d680d6f108",name="dockstat"} 1.0
container_inspect_state_running{id="db14abb41eec0ff06dc11b740b71839aec2b3855192b83a4ba31ee77bd21abfd",name="gotify"} 1.0
container_inspect_state_running{id="470e17a15751881cc0787f9aab6f1af000b7bbce7e590d82de987c583425b4ef",name="down-example"} 0.0
# HELP container_inspect_state_started_at Container's start time (int)
# TYPE container_inspect_state_started_at gauge
container_inspect_state_started_at{id="21ac232f35edc4e630ed0c6b19b828a40df3dbc280c6bcf779b02a1488a741c3",name="alertify"} 1.631792247e+09
container_inspect_state_started_at{id="73a3d19d996de90f15da6cea016d2b1733d0e63bca4d36b0a1bcb2d680d6f108",name="dockstat"} 1.631779075e+09
container_inspect_state_started_at{id="db14abb41eec0ff06dc11b740b71839aec2b3855192b83a4ba31ee77bd21abfd",name="gotify"} 1.631779073e+09
container_inspect_state_started_at{id="470e17a15751881cc0787f9aab6f1af000b7bbce7e590d82de987c583425b4ef",name="down-example"} 1.631779081e+09
# HELP container_inspect_state_exit_code Container's exit code (int)
# TYPE container_inspect_state_exit_code gauge
container_inspect_state_exit_code{id="21ac232f35edc4e630ed0c6b19b828a40df3dbc280c6bcf779b02a1488a741c3",name="alertify"} 0.0
container_inspect_state_exit_code{id="73a3d19d996de90f15da6cea016d2b1733d0e63bca4d36b0a1bcb2d680d6f108",name="dockstat"} 0.0
container_inspect_state_exit_code{id="db14abb41eec0ff06dc11b740b71839aec2b3855192b83a4ba31ee77bd21abfd",name="gotify"} 0.0
container_inspect_state_exit_code{id="470e17a15751881cc0787f9aab6f1af000b7bbce7e590d82de987c583425b4ef",name="down-example"} 137.0
# HELP container_inspect_downtime_alert_threshold Container's downtime alert threshold in seconds (int)
# TYPE container_inspect_downtime_alert_threshold gauge
container_inspect_downtime_alert_threshold{id="21ac232f35edc4e630ed0c6b19b828a40df3dbc280c6bcf779b02a1488a741c3",name="alertify"} 3600.0
container_inspect_downtime_alert_threshold{id="73a3d19d996de90f15da6cea016d2b1733d0e63bca4d36b0a1bcb2d680d6f108",name="dockstat"} 3600.0
container_inspect_downtime_alert_threshold{id="db14abb41eec0ff06dc11b740b71839aec2b3855192b83a4ba31ee77bd21abfd",name="gotify"} 3600.0
container_inspect_downtime_alert_threshold{id="470e17a15751881cc0787f9aab6f1af000b7bbce7e590d82de987c583425b4ef",name="down-example"} 3600.0
```

## Prometheus Alerts
```yaml
  - name: "Container status"
    rules:
      - alert: "Container unhealthy"
        expr: container_inspect_state_health_status == 0
        for: 15m
        labels:
          severity: error
        annotations:
          summary: "Container unhealthy"
          description: "{{ $labels.name }}: {{ $labels.value }}"

      - alert: "Container down"
        expr: container_inspect_state_running == 0 and ON(id) time() - container_inspect_state_started_at > container_inspect_downtime_alert_threshold
        labels:
          severity: critical
        annotations:
          summary: "Container down"
          description: "{{ $labels.name }}: DOWN"
```

# Notes
* Requires access to the Docker socket (`/var/run/docker.sock`)
* The port `dockstat` listens on can be changed using the `DOCKSTAT_LISTEN_PORT` environment variable.  Default: `8080`

    e.g. `DOCKSTAT_LISTEN_PORT=80 python3 dockstat.py`

# Docker
## Build
```bash
docker build . -t 'dockstat:latest'
```

## Run
```bash
docker run --name dockstat -p 8080:8080 -v /var/run/docker.sock:/var/run/docker.sock:ro -e TZ=Europe/London dockstat:latest
```

## Compose
```yaml
---
version: "2"
services:
  dockstat:
    image: dockstat:latest
    container_name: dockstat
    environment:
      - TZ=Europe/London
      - DOCKSTAT_LISTEN_PORT=80
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    restart: unless-stopped
```